Variability of social interactions in new versus established relationships in female degus

When an organism explores a new environment or stimulus it varies its behavior to ensure proper sampling. As contingencies are learned, variance can give-way to routines and stereotypies. This phenomenon is common across species but has not been well studied in the social domain, in which the stimulus an animal investigates, another individual, may react negatively to unexpected behaviors. Here we investigate the effects of social familiarity on interaction variability in degus, female members of which are predisposed to form relationships with new, same-sex individuals. Degus were presented with a series of 20 minute, dyadic "reunion" sessions across days, interleaving exposures to familiar and unfamiliar same-sex conspecifics. We found that session-to-session variability in males was higher between strangers compared with cagemates, suggesting males may establish relationships by testing different social roles. In contrast, following an initial exposure, female strangers showed lower session-to-session change compared with cagemates, potentially establishing new relationships by maintaining behavioral norms. Social novelty did not appear to affect variability of interaction timing within a session. Given ecological pressures on female degus to form large, stable social networks, the data are consistent with the notion that higher behavioral variability across encounters is maladaptive for establishing cooperative peer relationships.