Validation of an enzyme immunoassay and comparison of fecal cortisol metabolite levels in black and gold howler monkeys (Alouatta caraya) inhabiting fragmented and continuous areas of the humid Chaco region, Argentina.

CANTARELLI VI; PEREZ RUEDA A; KOWALEWSKI M; MASTROMONACO G; PONZIO M.F.

AMERICAN JOURNAL OF PRIMATOLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2017 vol. 79

0275-2565

In the last years, the study of how environmental stimuli influence the physiology and specificallythe endocrinology of an organism became increasingly important, relying mainly on thequantification of glucocorticoids to monitor animal welfare. Most studies investigating cortisollevels in primates were focused on the impact of social stressors; however, a major concern forthe conservation of howler monkeys is the increased habitat fragmentation led by theadvancement of the agricultural frontier.We compared fecal cortisolmetabolite levels (FGCM) inhowler monkeys (Alouatta caraya) living in fragmented and continuous forests of the ArgentinehumidChaco region, throughout thewarm season (spring-summer). Fecal samples (n = 114) werecollected fromadult individuals, and steroid extracts analyzed with an enzyme immunoassay alsovalidated in this work. Parallel displacement curves were obtained between dilutions of pooledfecal extracts and the cortisol standard curve (r2 = 0.99; P=0.23). Efficiency of the fecalextraction procedure was 79.4%± 38%; recovery of exogenous hormone added to fecal extractsindicated a low interference of components in the feces with antibody binding. The exogenousadministration of ACTH in captive-bred animals demonstrated a ?cause-and-effect? relationshipbetween the adrenal gland activation and increased FGCM levels. Contrary to our initialprediction, we were not able to demonstrate a significant difference in FGCM levels of carayamonkeys inhabiting the continuous versus fragmented habitats in our study site (83.2 ± 4.9 ng/g[n = 10 individuals] vs. 71.5 ± 4.9 ng/g [n = 7 individuals]; P = 0.29); this could be the result of lowlevels of disturbance imposed by a moderate and selective logging, which has proved to bebeneficial for this species with high resilience by adjusting their diet to cope with feeding indegraded habitats but with new leaves and buds. Regardless of the habitat, cortisol metaboliteswere significantly higher in females than in males (86.4 ± 4.2 ng/g [n = 12 individuals] vs.60.7 ± 5.0 ng/g [n = 5 individuals] respectively; P = 0.007).