Sex, stress and social status: Patterns in fecal testosterone and glucocorticoid metabolites in male Ethiopian wolves.
ABSTRACT Ethiopian wolves, Canis simensis, live in large multi-male family packs, where males are philopatric and do not disperse. Within a pack, mating and breeding is largely monopolized by the dominant male and female, although extra-pack copulations are common, and subordinate males may sire pups in neighboring packs. Regardless of paternity, all males in a pack help rear the pups. We non-invasively studied patterns in fecal testosterone and glucocorticoid metabolite concentrations using radioimmunoassays of fecal samples collected from nine wild male Ethiopian wolves between August 2007 and February 2008. We tested the predictions of the Challenge Hypothesis, namely that fecal testosterone metabolite concentrations would be higher during the annual mating season, which is the portion of the reproductive cycle when mating and increased aggression typically occur, and lower when there were pups in the pack for which to care. Contrary to the predictions of the Challenge Hypothesis, we did not detect patterns in fecal testosterone metabolite concentrations associated with reproductive stage during our study period. Similarly, we found no patterns associated with reproductive stage in male fecal glucocorticoid metabolite concentrations. Dominant males had higher average fecal testosterone and glucocorticoid metabolite concentrations than did subordinates, which may be related to higher rates of aggression and mate guarding in dominant males of group-living canids, a pattern also reported in African wild dogs, Lycaon pictus.
- SourceAvailable from: Jane Martia PackardBiology of Reproduction 01/1980; 21(5):1057-66. · 4.03 Impact Factor
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ABSTRACT: Alpha male rats from mixed sex colony groups were tested for aggressiveness toward nonaggressive male intruders. Afterward, they were castrated and implanted with testosterone filled Silastic tubes, castrated and implanted with empty tubes, or sham castrated and implanted with empty tubes. There were significant declines in the aggressiveness (lateral attacks, bites, and piloerection but not on-top) of castrated rats without testosterone replacement but not in castrated rats with testosterone replacement. At a second operation, castrated animals had their testosterone capsules removed or had their empty capsules replaced with testosterone filled capsules. When tested for aggression toward nonaggressive intruders, those alpha males which had testosterone removed declined in aggressiveness while those which had it implanted returned to a level of aggressiveness close to that emitted by sham castrated control animals. Subordinate males became dominant when alpha males were castrated and not given testosterone replacement. In a final series of observations, sham castrated males were found to be more aggressive than castrated males when pitted against one another. It is argued that testosterone plays a primary role in intermale social aggression and that the decline in aggressiveness following castration is typically accompanied by a loss of social dominance.Physiology & Behavior 02/1986; 36(3):401-7. · 3.16 Impact Factor
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ABSTRACT: Male CFW mice that had been isolated since weaning were placed in groups of four for six hours and 24 hours and observed for the development of aggressive behavior patterns and dominance hierarchies. Control animals were maintained in individual cages. At the end of the grouping period the animals were sacrificed by decapitation and plasma corticosterone levels and adrenal weight recorded.There was a distinct relation between position in a dominance hierarchy and plasma corticosterone levels with dominant animals having significantly lower levels than subordinate ones. Thus these data corroborate the findings of earlier workers who used indirect criteria for adrenocortical activity. The results further support the hypothesis that the psychological factor of defeat after fighting is important in eliciting adrenocortical activity. Thus subordinate mice were frequently defeated and chased resulting in a high frequency of wounding on the tail and rump. Dominant animals, on the other hand, were not frequently defeated and showed very few injuries to the tail and rump.General and Comparative Endocrinology 07/1967; 8(3):441-4. · 2.82 Impact Factor