Aspects of bats ecology in Kaptum cave in Mt. Elgon, Eastern Uganda

Abstract

Few studies have addressed the ecology of cave bats in Uganda. This study aimed at assessing the diversity; roosting and feeding ecology of micro chiropterans as well as aspects of human disturbance in Kaptum cave of Mt Elgon Eastern Uganda. Data collection was conducted during two field visits in July/August 2016 and October/November 2016 survey periods. Mist nets and a harp trap were used to capture bats for examination and identification of species present. Infrared trail trap cameras were used to augment the monitoring of roosting habits and activity patterns of the bats in the cave; as well as record instances of human disturbance in the cave. A portable weather station (Novalyx WS-18) was used to record the microclimatic conditions in the different sections of the cave to evaluate their influence on choice of roost. Kaptum cave contains three main chambers each dominated by different genera or species of insectivorous bats. These chambers vary in structural complexity and size. The cave contained six species of insectivorous bats namely; Nycteris thebaica, Rhinolophus landeri, R. hildebrandtii, Hipposideros caffer, H. ruber, and Myotis bocagii. These generally roosted and segregated themselves in the three different cave chambers and hence referred to as: “Nycteris”, “Rhinolophus” and “Hipposideros” chambers. The bats exhibited similar and slight variations activity and roosting patterns. From evidence of insect remains in the roost, the diet of the bats in Kaptum Cave consisted of eight insect orders (Lepidoptera, Coleoptera, Orthoptera, Dictyoptera, Hymenoptera, Isopteran, Hemiptera, and Odonata) with the order Lepidoptera constituting the bulk of insects preyed upon. The specific prey items of each bat species could not be established since most insect remains were recovered from a section the cave we referred to as the “Nycteris corner” dominated Nycteris thebaica, where most of the bats fed from. The Nycteris corner was however, frequented by the other species (Rhinolophids and Hipposiderids) at any time in a 24-hr period. Temperature and relative humidity varied significantly in all the cave chambers, and these had a big influence on segregation of bats in the cave. There were several encounters and signs of human disturbance and use of the cave such as: cave mass tourism, extraction of volcanic crystal stones, making fireplaces, and collection bat guano. Continued human presence in the cave could have serious implications for roost stability; but also, it could predispose humans to potentially harmful aerosols and pathogens associated with bats and bat guano