Composition and diversity of bat assemblages at Arabuko-Sokoke Forest and the adjacent farmlands, Kenya

Abstract

Recognized as a global biodiversity hotspot, coastal forests in eastern Africa are currently reduced to fragments amidst human modified habitats. Managing for biodiversity depends on our understanding of how many and which species can persist in these modified areas. Aiming at clarifying how habitat structure changes affect bat assemblage composition and richness, we used ground-level mist nets at Arabuko-Sokoke Forest (ASF) and adjacent farmlands. Habitat structure was assessed using the point-centered quarter (PCQ) method at 210 points per habitat. We captured a total of 24 bat species (ASF: 19, farmlands: 23) and 5217 individuals (ASF: 19.1%, farmlands: 82.9%). Bat diversity was higher at ASF (H′, ASF: 1.48 ± 0.2, farm: 1.33 ± 0.1), but bat richness and abundance were higher in farmlands [Chao1, ASF: 19 (19–25), farmlands: 24 (24–32) species (95% confidence interval [CI])]. Understory vegetation and canopy cover were highest at ASF and the lower bat richness and abundance observed may be the result of the under-sampling of many clutter tolerant and high flying species. Future surveys should combine different methods of capture and acoustic surveys to comprehensively sample bats at ASF. Nonetheless, the rich bat assemblages observed in farmlands around ASF should be valued and landowners encouraged to maintain orchards on their farms.

Diversity of invertebrates in Arabuko-Sokoke Forest and adjacent farmland, Gede-Kilifi County, Kenya

“…The current study investigated diversity and abundance of invertebrate in the interior of ASF and surrounding farmland. The ASF is a legally protected area, characterised by indigenous vegetation typical of the east African coastal forests [10,17] , while the farmland habitat is completely disturbed and modified into an agricultural landscape. Because the two contrasting habitats had been shown to host various types of insectivorous bat species [9,10] , there was need to provide data on diversity and abundance of invertebrates, which are the primary food items eaten by these bats.…”

“…The ASF is a legally protected area, characterised by indigenous vegetation typical of the east African coastal forests [10,17] , while the farmland habitat is completely disturbed and modified into an agricultural landscape. Because the two contrasting habitats had been shown to host various types of insectivorous bat species [9,10] , there was need to provide data on diversity and abundance of invertebrates, which are the primary food items eaten by these bats. The results of our study indicated that the farmland in the eastern part of ASF as well as the interior of ASF and had similar invertebrate abundance.…”

“…Nevertheless, many individuals of the order Dipterans, Lepidopteran, and Blattodea were more common in ASF than in the farmland. Therefore, though the interior of ASF has been shown to have low insectivorous bats abundance and activity than the farmland [9][10][11] , most of the invertebrate orders preyed by these bats were also common in the forest interior. This probably indicates that the farmland and the interior of ASF were suitable foraging habitats for the insectivorous bat species found in the two study sites.…”

“…This study investigated the diversity and abundance of invertebrates, which are preyed by insectivorous bats in ASF and the adjacent farmland. Insectivorous bats studies, previously conducted both in the interior of ASF and farmland (Table 1), had shown that the farmland had higher activity of insectivorous bats and individual bat captures than in the interior of ASF [9][10][11] . Therefore, we predicted that invertebrate would be more abundant in the farmland than in the interior of ASF.…”

“…Invertebrate sampling stations were established in the open areas of selected farms. The 12 invertebrate sampling stations each, in the farmland and in the interior of ASF, were established in the general areas, that had been previously been used to sample insectivorous bat species [9][10][11] . In addition, a number of bat roosts actively used by bats to roost, during invertebrate survey occurred in the sampling areas in the farmland [18] .…”