Environmental Correlates of Body Mass in True Lemurs (Eulemur spp.)

Abstract

An organism’s body size is intrinsically related to its metabolic requirements, life history profile, and ecological niche. Previous work in primates generally, and lemurs specifically, has shown that body size often correlates with ecological parameters related to temperature and energy availability in the environment, although other studies indicate the absence of any such patterns in lemurs. Here we test hypotheses that predict that body mass in Eulemur should covary with 1) overall food availability or resource seasonality and/or 2) temperature, i.e., Bergmann’s rule. We use data from 722 wild true lemurs to identify population-specific body mass for 27 populations representing 11 of the 12 described Eulemur species, and derive climatic data for each population from the WorldClim database. We use phylogenetic generalized least squares models to evaluate these hypotheses and find that body mass significantly negatively correlates with annual mean temperature and positively correlates with standard deviation of temperature, but does not significantly correlate with annual rainfall or number of dry months. These results indicate that body mass distribution across populations in Eulemur is consistent with Bergmann’s rule, but does not track resource seasonality as seen in other lemurs, e.g., Propithecus. We suggest that the fact that body mass in various lemur radiations correlates with different environmental variables may result in these patterns being obscured when such taxa are combined in a single analysis. This may help explain why some previous work has found little evidence of ecogeographical correlates with body mass across all Lemuriformes.