Frugivory in sun bears (Helarctos malayanus) is linked to El Niño-related fluctuations in fruiting phenology, East Kalimantan, Indonesia

Abstract

− 1 during the intermast period. Almost 100% of sun bear diet consisted of fruit during mast fruiting period, whereas sun bear diet was predomi- nantly insectivorous during intermast periods. The majority of sun bear fruit trees displayed 'mast-fruiting' and 'supra-annual' fruiting patterns, indicating sporadic productivity. Sun bears fed on 115 fruit species covering 54 gen- era and 30 families, with Ficus (Moraceae) being the main fallback fruit. The families Moraceae, Burseraceae, and Myrtaceae contributed more than 50% to the sun bear fruit diet. Sun bear fruit feeding observations were unevenly distributed over forest types with more observations in high-dry forest type despite fewer fruiting events, possibly due to a side-effect of high insect abundance that causes bears to use these areas more intensively. The possible evo- lutionary pathways of sun bears in relation to the Sundaic environment are discussed. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 89 , 489-508. ADDITIONAL KEYWORDS: Borneo - community fruiting - ENSO - fruiting synchrony - lowland dipterocarp forest - mast fruiting - Ursidae.