Female Marmosets' Behavioral and Hormonal Responses to Unfamiliar Intruders
ABSTRACT The endocrine control mechanisms for female mammalian aggression have been largely unstudied. Although it has been proposed that androgens may modulate female aggressive behavior in a similar manner to males, very little conclusive evidence exists. Previous work in male marmosets found that post-encounter increases in testosterone (T) were dependent on the intensity of aggression displayed during the aggressive encounter. We exposed female marmosets (Callithrix kuhlii), a monogamous and biparental primate, to aggressive interactions with unfamiliar intruders. Individual female marmosets exhibited changes in T and estradiol (E(2) ) that are associated with aggressiveness dependent on the intensity of aggression displayed as well as their role during the encounter. Resident females exhibited increased E(2) immediately following an encounter in which they displayed high rates of aggression. If resident females received high rates of aggression from the intruder, the resident displayed increased T 24 hr following the encounter. Interestingly, if the female was an intruder in the encounter, the intensity of her aggression was associated with increased cortisol immediately following the trials, whereas received aggression was associated with increased T and E(2) immediately following the trial. Female primates do exhibit situation-dependent changes in gonadal steroids in association with aggression that may serve to prime them for future aggressive interactions.
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ABSTRACT: Dimorphism on dominance and agonistic behaviour in mammals tends to be strongly biased toward males. In this review, we focus on a select few species of mammals in which females are as or more aggressive than males, and/or are dominant to males, and explore the role of androgenic hormones in mediating this important difference. While the data are not as clear-cut as those published on traditional laboratory mammals, our review highlights important endocrine substrates for both organizational and activational influences of steroids on female aggressive behaviour. We highlight areas in which further observations and experiments are crucial, especially the potential facilitative effects of androgens on female aggression. Finally, new and innovative techniques, including molecular genetics and receptor pharmacology, portend important insights into the ways in which androgenic hormones regulate aggressive behaviour in 'atypical' female mammals.Philosophical Transactions of The Royal Society B Biological Sciences 01/2013; 368(1631):20130084. DOI:10.1098/rstb.2013.0084 · 6.31 Impact Factor
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ABSTRACT: Testosterone is a key hormone for the development of secondary sexual characters and dimorphisms in behavior and morphology of male vertebrates. Because females often express detectable levels of testosterone, testosterone has been suggested to also play a role in the modulation of secondary sexual traits in females. Previous comparative analyses in birds and fish demonstrated a relationship between male-to-female testosterone ratios and the degree of sexual dimorphism. Furthermore, female maximum testosterone was related to mating system and coloniality. Here, we reevaluate these previous ideas using phylogenetic analyses and effect size measures for the relationship between birds’ male-to-female maximum testosterone levels. Further, we investigate the seasonal androgen response of female birds (the difference from baseline to maximum testosterone), which in males is strongly related to mating system. We could not confirm a relationship between male-to-female testosterone, maximum female testosterone, or the seasonal androgen response of females with any life-history parameter. We conclude that the expectation that testosterone regulates traits in females in a similar manner as in males should be reconsidered. This expectation may be partially due to hormone manipulation studies using pharmacological doses of testosterone that had similar effects in females than in males but may be of limited importance for the physiological range of testosterone concentrations occurring within ecological and evolutionary contexts. Thus, the assumption that circulating testosterone should covary with ecologically relevant secondary sexual traits in females may be misleading: selection pressures on females differ from those on males and females may regulate behavior differently.Behavioral Ecology 04/2014; 25(4):685-699. DOI:10.1093/beheco/aru019 · 3.16 Impact Factor
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ABSTRACT: The aim of this investigation was to study the welfare of 3 captive groups of cotton-top tamarins housed in different zoological parks. Ethological observations were conducted during 1 year. In addition, fecal samples were collected and the concentrations of glucocorticoids, androgens, and progestogens were measured. Within each group, no significant differences in fecal cortisol concentrations were found between subjects. The fecal concentrations of testosterone and progesterone significantly differed depending on the sexes and ages of the tamarins. A significant association was found among hormone concentrations, exhibit dimensions, and group composition. A highly significant correlation was found between all hormones considered and the space available for each subject. Significant differences in behavioral patterns were observed among groups, including social-individual, affiliative-aggressive, and anogenital-suprapubic scent marking. Correlations between hormone measurements and behaviors were detected. In conclusion, this study confirmed the associations between some behaviors exhibited by these nonhuman primates and both cortisol and testosterone; these data also highlight the role played by progesterone in these behaviors.Journal of Applied Animal Welfare Science 05/2014; DOI:10.1080/10888705.2014.916173 · 0.69 Impact Factor