BAT SPECIES DIVERSITY AND DISTRIBUTION IN A DISTURBED REGIME AT THE LAKE BOGORIA NATIONAL RESERVE, KENYA

Abstract

Rapid population growth in many parts of Kenya, has led to increased demand for land for agriculture and settlement. This invariably leads to loss, degradation and fragmentation of forests and other natural habitats. While many studies have assessed impacts of habitat loss on many wildlife species, especially the megafauna, little is known of its impact on small mammals). In Kenya’s Rift Valley, human impacts on bat species diversity and distribution have not been evaluated. Using standard mist nets and the Baun-Blanguet method in the sampling protocol, this study assessed bat species diversity and distribution along a gradient of human disturbance among dif ferent vegetation types in and around Lake Begonia National Reserve. The study was conducted from November, 2012 to July, 2013. Cluster analysis and Detrended Corre spondence Analysis (DCA) grouped the vegetation into two broad categories on the basis of cover-abundance estimates. The assemblages were: Acacia wood land/Acacia–Commiphora woodland and riverine vegetation. Two hundred and thirty three bats representing eleven genera in seven families were recorded. These were: Epomophorus minimus, Rhinolophus landeri, Hipposideros caffer, Cardioderma cor, Lavia frons, Nycteris hispida, Chaerephon pumilus, Mops condylurus, Neoromicia capensis, Scotoecus hirundo and Scotophilus dinganii. Species richness estimators indicated sampling was exhaustive: the abundance-based Cover Estimate mean was 11.34±0.42 while the Jack 1 mean was 11.94 ±0.94. Species richness (S = 10) and di versity (D =5.72) were highest in the Acacia woodland while the more homogenous farmlands recorded the lowest species richness (S = 5) and diversity (D =1.94). No significant differences were exhibited in interaction of bat diversity and plant diversi ty among the four vegetation formation (r = 0.52, P =0.658, n=16). One way ANOVA (F=0.34, df=15, P=0.81) showed no significant differences in relative bat abundance in the four vegetation types. The low species richness and increased dominance of a few generalist species on farmlands may be indicative of different levels of disturb ance, including historical grazing by cattle and vegetation clearance that may have resulted in a relatively homogenous habitat. Future studies should focus on use of state-of the-art equipment, especially acoustic monitoring, in combination with mist netting to provide more accurate and unbiased surveys. This information will strengthen the scientific basis for the management of the Lake Bogoria National Re serve and other related savanna habitats in Kenya.