Herpetologists' League

Food of Atelopus oxyrhynchus (Anura: Atelopodidae) in a Venezuelan Cloud ForestAuthor(s): Pedro Durant and Jim W. DoleSource: Herpetologica, Vol. 30, No. 2 (Jun., 1974), pp. 183-187Published by: Herpetologists' LeagueStable URL: http://www.jstor.org/stable/3892038 .Accessed: 09/04/2011 16:36

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June 1974] HERPETOLOGICA 183

were sighted and none were active on the partially-shaded primary sample sites.

Animals aggregate for many reasons, in- cluding advantages associated with feeding, breeding, and reduction of predation. It is most likely that the U. ornatus aggregations reported here are the result of a shortage of appropriate overwintering sites. This raises several questions: What cues over- ride territorial aggressive behavior in males allowing them to coexist in large aggrega- tions? Perhaps cues are not necessary as this behavior may break down from hor- monal changes associated with the winter nonreproductive state. Milstead (1970) ob- served late summer territorial behavior in U. ornatus but Martin (1973) noted that U. ornatus in Texas was nonreproductive by 17 August 1971. Since in lower deserts of Arizona these lizards are active through late October, nonreproductive associated hormonal changes could account for this territorial breakdown.

Acknowledgmn ts.-I thank Drs. M. J. Fouquette, Jr. and John Alcock, Arizona State University, for criticism on the initial drafts of the manuscript.

LITERATURE CITED

MARTIN, R. F. 1973. Reproduction in the tree lizard (Urosaurus ornatus) in central Texas: drought conditions. Herpetologica 29:27-32.

MILSTEAD, W. WV. 1970. Late sumer behavior of the lizards Sceloporus merriami and Urosaurus ornatus in the field. Herpetologica 26:343-354.

VITT, L. J. 1973. Reproductive biology of the anguid lizard Gerrhonotus coeruleus prncipis. Herpetologica 29:176-184.

WEINTRAUB, J. D. 1968. Winter behavior of the granite spiny lizard Sceloporus orcutti Stejneger. Copeia 1968:708-712.

WORTHINGTON, R. D., AND M. D. SABATH. 1966. Winter aggregations of the lizard Uros aurs ornatus ormatus (Baird and Girard) in Texas. Herpetologica 22:94-96.

Received: 15 June 1973 Accepted: 13 August 1973

Department of Zoology, Arizona State University, Tempe, Arizona 85281

FOOD OF ATELOPUS OXYRHYNCHUS (ANURA: ATELOPODIDAE) IN A VENEZUELAN

CLOUD FOREST

PEDRO DURANT AND JINI W. DOLE

ABSTRACT: Analysis of stomach contents of 63 adult Atelopus oxyrhywhus showed that in both sexes Coleoptera accounted for approximately 40% of the food biomass, while Hymenoptera (mostly ants), larval Lepido-ptera larval Diptera and Acarina constituted most of the remaining bulk. All other groups accounted for < 15%e of total weight of stomach contents. Stomachs of 9 9 usually contained almost twice as much food n aterial as did those of the smaller 8 .

Frogs taken in amplexus tended to have less material in their stomachs than did unpaired animals. Of eight amplectant 8 8, six contained no identifiable food items and one contained a single beetle; average wveight of stomach contents of these seven S S was about 25% of the average for unpaired & S. Ap- parently 8 8, which form amplexus several months in advance of spawning, feed only infrequently if at all during this period.

NUMEROUS studies of the food eaten by frogs and toads of the temperate zone have been published, but our knowledge of the feeding habits of tropical anurans is more

HERPETOLOGICA 30:183-187. June 1974

scanty. Berry ( 1965, 1966), Berry and Bullock (1962) and Inger and Marx (1961) have reported on the diets of several Afn- can and Asian species, but little has been

184 HERPETOLOGICA [Vol. 30, No. 2

published on the food of the anurans of tropical America. During a year-long study of the natural history and behavior of Atelopus oxyrhynchus in the cloud forest of the Venezuelan Andes we made a pre- liminary analysis of their stomach contents to determine the nature and quantity of food typically utilized. Because of the un- usual habit in this species of initiating amplexus as much as 6 months before spawning (Dole and Durant, 1974) we were particularly interested in comparing the feeding habits of the paired and un- paired animals.

METHODS

Sixty-three adult frogs (33 S ~, 30 9 9) were collected between 7 December 1970 and 23 November 1971, from the forest floor in the region surrounding our study area (see Dole and Durant, 1974 for a description of the site). Of the 63 animals 8 of each sex were in amplexus when taken, 2 on 29 March, 1 on 19 April and 5 on 7 May 1971. At capture each animal was immediately preserved in 10% Formalin.

After return to the laboratory each animal was measured, its sex determined, its stom- ach removed and the contents washed into petri dishes. All intact, identifiable food items were then sorted by type, counted and measured. Food collections were then dried at 100 C for 24 hours and weighed to the nearest 0.01 mg. Remaining debris from the stomachs was also dried and weighed. From these data were calculated: (1) the percentage of frogs containing each type of food item (number of frogs con- taining any quantity of a given food item - by the total number of frogs), (2) the percentage occurrence of each type of food item (number of individuals of each spe- cific food type . the total number of all intact food items identified), and (3) the percentage weight of each item (weight of each specific food type . the total weight of all identified items). In deter- mining this last measure the weight of un- identified debris was excluded; presumably the components of this material are in

roughly the same proportions as in the identifiable portion.

All insects, arachnids and crustaceans were identified to order, and in some of the larger orders, to family. All else was identified to class. Data for both sexes and for paired and unpaired animals were treated separately.

RESULTS AND DISCUSSION

Unpaired Frogs.-Beetles formed the largest portion of the diet of unpaired ani- mals of both sexes. Including immature forms, Coleoptera accounted for over 40% of the identifiable biomass among the male frogs and 39% in the females (Table 1). Over 95% of the stomachs of both sexes contained adult beetles attesting to the importance of these insects in the diet. Sixty percent of the biomass of adult Coleoptera taken by males and 50% of that eaten by females was composed of snout beetles (Curculionidae); no other coleop- teran family contributed more than 15% of the bulk.

Hymenoptera also contributed signifi- cantly to the diet, constituting over 28% of the identifiable biomass and occurring in 90% of the stomachs of females, while in males these insects made up 20% of the weight and were found in 76% of the stom- achs. Eighty-three percent of adult hyme- nopterans found were ants, and most of the biomass of these insects were derived from only a few frogs whose stomachs contained large numbers of individuals. One female's stomach contained 117 ants, another 79, and a third 60; these three stomachs alone ac- counted for 66% of all hymenopterans in the females and more than 65% of the hymenopteran biomass. Among males the largest number of ants in given stomachs were 43, 31, and 28, together accounting for 55% of all individual Hymenoptera and 70% of the hymenopteran biomass. It ap- pears that when these frogs chance upon an ant colony they tend to feed continuously until satiated.

Two other orders of insects, Diptera and Lepidoptera, contributed significantly to

June 1974] HERPETOLOGICA 185

TABLE 1.-Stomach contents of Atelopus oxyrhynchus, by sex. (A) 25 unpaired & & and 22 unpaired 9 9 and (B) 16 pairs.

A B ?9/d, _ ?9/Jc

Percent of Percent Percent Percent of Percent Percent stomachs occurrence weight stomachs occurrence weight

Item with item of item of item with item of item of item

INSECTA Coleoptera (adult) 95.5/96.0 18.6/19.3 35.9/37.1 87.5/25.0 23.1/25.0 35.5/64.4 Coleoptera (larval) 45.5/52.0 1.9/2.0 2.7/3.6 37.5/12.5 3.7/2.5 3.7/3.4 Hymenoptera (adult) 90.9/76.0 39.3/20.9 28.5/20.0 87.5/12.5 21.7/5.0 14.3/2.0 Hymenoptera (larval) 0/4.0 0/0.2 0/0.9 0/0 0/0 0/0 Diptera (adult) 27.3/28.0 0.6/1.0 0.3/3.2 50.0/0 2.2/0 1.1/0 Diptera (larval) 77.3/72.0 9.2/13.2 7.6/9.9 100.0/12.5 16.1/7.5 13.2/10.5 Lepidoptera (larval) 27.3/28.0 1.0/0.8 12.1/6.4 50.0/0 2.2/0 16.6/0 Hemiptera 22.7/12.0 0.5/0.3 3.8/0.4 25.0/12.5 0.7/2.5 0.8/2.5 Homoptera 31.8/20.0 1.6/0.7 1.7/0.8 25.0/0 0.7/0 0.6/0 Orthoptera 0/8.0 0/0.2 0/1.1 0/12.5 0/2.5 0/3.5 Trichoptera (larval) 9.1/8.0 0.3/0.2 0.4/1.7 0/0 0/0 0/0 Neuroptera (larval) 4.6/0 0.1/0 0.1/0 12.5/0 0.4/0 < 0.1/0 Thysanura 0/4.0 0/0.1 0/< 0.1 0/0 0/0 0/0 Thysanoptera 13.6/12.0 0.5/0.6 0.1/< 0.1 12.5/0 0.4/0 < 0.1/0 Collembola 31.8/32.0 1.7/2.1 0.2/0.4 25.0/0 1.1/0 0.2/0 Embiidina 4.6/4.0 0.1/0.1 < 0.1/0.1 0/0 0/0 0/0 Dermaptera 4.6/0 0.1/0 < 0.1/0 0/0 0/0 0/0

ARACHNIDA Phalangida 13.6/8.0 0.5/0.2 0.6/0.5 12.5/0 0.4/0 0.1/0 Acarina 86.4/100.0 21.4/34.2 3.4/7.1 75.0/12.5 23.4/52.5 3.3/10.7 Araneae 45.5/28.0 1.1/0.9 0.5/1.3 50.0/12.5 1.8/2.5 2.0/3.0 Pseudoscorpionida 27.3/20.0 0.4/0.8 0.2/0.7 0/0 0/0 0/0

CRUSTACEA Isopoda 4.6/16.0 0.1/0.9 0.1/1.9 0/0 0/0 0/0

CHILOPODA 9.1/8.0 0.2/0.3 0.1/0.2 12.5/0 0.4/0 0.6/0

DIPLOPODA 18.2/20.0 0.4/0.6 1.5/1.7 37.5/0 1.8/0 8.0/0

GASTROPODA 4.6/12.0 0.2/0.3 0.1/0.9 0/0 0/0 0/0

the diet. Only immature lepidopterans were encountered and among the dipterans, larval forms constituted the bulk of the insects taken. The small numbers of adult flies and the conspicuous absence of adult moths and butterflies is probably due to the fact that these very sluggish frogs are generally incapable of capturing them for at times they are abundant. A total of only 17 lepidopteran larvae were found, ac- counting for the very low percent occur- rence (1% or less).

In numbers of individuals, the Acarina outranked all other food items in the males (34.2% occurrence) and ranked second only

to adult hymenopterans in the females (21.4% occurrence). However, because of their small size the contribution of the mites to the biomass was only moderate, 3.4% and 7.1% of the weight of the identi- fiable contents in females and males respec- tively. Each male had at least one mite in its stomach, while 86% of the stomachs of females contained mites. The somewhat greater utilization of mites by males may be associated with the size difference between the sexes. Possibly the smaller males gen- erally select smaller prey than the females, hence more frequently take the mites, none of which measured over 1.5 mm in length.

186 HERPETOLOGICA [Vol. 30, No. 2

TABLE 2.-Mean weight of total stomach contents of paired and unpaired Atelopus oxyrhynchus.

% of % of Weight total animals

(xt + SE) in weight with any milligrams of which identi- total stomach was iden- fiable

contents N tifiable item

paired 39.7 mg ? 4.5 8 33.8 100 unpaired 45.4 ? 3.9 22 38.2 100

paired 10.9 ? 3.8 8 14.1 25 unpaired 28.5 ? 3.6 25 33.6 100

Representatives of several other animal groups were also found, but none in large numbers. All the remaining taxa together accounted for less than 10% of the identi- fiable biomass in females and less than 12% in males. Of interest, however, is the pres- ence in two males of aquatic trichopteran larvae, presumably indicating that they fed in a body of water, possibly one of the small pools occasionally found in the lower areas of the forest. Since no animals were taken near streams it is unlikely that they had fed in running water.

The stomachs of females on the average contained almost twice as much material as did those of males (Table 2). This dif- ference (statistically significant at the 0.1% level, Table 3) presumably is a reflection of the larger size of the females (Dole and Durant, 1974), their greater stomach capac- ity and their greater nutrient requirements. In males there was a significant positive cor- relation between body length and total weight of stomach contents (r = 0.5671 with 23 df; P < .01) but in females the correlation lacked statistical significance (r = 0.2868 with 20 df; P > .10).

Paired Frogs.-Reduced variety in the stomach contents of the eight pairs of frogs in amplexus reflects the smaller sample size (Table 1). All differences were among taxa which were only minor contributors to the diet of unpaired animals. The relative con- tributions of Coleoptera, Hymenoptera, Diptera, Lepidoptera and Acarina were similar in both paired and unpaired ani-

TABLE 3.-Analysis of variance for weights of total stomach contents of paired and unpaired

Atelopus oxyrhynchus of both sexes.

Source df MS F P

sex 1 6241.8 22.17 <.001 pairing 1 1655.7 5.88 <.025 interaction 1 424.3 1.51 > .10 error 59 281.5

mals. Together these five groups accounted for 87.6% and 93.5% of the identifiable biomass in paired females and males re- spectively, closely approximating the com- parable figures (90.5% and 88.2%) for the unpaired frogs.

Paired animals of both sexes tended to have less material in their stomachs than did unpaired frogs (Table 2). The differ- ence is statistically significant at -Lhe 2.5% level (Table 3). On the average, stomachs of paired males contained only about two- thirds as much biomass as did those of un- paired males, most of it in an advanced state of digestion. In the stomachs of six of the eight paired males nothing could be identi- fied; a seventh frog contained a single beetle, and only in the eighth were several intact food items found. The stomach con- tents of this one animal accounted for 37.8% of the total biomass of food among the paired males. Eliminating this one animal from the sample, the average weight of the stomach contents of the remaining seven paired males drops to 7.7 mg or about 25% of the average for unpaired males. All un- paired males contained numerous intact food items. This very low biomass and the well-digested state of the gut contents among seven of the eight paired males suggests that males seldom feed after forming amplexus. It is very likely that the male with a full stomach had only recently paired. Since males in amplexus tenaciously and continuously grip their partners until spawning occurs, often several months later (Dole and Durant, 1974), the emptiness of their guts is not surprising. Presumably they subsist upon occasional arthropods which chance to wander across their part-

June 1974] HERPETOLOGICA 187

ner's head directly in front of them, and on their fat reserves. In view of the near starvation of the males during this period the adaptive advantage of forming pairs so much in advance of spawning is difficult to see, though it may be related to the fact that males outnumber females about 3:2, thereby decreasing the probability that an unpaired male will find a mate late in the season.

Females are apparently not so much af- fected in their feeding habits by pairing. Though paired females averaged slightly less biomass in the stomach than unpaired females, the difference was less pronounced than in males. Even after pairing the fe- males still largely control their own move- ments hence have an advantage over their male partners in obtaining food. This prob- ably accounts for the fact that paired fe- males averaged almost 4x as much biomass in the stomach as did their partners. Pre- sumably this difference reflects both the larger size of the females and the limitations which pairing puts on feeding by males.

Acknowledgments.-We thank Dr. Hernan Finol, Director of the Silviculture Institute for permis-

sion to use the Forestry Station, Dr. Luis Fernando Chaves V., Dr. Juan B. Castillo and Mr. Jesus Petit from the Institute of Geography for providing vehicles. Mr. Manual A. Guevara aided us on several occasions and for this we are grateful.

LITERATURE CITED

BERRY, P. Y. 1965. The diet of some Singapore anura (Amphibia). Proc. Zool. Soc. London. 144:163-174.

. 1966. The food and feeding habits of the Torrent frogs, Amolops larutensis. J. Zool. (London) 149:204-214.

AND J. A. BULLOCK. 1962. The fQod of the common Malayan toad, Bufo melanostictus Schneider. Copeia 1962:736-741.

DOLE, J. W., AND P. DURANT. 1974. Movements and seasonal activity of Atelopus oxyrhynchus (Anura: Atelopodidae) in a Venezuelan cloud forest. Copeia 1974:230-235.

INGER, R. F., AND H. MARX. 1961. The food of amphibians. Exploration du Parc National de l'Upemba. Fascicule 64: 1-86.

Received: 19 June 1973 Accepted: 7 September 1973

Facultad de Ciencias, Universidad de los Andes, Merida, Venezuela and Department of Biology, California State University, Northridge, California 91324

THE OCCURRENCE OF MULTIPLE TESTES IN THE GENUS EURYCEA (AMPHIBIA: PLETHODONTIDAE)

DAVID M. SEVER

ABSTRACT: Multiple testes in urodeles consist of a series of enlargements which when fully developed are morphologically and functionally similar to each other or to a simple testis. Such testes are known within the tribe Hemidactyliini for only Eurycea lucifuga, E. nana, and E. neotenes. Studies on the mor- phogenesis of multiple testes are needed to settle conflicting reports concerning their formation and to ascertain definitely the time interval between formation and regression of successive testicular lobes.

A MULTIPLE testis is made up of a series of enlarged lobes that are linearly arranged and separated by constricted areas that may be of greater length than the lobular en- largements (Humphrey, 1922). Multiple testes have been described in Desmognathus (Kingsbury, 1902; Humphrey, 1921, 1922;

HERPETOLOGICA 30:187-193. June 1974

and Burger, 1937), Salamwndra (Kingsbury, 1902; Nussbaum, 1906; Champy, 1913; Humphrey, 1922; Baker, 1965), Notophthal- mus (Humphrey, 1922, 1926; Obreshkove, 1924; Adams, 1940; Baker, 1965), Taricha (Humphrey, 1922; McCurdy, 1931; Miller and Robbins, 1954; Baker, 1965), Leurog-