Large Lemurs: Ecological, Demographic and Environmental Risk Factors for Weight Gain in Captivity

SIMPLE SUMMARY: Excessive body mass, i.e., being overweight or obese, is a health concern. Some lemur species are prone to extreme weight gain in captivity, yet for others a healthy body condition is typical. The first aim of our study was to examine possible ecological explanations for these species’ differences in susceptibility to captive weight gain across 13 lemur species. Our second aim was to explore demographic and environmental risk factors across individuals from the four best-sampled species. We found a potential ecological explanation for susceptibility to captive weight gain: being adapted to unpredictable wild food resources. Additionally, we also revealed one environmental and four demographic risk factors, e.g., increasing age and, for males, being housed with only fixed climbing structures. Our results indicate targeted practical ways to help address weight issues in affected animals, e.g., by highlighting at-risk species for whom extra care should be taken when designing diets; and by providing a mixture of flexible and fixed climbing structures within enclosures. ABSTRACT: Excessive body mass, i.e., being overweight or obese, is a health concern associated with issues such as reduced fertility and lifespan. Some lemur species are prone to extreme weight gain in captivity, yet others are not. To better understand species- and individual-level effects on susceptibility to captive weight gain, we use two complementary methods: phylogenetic comparative methods to examine ecological explanations for susceptibility to weight gain across species, and epidemiological approaches to examine demographic and environment effects within species. Data on body masses and living conditions were collected using a survey, yielding useable data on 675 lemurs representing 13 species from 96 collections worldwide. Data on species-typical wild ecology for comparative analyses came from published literature and climate databases. We uncovered one potential ecological risk factor: species adapted to greater wild food resource unpredictability tended to be more prone to weight gain. Our epidemiological analyses on the four best-sampled species revealed four demographic and one environmental risk factors, e.g., for males, being housed with only fixed climbing structures. We make practical recommendations to help address weight concerns, and describe future research including ways to validate the proxy we used to infer body condition.