Relationships between steroid hormones in hair and social behaviour in ring-tailed lemurs (Lemur catta)
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Relationships between the hypothalamic-pituitary adrenal and hypothalamic-pituitary gonadal axes and social behaviour in primates are complex. By using hair to quantify steroid hormones, one can obtain retrospective estimates of long-term free hormone levels from a single sample. In this study, hair was used to quantify long-term levels of cortisol, testosterone, and estradiol among members of a colony of ring-tailed lemurs (Lemur catta) to explore associations between intra- and intersexual levels of these hormones and social behaviour between the breeding and birthing seasons. Positive trends between hair cortisol and rates of receiving aggression approached significance for males and females after controlling for age. While there was no relationship between sex steroid concentrations and intrasexual social interactions, high rates of aggression in females over the study period coincided with females exhibiting the same average concentrations of testosterone as males. We, therefore, conclude that being the recipient of aggression might be more stressful than being aggressive in ring-tailed lemurs, and that testosterone potentially mediates female dominance in this species. We suggest that further investigation of hair hormones and behaviour in additional primate species could provide a useful comparative framework to guide interpretation of these novel findings.
KeywordsDominance Hormone Aggression Primate Cortisol Sex steroids
We thank M. Schillaci, J. Parga, M. Silcox, J. Teichroeb, and two anonymous reviewers for providing helpful comments on this manuscript. Thanks to E. Ehmke and all of the staff at the Duke Lemur Center for assistance with carrying out research. This research was funded by the University of Toronto, an American Society of Primatologists Small Research Grant, and a Natural Sciences and Engineering Research Council of Canada Postgraduate Scholarship to E.M.T.
Compliance with ethical standards
All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. Research protocols were approved by the Institutional Animal Care and Use Committee (IACUC) of Duke University (protocol #A134-14-05) and the Local Animal Care Committee (LACC) of the University of Toronto Scarborough Campus (protocol #20010916).
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