The behavioral endocrinology of domestication: A comparison between the domestic guinea pig (Cavia aperea f. porcellus) and its wild ancestor, the cavy (Cavia aperea)

In this study spontaneous behavior and endocrine parameters were compared b etween the domestic guinea pig (Cavia aperea f. porcellus) and its wild anc estor, the cavy (Cavia aperea), to elucidate the process of domestication i n this species. In 120 h of observation time the behavior of five groups of wild and seven groups of domestic guinea pigs, each consisting of one adul t male and two adult females, was analyzed quantitatively. To assess the ac tivities of the pituitary-adrenocortical (PAC), the pituitary-gonadal (PG), and the sympathetic-adrenomedullary (SAM) systems, serum cortisol, testost erone, epinephrine, and norepinephrine concentrations, as well as adrenal t yrosine hydroxylase activities, were determined in males of both forms. The following significant differences between wild cavies and domestic guinea pigs were found: the domesticated animals displayed less aggressive but mor e sociopositive and more male courtship behavior than their wild ancestors. In addition, they were distinctly less attentive to their physical environ ment than the wild cavies. The basal activity of the SAM system, as well as the reactivity of the SAM and the PAC systems, was distinctly reduced in t he domesticated animals. In contrast, the basal activity of the PAC system did not differ between both forms. The activity of the PG system was signif icantly higher in males of the domestic guinea pig than in male wild cavies . Thus, in guinea pigs the process of domestication has led to typical beha vioral traits-reduced aggressiveness, increased social tolerance-which have also been found in comparisons between wild and domestic forms of other sp ecies. The decreased reactivity of the organism's stress axes can be regard ed as a physiological mechanism which helps domesticated animals to adjust to man-made housing conditions. (C) 1999 Academic Press.