The effect of extreme weather events on hair cortisol and body weight in a wild ring-tailed lemur population (Lemur catta) in southwestern Madagascar

Madagascar is known for its hypervariable climate with periodic droughts and cyclones, but little is known of the impact of such events on lemur physiology. We examined the effects of sequential weather periods, drought, normal, cyclone and post-cyclone, on hair cortisol concentrations (HCC) and body weight in wild ring-tailed lemurs, Lemur catta (n=185), at the Beza Mahafaly Special Reserve in southwestern Madagascar. Data were modeled and analyzed by sex, age, and troop. Given the ecological consequences of extreme climatic perturbations, we hypothesized that drought and cyclone would significantly impact lemur HCC. Among adults, drought was associated with higher HCC than other periods and the lowest HCC was associated with the post-cyclone period. Adult females had greater variation in HCC during drought and males had greater variation during cyclone and Post-cyclone periods, suggesting sexes were differentially affected in terms of how individuals responded to extreme weather events. Low HCC in the post-cyclone period followed a 12-month period of reduced availability of primary and fallback food resources. Based on the known extreme and chronic nutritional stress during this time, our results indicate hypocortisolism in the animals included in our analysis. Higher HCC in sub-adults during the cyclone also suggests that immature lemurs may experience extreme weather events differently than adults. Body weight, used as a gauge for environmental stress, was lowest during the post-cyclone for sub-adults, young adults, and adults. Body weight did not differ by sex among adults across any of the weather events. Overall, ring-tailed lemur's HCC appear to be more immediately impacted by drought, or stressors associated with that specific weather event, and influenced by the long-term impact of cyclones on resource availability evidenced by data from the post-cyclone period.