the amphibians of the mamfe division, cameroons.–ii. ecology of the frogs

AMPHIBIANS O F THE MAMFE DIVISION. CAMEROONS . 165

10 . The Amphibians of' the Mamf'e Division. Cameroons.-11. Ecology of the Frogs . By IVAN T . SANDERSON. B.A., F.Z.S.

[Received October 23. 1935 : Head February 18. 1936.1

(Plate I . * ; Text-figures 1-8.)

CONTENTS . I . Introductory .............................................. . . . . . . . . . . . . . . . . . . . . I1 General Geography and Climatic Conditions

111 . Vegetational Zones and Habitats ............................ ( 1 ) The Zoning of Vegetation ........................... (2) Collecting Stations ..................................

IV . Ecological Distribution of Species ............................ (1) Specialization in Ecological Distribution . . . . . . . . . . . . . . .

(3) Habitats ..........................................

(2) Comparative Popularity of Vegetational Zones and Habitats ......................................

V . Results of Deforestation ................................... (1) Botanical Results of clearing Virgin Ground ........... (2) Results of Deforestation upon Frog Ecology ........... (3) Alteration of the Facies of the Frog Fauna ............. (4) Alteration of the Habitats due to Deforestation (5) The Repopulation of Isolated Areas of Cleared Forest . . .

.......

(6) Effects of Deforestation upon Numerical Strength of Frog Population .......................................

VI . Colour Variation ........................................... Note on Colour Description .............................

VII . Life-Colour and Observations ............................... (1) Ranidae ........................................... (2) Rhacophorid ae ...................................... (3) Bufonide .......................................... (4) Pipide ...........................................

IX . References ................................................ VIII . Summary of Conclusions ....................................

65 166 168 168 170 171 171 171

175 176 176 178 179 183 184

185 186 187 187 187 200 204 207 207 207

I . INTRODUCTORY . The observations and conclusions contained in this paper. together with the

notes on natural coloration of the species. are derived from data accumulated during the course of collecting amphibian material in the British Cameroons during the years 1932 and 1933 . An expedition to this locality was made possible by the Percy Sladen Memorial Trust. as well as by Cambridge University. the British Museum (Nat . Hist.), and the Royal Society . The production of the present paper and that of others to follow has been rendered possible by the further generous assistance of the Percy Sladen Memorial Trust. I am

* For explanation of the Plate. see p . 208 .

l6ti MR. IVAN T. SANDERYON ON THlC

also deeply indebted to Mr. H. W. Parker, of the Departlnent of Herpetology of the British Museum, not only for the naming of the collection, but also for his encouragement, help, and advice.

I wish also to take this opportunity of expressillg niy appreciation to niy companion in travel, I&-. W. M. Russell, who was personally responsible for the preservation of all the herpetological material, as well as the collection of the greater part of it, and to whose untiring energy and perseverence is due the recording of practically the whole of the extensive detailed notes which form the basis of the following summary.

Abbreviations. A number has been assigned to each of the species (see Table I., facing

page 207)) and these have been employed in all the tables as well as in the text where necessary, for the sake of brevity.

H.D.F.=High deciduous forest. M.P.= Mountain forest. M.G.= Mountain grass. Cult.=Cultivated land. Tert.=Tertiary growth.

Second.=Seeondary forest.

11. GENERAL GEOGRAPHY AND CLIMATIC CONDITIONS. The locality in which the Expedition operated lies ostensibly within the

Rain-forest Area of West Africa, between lat. 5" and 6" 30' N., and long. 8" and 10" E. This territory, apart from the Cameroons Peak in the extreme south, comprises the entire drainage basin of the Cross River. This river finds its source and main tributaries in the mountainous Cameroons country mandated to Great Britain, but subsequently flows for more than half its total length through the extreme south-western corner of Nigeria, and enters the sea a t Calabar .

The collections now under review were, however, with but a handful of exceptions, made in the Mamfe, Ikom, and Obubra Divisions, which by reference to the Map (text-fig. 1) will be seen to hold a central position in the area particularieed above.

These three political Divisions form a low plain confluent with the great South Nigerian lowlands in Obubra, which enter a bottle-neck in Ikom, and terminate in a roughly circular cul-de-sac or basin in Mamfe. The last-named locality is ringed round on the north, east, and south by high hills and mountains, never less than 1500, and often more than 5000, feet in height, which act as a continuous horseshoe-shaped watershed. These mountains are mostly grass-covered, and therefore act not only as a divide between the headwaters of the Cross River and the numerous systems which surround the area, but also as a positive interruption to the continuity of the high forests.

With the exception of a narrow belt bordering the large river in its passage through Nigerian territory, this country is thinly populated, a village of a hundred souls being an extreme rarity, and modern roads being non-existent, apart from some 25 miles to east and west of Mamfe station itself. The land under cultivation or cleared of forest again comprises a strip bordering the Cross River in Obubra Division, and also two small areas in the southern portion of the Mamfe Basin. Otherwise this type of country is only met

AMPHIBIANS OF THE XAMBE DIVISION, CAMEROONS. 161

with in tiny clearings surrounding the '. bush " villages which are strung out along the forest paths a t irregular interrals.

The surrounding mountains rise abruptly in the north and east, forming an exceedingly steep escarpment. h i the south their rise is more gradual,

Text -figure 1.

more subdued, and less great. In the north and east the watershed forms an almost knife-edged ridge, which can in some places be spanned in two paces, but to the north-east the high land continues for some hundreds of miles, forming the plateaux of Bamenda, Amadawa, and Shari-Chad.

168 811%. IVAN T. SANDERYON ON THE

Rainfall is high, but is mostly concentrated into a long wet season extending from the end of March to the end of October, with a period of maximum intensity during June, July, August, and September. The average yearly rainfall is approx. 81" (Knox, 1911), being 71" during the wet season and 10" during the dry. The dry season opens with six weeks during which the Har- inattan blows from the north. This is a continuous drift of the air rather than a wind, and being so highly charged with minute sand particles from the dry desert country, causes a more or less permanent haze, which in some cases partially obscures the sun. The remainder of the dry season is subject, to frequent showers and storms, and the last two months of the rainy season are almost without exception devoid of sunshine.

During the present expedition the maximum recorded was 92" B. and the minimum 67" F., though the latter was recorded at an altitude of 5000 feet. The hygro- meter, on the other hand, fluctuates violently, though usually remaining disagreeably high, and often almost reaching saturation point in the forest. Humidity does not seem to depend upon seasonal variation of climate in the mountainous Cameroons area.

Prevailing winds a t Mamfe vary throughout the year and depend to a great extent upon the conformation of the surrounding country. In the dry season during the Harmattan sudden storms invariably come from the south-west ; towards the close of the dry season and a t the onset of the light rains the prevailing wind is from the east. This latter condition continues throughout the rains a t Mamfe, but in Asumbo (in the north), and at Obubra, where there are no protecting mountains, winds from the north predominate and bring most of the rain.

The mean annual temperature (78" F.) is not excessively high.

111. VEGETATJONAL ZONES AND HABITATS.

(1) The Zoning of Vegetation. The above-mentioned characteristics of geography and climate are re-

sponsible for a markedly regular distribution of vegetation into zones which to a very large extent determine the ecological distribution of amphibians in the area, as well as that of the mammals, and probably of other groups. This zoning may also serve as a concrete basis for the classificat,ion of the numerous habitats and the ecological groups which they support.

Altitude is undoubtedly the chief factor controlling the areas of the vegetational zones, which, in turn, to a great extent determine the light, cover, food, moisture, and temperature available to the fauna. In the area under review only two other factors seem to contribute to this vegetational distribution. They are latitude and human agency, of which the former is here somewhat modified through major geographical causes.

The vegetational zones recognised in this paper and to which constant reference is made are as follows :-

Vegetational Zones. Altitnde. Latitude. (1) Mangrove swamps ............... Sea-level. (2) Rain forest ........................ (3) Cleared forest :

Below 1000 ft. South of 5" 30'

( a ) Cultivated land. ( b ) Tertiary growth. 1300-3000 f t . 5" 30'-6O 30' ( c ) Secondary forest. J

AiVlPHIBIANH O F 'I'HS h1"LMHlC DIVIY1ON, CAMEROONS. 169

Vegetational Zones. Altitude. Latitude. (4) High deciduous forest . . . 300 3000 ft. 5' 3 0 ' - 6 O 30' (5) Palm-belt . . . . . . . . . . . . . . . . . 1500-2000 f t . (6) Mountain forest . . . . . . . . . . . . . . 3000-G000 f t . (7 ) Mountain grass . . . . . . . . . . . . (8) Northern plains. (Savannah Korth of tio.

2OOO f t . upwards.

etc.)

No collections were made in the Mangroves with the exception of few toads from Calabar. The Rain Forest proper, consisting of the permanently damp creeper-covered growth typical of the Congo area, was similarly not penetrated. The greater part of the collections were made in the high deciduous forest, with only one extended visit paid to the mountain grass and mountain forest. The term high deciduous forest refers to the stature of the trees and not to altitude, but it must be stressed that in the Mamfe area it is fairly bare beneath the continuous canopy of the head foliage, carpeted with a considerable thickness of mould, and always poorly lighted.

When this type of forest has once been cleared it has never been known to return (a belief held also by the natives). but in its stead a secondary growth appears of a different botanical constitution, which, if left, will itself grow into a gigantic forest. The hardwood trees characteristic of the primary growth, are, however, mostly absent, and the natives therefore prefer to reclear such ground for the purposes of cultivation. This acts as a strong secondary de- terrent to any primary-forest animals which might gain a footing in secondary growth, in which, with a few notable exceptions, they are never found. This secondary forest, then, may be clearly divided into three types :-(u) that which has been cleared once and been left quiescent sufficiently long to return to the tall tree condition (secondary forest), ( b ) that which is regularly cleared (tertiary growth), and, lastly (c) , that which is actually cleared (cultivated land). Each retains its separate amphibian fauna, though the two last-named are more closely associated, and all are widely different from the high or primary forest grouping which disappears with its habitat.

At an altitude of approximately 1500-2000 ft. a highly peculiar belt of vegetation is met with in this area, consisting almost entirely of palm-trees. This appears to be a natural zone, but is often considerably augmented and extended by native plantations of palms that are not indigenous to the country. In association with the palms, which are almost the only trees, are masses of ground creepers which often envelop the trunks to a considerable height. Although the expedition camped for some time near this belt (Bashauo), and visited it a t Manta and Bamumbu, not a single amphibian was taken or seen in it, although reptiles were fairly numerous. This sterile belt is quite wide in the north and north-east.

At 2000 ft. there is everywhere an abrupt change both of vegetation and scenery. The forest ends like a wall, and waist-high grass commences, choked with herbaceous growth, and thin stick-like shrubs. The extent of this grass is enormous to the north and north-east, where it may extend right up to the summits of steep rocky mountains. The peculiarity of the scenery is, however, afforded by the clumps and patches of mountain forest, which either cap the very summits of the high hills and mountains, choke the ravines of the clear, rushing streams, or border the rivers a t the bottom of the valleys, which are in some cases on the northern incline, below the 2000-ft. level. This mountain forest consists of evergreen trees, having the appearance of over-grown

I70 MR. IVAN T. SANDERSON ON THE

shrubbery with thin branches. The trees are seldom iiiore than $0 feet in height. It is excessively damp, festooned with lichens and mosses, and often mis&enshrouded.

The mountain grass, in localities where native tribesmen dwell, is burnt annually, but this seems to have remarkably little effect upon its growth and fauna. as compared with areas that are not thus annually denuded.

Under the heading of Northern Plains, a number of vegetational types are being spoken of collectively, which can only be strictly separated from the above-mentioned zones on zoological grounds. The scenery is indeed different, being open country, as opposed to forests, but in the extreme north of Asumbo, the mountain grass, as it descends to the 2000-ft. level, givesplace to true orchard- bush, whereas the forests of Obubra merge into it through a belt of swamps and elephant grass. These two types of vegetation are both grouped under the heading Northern Plains, which includes also areas of grass, savannah, and park land. The amphibians of this vegetational zone are quite distinct from those of the forest, with the very few exceptions afforded by some universally distributed species.

(2) Collecting Stations. The expedition moved about the country collecting continuously for a

period of one year. As, however, a great deal of the work was done while under canvas, camp sites have been named according to the village upon whose hunting ground it was situated, the whole country being thus nominally divided. These stations are as follows :-

Vegetational Zone. Locality.

(1 ) Mangrove swamps . . . . . . . . . . . Calabar . . . . . . . . . . . . (2) Rainforest ................ I tu . . . . . . . . . . . . . . . .

Akunakuna . . . . . . . . . c Ekuri. .............. Nko ...............

(3) High deciduous forest (cleared) .-! Ikom .............. Mamfe ............. Okoiyong ........... Besongabang . . . . . . . . Akwa . . . . . . . . . . . . . . . Eshobi . . . . . . . . . . . . . . Mokonyong . . . . . . . . . Bakebe . . . . . . . . . . . . . Fineschang ......... Nyang ............. Bashauo . . . . . . . . . . . . Atolo

Makumunu (6) Mountain forest . . . . . . . . . . . . . . Balegete ............

N’da-Ali . . . . . . . . . . . . (7) Mountain grass . . . . . . . . . . . . . . Tinta .............. (8) Northern Plains .............. Obubra .............

(4) High deciduous forest (virgin). . 1 I ..............

(5) Palm-belt . . . . . . . . . . . . . . . . . . . Bamumbu, Manta ... .........

Altitude, feet.

10 20

200 200 300 350 400 400 450 400 450 500 600 650 700 750

1400 1500 2200 3000 4000 2300 300

Ma,ny other villages and localities were visited where general topographical observations were made, but no amphibians collected.

BMPKUJIANS Oh' THE AlAhlFX UIVISION, CAMEROONS. 171

Major habitat. Minor habitat. ____

1. Clear runiiing water. 2. Muddy running water.

4. Clear still water. 1. Water . . . . .I 3. Large rivers.

I 5. Muddy still water. -- 1

(3) Habitats. Frogs are to be met w i t h in almost all possible habitats in this country

which can support animal life. Proximity to water seems to be no particular consideration in their choice of environment, and the numerical strength of the frog population is very great.

Twenty-one clearly recognisable habitats may be distinguished which caii be grouped under six heads as follows :-

TABLE A.

10. Damp grass.

12. Dry grass (rocky soil). 111. Grass . . . . . .!{ 11. Dry grass (sandy soil).

13. Bananas and plantains. 14. Stunted and low trees. 15. Giant forest trees.

lfit3: Natural. Below trees (damp). Below trees (dry).

Dried water courses. 1 1 ii: Human habitations.

V. Clear ground., 18. Bare rocks.

I ih6,Soil . T. :[- 21. Subterranean.

I

All of these can, and practically without exception do, occur in any of the above enumerated vegetational zones, except in the mangrove swamps. Trees are met with in the mountain grasslands and grassfields in the high deciduous forest.

1V. ECOLOGICAL DISTRIBUTION OF SPECIES.

(1) Specialization in Ecological Distributim. The 46 species of frogs were collected from 56 out of a possible or hypo-

thetically possible total of 147 minor habitats. Mangrove swamps, rainforest, and the Northern Plains are not taken into account in the following generalizations, since no complete collections were made in these zones. The palm-belt, however, has to be included as it was painstakingly searched for frogs, though it failed to yield a single specimen.

172 MR. IVAN T. SANDERSON ON THE

Damp grass.. ............... Dry grass, sandy soil. . . . . . . . . Dry grass on rocks ..........

The following table summarizes the distribution of the species according to the vegetational zones, major and minor habitats.

TABLE B.

Number

species. 1-

Ecological group. Species numbers. I -

Vegetational zones. I High deciduous forest . . . . . . . ~ 28

14

3 27

14 11 18

15

17

8 16

12 1

10 2 2 2 3 1 5 9 8 5 8 2 4

14

2 5 6 2 1 2 1

1, 3, 6, 9, 10, 11, 12, 13, 14, 17, 18, 19, 20, 22, 23, 25, 28, 29, 31, 32, 33, 36, 40, 41, 42, 43, 45, 46.

10, 11, 12, 13, 16, 18, 20, 25, 26, 28, 29, 35, 38, 45.

6, 21, 44. 2, 3,4, 5, 6, 7, 8, 9, 13, 15, 16, 18, l9,20, 21, 22

24, 27, 30, 31, 33, 34, 37, 39, 42, 44, 46. 2, 3, 5, 6, 7, 9, 19, 20, 27, 30, 34, 39, 44, 46. 2, 3, 5, 9, 13, 15, 19, 21, 37, 44, 46. 3,4, 7,8, 9, 13, 16, 18, 19,22, 24,27,31,33,34:

39, 42, 44,

1, 2, 3, 8, 10, 11, 12, 13, 15, 17, 19,27, 42, 44, 46.

2, 4;5, 10, 11, 12, 13, 16, 18, 19, 20, 22, 23, 26, 33, 40, 44.

5, 6;7, 9, 10, 13, 19, 21, 24, 42, 44. 6, 13, 14, 25, 28, 29, 30, 31, 32, 34, 35, 36, 37,

9, 10, 13, 14, 18, 19, 20, 22, 25, 43, 44, 45. 11.

38, 39, 41.

1, 8, 10, 11, 12, 13, 15, 17, 19, 42. 2, 3. 3, 46. 10, 44. 3, 27, 46. 5. ..

13, 18, 19, 23, 40. 2, 10, 12, 13, 16, 19, 26, 33,44. 4, 13. 16, 18. 19, 20. 22. 44. _ . . 5; 6, '7, 9, 21: 6, 9: 13, 19, 21, 24, 42, 44. 9, 19. 30, 34, 37, 39. 6, 13, 14, 25, 28, 29, 31, 32, 34, 35, 36, 38,

39. 41. 28, 31. 19, 20, 25, 43, 45. 10, 13, 14, 18, 19, 22. 9, 44. 13. 18, 44. 11.

______ . . .

Further analysed to determine the number of species that are confined to a single vegetational zone, major or minor habitat, or are encountered in more than one, more significant facts become apparent (see text-fig. 2).

AMPHIBIANS OF THE MAMFE DIVISION, CAMEROONS. 173

These figures are based on a year’s collecting, during which time over 900 specimens were taken.

From text-figure 2 it will be seen that the greatest number of species are confined to a single vegetational zone (24 species or 52 per cent. approx.), a single major habitat (30 species or 65 per cent. approx.), and even to one minor division of the habitats (17 species, or 37 per cent. approx.). The great preponderance of species that are confined to but a single major habitat shows this factor to be one of great importance in the frog ecology.

Considering also the recurrence of most major habitats in nearly all vegetational zones (e . g., water), i t is surprising that more species are not found in two, three, or four vegetational zones instead of only in one or two. This fact therefore tends to show that the vegetational zones are in some measure

Text-figure 2.

26 25

Number of vegetational zones, major and minor habitats to which specie8 are confined.

faunistically distinct, as they are to a very great extent botanically. Frogs which are closely linked to their major habitats (vide 65 per cent. confined to a single major habitat) can yet be confined to one or two vegetational zones for the most part.

The number of species that are confined to but a single minor habitat is even more noticeable in the field than from any chart that may be compiled from data collected over a period. The presence of a single specimen in a vegetational zone, major or minor habitat, extends the range of that species to that division. Thus many species that appear to be found only in very specialized situations in the field may prove later to extend over three or four minor habitats. Nevertheless, seventeen species still remain confined to a single minor habitat, among which are species represented by specimens collected


in four different months of the year a t localities over fifty miles apart. While in the field it was possibIe to predict the type of soil in certain areas of grassland from the frogs collected by natives, which surmise was later corroborated by visiting the locality. Minor habitats, moreover, may be defined nlerely by a variation of humidity (e. g., damp or dry grass).

When it is remembered that most frogs have to return to water a t the breeding season, and that during the course of a year all species will presumably make an attempt to breed, it is very remarkable that more species were not found in a t least two major habitats and vegetational zones, as a migration to water would, in a great number of cases, necessitate traversing several habitats, and even passing from one vegetational zone to another.

Of the twenty-two species taken in more than one vegetational zone, six were in the coiirse of a breeding migration (nos. 9, 12, 13, 19, 42, and 44). Sixteen species were recorded from more than one major habitat and, of these, eight (species nos. 2, 9, 11, 12, 13, 19, 32, 44) were presumed to be in water for the purpose of breeding or were actually observed doing so (Rana mascareni- pnsis, il'richobatrachus robustus (tadpoles), Petropedetes johnstoni (immature frogs and females with ripe ova), Arthroleptis pcecilonotus and Bufo regularis (spawn and tadpoles).

Thus it can be seen that the foregoing tables give an under- rather than an overestimate of the degree of correlation between species and vegetational zones and habitats.

If those frogs that are found in two vegetational zones and major habitats on account of a breeding migration be added to the numbers that are found in one vegetational zone and major habitat respectively, and similarly, those that are found in three vegetational zones and major habitats for the same reason he added to the totals found in two, the following results are obtained :-

Frogs in one veg. zone . . 24 Migrational correction . . +5=29 Frogs in two veg. zones . 18 Migrational correction . . --5+1=14

Total . . . . 42 Total . . . . 43 - -

Frogs in one maj. hab. . . 30 Migrational correction . . +4=34 Frogs in two maj. habs. . . 11 Migrational correction . . -4+2= 9

Total . . . . 41 Total . . . . 43

When, therefore, adjustments are made to correct the incidence of breeding migrations, the number of frogs found in one or two vegetational zones and one or two major habitats becomes equal. The t,ot,al of forty-t,hree is not, however, altogether composed of the same species.

This we are inclined to regard as a mere coincidence, though it might con- ceivably result from some direct relationship between vegetational zones and major habitats in general.

The frogs found in more than two vegetational zones, after allowance has been made for known breeding migrations, are : - - R a m albolabris, Arthroleptis calcaratus, and A. variabilis ; in more than two niajor habitats :-A. pcecilonotus, Bufo regularis, and Petropedetes johnstoni. The last-named species is doubtless present by reason of its extensive breeding migration from the trees to the rivers. A . pcmilonotus and B. regularis are widely distributed species of catholic tastes.

- -

- -

175 AMPHIBIANS O F THE MANIFE DIVISION, CAMEROONS.

Among the frogs collected in this area are several species which have an exceedingly wide geographical range, Rana occipitalis, fifty-three specimens collected in six different months ; R a m (Ptychaclwna) mascareniensis, seventy- two specimens collected in seven different months. These were collected in large numbers and were found to be confined to clearly demarcated habitats just as much as the endemic local species.

( 2 ) Comparative Popularity of Vegetational Zones and Habitats. From tables B and H it will be seen that certain vegetational zones,

major and minor habitats support a more diverse fauna than others. Among these, low and stunted trees are most popular with fourteen species, more especially so in H.D.F. (eight species), mountain forest (six species), and secondary forest (four species). Second in popularity are clear running water and damp herbage, also principally in H.D.F., dry herbage and dry grass 011

sandy soil (eight species each) are preferred in cleared land. Dry ground below trees in cleared forest areas is well supplied with species, whereas in high deciduous forest this habitat swarms with individuals, but of a more limited number of species.

In all vegetational zones, water, herbage, clear ground, and trees are of equal importance. A preponderance of terrestrial forms (including grass, clear ground, and herbage-dwelling species) over arboreal forms is apparent. In the forest belt natural grass is only found where lack of soil or climatic conditions prevent the growh of other vegetation. The former occurs in natural clearings in the H.D.F.

Subterranean habits are attributed to two species, Cardioglossa escalerz and Hemisus marmoratum, which were not found in such situations on the present expedition. The female of Trichobatrachus robustus, however, was confined to this highly specialized habitat.

This possibly indicates that it is the oldest environment which has acquired its own specialized populations. The H.D.F., with its canopy of giant trees raising the sunlight and insect food high into the a r , leaving the broad-leafed, stunted trees in gloom, and the clear floor below covered by a blanket of dead leaves, in mnre or less permanent semi-darkness, offers a greater variety of environmental niches than is found in other vegetational zones.

Those types of vegetation which are grouped under the heading of cleared forest show a range of conditions far more varied than an area of similar extent would show in temperate regions. Secondary forest is in some cases as tall as high deciduous forest, tertiary growth may be as dense as a gorse- bush, or as open as a blrch wood, while cultivated land varies from yam- plantations having the appearance of a cabbage-plot to groves of rubber trees or open lawns around human habitations. This variety, in all probability, accounts for the number of species found therein.

The mountain forest is a specialized type of growth devoid, as far as was ascertained, of standing water and only traversed by swift-flowing mountain brooks and rills. This absence of suitable breeding sites for frogs, coupled with the scarcity of food and a lower temperature than in H.D.F., makes the whole less suitable for frogs (as well as other animal groups), and possibly accounts for the lesser numerical frog population and the paucity of species (see p. 185).

The mountain grass is a still less inviting locality for frogs, there being even less water and humidity, greater sunlight with a consequent wider variation between night and day temperatures, a superfluity of snakes, large flocks of birds, and less cover, although there is a far greater amount of insect and

The high deciduous forest contains the greatest number of species.

176 MR. IVAN T. SdNDERSON ON THE

other invertebrate food. Only three species, Phryobatrachus acridoides, Rana albolabris, and Bufo regularis, seem to be able to withstand these conditions, and they are extraordinarily tenacious. In some localities patches of grass are burned annually by natives, but these three species return every year seemingly in greater numbers, SO that a plague of Phrynobatrachus acridoides occasionally occurs.

The Palm-Belt lying usually between high deciduous and mountain forest, though sometimes between high deciduous forest and mountain grass, failed to yield a Ringle frog specimen, though it is plentifully supplied with suitable food and well watered, despite the fact that a considerable time was spent in organised searches therein. Frogs were taken in cultivated land planted with palms, provided that other vegetation was also present. Near Bashauo, a river passed through this belt in which Trichobatrachus was caught both higher up and lower downstream, but failed to yield any frogs when actually bordered by the Palm-Best.

The peculiarities of the Palm-Belt are (1) the density of its creeper-like undergrowth, (2) its persistent, slightly aromatic smell, (3) the great number of ants with which it is infested, and (4) the presence of no other trees except palms. Of these, number (3) alone seems capable of effectively influencing the frog fauna, and may well be a controlling factor in view of the extraordinary voracity of the ants. During the months of immaturity the frogs could not defend themselves against their lesser foes. It is from the Palm-Belt that the armies of driver ants frequently issue, and one such exodus a t Bashauo left in its wake, or was seen to be carrying with it, numerous full-grown Bufo lat+-ons. These toads were common in the forest clearings, but non-existent in the Palm-Belt less than a hundred yards away.

Reptiles are, however, numerous.

V. RESULTS OF DEFORESTATION. Of vital biological and, to some extent, economic importance (destruction

of insect populations by frogs, see H. B. Cott, 1932, Proc. ZOOS. SOC. pp. 488491) is an investigation of the results of clearing " virgin land," particularly virgin or primary forest. This has been done from time immemorial by natives over small areas, but with the advance of civilization greater inroads are now being made into virgin land, This process will probably continue until all but isolated and inaccessible patches of primary forest have become extinct.

The nomenclature and behaviour of vegetation in the Mamfe area, as in other parts of tropical Africa, are, however, somewhat complicated and mis- leading. Before proceeding to enumerate the results upon the frog fauna, it is therefore necessary to clarify certain points from a botanical standpoint.

(1) Botanical Results of clearing Virgin Ground. From the chart (text-fig. 3) it will be seen that the result of clearing forest

(either H.D.F. or mountain forest) is the production of a new type of growth termed secondary forest. This differs from primary high deciduous forest, not only in that it has once been cleared, but also by the absence of certain trees and the presence of an entirely new flora. Secondary forest never returns to H.D.F., however tall it may grow, or however long it may remain undisturbed.

Secondary forest cannot be produced without first clearing away the H.D.F., and then allowing another and botanically distinct type of growth to spring up, spoken of as tertiary growth. This as it grows, and by a process of elimina- tion of certain species and the addition of others, gives rise to secondary forest. Tertiary growth (and cultivated land) are transient and unstable


conditions. Both can be produced only by a process of clearing, and one or the other always occurs after clearing in this area, except upon one occasion. When mountain grass is cleared and merely left or cultivated (if possible) and then left, it invariably returns to mountain grass within a very short space of time (6-9 months). If mountain forest be cleared, however, it either gives rise to tertiary growth and, subsequently, to secondary forest, or passes to mountain grass, either through a phase of cultivation or directly if left alone. This is of considerable economic importance in view of the fact that mountain grass is not only sterile in itself, but tends to render the soil permanently sterile both for agriculture and stock-raising, as well as generally heralding arid conditions.

Also, in Asumbo a considerable area of tertiary growth produced by clearing mountain forest for cultivation (bordering mountain forest) was observed to be giving way directly to mountain grass. This seems to indicate that even

Text-figure 3.

//T\\\ ( U O U N T A l y R E S T ) ? MOUNTAIN GRASS

r l a ~ 7 Teittary S e c o f d q \ , j ? l \II* pi.F/ I ItG\ / I

T w t l a r , SLEOndary CUltirrsted Tertiary Seeondsry

Cul 1 ivated T c r t l a r y i u/R\ Secondary

-1 Utl/ Cultivated MOUNTAIN GRABS Cultivated

c nitursl $Ilo*th. HIGX DECIDWDVS WREST YOUNTAIY FOREST MOUNTAIN GRASS w land cleared.

-planting.

Botanical results of clearing virgin land.

tertiary growth, when in direct contact with mountain grass, can give way to the latter type of flora. Tertiary growth is similar whether i t be the result of clearing H.D.F. or mountain forest, and it is therefore interesting to speculate whether high deciduous forest may not in time succumb to the relentless southward encroachment of the grass, which is only a forerunner of the deserts.

Natives affirm that secondary forest produced from clearing mountain forest can return to mountain forest, a statement which they should be well qualified to make, but which cannot be accepted without corroboration, which is not forthcoming from a study of frog faunas.

An interesting point is that cultivated land, tertiary growth, and secondary forest have exactly the same frog faunas and facies whether they be produced from high deciduous forest, mountain-forest, or palm-belt growth, though botanically they are not absolutely identical.

PROC. ZOOL. Soc.-1936. 12


1 When H.D.F. is changed t o Secondary . . . .~

. i I When M.F. is changed to Second. (if stable)

19

. . . . . . . . . . 14 1 When M.F. is changed to M.G.

1 1 - 1

9 , -10

0 1 3 i -11

15 1 + 4

9 l I

3

Deforestation, therefore, more than halves the frog fauna unless secondary forest produced from mountain forest remains stable, in which case the fauna is somewhat less than halved though still greatly reduced.

In order to obtain these broad results a cycle or series of half-cycles can or must be passed through (see text-fig. 3), and during the process several peculiar circumstances arise. These possible minor changes are thirteen in number, and their results are as follows :-

TABLE D.

j H.D.F. to Cult . . . . . . . . . ' 22 H.D.F. toTert . . . . . . . . . . 23 M.F. to Cult. . . . . . . . . . . . ' M.F. to Tert. . . . . . . . . . . I i: M.G. to Cult.

Cult. t o Tart. . . . . . . . . . . . 1 7 9

Tert. t o Cult. .......... . I 4 1 Tert. to Second. . . . . . . . . ' 6 Second. to Cult. . . . . . . . . I 10

1 Second. to Tert. . . . . . . . . 13 15

. . . . . . . . . . l 1 ;Cult . t0M.G. .......... 1 12

l Tert. t o M.G. ...........

, (Second to M.F.) . . . . . . . .

6 5 1 0 2 2 7 2 7 5

5 3

8

8 I -14 6 1 -17

3 12 , +11 1 - 11

1 - 8

13 I . .

6 - 4 6

Only three gains are possible (two of which give rise to an unstable condition, i. e., cultivated land), though vegetation may be altered by " constructive " planting or by merely leaving to nature. Secondary forest can only be produced by a natural process acting upon tert,iary growth, and is apparently nature's attempt to return to normal conditions-in this latitude, tall forest.

The clearing of land, therefore, must result in a reduction of the frog fauna, and thereby of the frog population generally (see p. 185). An increase in the clearing of land will accelerate this process, and nothing that Man can do thereafter will rehabilitate the fauna.

There are three cases not included in the above enumeration which require mention, since they may initiate minor plagues of short duration but great intensity. When M.G., Cult.., or Tert. is cleared and the ground left " fallow," M.G., Cult., or tertiary respectively will spring up again In these cases the status quo of the frog fauna is upheld, though the numerical

AMPHIBIANS OF THE MANFE DIVISION, CAMEROONS. 179

Veg. zone.

__ ..

strength of certain species may be temporarily increased to a prodigous degree. Swarms of Phrynobatrachus acridoides sometimes occur when M.G. is burned, of Rana occipitalis when tertiary growth, bordering streams, is cleared away, and of Bufo regubris when crops or plantations are cleared and replanted.

(3) Alteration of the Facies of the Frog Fauna. Tt is in a qualitative analysis and comparison of the faunas of the various

vegetational zones and sub-zones that the true significance of deforestation can be most clearly observed.

The forty-six species a t present under review may be divided into five groups according to the ( 'habitat" which they are adapted to occupy not merely in the Mamfe basin but throughout their known range.

TABLE E. . ._____-___-- -~ - - -

1

Total no. of

species. ~ __

No. of 1 species. Form. --- I- , Aquatic . . . . . . . S

. . . . . 4

Tree . . . . . . . . . 18

Grass

Terrestrial 1 1 I Burrowing .. . I 2

" * i I ...

I ~ ~-

-~

Per cent.

21 27 39 33 32 43 67

___

Species numbers. I

-

1 0 2 2 0 0 0

~~ ~

1, 2, 3, 10, 11, 12, 17, 46.

5, 7, 8, 9.

6, 13, 14, 15, 28 to 41 inrlusive.

4, 16, 18, 19, 20, 21, 22, 23, 25, 26, 42 to 45.

24 and 27. -~ ~~~~~

~ _.

3 2 3 4

0 0

In the Mamfe area three species were found to inhabit two major habitats, to one of which they were clearly not adapted. Rana albolabris, an arboreal form, was taken in grass in two widely separated localities, the female of Trichobatrachus robustus was found to be fossorial, and several specimens of Cardioglossa 1eucornysta.c were taken a t a considerable height in trees in Asumbo.

There are, in addition, Nectophryne afra, taken upon herbaceous growth though clinging to the foliage as a tree-frog does to a leaf; Cardioglossa escul- era?, upon the surface instead of below the ground ; and Hemisus marmoratum, in water, where it was breeding.

The behaviour of female T . robustus and of C . leucomystax affects but little the percentages arrived at below. R. albolabris, if regarded as a substitute

~~

Per cent.

21 18 17 15

1 3 .. ..

TABLE F. I

Cult. ........... 14 Tert. .......... ., 11 Second. ......... i 18 (Cleared) ....... .I 27 H.D.F. ......... 28 M.F. ........... 14 M.G. ........... 3 1

Aquatic.

-

3 3 1 3 7 3 0 -

Per :ent. 21 27

5 11 25 21 ..

Arboreal. I

Terrestrial. Fossorial.

1 Per ~ cent

4 ' 29 3 27 5 1 28 9 33

5 36 1 33

11 ~ 39

- - .

Per :ent.

7

11 8

..

.. .. ..

182 MR. IVAN T. SANDERSON ON THld

Text-figure 6. MOVNTAIR

FORKST. Tertiary &Forth Secondary Mrest

Changes in composition of frog faunas when M.H. is cleared, cultivated, and subsequently left. (Symbols as text-fig. 5.)

Text-figure 7.

.\ POUNTAIW GRASS

2 4 6 8 1 0 : (aec3nd)

, ~ ~ . ~ o ~ o ~ . * , o c

, . . . . . . . . . . . . , . . , . . .

A

%&,* 2 4 6 B 1 C

( t h i r d )

Changes in composition of frog faunas when M.F. is cleared, cultivateti, and then left giving way to M.G. (Symbols as text-fig 5.)

AMPHIBIANS O F THE AIAMFE DIVISION, CAMEROONS. 183

are aquatic. These three divisions are quite in accordance with the nature of the H.D.P. and its countless streams and water-courses. The presence of 3 per cent. of grassland forms (which also tallies well with the actual bulk of specimens of this type caught in H.D.F. territory, when compared with all other forms) is explained by the occurrence of small natural grassfields in the depths of the H.D.F. due to a complete lack of soil.

In Mountain Forest grassfields do not occur as they would automatically be classed as Mountain Grass. The frogs are, therefore, divided between the terrestrial, arboreal, and aquatic forms with somewhat less emphasis on the two latter, possibly due to the lesser development of the trees and the swifter and more meagre drainage system.

The mountain grass is divided between terrestrial and arboreal species with double the percentage of the former. Now the grass is a recent innovation -perhaps even of the historical period,-being a “ conqueror ” of the mountain forest. The total absmce of grass-dwelling forms in this ideal habitat, moreover, probably indicates that the frog fauna is a struggling survival of a tertiary fauna rather than an assemblage that would be formed in real grassfields-the tertiary vegetation itself being excluded by the all-powerful grass. This hypothesis is somewhat fortified by the presence of an arboreal species, Rana albolabris, in this area (where there are no trees). The fact that R. albolabris was not found by the present expedition in the mountain forest does not preclude the possibility of its being indigenous to this vegetational zone, and it is found in grass in tertiary growth a t Obubra. In the mountain grass, however, it had resorted to living in the grass stems, far from any woods. From this it would appear that mountain grass brings with it but one species, P. acridoides, a native of the Northern Plains which is not especially adapted to life in grass.

Is the “grass” in the mountains, then, itself a substitute for tertiary growth or the savannah and orchard bush of the Northern Plains which cannot exist on account of the altitude of this locality !.

During the course of the three principal cycles initiated by the clearing of primary forest, the following series of changes in facies of the frog fauna take place, the cogency of which have been remarked above (Graphs, text-

(See Map. text-fig. 1.)

figs. 5-7). (4) Alteration of the Habitats due to Deforestation.

During the clearing as well as the regrowth of vegetation both major and minor habitats are altered in the majority oE instances. Moreover, since the frogs are so closely associated with their major habitats, such a change necessitates a more or less complete replacing of the frog fauna.

The repopulation of an area can be astonishingly rapid, as was observed at Mamfe Station a t the end of the rains, when a large area of secondary forest was cleared of tall trees. Within two days frogs of a different Gype were encountered (nos. 7 and 44) among the low damp and dry vegetation which had not been cleared away together with the trees. Almost daily search had previously been made of this plot of ground for over two months and only certain species recorded (species nos. 34, 19, and 22).

Habitats (both major and minor) can change rapidly due both to human agency and natural causes. The falling of a giant forest tree will create a small area of low tangled herbage where formerly there had been only high trees with clear ground beneath. The damming of rivers and streams may produce swamps and lush growth, in place of clear running water and so on. These alterations are perpetually taking place, and as often as not, the site

184 MR. lVAN T. SANDERSON O N THE

subsequently returns to its former state, provided the Veg. Zone has not been altered.

Grass alone seems capable of permanently replacing other forms of vegetation. Any area also, that is completely denuded of vegetation enters a phase of grass which may or may not give way to other growth. This tendency seems to be a precursor of the relentless encroachment of the grassfields of the north. (For details, see text-fig. 3.)

( 5 ) The Repopulation of Isolated Areas of Cleared Forest. A close observation of the changes wrought by alteration of vegetational

zones and habitats upon the frogs reveals one surprising and apparently inexplicable phenomenon. Many native villages (Mukonyong, Eshobi, Nyang, Bashauo, and others) are situated in the depths of the H.D.F. Farming by the native inhabitants of these places has resulted in the formation of little islands of secondary, tertiary, and cultivated land around the villages. These support typical frog faunas, which are universal to such zones. These areas are, however, entirely isolated, and apparently have always been so. How, then, is it that the species constituting these faunas have reached these areas 1

The faunas of Cult., Tert., and Secondary cannot be supplied by the surrounding H.D.F., as thirteen of their twenty-seven species are not found in that vegetational zone. The introduction of eggs and larvze by running water is precluded by the absence of large enough rivers from some of these areas, and the total lack of any running water in others. Spontaneous parallel evolution of so many species in so many isolated situations is obviously unworthy of consideration, and the possibility of their introduction by human agency or by other animals is well nigh inconceivable.

Js it possible, then, that so many species can be indigenous to H.D.F., but so exceedingly scarce as not to be detected during the course of a year’s intensive collecting, and, still further, in the case of B. regularis, during many years of investigation throughout Africa Z The production of suitable low-growth habitats by the falling of large trees would presumably bring such species as B. regularis, Dirnorphognathus africanus, Rana oxyrhynchus, and others to light, should they be lurking in the surrounding H.D.F. Such circumstances, however, do not produce such effects.

The feasibility of H.D.F. when once cleared being able to return to H.D.F. is doubtful in the extreme. If it were possible, an explanation of this phenomenon could be put forward by an hypothesis of contiguous areas of cleared land arising in succession from the border of H.D.F., and eventually arriving a t their present day positions of remote seclusion. At Bashauo 11.) however, this is definitely not the case, as the establishment of this village (a sub-group of Bashauo natives) and the clearing of its isolated farm-land have taken place not only within the memory of living man, but also since the German occupation in 1911. On this land are found Rana zquiplicatu and Dimorphognuthus africanus, both species which are not found in the surrounding H.D.F., which is unbroken for not less than three miles in all directions. These two species are found upon the nearby farm-lands of the parent village, known as Bashauo I. (a little over three miles distant), and they must therefore have traversed a t least this three miles of H.D.F. A portion of the farm-land of Bashauo I. is incidentally separated from the main body by a strip of the true Palm-Belt, while surrounded by K.D.F. on all other sides. Upon this land were found Petropedetes johnstoni, Arthroleptis calcaratus, A. yoxilonotus, and Leptopelis boulengeri, all species indigenous to the H.D.F., whereas R a m zquiplicatu and Dimorphognathus africanus and other species not found in that Veg. Zone were absent.

AMPHIBIAKS OF THE MAMFE DIVISION, CAMEROONS. 185

The sterile Palm-Belt apparently arrests the movements of frogs (see above), whereas three miles of H.D.F. is incapable of doing so.

Upon this piece of isolated though significant evidence, an explanation may be tentatively advanced as to the method by which these detached areas of Cult., Tert.. and secondary growth are populated by their typical frog fauna. This is that they migrate, possibly in swarms during immaturity, and pass through the H.D.F. ; those that reach the cleared land surviving and those that do not perishing through the failure to encounter suitable environmental conditions.

That such migrations can take place in an opposite direction is proved by observations made upon Petropedetes johnstoni a t Okoiyong in June. Here, this obviously arboreal forest species was taken in a belt of secondary grass lying between the H.D.F. and a river, to which they were obviously going to breed. If this species can descend to the ground for a seasonal migration, can truly arboreal types of the genus Leptopelis do so in order to traverse H.D.F. or do they migrate via the upper foliage ?

The greatest distance of any of these village clearings mentioned above from its nearest neighbour is approximately 10 miles as the crow flies. This distance must therefore be less than the maximum over which some species can travel with the somewhat doubtful assistance only of a four-foot human track and occasionally small streams and rivers. This is not an impossible feat for some frogs, in view of the fact that a frog with only three legs has been known to cover a distance of a quarter of a mile in one night (McAtee, 1921, ' Copeia,' no. 96, pp. 39-40).

Frogs can and do appear in completely isolated and recently cleared patches of land entirely surrounded by undisturbed H.D.F., and the theory of their arrival by direct migration, in which rivers when present probably assist, seems to be the only feasible explanation of this phenomenon. The reasons for such migrations may be merely haphnzard, but are probably initiated by the pressure of over-population upon the somewhat limited breeding sites.

(6) Effects of Deforestation upon Numerical Strength of Frog Population. The effects of deforestation cited above are only of zoological importance

in so far as they deal only with the interchange of species. This may indeed be of some significance when the facies is drastically altered as with aquatic forms in secondary forest. Such results may, however, be entirely counteracted by an altered balance of the numerical strength of certain species.

Judged by the behaviour of the species, the balance should be retained when H.D.F. is replaced by secondary and completely upset when mountain forest is replaced by mountain grass (great loss) or secondary (considerable increase). This, in fact, proves to be the case, as is shown by the following table.

TABLE G.

1 H.D.F. M.F.

Number of species . . . . . . . ./ 14

Total no. ofspecimens taken. 1 378 72

28 Same expressed as percentage 39 19 Collecting days spent in . . . , 107 47

Average no: of specimens'l 3.53 1.42 taken in one day.

taken in one day. Percentage of specimens ii 43 ~ 17

M.G.

3 4

47 12

.25

3

i Cleared. I

27 1 37 I

373 I 122

3-06 1 37 I

186 MR. lVAN T. SANDERSON ON THE

The total number of collecting days (details from diary of expedition) were 323, of which approximately equal time was devoted to H.D.F. and cleared land and to M.F. and M.G.

From this table it will be observed that the percentage of frogs caught in any one Veg. Zone in a given time is approximately proportional to the number of species found in that zone.

The above conclusions, drawn from observations upon the species, may therefore be applied quite closely to calculations upon the universal strength of the frog populations and the quantitative results of deforestation.

VI. COLOUR VARIATION. During the course of recording the colours of each individual frog in the

field it was noticed that, in addition to the great diversity of individual coloration within the species, the species themselves varied in several different manners.

Frog species in the present collection apparently vary by three different methods. Most display, to a greater or lesser extent, specific variation, the individuals being immutable. A second group (i. e., Phrynobatrachus plicatus, C. leucomystax, and others) display individual colour change, which may conveniently be termed chameleonism, a t which all the individuals seem to be equally adept if circumstances warrant. The third group is composed of those species which are made up of two or more easily recognisable “ colour- types,” one or both of which may behave in the manner of either of the preceding groups. A. pmcilonotus is an example of the third class, the majority being capable of chameleonism, whilst the clearly-defined steel-blue type indigenous to the H.D.F. grassfields remains very constant, only varying specifically to a small degree.

A few species of which sufficient material was collected prove to be very constant in coloration, notably Ram oxyrhynchus, Leptodactylodon ovatus ovatus, Phrynobatrachus acridoides, Hernisus murrnoraturn, and Bufo latifrons, though still varying specifically to a slight extent. The majority, however, vaned greatly within the species, many displaying ontogenetic variation. The following, however, showed chameleonism or more than one colour- type ;-

R a m albolabris . . . . . . . . . . . . . Two colour-types. Two habitats. Trichobatrachus robustus. . . . . . Two colour-types. Two habitats. Petopedetes johnstoni (‘1) . . . . . . Two colour-types. Two habitats. Arthroleptis pacilonotus . . . . . . Chameleonism. Two habitats. Phrynobatrachus plicatus. . . . . . Chameleonism. Two habitats. Cardioglossa leucomystax ..... Chameleonism. Two habitats. Chiromantis rufescens . . . . . . . . Two colour-types. 2 Veg . Zones. Leptopelis palmatus .......... Two colour-types. 2 Veg. Zones.

Xe- tropicalis ........... Two colour-types. Two Veg. Zones. Bufo regularis .............. Chameleonism . . . Four habitats.

Those that remain most nearly constant are, for the most part, confined to a single habitat in a single Veg. Zone. On the other hand, those that show two types or Chameleonism are distributed between two widely different major habitats, or, in the case of the Tree-Frogs (Chiromantis rufescens, L. pal- rnatus) and of Xenopus tropicalis, between two Veg. Zones.

It seems possible therefore, that Veg. Zones and, more especially, major habitats are responsible for the degree of colour-variation displayed by frogs. An insight into the exact manner in which these factors produce such effects

AMPHlSlANS OH THE I11AXFE DIVISIOY, CAMEROONS. 187

n i ; ~ y be gleaned from such examples as C'urdioglossa leucomystaz and Chiro- mantis rufescens, where temperature is very probably the cause. Humidity similarly affects the colour variation of Bufo regularis. Other stimuli are doubtless presentfood, light, etc.,-but these are also greatly dependent upon the vegetation, which is the controlling factor in both Veg. Zones arid habitats. Chameleonism would be a most convenient mechanism to frogs that indulge in oft-repeated and exaggerated change of habitat, whereas the adoption of two separate colorations, as of Raw ulbolabris, would better suit species that are permanently represented in widely divergent conditions.

Specific variations of colour do not, however, seem to bear any close relation to habitat (vide Arthroleptis calcaratus), though further investigation may show that there is a close connection with some environmental conditions hitherto not taken into account. In this respect Hyperolius sordidus is of great interest. Here all the diversity of intense and sombre coloration has its counterpart on a single banana-tree in more or less the proportions that those colours are found among the frogs-the metallic-blue of the flower petioles, the golds and browns of the dead leaves, sometimes stippled or spotted with fungoid growths, and the vivid green of the fresh leaves.

The three processes are closely linked, specific variation being often in reality a great number of colour-types and sub-types. Chameleonism is an ordered affair. proceeding through regular phases, so that in order to reach stage E from stage A, B. C, and D must be passed through and vice versa. Colour-types map, indeed, also be produced by a form of chameleonism though of excessively slow action. When a frog moves from one environment to another it may remain out of keeping with its surroundings in colour for some time, but will eventually by gradual alteration adjust itself. This has been observed to take place, but no records have as yet been kept of exact colour, time, and other factors. No data of this nature were recorded by the present expedition.

Note on Colour Description. In the following descriptions of life-coloration reference is frequently made

to the " basal " colour. This is a somewhat unorthodox term, but has been devised to signify that colour which remains when markings fade due to either specific variation or chameleonism. All frogs appear to possess a dorsal colour which is often apparent on the flanks, and which commonly fills m the gaps between the dorsal markings. It may, however, be totally obscured except at one phase of the colour-change, though its presence is belied by its reaction upon the overlying colours. Thus, male Trichobatrachus have a purple sheen which is due to the red basal colour clearly displayed in the juveniles and to some extent in the females. It appears that this basal colour itself may be parti-coloured, though always with an extremely simple pattern (dark dorsum and light ventrum). Certain areas are, however, constant in most species, noticeably soles of feet, canthal, and anal regions.

VII. LIFE-COLOUR AND OBSERVATIONS.

(1) RANIDB. 1. RANA (CONRAUA) NIEDENI Parker. $, 9, and juv. from clear runnlng water in H.D.F., N'da-Ah mountain. The species was not found elsewhere, although special search was made

in streams a t the same altitude on the other mountains visited. Natives report that this species calls a t the beginning of the breeding

season (onset of the rains, March-May), and that at this time the animals are


on land. The food consists of river-crabs (Potamon sp.), which abound in the streams.

The colour in life was olive-green above, with black marblings, and olive, turning to yellowish around the upper jaw ; lower surfaces dirty white, with a pink tinge and a slight iridescence on the gular region. Iris greenish grey, with a cruciform dark mark centred on the pupil, the limbs of the cross being vertical and horizontal, and broader distally than centrally.

2. RANA (CONRAUA) CRASSIPES (Buch. & Peters). 9, Mamfe, damp vegetation in Second. Juv., from Ekuri, muddy running water in Cult. In life the frog is very dark brown above, becoming reddish on the aiiterior

part of the back and head ; the hinder part of the back and the flanks are flecked with yellow. Belly and throat white, the latter with scattered brown flecks which almost form a collar ; lower surfaces of the thighs primrose-yellow. Iris golden, with a horizontal grey bar through the pupil and vertical bar of the same colour below it.

3. RANA OCCIPITAIZS Giinther. 9 from muddy still water in Cult., Tert., and Second., Mamfe, Rinjong,

37 from muddy running water in Cult., Tert., and Second., Ikom, Calabar,

Six from large rivers in H.D.F., Mamfe. In the area visited this species is completely aquatic, being usually found

in muddy, slow-moving streams ; it is a plains form, not having been found a t an altitude of more that 800 ft., and appears never to occur in primary deciduous forest except in the large rivers.

Noble (1924, p. 213) has drawn attention to the colour-variation shown by a series of specimens collected in the Belgian Congo. There it was found that juveniles were most spotted, the markings tending to become obscure with increasing age. No such general tendency is apparent in the present series ; in fact, the older specimens tend to be more boldly marked with rounded spots, whereas the colour-pattern of juveniles consists of larger, ill-defined, and less conspicuous blotches. Older examples are frequently bright green ; this colour was found to rub off with the mucous secretion of the skin, and, on micro- scopic examination, the slime was found to contain chains of small spherical algB. The lower surfaces exhibit an enormous amount of variation. In very young post-metamorphic examples the throat and abdomen are immacu- late white ; rarely this condition persists, but as a rule a more or less intense dark spotting makes its appearance, but there appears to be no correlation between the intensity of this spotting and age or habitat. The pupil is rhom- boidal, bounded by a narrow golden line ; the iris resembles powdered aluminium, sometimes with an amber sheen, and occasionally a cruciform dark marking is present, as in Ram (Conraua) niedeni (q.v.).

Spawn and tadpoles were collected in September, the eggs being found in huge floating masses in still waters.

4. RANA SUBSIGUATA Dum. 1 juv. In life this specimen was black above and dark grey with numerous small

white dots beneath ; pupil horizontal, surrounded by a fine silver line ; iris dark grey.

and Nko.

and Ekuri.

Dry herbage in Secondary, N’ko.


5 . RANA CALAMEXSIS Dim. & Bibr. 2 from damp grass in Tert., Ekuri, and N’ko. 1 from swamp in Cult., Obubra. This species frequents swampy district in low-lying river basins, below

300 feet. In life the upper surfaces are dark, iridescent brownish or green, marked with dark brown ; the flanks below the amber dorso-lateral fold are somewhat darker and greener than the dorsum ; upper lip and lateral fold white ; lower surfaces mother-of-pearl, except where the marblings of the upper surfaces encrocah on the lower surfaces of the hind limbs. Pupil horizontal ; upper half of iris reddish amber, continuing the colour of the dorso- lateral fold : lower half rufous brown.

6. RANA ALBOLABRIS Hallowell. 3 from damp grass in Cult., Obubra. 2 from dry grass, sandy soil in M.G., Makumunu. 1, low trees in H.D.F., Eshobi. The Obubra and Tinta examples were found among grass, but the male

from Eshobi was caught in a tree in the primary forest. The ground-colour of immature examples is bright grass-green, the limbs being darker ; iris coppery red ; tympanum light brown. The forest adult is also vivid green, including the tympanum, and the iris is metallic golden, but the grass-land adults were uniform rufous brown above with darker flanks and with a dark brown tympanum ; the amber colour of the dorso-lateral line continues forwards through the upper half of the iris whose lower half is rufous brown. Whether these differences of habitat, webbing, and colour indicate a confusion of species, or whether there may be seasonal changes, cannot be decided on the data available, but i t seems possible that this frog is capable of adapting itself to a life in the grass when the forests are cleared (see above, in the M.G.).

7. RANA (PTYCHADBNA) OXYRHYNCHUS Smith. 21 specimens, damp grass in Cult. and Second., Mamfe, Ikom, N’ko. This species was only found among damp grass on cleared land in forest

country. Co1our.-Dorsal surfaces dark olive blotched and spotted with dark brown

and black. Under surfaces white and slightly transparent. Flanks yellowish green with black spots.

At the close of the rainy season (October, November), when immature specimens were taken and related species observed breeding, the coloration was much more brilliant, the flanks and underside being bright blue with large brown mottlings, and narrow reddish longitudinal ridges appeared on the dorsum.

8. RANA (PTYCHADBNA) BQUIPLICATA Werner. 2 specimens from clear running water in Second., Mamfe, Bashauo. In life the upper surfaces are brown, suffused with pink and with .longi-

tudinally arranged black spots ; hinder side of thighs black, with a dirty- yellow longitudinal stripe ; lower surfaces-sulphur yellow, tinged with orange on the legs ; iris dull amber and gold.


9. RANA (PTYCHADZNA) MACSARENIENSJS Dum. & Bibr. 36 from Eshobi, 1 from Nko. 32 fromokoiyong, 3 from Mamfe. This widespread species was collected both in natural forest clearings and

upon Cult., Tert., and Secondary. (a ) 39 juveniles taken during November and December from damp arid

dry grass, and bare rock In Secondary, and natural grassfields in H.D.F. Spawn was also observed in H.D.F. grass where the conditions are peculiar ; there is practically no soil, and the only vegetation is grass, which appears to be burnt annually, the fires breaking out through natural causes. After one of these grass fires the frogs were found congregated in incredible numbers in the few small unburnt patches where water seeped out from the underlying rock. It was in these areas of seepage, where the water formed small channels a few inches wide, that the frogs were found breeding during the last month of the rainy season (October). The temperature of these small rills was decidedly high ; no temperature observations were taken, but the water was warm to the hand.

The specimens fall into four groups :-

( b ) 4 adolescents from dry grass in the H.D.F. grassfields. (c) 9 small mature specimens taken in damp grass in Secondary and dry

grass in H.D.F. in June. (d) 20 mature specimens from dry grass in Cult,., Tert., Secondary, and

H .D.F . grassfields. Co1our.-The colour shows a gradual change from immature to mature

specimens. The dorsal surfaces are olive-brown with roundish black markings with vivid white labial and dorso-lateral stripes. In immature specimens the underside is greyish and sometimes mottled with darker grey. This colour gradually gives way to white which, in adult specimens, becomes suffused with creamy yellow, especially on the legs. Both juveniles and adults bear a broad or narrow median dorsal stripe which varies from blood-red through amber, gold, and yellow to white or is grass-green. Reddish longitudinal ridges also appear in the larger specimens.

The iris in juveniles varies with the degree of contraction of the pupil. When the latter is fully dilated the iris is yellowish gold, but as it contracts a peripheral silvery region comes into view until, when the pupil is fully con- tracted, the whole iris map appear silver with only a narrow bright gold area round the pupil. In adult specimens it is reddish amber, the lower half tending to darken to conform with the dark canthal-temporal stripe.

10. SCOTOBLEPS GABONICUS Boulenger. 6 from Makumunu. 5 from Bashauo. 2 from Eshobi. 1 from Ekuri. From clear still water and dry leaves below trees in the H.D.F., and from

clear running water and damp herbage bordering same in M.F. Vertical distribution from 500-2500 ft.

In life the colour is dark brownish grey above, with the dorsal warts darker ; the limbs, toes, and outer two fingers are cross-barred in black. Lower surfaces pinkish white to purplish grey, this colour merging into the dorsal coloiir in an area of speckled grey and cream on the flanks. Iris stone-grey.

In one specimen the whole dorsal surfaces were a light ochre.

AMPHIBIANS O F THE MAMFE DIVISION, CAMEROONS. 191

11. TRICHOBATRACHDS ROBUSTUS Boulenger. 41 from N’da-Ali, 1 from Bashauo. 14 from Makumunu, 1 from Akwa. 4 from Atolo. The present series comprises specimens of five types.

(a ) Mature hairy males-clear running water. ( b ) Mature females-holes in damp soil. (c) Mature hairless males-clear running water. (d ) Immature males-damp herbage. ( e ) Immature females-clear running water, damp vegetation, hole in damp

The females and immature specimens were all collected in a patch of M.F. a t Makumunu.

One hairless specimen from Bashauo with typical female coloration proved to be a male.

In juveniles of both sexes the ground-colour of the dorsum is beige, the markings being dark brown and very prominent, each being narrowly outlined by a pecked line of yellow ; the flanks are orange, mottled with blue and strongly papillated, the lower surfaces are yellow except beneath the throat and hind limbs, which are grey. The adult females retain the outlined pattern of the juveniles, but the ground-colour changes to bright brick-red and the flanks are still orange. The lower surfaces are yellow, except on the hind limbs, which are grey ; the edge of the lower jaw bears a varying number of black spots, and the ground-colour of the lower surfaces spreads on to the light areas of the upper lip. Males are dark olive-brown tinged with purple, and this dark colour obliterates the dark markings to a greater or lesser degree ; the warts on the tympanic region and upper lip are white, whilst the lower surfaces are dirty white or yellow, with a pink tinge beneath the throat and on the hind limbs. The hairs are usually black, but towards the under surface they become reddish pink. The iris in both sexes and at all ages is brown- amber.

Equally as great as the difference between the sexes is the difference between their habitats. All males (52 ) of over 62 mm. (i. e. , all those with the secondary sex characters well developed, and also the single, abnormal, hairless male from Bashauo) were found in clear mountain streams; immature males (two examples) were collected in damp vegetation near water. Females (six), both mature and immature (including an example with vestigial larval tail), were all found in deep holes in the ground ; a late tadpole stage with all limbs well developed was taken in the water. Females when handled emitted a long drawn out scream. This great diversity of habitat and appearance led to confusion in the field ; the two forms were not recognised as conspecific, and this in turn was the reason why so many more males were collected. In many localities males were abundant in the streams and were collected in series, but since it was not realised that only one sex was represented no search was made for the other.

In addition to their respiratory function, the “ hairs ” of the male give it an astonishing resemblance to the weed-covered pebbles amongst which it is found. The beds of the streams are covered with a mass of rounded pebbles, which are fringed laterally with a growth of reddish filamentous algz ; when the frog is a t rest on the bottom with legs folded the ‘‘ hairs ” fringe its outlines in exactly the same manner as the algz do the stones. The mountain-brook

soil.

The vertical range seems to be 500-4000 ft. in H.D.F. and M.F.

(See Parker, P. Z. S. 1936, p. 141.)


habitat on the high ground surrounding the Mamfe basin appears to have only four Salientian inhabitants, Rana (Conraua) niedeni, Trichobatrachus robustus, Astylosternus diudematus, and Scotobleps gabonicus. Three of these forms have claw-like terminal phalanges which pierce the skin on the tips of some of the toes, and it is not unreasonable to suppose that this development is correlated with the habitat just as are the claws of the mountain-brook-dwelling Onycho- d a c t y h . Claws, which will assist the animals to maintain a foot-hold among the slippery stones, must manifestly be of considerable value, especially a t the breeding season, when the streams are swollen from the rains.

Tadpoles just completing their metamorphosis were taken in April, so that the beginning of the breeding season is presumably in the early part of the rainy season. The claws seem to be retractile a t will, for when the living animal is handled its claws are used in much the same manner as a cat’s.

12. ASTYLOSTERNUS DIADEMATUS Werner. 2 from Fineschang-damp herbage in H.D.F. 3 from Eshobi-damp herbage in H.D.F. 4 from Makumumu-damp herbage in M.F. (one specimen from clear stream). The colour in life is as follows :-Dorsal ground-colour various shades of

sienna-brown, the insuliform spots brown, edged with black; a constant cream-coloured bar between the anterior halves of the orbits ; flanks orange to flame colour, with round black spots. Chin dirty white, merging into yellow on the belly and becoming vivid flame-colour in the groins and beneath the thighs. The flame-colour of the groins, flanks, and thighs is only developed with age ; young specimens are yellow in these regions. The insuliform spots on the dorsum, in addition to being edged with black, are sometimes surrounded by a thin white line.

Iris golden reddish brown.

13. PETROPEDETES JOHNSTONI (Boulenger). 42 from Bashauo, 3 from Tinta. 28 from Eshobi, 3 from Makumunu. 18 from Mamfe, 1 from Akwa. 17 from Atolo. As a result of the examination of the present large series (114 individuals),

a surprising amount of variation-seasonal, sexual and ontogenetic, was noticed. Furthermore, it proved possible to correlate this very closely with the great diversity of habitat and coloration. The morphological aspects are fully discussed by Parker (P. Z. S. 1936, p. 143), and the whole problem is summarised in the accompanying chart (text-fig. 8).

The series is divided into the following groups :- A. 26 juveniles collected between October and March ; also one speci-

men in November and one in June. B. 12 38, 6 yearlings caught during the dry season (October-May),

with secondary sex, but without nuptial characters. C. 4 $8, transitional males taken in March, without seasonal characters,

but with certain details of the nuptial dress becoming apparent. D. 24 88, 22 mature individuals collected a t the commencement of

the rainy season (March to June), in complete nuptial dress. E. 6 88, non-breeding males without nuptial characters, though with a

further development of ontogenetic features. November (1 specimen) and March.

F. 14 $6, Full-grown breeding males collected during March to June.

AMPHIBIANS OF THE MAMFE DIVISION, CAMEROONS.

Text-figure 8.

193

Chronology of the development of Petropedetes johneloni.

BOO. ZOOS. $OC,-1936, 13

194 MR. W A X T. SANDERSON ON THE

Adult P. johnstoni are arboreal, being commonly found upon the lower broad-leafed trees in H.D.F. and other areas of tall growth where there is abundant shade. They were never observed on the high trees. They indulge in an annual migration to water which necessitates traversing considerable distances of bare forest floor and the herbaceous growth bordering the streams and rivers. The young frogs subsequently have to follow their parents’ trek in a reverse direction before attaining their final habitat.

There is no direct evidence of a free-swimming larval stage, but it seemr very improbable that the species practises direct development ; the ovarian eggs of mature females are very small, and another species of the genus is reported to have a tadpole stage (Boulenger, 1906, p. 9). Ten of the young ones were found in clear running water, ten under rocks in dried water-courses or near water, four in damp vegetation, and two in low dry vegetation ; as n rule it was the smaller specimens which were found in water and the larger on land.

One was in damp herbage near water, four were in dried water-courses, six upon dry ground below the forest trees, and seven actually in stunted trees. This represents a continuation of the migrational phase.

All the males in the transitional stage (C) were taken in low trees. Mature males and females (D) appear to have reached the arboreal habitat,

and some to be returning to water to breed. Thirty-one individuals were in trees, seven on the dry ground below or in dried water-courses, six in a patch of dry grass, one in low damp herbage bordering a river, and one actually in the clear water. The patch of dry grass lay between the H.D.F. and the only river in that area ; this was bordered by herbaceous growth. Only those taken in June were on the ground or in water.

All the non-breeding males (E) were confined to the trees, whereas the fully mature examples (F) were found both in the trees (lo), and during June, in the grass described above (4). Many non-breeding specimens (E) show laceration on the gular region presumably relics of the preceding breeding period.

Colour of the juvenile olive-grey above and on the flanks, with dark brown mottlings. Limbs with a series of transversely oval, rich brown spots encircled and separated by narrow golden lines ; a golden area enclosing the vent. Lower surfaces white marbled with bluish smudges.

In all other stages (B, C, D, E, and F), the coloration is as follows :-The dorsum varies from iridescent green through gold, orange, and light ochre-brown to a rich brown, or a deep iridescent ruby with superimposed mottlings of varying shades of brown from light ochre to almost black ; individual frogs show much colour-change, conditioned by changes of hght and humidity, and all have a certain iridescence. Flanks dirty greenish yellow with brown markings similar to those of the dorsum. Limbs with transversely oval blotches of dark brown separated by broad bands of a similar colour to that of the dorsum, but somewhat lighter in shade. Lower surfaces mother-of-pearl, tending to yellowish in females and young males and to mauve in adult males ; gular region of the latter bright purple. Pupil horizontal, sloping obliquely downwards anteriorly, and bordered by a narrow golden line ; iris golden, shot with green (the amount of the latter colour being proportional to the amount of green in the dorsal ground-colour), and with three smoky black rays radiating from the pupil (see Parker, P. Z . S. 1936, P1. I. p. 135).

Yearlings (B) of both sexes were found in diverse habitats.

Iris golden.


14. PETROPEDETES NEWTONI (Bocage). 2 from Eshobi (39). One on low tree, the other upon the carpet of dry leaves covering the forest

floor, in H.D.F. The femoral glands were strongly adhesive and appear to be employed by

the frog when clinging to leaves and stems-their favourite resting places. In life the dorsal surfaces are dark green, mottled with deep red inter-

spersed with large dark brown spots which surround the dorsal warts ; on the limbs the ground-colour becomes 'yellowish and the mottlings are converted to spots of rich brown. Tympanum wine-coloured. Lower surfaces yellowish white smudged with brown. The pupil is similar to that of the preceding species and the iris is golden with three radiating triangular rays of smoky- black arranged as in P. johnstoni.

15. PETROPEDETES CAMERONENSIS Reichenow. Juv. $? from Mamfe in clear running water in Tert. Colour in life olive-green, with insuliform brown markings edged with darker

Eye similar to that of P. johnstoni, brown. Lower surfaces chrome-yellow. but with the iris uniform satiny-mauve.

16. DIMORPHOGNATHUS AFRICANUS (Hallowell). 5 from Makumunu-damp herbage in M.F. 3 from Tinta-dry herbage in Second. 1 from Bashauo-dry herbage in Second. Vertical range from 700-3000 ft., confined to the northern escarpment

of the Mamfe basin. The dorsal surfaces are, in life, from dark olive-brown to olive-green, with

diffuse black markings ; the mid-dorsal line, when present, is bright gold. Lower surfaces lemon-yellow ; chin and throat grey, with black marblings. Iris stone grey.

17. LEPTODACTYLODON OVATUS OVATUS Andersson. 3 33, 4 ?$!, and 2 hgr. from Fineschang in H . D . F .

The species was collected a t an alt,itude of 700-800 ft. in one clear stream only which descends from the summit of N'da-Ali Mountain.

CoZour in Zi&-Dorsum variable from black to yellowish ochre, with small dots and pin-head spots of dark grey and white, Legs the same with posterior surface of thighs black. Groin black with a series of large subcircular pink spots which may invade the flanks and extend backwards to the anus.

Underside of body and limbs pinkish white or pinkish ochre, unblemished below the thighs, but elsewhere almost completely obliterated by an intense marbling of dark grey, becoming almost black in the gular region.

18. ARTXROLEPTIS CALCARATUS (Peters). 31 from Eshobi, 2 from Bashauo. 3 from Makumunu, 1 from Tinta. 533, 32 99. Dry ground below trees in M.F. and H.D.F. (33), dry herbage

in M.F. (2), and precincts of human habitation in secondary forest (2). 13*


Co1our.-In life the upper surfaces are various shades of brown mottled with lighter browns ; the warts are picked out in dark brown. There is often a median dorsal line of bright gold, which is bordered by rufous brown areas. The upper surfaces of the limbs are indistinctly cross-barred with dark brown on varying shades of light brown. A golden line above the vent extends along the hinder side of the thighs to a greater or lesser extent. Under-surfaces usually yellowish cream, but sometimes white suffused with pale grey. A few small brown spots are frequently present on the chest and gular region. Iris brown-amber. The four examples collected in March, among which are the two males with well-developed femoral glands, are olive-green rather than brown above and flushed with grey beneath ; they were collected in mountain forest, a t a higher altitude than any other of the series.

19. ARTHROLEPTIS P(ECILONOTUS Peters. 97 83, QQ, and juvs. from Ikom, Mamfe, Eshobi, Mokonyong, Bashauo,

Tinta, Makumunu, and Nko. In H.D.F., both damp and dry ground below trees, damp herbage, lush

herbage, and dry grass on rocky soil ; in cleared land in dry herbage, dry grass upon sandy soil, and in clear running water, where it was apparently breeding, as swarms of recently metamorphosed individuals were observed. The vertical range is 2004000 ft. Dry situations seem to be preferred (85 specimens), whereas the nine taken in damp herbage and the three in water possibly represent a breeding migration.

The great variation in colour which this species exhibits has already been commented upon (Noble, 1924, p. 206), and the present series fully confirms previous statements. The ground-colour varies from dark rufous brown to dull gold, and the dorsal markings may be well developed or completely absent with any particular type of basal colour. When fully developed they consist of a dark lateral band and a median chain of diamond-shaped marks similar to those of A . variabilis, but much more distinctly angular. These markings may be entirely absent, but when present they show little variation, the principal one being a broadening of the dorsal band to form a regular, parallel-sided, and clearly-marked stripe ; when this occurs the dorsal ground-colour is usually lighter than the normal and a white median line is present, so that the frog presents an appearance of regular alternating darker and lighter stripes. These dark markings are frequently bordered with orange, a colour which often appears irregularly scattered in flecks and dots over all the dorsal surfaces. The flanks below the lateral stripe are usually spotted with blue, brown, and white, whilst the under surfaces are transparent white merging into a bluish grey peripherally ; the belly is sometimes mottled with a dirty cream colour. Iris iridescent golden to bronze.

Individual frogs have the power of colour-change developed to a remarkable degree, the changes being conditioned by light, and more particularly, by heat. Under the influence of warmth the colour-pattern becomes more defined and conspicuous, and in bright sunshine the colours become more vivid, with increase in the amount of orange and blue. No particular type of colouring was found to be associated with any definite habitat except in the case of fifteen individuals found among the grass and on the rocks of the natural clearings which have been previously discussed under Ram nzascureniensis ; in this peculiar environment the frogs were always a uniform pale slate-blue, or grey above, without any trace of markings except the cantho-temporal dark stripe and pure white below.

AXPHIBIANS OF THE MAMPE DIVISION, CAMEROONS. 197

20. ARTHROLEPTIS VARIABILIS Matschie. 1 from Ikom-dry herbage in Cult. 2 from Eshobi-damp ground below trees in H.D.P. 1 from Tinta-Atolo-damp ground below trees in M.F. 1 from Mukumunu-damp ground below trees in M.F. This species was met with in damp situations in the depths of the forest

with the exception of one specimen caught on a cassava plantation a t Ikom. The great variations of the dorsal markings of this species have already

been adequately dealt with ; the variations in the ground-colour in life appear to be from yellowish brown, through reddish brown to very dark grey on the dorsum, from jet-black on mauve-brown to uniform dark maroon on the flanks, and from pure white to maroon below except for an area on the centre of the belly, which is cream. Iris brownish bronze.

21. PHRYNOBATRACHUS ACRIDOIDES Cope. 38 from Obubra. 2 from Ekuri. 1 from Tinta. The distribution of this species is of considerable interest It is not a forest

form and is never found in clearings in the forest country, but extends south- wards on the " Northern Plains " to their juncture with the forests a t Obubra. Great quantities were collected at Tinta from the M.G. a t an altitude of 3000 ft. Only one was preserved in a small tube as the supply of spirit had temporarily failed. These specimens were all identical in colour and size, agreeing in every detail with the darkest phase encountered later at Obubra. The whole ground was alive with them for three days over an area of several acres, and the natives assured us that such swarms were of common occurrence after grass fires.

Other animals (notably rats) found in the Asumbo grasslands were common to the plains of Obubra, but entirely absent from the forest area, even where it extends northward by some 100 miles in Ikom Division.

The two specimens from Ekuri are distinguishable by a dark interorbital band. They were taken upon damp grass in a peculiar area of cleared forest which is in direct contact with the Northern Plains which border the forests along their northern limit.

Colour.-The dorsal surfaces are of varying shades of brown from olive, through rufous to almost completely black, with darker or lighter indefinite markings ; lower surfaces yellow, dappled with brown on the chin and chest ; hinder side of thighs constantly with a longitudinal, slightly oblique, yellow stripe. Iris grey.

22. PHRYNOBATRACHUS PLICATUS (Gunther). 23 33, from dry herbage and ground below trees in H.D.F. and secondary

forest, a t Eshobi, Bashauo, and Besongabang. A forest form confined to the deep shade between 400-700 ft. altitude.

The pointed snout is very characteristic and possibly has some connection with the aptitude displayed by the frog for continued rapid and prodigious leaps in a straight line, behaviour reminiscent of the grass-dwelling species with bullet-shaped bodies.

Noble (1924, p: 195) has drawn attention to the great variation in colour found in this species, but it must also be pointed out that it is capable of individual colour-change to a very high degree. One specimen when captured

198 MR. IVAX T. SANDERSON ON THE:

was coloured as follows :-The head above and anterior part of the back between dorso-lateral folds, chartreuse green ; posterior part of back dark brown ; sides of head, flanks, and limbs, beige, the legs being faintly barred with darker tone of t,he same. When taken into a tent, i. e . , into diffuse daylight, the whole of the upper surfaces changed to dark brown, almost black, with the exception of a broad median dorsal band which turned terra-cotta ; the baring of the legs was scarcely visible. The same specimen, taken back into full daylight, resumed its original pattern, but the colours were less brilliant, the green of the anterior part of the head and back being now a greenish brown, the rest of the back a mottled dirty brown, and the fore limbs cream ; a black canthal line appeared and the dorso-lateral folds were edged with dark brown.

The range of colour observed in the twenty-three specimens of the present series was pure white, yellow, gold, orange, brick, various browns, maroon, purple, mauve, pink, sea-green, grass-green, and dove grey. The only constant colour-features are the creamy white lower surfaces and the black lining of the groin, hinder side of the thigh, tibia, tarsus, and foot ; in life the centre of the dark areas of the groins, femora, and tibiae is a brilliant azure blue.

23. PHRYNOBATRACHUS LIBERIENSIS Barbour & Loveridge. 2 dd from Eshobi. The specimens were collected on water plants in streams in high deciduous

forest. Above the colour is uniform greyish brown. On fixation a faint, dark,

W-shaped marking appeared on the scapular region. Belly white; throat with regular, large, black spots ; thighs and groins lemon-yellow, clearly marked off from the white of the abdomen.

24. CARDIOGLOSSA ESCALERZ Boulenger. Q from Okoiyong. This individual was found in dry grass on sandy soil in the secondary

forest. The dorsum was bright olive-green, the dorsal markings black edged with

white ; beneath the ground-colour is continuous with the green of the dorsum, but mesially changes to bright blue ; the ventral spots are brown. Iris iridescent green.

25. CARDIOGLOSSA LEUCOMYSTAX (Boulenger) . 2 from Tinta-damp ground below trees and low trees, 14 from Makumunu-damp ground below trees and low trees. 7 from Eshobi-damp ground below trees H.D.P. This frog has a chameleon-like ability to change its colour, and in doing so

ik .$ways seems to proceed through the same ordered series of colour-changes. The extreme types in this series are light above and dark below and its converse ; the rate of change of the colour of the dorsum and venter are not always exactly proportional for the one may lag behind the other, but an average series of five stages in the transition from one extreme to the other may be described

(a) Upper surfaces uniform greyish white ; under surfaces greyish black ; flanks dark grey with brownish-black spots outlined faintly with white ; cantho- temporal region black, not margined with lighter.

thus :-

AMPHIBIANS OF THE MAMFE DJVISION, CAMEROONS. 199

( b ) Dorsum pale flesh-colour ; underside grey-black, uniform except on the belly, which has a strong mottling of turquoise-blue ; flanks with jet-black spots which are strongly outlined in white ; cantho-temporal spot outlined in white.

(c) Dorsal surfaces beige with vague darker areas ; gular region and thighs like a brown-tinged opal with its flecks of reds, blues, greens, and gold ; belly turquoise-blue with moderately large jet-black spots circled in gold. Flanks as in ( 6 ) ) but the turquoise extending upwards and the white lines encircling the spots changing to gold.

(d) Dorsum olive-brown with an obscure pattern of confluent darker spots. Underside of throat, chest, and thighs yellowish ; belly turquoise with small, black, gold-margined spots. Flanks as before, but the spots diminishing in size ventrally and increasing dorsally.

( e ) Upper surfaces smooth dark grey with confluent black spots surrounded by vivid white lines. Lower surfaces white, save for a yellowish-grey flush on the belly. Flanks showing a gradual transition between these two.

At night all individuals of this species kept alive turned more or less pure black all over.

The iris is, as already described (Noble, 1924, p. 210)) brown below, and golden above in the darker stages (d and e ) , but in the lightest phases (a and 6 ) it is uniform mother-of-pearl. Transition from one to the other takes place by a loss of brown and the transformation of gold through silver to mother- of-pearl.

It was found in the field that the examples frequenting trees were all very light above and dark beneath (type a) , and those on the ground just the reverse (type e) ; individuals were on two occasions observed to undergo complete transformation from one to the other. It is suggested that this difference in coloration may be a reaction to heat rather than to light. The dorsal surfaces are exposed to light and the venter shaded in both situations, but the heat conditions are just reversed. On the leaves of trees the lower surfaces are in contact with a cool medium, since the leaves are constantly being cooled by the evaporation of moisture and the dorsum is exposed to the sunlight and to the warm air. It was noticed that in the forest there is a belt of cool air close to the ground, approximately 3 feet deep, in which the air temperature was less than it was a t higher levels, and so frogs on the ground in the shade of the trees would be exposed dorsally to this cooler medium, whilst their lower surfaces were in contact with the relatively warm decaying mould of the forest floor.

A pair in amplexus was taken in a tree a t Makumunu a t a height of 15 feet from the ground in April. The male was grasping the female around the axillary region, the hands being crossed beneath the female’s head and slightly twisted forward and upward so that the palms faced outwards, and the long finger gripped the angle of the female’s jaw on the opposing side by twisting backwards at the tip. Thus the long third finger lies along the anterior border of the pectoral muscles, and the serrations along its inner surface afford the male a firm grip upon the skin of the female’s throat.

The long finger of the male in this species is therefore analogous to the nuptial pads on the inner side of the first finger of T. robustus and B. regularis, and would be of especial service to this frog if amplexus is habitually initiated in the swaying trees and continued during the descent to the ground on the way to the water to breed. The pair was firmly anchored to the leaf petiole by the hands of the female and the feet of both individuals.


26. CARDIOGLOSSA ELEOANS Boulenger. Juv. 9 from Tinta. In life the ground-colour above is wood-brown, the markings nigger-brown

narrowly edged with cream-yellow. Lower surfaces dark greyish brown, mottled on the belly with mauve. Iris golden above in continuation of the golden line bordering the temporal spot above and nigger-brown beneath.

From damp herbage in mountain forest at 2400 feet.

27. HEMISUS MARMORATUM GUINEENSE Cope. 6 from Ekuri and Nko. All these examples, caught during June and July, were found in water,

presumably this being the breeding season as in the Congo and Gambia (Noble, 1924, p. 282, and Bles. 1907, p. 443). It is rather extraordinary that three of the specimens, though found in the water, are quite immature sexually, which suggests that the breeding migration may occur in the seasons preceding the first ripening of the gonads.

The colour in life was very similar to that of the specimens described by Lang (in Noble, 1924, p. 283).

This species forms a regular article in the diet of some tribes, and is supposed to have certain properties connected with fertility.

Pupil surrounded by a thin gold line.

2. RHACOPHORIDB. 28. CHIROMA~TIS RUFESCENS Giinther. 11 from giant forest trees in H.D.F. (Eshobi). 1 from low tree in M.F. (Tinta). The single male from Tinta differs slightly from the remainder of the series

both in its habitat and life-colour, but does not appear to represent a different species or subspecies ; the colour in alcohol is the same for both localities. The habitat of the remainder, utterly unlike that reported by Noble (1924, p. 230) in the Belgian Congo, is the top foliage of giant trees in the high deciduous forest. At Tinta (2500 ft.) an area of mountain forest and grassland without the high deciduous forest, a specimen was taken in a stunted tree only a few feet from the ground. Although these habitats were searched in other places at similar and other elevations, and a t about the same time of year, no further specimens were seen, suggesting that it may be very local in its incidence.

Upper surfaces leaf-brown, obscurely mottled and blotched with grey and ochre. Under surfaces of throat, chest, arms, and lower half of flanks white with a faint blue-green tinge ; remainder of belly, lower and concealed surfaces of the hind limbs, copper-sulphate green. Iris golden. The single Tinta male was observed to conform to this general type of colouring during the afternoon, except that the green of the lower surfaces was replaced by a steely-blue and the iris was pearl-grey-at other times it was a light grass- green above suffused with pale grey.

In the forest around Eshobi the temperature was high (mean average 834"F.), but a t Tinta it was definitely much cooler and the temperature remained lower (73.5" F.) until about noon ; after that time it remained hot (81.2" F.) until between 4 and 5 P.M., when the evening thunderstorm broke and the shadow of the mountains fell across the house where the frog was held in captivity.

The call of the male consists of two notes repeated almost continuously from about 8.0 P.M. till 2.0 or 3.0 A.M. It is a metallic click-clock, like the noise made by a pebble falling on ice.

Inside of mouth green.

This colour-difference may, again, be correlated with temperature.

AMPHIBIANS O F T€IE MAMFE DLVISION, CAMEROONS. 201

29. LEPTOPELIS PALMATUS (Peters). 3 from Tinta, B from Bashauo, 2 from Makumunu, 1 from Nyang, and

1 from Bakebe. Habitat.-Low trees in both H.D.F. and M.F. from 700 to 3000 feet, and

always in the vicinity of water. Colour.-There is considerable difference between the sexes both in size

and colour. The exceptionally coloured individual from Makumunu was kept alive but showed no signs of chameleonism, though subjected to a series of radical changes of light, heat, and humidity.

The ground-colour of the dorsum is usually greenish olive, but in one specimen was iridescent gold ; the dorsal markings are either vivid green or dull brown as a rule, but in the golden example, ruby red, bordered by a narrow dark brown line. Lower surfaces greyish yellow, or, in males, mother-of-pearl, except the throat, which is dirty white ; underside of elbow and groin salmon-pink in females, yellow in males, and the latter sex has the back of the femur and tibia greenish black. The white lines above the anus and along the foot from the heel to the tip of the fifth toe form a continuous series when the animal is a t rest, demarcating the greenish upper surfaces from the brown of the anal region and the sole of the foot. Iris coppery brown.

30. LEPTOPELIS MILLSONI (Boulenger) I Hgr. 9 from a plantain leaf in cultivated land a t Nko. In life the dorsal surfaces are orange-biege and the markings somewhat

Lower surfaces of the body white, of the limbs The supra-anal and

darker with a rufous edging. bluish grey, both being spotted peripherally with black. tarsal lines are cream. Iris dark grey flecked with amber.

31. LEPTOPELIS BOULENGERI (Werner). 3 99 from Eshobi, Bashauo, and Bakebe. The specimens were collected both in the head foliage of giant forest trees

and in low trees in H.D.F. and in low trees in secondary forest, and although the other species of the genus were shade-loving, these examples were found in the full glare of the sun. The suctorial properties of the digital discs of this species are amazing ; one individual placed in an enamelled metal dish, adhered so firmly that, when picked up, it carried the dish, weighing 104 ozs. with it.

Dorsal surfaces beige-green with a canthal stripe, interorbital line, and a large triangle on the dorsum olive-brown edged with an orange line ; the dorsal triangle diminishes in intensity posteriorly, where it gradually merges into the ground-colour, and is only edged with orange anteriorly. Limbs orange-yellow, cross-barred in dark olive ; anal region and hinder surfaces of fore-arms, tarsus, and foot dark brown, edged above with orange, a triangular cream spot below the eye. Flanks white, with granules of black, blue, and yellow forming multicoloured spots. Lower surfaces like the flanks, but the spots have no yellow constituent, though the white ground-colour is tinged with yellow.

Iris like powdered aluminium with a slight brown tinge.

32. LEPTOPELIS CALCARATUS (Boulenger). 9 from low tree in H.D.F. a t Bashauo. Dorsal surfaces of head, body, and limbs light ochre, irregularly patched

with orange ; flanks ochre suffused with orange in the axilla and groin ; lower


surfaces yellow, the belly and thighs heavily marbled and spotted with dark ochre ; hinder side of tibia orange ; anus in an oval dark-brown patch which is ringed with a circle of cream-coloured dots. Iris bright orange above and gold with grey flecks below.

33. LEPTOPELIS BREVIROSTRIS (Werner). 3 Caught in damp herbaceous growth, where they were clinging to the under-

side of large leaves. The powers of concealment, coupled with the coloration, create a degree of camouflage surpassing even that of the Chamaleons. Even the monstrous eyes failed to reveal two that were kept in a small cage filled with green leaves, and which were thought to have escaped until the foliage was taken out and carefully scrutinised.

Upper surfaces and flanks vivid leaf-green ; lower surfaces saffron- yellow, becoming white beneath the throat, hinder side of the thighs and tibis light ochre. Iris glistening mother-of-pearl, contrasting vividly with the general green hue of the upper surfaces.

and 1 juv. from Eshobi, Bashauo, and Akwa.

34. HYPEROLIUS SORDIDUS (Fischer). 40 38, 11 From plantains and low trees in Cult., Tert., and Second. In life the females were, with a single exception, uniform grass-green above

and saffron-yellow beneath, with the digital discs, the inner toes, and the two inner fingers blood-red ; this colour extends up the inside of the leg to the knee as a narrow band, and on the inner side of the forearm almost to the elbow. The only variations among females were a single individual from Mamfe, which was metallic blue above, with the anterior and posterior aspects of the thighs orange, and another from the same locality which was white beneath instead of yellow.

The dark markings of the male, of which traces are usually present in alcohol, were only rarely discernible in life ; three specimens only showed the dorsal blotches, and a few others had traces of the dorso-lateral white line. The upper surfaces varied from grass-green through ochre to gold, through fawn to brown (Pl. I. figs. 2, 4 6 ) . Greens are the commonest colours, though gold is also of frequent occurrence ; a green tinge may also be present with any of the other colours producing olive tones (PI: I. fig. 6). In the brown examples there is often stippling of darker tones. The ventral surfaces range from white through yellow to pale orange or marbled brown, and white, speckled grey, pinkish, mauve, or mauve with yellow marblings (Pl. I. figs. 7-10) ; the vocal sac is always some shade of yellow, and this is also the commonest colour of the whole venter. The hands and feet, forearms, and tibis are tinged with blood-red just as in the female.

The iris in both sexes is constantly golden with a dark cruciform marking centred on the pupil.

33. HYPEROLIUS RIGGENBACHI (Nieden), 2 $!? from low trees in M.P. a t Tinta. Some dried specimens of this species have subsequently been received

from Bali, Bamenda. This locality is situated a t the same altitude as Tinta, though some hundred miles farther east on the northern escarpment of the Mamfe basin.

(PI. I.) from Mamfe, Ekuri, Nko, and Tinta.

AMPHIBfBNS OF THE BlAJlFE DIVISION, CAMEROONS. 203

All these examples differ from the figures of the type only in having the verniiculations narrower and more numerous and in the light edging of the dark zones merging into the lighter ground-colour.

The general colour-pattern in life is, as described by Nieden, but the actual colours are somewhat different. The ground-colour pattern is dark red. with chocolate-brown vermiculations edged with greenish cream ; fore and hinder side of the thighs, inner side of the tibiz, feet, and hands brilliant flume- colour, gradually merging into the vivid orange-coloured lower surfaces. Iris coppery red.

36. HYPEROLIUS L A G ~ N S I S (Gunther). 1 from Ekuri. This specimen was found in a low tree in high deciduous forest. The colour is dull gold, with a dirty brown reticulum, M hich on the middle

of the back breaks up into insuliform spots ; upper surfaces of the limbs olive- grey with faint, transverse, darker spots ; lower surfaces greyish white. Iris iridescent gold.

37. HYPEROLIUS sp. 18 and 1 For relationship of these specimens to H . pusillus see Parker, P. Z. S. 1936,

p. 152. The specimens were found in the axils of plantains on farm-land (Cult.)

in high forest country. The colour in life was olive or grass-green above, sides of the body, legs (except a yellow line on the outer side of the thigh), hands, and feet cherry-red ; a black stripe along the canthus rostralis through the eye to the angle of the jaw ; lower surfaces translucent white. Iris dull amber with a black horizontal streak.

from Mamfe and Ekuri respectively.

38. MEGALIXALUS LBVIS Ahl. 9 from Makumunu. There is some doubt as to the identification of this species (see Parker,

P. Z . S. 1936, p. 152). It was collected in a stunted tree in the mountain forest, and the colour in

life was as follows :-Upper surfaces as far back as the sacrum iridescent gold, with scattered dark brown pin-points, which form a more or less distinctive canthal stripe. Remainder of the dorsal surfaces transparent greenish grey. Under surfaces translucent white, except for a belt across the pectoral region (pectoral musculature), which is opaque white. Eye exceedingly prominent and the iris flecked with golden-amber.

39. MEGALIXALUS DORSALIS Peters. 17 $6,7 99 from Nko. The habitat is low trees and plantains in Cult. and Second. Co1our.-The dorsal surfaces vary from dark red brown to olive, fawn

being the commonest variant, and the light markings are cream, sometimes white or brown tinged. There is great variety in the arrangement, of the colour-pattern on the dorsum ; the darker basal colouring may predominate, forcing the cream into isolated insuliform patches or vice versa. Lower surfaces delicate white. Iris dull greenish amber.

204 MR. IVAX T. SAhDXRSON US THE

3. BUFONIDA:.

-10. NECTOPHRYNE AFRA (Buch. & Peters). 9 from Eshobi. Caught among luuh vegetation near water in the high deciduous forest. The colour in life was as follows :-Upper surfaces dark grey except for a

broad dorso-lateral band from the eye to the groin, which is white. Under surfaces closely stippled with grey and black, giving a blue effect ; posterior part of abdomen tinged with orange ; the two inner digits and inner edge of the tarsus bright orange.

The oolouring is vivid, the limbs excessively thin, and the head appears to be very small. The feet and hands are, on the other hand, grotesquely large, the filamentous fringe giving them the appearance of clots of orange-coloured jelly with ill- defined outline. Its method of progression is a precise walk as if it were stretching each of its limbs in turn, and the adhesive powers of the feet and hands are prodigious.

Iris golden. The general appearance of this frog in life is very remarkable.

41. NECTOPHRYNE BATESI Boulenger. 6 from Eshobi. The single example was taken on a broad leaf on a low tree in the high

deciduous forest. The upper surfaces were apple-green, with dark, bottle-green markings ; sides of the head black ; a vague white line extending from the upper eyelid to the middle of the flank. Fore limbs pale green ; hind limbs ochre, mottled and dotted with dark brown and green. Lower surfaces mother- of-pearl, with tiny deep-seated flecks of dark brown pigment. Inner sides of feet and hands bright orange.

In contradistinction t,o the last species this frog was very active and agile, leaping from leaf to leaf. It also, however, employed the same precise and seemingly painful walk.

Iris golden.

42. BUFO LATIFRONS Boulenger.

9 66, 2 This species was found in natural clearings in the high deciduous forest.

All the specimens except one were taken amongst dry grass on sandy soil ; the single exception was found in December in clear running water in secondary forest.

The ground-colour varies from light dirty yellow to dull ochre, and the dorsum is beset with irregular but evenly distributed small dark brown blotches. Lower surfaces bright uniform sulphur-yellow ; under surfaces of hands and feet very dark grey. Iris gold, flushed with pink during the day but silvery- pink by night, always with a h e reticulum of black lines.

from Bashauo and Mamfe.

43. BUFO CAMERUNENSIS CAMERUNENSIS, sp. n. 2 $6, 2 99, and 3 juvs. from Eshobi. Found only among damp leaves in the depth of the H.D.F. In life the dorsal surfaces are cream and the large dorsal blotches are dark

satiny green tinged with white ; scatted over the rest of the dorsum between the large conspicuous blotches are small irregular markings of reddish brown. The light interorbital bar is golden-yellow, the flanks are cream spotted with dark green and suffused with pink. Juveniles are cream, with a regular mottling


of dark green, a colour which is very characteristic and readily distinguishes them from young toads of the other species which occur in the same region. Tris dark grey without reticulations.

44. BUFO REGULARIS Reuss. 17 from Tinta, 4 from Makumunii. 13 from Calabar, 2 from Obubra. 12 from Mamfe, 4 from Ikom, 1 from Akunakuna. This widely distributed species is found in a variety of habitats (see below),

but is not found below trees. There has been a tendency in recent years for authors working on relatively

small series from one locality to describe races of this very widespread and very variable species. But it shows so much variation from place to place, even in localities only a few miles apart, and also appears to undergo such a variety of seasonal changes that the recognition of distinct subspecies should be preceded by a comprehensive survey of the species as a whole and an investigation of the status of some of the many alleged " synonyms ') of regularis.

The variations exhibited by the present series in the field and the changes of habitat and habits can be summarised as follows :-

January, February, March.-Ikom and Mamfe. Ground-colour pale putty or rich reddish brown. Iris iridescent old-gold or soft dark brown. Toads not in water ; voice not heard a t Mamfe, but a t Ikom, on a sand-bank near the river, they were producing a continuous, unsynchronised roar, composed of individual staccato, diminuendo clucking- quacks.

April, May.-Tinta. Ground-colour varying from dull ochre-brown to reddish brown and individuals showing the power of changing from one extreme to the other, Iris soft dark brown. Toads not near water ; vocal chorus composed of two notes, the staccato clucking-quack mixed with a much louder, snoring, rolling croak.

June.-Obubra. Males lemon-yellow and females darker in ground-colour. Power of colour-change not observed. Iris golden. Toads in dry, sandy, places ; choruses composed of the rolling croak only, not s-mchronised, and producing a continuous whirring.

No individual colour changes.

July, August.-No observations. September.-Calabar. Males lemon-yellow in ground-colour, females

somewhat darker when first captured. The power of colour-change is highly developed ; specimens placed in a damp badly lit cage became almost black, but when confined completely in the dark both sexes changed to a bright light yellow. These specimens, transferred back to the damp cage, returned to their previous colouring, females being rather darker than males. The iris remained constantly mother-of-pearl. All the toads were in the water or its vicinity a t this time and the call-note of the rolling variety was given in unison ; a single toad commenced the chorus, which was then taken up by all the com- munities, and the whole choir ceased simultaneously after a period of a few minutes. Following a shorter interval of silence, the " precentor ) ) began a fresh chorus, which was taken up in unison once more.

Those found a t Ikom during the early part Of the month varied from ochre-buff to grey or yellowish brown, but showed little power of colour-change. The iris was iridescent old-gold, with a narrow bright golden line bordering the pupil. These toads were all in dry situations,

October.-Ikom and Mamfe.


and the calling was similar to that a t Calabar in September, except that there was now no definite synchronised cessation to each chorus.

At Mamfe, later in the month, all toads were a rich reddish brown without any ability to change colour, the iris was a soft dark brown, and the specimens were all in the dry grass. The call-note is still the rolling snore, but it was now given without any attempt a t synchronisation and no longer in organised chorus.

November, December.--No observations. Whether or not these observations indicate a regular series of cyclical

changes is uncertain. The colour-change from month to month may only mean that each locality hasitsown local race ; but, on the other hand, it certainly seems possible that there may be a seasonal cycle of this nature. In April and May, with the onset of the light rains, sloughing possibly occurs, individuals are more brightly coloured, and the chromatophores are apparent, so that there is a degree of colour-change. During the heavy rains (June onwards) the bright colours persist and there is a lightening of the iris colour ; in September (the height of the breeding season) the toads are in water, so that colours appear a t their brightest and the iris has become mother-of-pearl. Towards the close of the rainy period (October) the toads have left the water and colours have become dull, the iris darkening from mother-of-pearl, through old-gold to brown ; there is now no apparent ability to change colour, possibly owing to the drying and thickening of the cuticle and consequent masking of chromatophore movement, This condition persists until the commencement of the light rains in the following April.

There certainly seems to be a series of seasonal changes in the voice and manner of its use. During the dry season the note is the '' clucking-quack " or it is absent. In April and May, with the commencement of the rains, the nuptial note ( 2 ) ) of the " rolling snore " type makes its appearance. This is a t first given without any attempt a t synchronisation ; but by September, when the toads are in water, it is produced in concert with the precision of a trained choir. Later in the year this power of concerted '' singing " is gradually lost, and though observations are lacking for November and December, it is assumed that the " snoring " changes to the " clucking " note during that period.

The method of sloughing in this species is rather different from that of the European toad. Instead of the primary slit being dorsal, the first rents to appear are a mesial longitudinal one beneath the chin and a transverse one from knee to knee on the lower surfaces of the thighs. The feet are used to enlarge the gular slit and to tear off the skin from theventral surfaces, the arms, and the opposite leg ; but the dorsal skin is apparently not removed and swallowed with that of the lower surfaces, but left to wear off gradually.

45. BUFO SUPERCILIARIS Boulenger. 2 99 and 1 juv. from Balegete, Tinta-Atolo, and Eshobi. These specimens did not differ in colour appreciably from those already

described by other authors (Boulenger, 1887 ; Noble, 1924, p. 181)) except that the upper surfaces in all specimens were cream and the lower surfaces were either entirely red or with the ventral granules each alternately red and white ; the immature example was greyish, The habitat has already been described by Noble (Zoc. ci t . ) .

AMPHIBIANS OF THE MAMFE DIVISION, CAMEROONS, 267

4. PIPIDB.

46. XENOPUS TROPICALIS (Gray). 96&J, 99, and juvs. from Mamfe, Nko, and Ekuri. The majority of the specimens collected by the present expedition were

found in still muddy water in secondary and tertiary forest ; five, however, were caught in a swift-running large river in H.D.F. These latter differed appreciably in colour from the others, being uniform dark olive-green above and whitish beneath, occasionally with a green alga ( 1 ) in the mucous secretion of the dorsum (cf. Ram occipitalis). The remainder were from grey-brown to light ochre- yellow above and yellowish grey beneath, with sometimes an indefinite light interorbital bar and a lighter patch around the vent ; both dorsal and ventral surfaces may be more or less profusely speckled with brown. Iris greyish yellow.

VIII. SUMMARY OF CONCLUSIONS.

An area within the tropical forest of Africa under climatic conditions more or less typical of such a region supports a large and varied frog fauna. The numerical strength of this fauna can be shown to bear a close relationship to its specific strength, both as regards its local and ecological distribution and in the facies of that distribution.

The local distribution of the frogs is largely dependent upon the habitats, which are themselves divided into a number of separate groupings by the zoning of vegetation. This zoning is the result of altitude, latitude, and human agency.

The clearing of forests alters the environment and encourages a relentless encroachment of arid conditions from the north. By this process primary forest is rapidly disappearing and will probably become extinct. A little over half of the species of frogs will be evicted by this process, with a consequent loss in numerical strength. This will and already does upset the balance of general animal ecology, and may tend to increase the potentiality for insect pests over the whole area.

Isolated areas of cultivation can be populated by frogs that probably traverse considerable distance to reach such localities. A belt of palms alone seems capable of preventing such migrations.

The variation of colour displayed by frogs in life can be both individual and specific, and bears some relationship to the ecological or local distribution of the species. Individual colour-change displays a regular cycle dependent upon environmental conditions.

IX. REFERENCES. BLESS. 1907. BOULENQER. 1887. BOULENOER. 1906. COTT. 1932. KNOX. 1911. MOATTEE. 1921. NOBLE. 1924. PARKER, H. W. 1936.

The Work of John Samuel Budgett. Proc. Zool. SOC. London, pp. 565-5. Ann. Mus. Civ. Genova, (3) ii. pp. 9 BE 157 -72.

The Climate of the Continent of Africa, pp. 193-202. Proc. Zool. SOC. London, pp. 488-491.

Copeia, no. 96, pp. 39-40. Bull. Amer. Mus. Nat. Hist. xlix. pp. 147-347.

Proc. Zool. Soc. London, 1936, p. 136.

208 THE AMPHIBIANS OF THE MAMFE DIVISION, CAMEROONS.

FXLSNATION O F THE PLATE.

PLATE I.

Hyperolius sordidus (colour variations).

2. Ordinary green male (extended). 3. Male, showing dorsal markings. 4. Male, with white dorpal line. 5. Male, gold variety. 6. Male, speckled olivaceous type. 7. Underside of male. 8. Underside of female (extended). 9. Underside of male.

10. Underside of male.

Fig. 1. Metallic blue female.

the amphibians of the mamfe division, cameroons.–ii. ecology of the frogs

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