Pregnant female guinea pigs adapt easily to a new social environment irrespective of their rearing conditions.

For male guinea pigs, the social rearing conditions are crucial for the course of social interactions and endocrine stress responses in later life. While colony-reared males adjust easily to new social situations, high levels of aggression and extreme endocrine responses are found in males that were raised in pairs [Psychoneuroendocrinology 23 (1998) 891]. This study investigated whether the same finding also applies to females. Therefore, 8 females reared in mixed-sexed colonies of 8-10 males and 12-13 females (designated as CF) and 8 females reared in mixed-sexed pairs (designated as PF) were transferred to an unknown colony for 3 days. Control females remained in their respective housing conditions. Serum cortisol concentrations (CORT) were determined before, during and after the transfer. The behavior of the CF and PF was recorded on the first, second and third day of transfer. All females adjusted easily to the new social situation, but frequencies of some behavioral patterns were significantly different between CF and PF. In the new social situation, PF displayed social orientation as well as defensive aggressive and avoidance behavior more frequently than CF. On the day of transfer, resident males displayed courtship behavior more frequently towards PF than CF. CORT did not differ between PF and CF either before, during or after the transfer. Furthermore, the transfer to the new social situation did not result in significantly increased CORT 4 h later either in CF or PF. We conclude that-in contrast to male guinea pigs-females are able to adapt to unfamiliar conspecifics independently of their social rearing conditions.