Seasonal changes in dietary compositions of the Malayan flying lemur ( Galeopterus variegatus ) with reference to food availability

Flying lemurs are able to glide using a thin membrane of skin (patagium) connected to their limbs, body, and part of tails. The Malayan flying lemur ( Galeopterus variegatus ) is endemic to Southeast Asia. Previous information on food habits of this species has been anecdotal, and few studies on their dietary composition have been conducted. From the information of sibling species, we predicted that the Malayan flying lemurs to be folivorous. We firstly tried a quantitative analysis of the dietary compositions of the Malayan flying lemurs together with food availability in West Java, Indonesia, throughout the year. The Malayan flying lemurs seasonally changed foods: leaves from December to July largely overlapping with the rainy season (October–June) and fruits from August to November largely overlapping with the dry season (July–September). When fruits were abundant, the proportions of fruits in the feces increased while proportions of leaves in the feces decreased, or the flying lemur shifted their foods from leaves to fruits. In this period, tree leaves were abundant, which did not explain the decrease in the feces. This implies that the flying lemurs fed on tree leaves in the majority of the year but they shifted to fruits when they were abundant though leaves were also abundant. The abrupt changes in the dietary composition of the flying lemurs were different from those of the sympatric folivorous primate, Javan lutung ( Trachypithecus auratus ), for which dietary composition showed a gradual change from leaves to fruits. Such inter-specific differences would be caused by differences in body sizes and/or digestive physiology.