Thermal and morphometric correlates of the extremely low rate of energy use in a wild frugivorous primate, the Mayotte lemur

Abstract Primates spend on average half as much energy as other placental mammals while expressing a wide range of lifestyles. However, little is known about how primates adapt their rate of energy use in the context of natural environmental variations, particularly at the individual level. Moreover, measurements of total energy expenditure (TEE) in wild primates are currently available for only seven species. Using doubly labelled water, behavioral and accelerometric methods, we show that the TEE of Eulemur fulvus, a medium-sized cathemeral primate with a fruit-based diet, is one of the lowest recorded to date in eutherians. Regression models show that individual variation in the rate of energy use is predicted by a few morphometric characteristics and climatic factors. The TEE increases considerably with increasing temperature, suggesting that thermoregulation is an important component of the energy budget. The mass-specific TEE measured in an anthropogenic environment is only 10% lower than that of a closely related species previously studied in a gallery forest, consistent with the assertion that TEE varies within narrow physiological limits. As lemur communities include many species with unique thermoregulatory adaptations, circadian or seasonal temperature variations may have constituted a major selective pressure on the evolution of lemur metabolic strategy.