The relations between stress, social rank, personality, and cognitive performance in Yucatan minipigs (Sus scrofa)

Abstract

Individuals differ consistently in their behavioural and hormonal responses to environmental challenges, and these differences can impact cognitive ability. In gregarious species, individual differences in personality, stress hormone concentrations, and cognitive performance can correlate with social rank, although studies have yielded conflicting results on the relations among these variables. Using 10 male and 10 female Yucatan minipigs (Sus scrofa), we aimed to: (1) explore the potential for inter-individual consistency in behavioural and hormonal traits; and (2) characterize the relations among personality, social rank, the stress response, and cognitive performance on an object location memory task. We found that pigs varied along two personality dimensions, labeled curiosity and timidity. Some stress hormone biomarkers were repeatable in males, but not females. The sexes also differed in activity of the two major stress systems, with females showing a greater asymmetry between HPA axis and sympathetic nervous system activity, symptomatic of chronic stress. Application of an acute stressor immediately before the object location memory task impaired subsequent performance, but only in the males. Finally, the effect of timidity on object location memory differed between the sexes, with performance tending to be better among less timid males and more timid females. The plethora of sex differences in our study suggests that results from one sex cannot be generalized to the other and underscores the necessity of considering both sexes in behavioural and physiological studies.