Invertebrate prey diversity and dietary analysis of rehabilitating sun bears (Helarctos malayanus euryspilus) in Sabah, Malaysia

Diet plays a critical role in the survival of released wildlife, with success heavily depending on an animal’s ability to locate and exploit natural food sources through effective foraging behaviors. Sun bears (Helarctos malayanus) are opportunistic frugivores, with invertebrates and opportunistic prey forming a crucial food source when fruit is not available. In the dense dipterocarp rainforests of Southeast Asia where sun bears occur, fruit availability varies between mast fruiting seasons and effective foraging of invertebrates is likely to be vital for survival during inter-mast periods which can last up to a decade. Understanding dietary composition in sun bears undergoing in-situ rehabilitation is important for assessing foraging competency and release readiness to increase the likelihood of release success, yet baseline dietary information remains limited. This study outlines an approach taken to identify invertebrate species foraged by two orphaned sun bears undergoing in-situ rehabilitation in Sabah, Malaysia. A total of 138 samples were analysed, identifying 161 invertebrate specimens across 7 orders, 8 families and 17 taxa. Hymenoptera, Blattodea and Coleoptera were most prevalent throughout the samples. Several taxa were recorded for the first time in sun bear dietary studies; the orders Diptera, Mantodea and Dermaptera as well as the species Oecophylla smaragdina and Crematogaster inflata. These findings contribute to the baseline dietary data available for sun bears undergoing soft rehabilitation programs in tropical forest environments and as a potential indication of the diet of local sun bears in the region. Additionally, we present an accessible methodology for those wishing to document sun bear diet in rehabilitation settings and for future studies to assess how dietary composition may influence survivability and release success of sun bears in the wild.