Zeitschriftenartikel
Influence of reproductive season and rank on fecal glucocorticoid levels in
free-ranging male Verreaux´s sifakas (Propithecus verreauxi)
Fichtel, C., Kraus, C., Ganswindt, A., Heistermann, M.
Hormones and Behavior, 51:5, 640–648 (2007)
Abstract
Studies in anthropoid primates and other mammals suggest that reproductive season, rank, reproductive skew, aggression received, and social
support are the major factors influencing glucocorticoid output. In which way these are also affecting adrenal function in lemurid primates has
been studied rarely. Here, we examine the influence of reproductive season and rank on glucocorticoid output in male sifakas (Propithecus
verreauxi), a species characterized by high breeding seasonality, a hierarchy among males and extreme reproductive skew towards dominant
males. We established a fecal assay for non-invasively monitoring adrenal activity and collected 315 fecal samples during the reproductive and
birth season from 10 male sifakas living in 5 groups in Western Madagascar. We found a significant effect of season on glucocorticoid output, with
males exhibiting higher fecal glucocorticoid levels during the reproductive compared to the birth season in conjunction with an increase in overall
aggression rates during the former period. Moreover, our data indicate a significant effect of rank on adrenocortical activity with dominant males
exhibiting higher glucocorticoid levels than subordinate males in the reproductive season. However, dominant males did not differ significantly in
rates of initiated or received aggression and rates of affiliative behavior from subordinates but showed significantly lower rates of submission.
Given their highly formalized dominance relationships, we conclude that higher glucocorticoid output in dominant males during the 4-month
reproductive season is likely related to higher energetic demands necessary to cope with the challenges of male reproduction rather than to
physical demands of increased fighting frequency to maintain dominance status. High rank in sifakas may thus carry high costs, which, however,
may be outweighed by monopolization of almost all paternities. In sum, our data generally support the findings on the relationship between
environmental and social factors and glucocorticoid output found in non-lemurid primates.