No abstract

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.

Because of poor reproduction after the lifting of an 8-year breeding moratorium, a biomedical survey of female lions in U.S. zoos was initiated in 2007. Fecal estrogen (FEM), progestagen (FPM) and glucocorticoid (FGM) metabolites were analyzed in samples collected 3–4 times per wk from 28 lions at 17 facilities (0.9–13.8 yr of age) for 4 mo—3.5 yr and body weights were obtained ~monthly from 17 animals at eight facilities (0.0–3.0 yr of age). Based on FEM, estrous cycle length averaged 17.5 ± 0.4 d in duration, with estrus lasting 4.4 ± 0.2 d. All but one female exhibited waves of estrogenic activity indicative of follicular activity; however, not all females expressed estrous behaviors (73%), suggesting silent estrus was common. Female lions experienced puberty earlier than expected; waves of estrogenic activity were observed as young as 1.1 yr of age, which may be related to a faster growth rate of captive vs. wild lions. Mean gestation length was 109.5 ± 1.0 d, whereas the non-pregnant luteal phase was less than half (46.0 ± 1.2 d). Non-mating induced increases in FPM were observed in 33% of females housed without a male, consistent with spontaneous ovulation. A number of study animals had been contracepted, and the return to cyclicity after treatment withdrawal, while variable, was ~4.0 yr and longer than the 1-yr expected efficacy, especially for those implanted with Suprelorin. For FGM, there were no differences in overall, baseline or peak mean concentrations among the age groups or across seasons, nor were there any relationships between reproductive parameters and FGM concentrations. Overall, results suggest that poor reproduction in lions after the breeding moratorium was not related to altered adrenal or ovarian steroid activity, but for some females may have been a consequence of individual institutions’ management decisions.