Department of Anthropology, University of Colorado Boulder
March 28, 2015 , Gateway Ballroom 2/3/4/5
Lemur life histories are significantly influenced by environmental change and climatic events, such as drought and cyclone which impact food resources, birth and mortality rates. The measurement of cortisol in hair, time-averaged over the period of hair growth, offers a method to investigate the interaction between broad-scale environmental patterns and stress physiology. We compared hair cortisol profiles of wild ring-tailed lemurs exposed to unexpected environmental events, and considered age effects. Tail hair samples (N=250) were collected from 15 troops across seven sample years with varied precipitation: normal, drought, cyclone, and post-cyclone. We predicted higher cortisol in troops during drought, cyclone, and post-cyclone years and in subadults compared to older age groups. Using previously validated enzyme immunoassay protocols, we measured hair cortisol and determined significant differences among troops, sexes, and age groups using Kruskal-Wallis nonparametric tests with Student’s t post hoc test. As expected, subadult cortisol levels were significantly higher than other age groups (subadults> adults, p=0.007; subadults>young adults, p=0.0028). Cortisol levels in adults were greater during drought compared to post-cyclone (p=.041) and normal years (p=.015); however, individuals sampled in cyclone and post-cyclone years had the lowest cortisol levels. Two troops had higher hair cortisol concentrations than other troops, possibly linked to anthropogenic disturbance. Our results suggest hair cortisol levels may reflect climatic effects on intragroup competition, anthropogenic disturbances, and high levels of predation.
Lindbergh Fund, The Saint Louis Zoo, The John Ball Zoo Society, The National Geographic Society, and the University of Colorado, Boulder.