Tropical rainforest ecosystems have high levels of both animal and plant biodiversity with many aspects of their ecology understudied. In particular, extensive research is still required to gather accurate estimates of distribution and abundance of forest-interior bat species in Borneo. Accurate abundance data and further knowledge of individual species’ ecology is vital for implementing effective conservation. Bats were captured using a harp trap, set up along established trails and around buildings, at Kuala Belalong Field Studies Centre, Ulu Temburong National Park, Brunei Darussalam between 14th-19th January 2018. Ulu Temburong National Park is comprised of pristine primary mixed dipterocarp lowland rainforest that has not been exposed to logging or fragmentation. A total of nine bat species were recorded, with two new records for Brunei, Miniopterus australis (Lesser bent-winged bat, N = 1) and Myotis horsfieldii (Horsfield’s myotis, N = 5). Furthermore, a coincidental sighting of a colony of Megaderma spasma roosting on the mangrove island Selirong, in Temburong District is reported here. The bat species captured and encountered in this small-scale study expand our understanding of bat communities in Temburong as well as indicate that current records for the area are far from complete. This affirms the need for further work in building up accurate abundance and diversity estimates, both for Ulu Temburong National Park and Brunei Darussalam.
