Social dynamics and the cortisol response to immobilization stress of the African wild dog, Lycaon pictus.

The aims of the study were to characterize the cortisol response to immobilization stress in African wild dogs (Lycaon pictus) and to investigate the relationship between stress and sociality in these pack-living canids. Ad lib. observations were made on a captive pack of 19 wild dogs. Individuals were classified as either dominant or subordinate. Cardinal and ordinal dominance indices were also calculated for pack members, as were three other behavioral indices. Active and passive dominance styles were distinguished. Serial blood samples were drawn from animals after chemical immobilization and again after ACTH challenge. The relationship among rank, plasma cortisol concentration, and behavioral style was investigated. When data were combined over the entire study period, there was no obvious relationship between rank and cortisol concentrations or cortisol responsiveness to immobilization stress. Instead, younger animals had higher cortisol concentrations than older ones. Age cohorts were also clearly separated on the basis of behavioral profiles. For males, these distinctions among age classes were especially apparent during the second part of the study period, when subadults occupied dominant positions in the hierarchy. Adult males maintained relatively low cortisol concentrations, despite being involved in and losing a high proportion of dominance interactions. Age-related differences in cortisol profiles of dominant individuals may be explained by differences in the style of dominance employed, with younger males using proportionately more active dominance (threats used to elicit submission). The separation of age classes according to rank, behavioral styles, and cortisol concentrations may reflect improved social skillfulness with age.