Ecological observations on an East African bat community

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Abstract
The bat fauna of a south-central Kenya study area was monitored from May 1973 to July 1974. Bats in 7 families [Pteropodidae, Emballonuridae, Nycteridae, Megadermatidae, Rhinolophidae, Vespertilionidae and Molossidae] were collected. This fauna is depauperate compared to neotropical areas due to a lack of non-insectivorous feeders. The number of species and families of insect eating bats is nearly identical to that found at a Costa Rican site with a similar climate sampled in a comparable manner. The area had a pronounced dry season from May to late Oct., 2 rainy seasons in Nov. and March-April, and a short and less severe dry season from Dec. through Feb. The maximum number of species was detected from Nov. to May. About 1/2 of these species were found during the long dry season, and many of those present seemed to occur in lower densities. Seasonal migration to areas with complementary rainfall patterns account for these differences. All but 1 sp. reproduced with the more predictable Nov. rains; a few also gave birth in the March-April rainy season; none bred in the long dry season. Most annual residents bred only in Nov. and most of those species which gave birth in March-April probably were migratory. Suspected migrants tended towards smaller litter sizes. Several foraging-related characters were examined as indicators of food resources partitioning. The aspect ratio was significantly correlated with estimates of foraging height. Most of the common non-molossid insectivorous bat species may coexist on the basis of differences in pursuit strategy, prey size orientation pulses or feeding heights. A greater proportion of coexisting species overlap in size during Nov.-May than during the long dry season. This may indicate a greater degree of selective feeding when insect abundance is high, and greater partitioning on the basis of size when abundance is low.