Populations of Eidolon helvum in Kampala Over 40 Years

Abstract

A decline in population of the straw-colored fruit bat, Eidolon helvum in Kampala has been observed on and off for the last 40 year, but with seasonal variability, noticeable with the numbers of the bats surviving in Kampala at present. The first known count of the bats by Mutere (October,
1962) estimated their population at over 200,000 bats while estimates for the same month in 2002 stand at just over 23,000. A lot of impressions have been drawn from studies carried out from 2002-08. Counts of bats were carried out using the single Stage Systematic system. The decline in population could be due to habitat destruction/ fragmentation; more noticeably tree cutting and other human effects such as negative attitude towards the bats. The present day pattern is of the Kampala colony broken up into several small sub-colonies roosting in a variety of tree species. This pattern is greatly varied from that of the 1960s when the first counts were done at the then Bat valley where Eucalyptus saligna was then the prime roosting tree. The surviving populations of E. helvum are now distributed in smaller colonies in several areas of the city. During 2002, counts were also conducted in selected other areas within a radius of 80km from Kampala in an attempt to evaluate the bearing of these populations on that in Kampala. Populations of the bats were higher at locations further away from the city as compared to those in Kampala.

Key words: Eidolon helvum, roost trees, population changes, roost sites.