title: 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.
abstract: In the last years, the study of how environmental stimuli influence the physiology and specifically the endocrinology of an organism became increasingly important, relying mainly on the quantification of glucocorticoids to monitor animal welfare. Most studies investigating cortisol levels in primates were focused on the impact of social stressors; however, a major concern for the conservation of howler monkeys is the increased habitat fragmentation led by the advancement of the agricultural frontier. We compared fecal cortisol metabolite levels (FGCM) in howler monkeys (Alouatta caraya) living in fragmented and continuous forests of the Argentine humid Chaco region, throughout the warm season (spring-summer). Fecal samples (n = 114) were collected from adult individuals, and steroid extracts analyzed with an enzyme immunoassay also validated in this work. Parallel displacement curves were obtained between dilutions of pooled fecal extracts and the cortisol standard curve (r2= 0.99; P = 0.23). Efficiency of the fecal extraction procedure was 79.4% ± 38%; recovery of exogenous hormone added to fecal extracts indicated a low interference of components in the feces with antibody binding. The exogenous administration of ACTH in captive-bred animals demonstrated a "cause-and-effect" relationship between the adrenal gland activation and increased FGCM levels. Contrary to our initial prediction, we were not able to demonstrate a significant difference in FGCM levels of caraya monkeys 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 low levels of disturbance imposed by a moderate and selective logging, which has proved to be beneficial for this species with high resilience by adjusting their diet to cope with feeding in degraded habitats but with new leaves and buds. Regardless of the habitat, cortisol metabolites were 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).
  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. Contrary to our initial prediction, no significant differences in Alouatta caraya fecal cortisol metabolite levels were detected; cortisol metabolites were significantly higher in females. Probably, animals adjusted their diet to cope with feeding in degraded habitats, but with new leaves and buds.
authors.affiliation: INICSA-CONICET and Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Cátedra de Fisiología Humana, Córdoba, Argentina.
authors.forename: Verónica Inés
authors.initials: VI
authors.lastname: Cantarelli
authors.affiliation: Estación Biológica Corrientes, Museo Argentino de Ciencias Naturales-CONICET, Corrientes, Argentina.
authors.forename: Maria Amparo
authors.initials: MA
authors.lastname: Perez-Rueda
authors.affiliation: Estación Biológica Corrientes, Museo Argentino de Ciencias Naturales-CONICET, Corrientes, Argentina.
authors.forename: Martin M
authors.initials: MM
authors.lastname: Kowalewski
authors.affiliation: Reproductive Physiology, Toronto Zoo, Toronto, Ontario, Canada.
authors.forename: Gabriela F
authors.initials: GF
authors.lastname: Mastromonaco
authors.affiliation: INICSA-CONICET and Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Cátedra de Fisiología Humana, Córdoba, Argentina.
authors.forename: Marina Flavia
authors.initials: MF
authors.lastname: Ponzio
mesh_terms: D000508:Alouatta / Q000502:physiology*; D000818:Animals; D001118:Argentina; D004032:Diet; D004777:Environment; D005243:Feces / Q000737:chemistry; D005260:Female; D006854:Hydrocortisone / Q000032:analysis*; D007124:Immunoenzyme Techniques / Q000662:veterinary*; D008297:Male; D012919:Social Behavior
chemical_list: D006854:Hydrocortisone
keywords: caraya; cortisol; feces; fragmentation; glucocorticoids