Variable Energetic Strategies in Disturbed and Undisturbed Rain Forests: Eulemur rubriventer Fecal Cortisol Levels in South-Eastern Madagascar

Abstract

Habitat disturbance in Madagascar is pervasive. Researchers have assessed anthropogenic impacts on lemurs from alterations in locomotion, behavior, diet, distribution, and density. Such strategies may help lemurs cope with environmental change, but the underlying mechanisms facilitating such flexibility remain poorly understood. To document a physiological response to ecological stress, I investigated stress hormones in wild adult Eulemur rubriventer, the red-bellied lemur, in disturbed and undisturbed rain forests in south-eastern Madagascar over 17 months, from November 2003 to March 2005. My goals were to compile E. rubriventer cortisol excretion profiles, observe E. rubriventer’s response to food fluctuations, and compare these responses among groups in disturbed and undisturbed sites. Fecal glucocorticoid metabolite levels (fGCs) did not differ by sex and were lowest during the prebreeding season when fruit was abundant and highest during parturition and early lactation when fruit was scarce. Though fGC patterns were similar across sites, levels were significantly higher in the undisturbed site, contrary to expectations. fGCs were invariable in the disturbed site, despite lower and less seasonal fruit availability. A severely attenuated response to known ­environmental challenges, coupled with high infant mortality in the disturbed site, indicates that this population may be at risk of decline.