Activity, diet and food chemistry of two small nocturnal lemurs, Avahi laniger and Lepilemur mustelinus.

Collecting observational data on nocturnal lemurs in the wild is challenging, resulting in limited information on their natural history, ecology, and evolution. Avahi laniger and Lepilemur mustelinus are two small, nocturnal lemurs that appear to defy the rules of folivory (being almost exclusively folivorous despite small body size) and are highly understudied. This research aimed to describe the nutritional ecology of these lemurs to better understand their adaptations to a folivorous diet. We collected eight weeks of behavioural data, including feeding behaviour, in October-December 2020 in Tsinjoarivo, Madagascar. Additionally, we collected thirty-three plant foods, which we observed the two species consuming, for nutritional analyses. Both species were mostly observed resting, a common behavioural adaptation for processing a folivorous diet, but differed in periods of peak feeding behaviour. A. laniger and L. mustelinus had very little dietary overlap: only five of 34 total plant species were consumed by both species and one of these shared foods was the same species, but different parts. The nutritional composition of A. laniger and L. mustelinus' foods were largely similar, but diverged in one nutritional variable: L. mustelinus consumed foods higher in available protein than A. laniger. Both species also approached plant secondary metabolites differently: A. laniger tolerated tannins while as L. mustelinus tended to avoid them. This research, the first nutritional ecology study of Avahi laniger and Lepilemur mustelinus in Tsinjoarivo, is consistent with previous suggestions of niche separation through food chemistry.