Afr. J. Ecol. 1996, Volume 34, pages 83-85

Notes and Records

Census of hippopotamus (Hippopotamus amphibius (L)) in the Upper Shire River, Malawi

Until recently, little was known about the numbers of hippopotami (Hippopotamus amphibius) outside protected areas along the Shire River in Malawi. Several counts have been carried out in the segment of the river in Liwonde National Park, but only one aerial count by Simons et al. (1 99 1) in 1989 has covered the entire river. Another aerial count, covering only the upper Shire segment, from the outlet at Lake Malawi to Zalewa Bridge (Fig. l), was undertaken in October 1993. This paper reports on this count. The count was part of a proposed hippo management plan to alleviate human-hippo conflicts along the river. The hippo is a major vertebrate pest in Malawi and the extent of conflicts with humans is reported by Mkanda (1 994).

The Shire River is the only outlet of Lake Malawi. The upper segment covered in this study is about 106 km long (excluding Lake Malombe). About 15 km from the outlet is Lake Malombe which has about 85 km of shoreline. Anonymous (1971) divides the Upper Shire Valley into two natural regions; the flat to gently undulating Shire floodplain with grey/brown earth, and the level mopane area with soils classified as mopanosols. The dominant natural vegetation type in these areas is mopane woodland. Most land along the Upper Shire is customary land. However, a 40 km segment of the river just south of Lake Malombe is in Liwonde National Park.

Counts to estimate hippo numbers were carried out by air using a fixed-high- wing Sky-hawk aircraft on 12 and 13 October 1993. The aircraft was flown at a height of about 91 m with transects at 500 m apart. All the hippos seen were counted and the numbers per school recorded. Due to the tendency to under- count from the air (Norton, 1988; Tembo, 1987), a correction factor of 1.2 obtained by comparing the results of a boat count and an aerial count in Liwonde National Park in 1992 was used.

The study area was divided into several segments using identifiable physical features (Fig. 1). For each segment, estimates of distance (km), hippo population and the hippo density (number per river km) were calculated. The results of this count were compared to those of the 1989 count using the Kolmogorov-Smirnov two-sample test (Seigal & Castellan, 1988) to determine whether or not the counts had the same distribution pattern.

The results of the count are shown in Table 1. Hippo densities were highest in Liwonde National Park (20.2 per km); and in the rest of the river, the densities did not differ much, ranging from 4.6 to 6.8 per km. The Lake Malombe shores had the least densities. The total population estimate for the whole study area was 1234.

Table 2 compares the results of this count and those of the 1989 count by Simons et al. (1991). The total estimate of 1234 from this count is only thirty-two 0 1996 East African Wild Life Society.

84 Notes and Records

Fig. 1. Map of the upper Shire River with the different segments used in this study.

Table 1. Results of the hippo aerial count and other vital statistics in the Upper Shire River by river section

Segment of river

Zalewa Bridge to Shire North Shire North to Liwonde Barrage Liwonde Barrage to Mvera Ferry (Liwonde National Park) Lake Malombe shore Lake Malombe to Mangochi Bridge Mangochi Bridge to Lake Malawi Total

Estimated length

(km) Number counted

Corrected estimate

( X 1.2) No. of

schools

18 31 42

85 6 9

I06

82 I15 106

47 28 51

1029

98 138 847

56 34 61

1234

14 14 59

3 2 4

96

more than the total of 1202 from the 1989 count. The Kolmogorov-Smirnov two-sample test showed no significant difference in distribution patterns between the two counts, despite some discrepancies in the segment between Zalewa

0 East African Wild Life Society, Afr. J. Ecol., 34, 83-85

Notes and Records 85

Table 2. Comparison of hippo numbers in the Upper Shire Segment of river 1989 1993 River between 1989 and 1993

Zalewa Bridge to Liwonde Barrage 148 236 Liwonde National Park 81 I 847 Lake Malombe shore 182 56 Lake Malombe to Lake Malawi 61 95 Totals 1202 1234

Bridge and Liwonde Barrage and in Lake Malombe. The results should be representative of the actual population in the study area.

The high density in Liwonde National Park is certainly a result of the protection of the species in the park. The population has been growing over the years as no hunting takes place in the area. Mortality is from natural causes only. Movements of the hippo in the park to the outside area also restricted by the barrage at Liwonde and the crop protection fence along the park boundary. In the rest of the river, the densities have been kept lower probably by the conflict with humans which Mkanda (1994), classified as moderate to high in this area, and reported 199 hippos shot between 1985 and 1989 in the area.

In the Liwonde National Park segment, the hippo population trend is an upward one. In 1987, Whelen (unpubl. data) counted 513 and Bhima (unpubl. data) counted 614 in 1991 and 949 in 1992. These counts were conducted from a boat. Little can be said in the other segments from the two aerial counts carried out in the area so far. It is hoped that in future, there will be more regular counts in the whole river for the formulation of sound hippo management strategies.

Acknowledgments The aerial count was funded by the UNDP/FAO Wildlife Utilization Project. I wish to thank the Project Manager for giving permission to undertake the count. I also thank Messrs D. Mwafulira and A. Rollins for taking part in the count as observers and finally, the Director of National Parks and Wildlife, Mr M. Matemba, for granting permission to publish the paper.

References ANONYMOUS (1971) Malawi natural regions and areas map, sheet 3-southern Malawi. Government of

MKANDA, F.X. (1994) Confficts between hippopotamus (Hippopotamus amphibius (L)) and man in

NORTON, P.M. (1988) Hippopotamus numbers in the Luangwa Valley, Zambia, in 1981. Afr. J. Ecol. 26,

SEIGAL, S. & CASTELLAN, N.J. Jr. (1988) Non-parametric Statistics for the Behavioural Sciences. 2nd Ed. McGraw Hill, New York.

SIMONS, H.W., ROGERS, P.M., BHIMA, R., CHIWONA, E.A. & BANDA, H.M. (1991) Mammal Inventory, Malawi, 1991. F A 0 Wildlife Management and Crop Protection Project MLW/87/010 Field Document No. 9. F A 0 Lilongwe.

TEMBO, A. (1987) Population status of the hippopotamus in the Luangwa River, Zambia. Afr. J. Ecol. 25,

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71-77.

Roy Bhima, Liwonde National Park, PO Box 41, Liwonde, Malawi 0 East African Wild Life Society, Afr. J. Ecol., 34, 83-85