Sex-specific difference in social support--a study in female guinea pigs.

In challenging situations, the male guinea pig's hormonal stress responses can be ameliorated by the presence of his female bonding partner. Such social support cannot be provided, however, by a female with whom the male is familiar but has no social ties. In this study, we investigated whether the same phenomenon also accounts for female guinea pigs. First, the spontaneous behaviour of 14 females was recorded in their home colonies to determine their male bonding partners. Then, a so-called challenge test was conducted with 22 females: they were placed into an unknown enclosure for 4 h either alone (n=8), or together with their bonding partner (n=7) or with a familiar male from the same colony, who was not their bonding partner (n=7). Immediately before as well as 1, 2 and 4 h after the beginning of the challenge test, blood samples were taken to determine cortisol levels (CORT). Further on, the behaviour was recorded during the first 2 h of the challenge test. Placing a female guinea pig into an unknown enclosure led to significantly increased CORT independently of whether she was tested alone or with a social partner. However, females that were tested together with their bonding partner showed significantly lower CORT than females tested alone. In females who were tested with a familiar male CORT was in between. The behaviour during the challenge tests reflected the magnitude of the stress response. Thus, also in female guinea pigs social support can be provided by social partners. In contrast to males, however, not only the bonding partner is able to reduce the female's stress responses, but also a familiar conspecific, though in a less effective way.