• Eulemur collaris
• Faecal glucocorticoids
• food availability
• habitat degradation
• reproductive stages
• stress

This study investigates the relationship between Madagascar’s environment and the stress physiology of the red collared brown lemur, Eulemur collaris. Habitat disturbance in Madagascar is pervasive and lemurs possess many unique traits compared with other primates that are primarily attributed to environmental or nutritional stress. Glucocorticoids (GCs) like cortisol are stress indicators. The assessment of welfare in animals is a developing field of study, and stressors in natural habitat can be estimated by measuring GC metabolites (GCM) in faeces. The littoral forests of southeastern Madagascar are among the most endangered habitats in the world and Eulemur collaris is well adapted to survive in these forests. The red collared brown lemur is a mostly frugivorous and cathemeral lemur with an extraordinary ecological flexibility that allows it to tolerate a certain degree of habitat changes. The goal of this study was to assess whether the health state measured by GCM levels of animals which living in a degraded habitat is comparatively different than the state of con-specific individuals living in a more pristine area. For this we compared faecal GCM levels in wild adults Eulemur collaris in a degraded (Mandena) and an intact littoral forest (Sainte Luce) in South-eastern Madagascar over a one year period (February 2011- January 2012). We analysed how GCM levels varied among reproductive stages and phenological seasons, using forest degradation, rank and sex as covariates. In general, lemurs at Mandena were more stressed than lemurs at Sainte Luce. Lemurs showed higher GCM levels during the mating season, followed by gestation season, lactation season and the non-reproductive season. We found that females at Mandena were more stressed than females at Sainte Luce during the gestation season. In relation to phenological seasons, individuals at Mandena were significantly more stressed than individuals at Sainte Luce, and lemurs at Mandena were more stressed during the lean season than lemurs at Sainte Luce. This study found no rank-related GCM levels. These results showed, as predicted, that lemurs in a degraded habitat are more stressed and this has important implications for future conservation plans. Eulemur collaris is the largest frugivorous primate present in the littoral forest and is an important seed disperser, its presence is of vital importance for the forest per se. Due to its role of seed disperser, protecting this lemur species also means helping regeneration of degraded habitats.