In female degus, reunions are less variable when relationships are new

Abstract When establishing new peer relationships, animals may explore different modes of interaction, testing-out dominance roles, reciprocation of affiliation, and responses to investigation. This exploration is potentially risky, as higher variability may be counterproductive to establishing expectations and trust. There is therefore a tradeoff between exploration within a new social relationship and maintaining predictable, ‘safe’ behaviours, raising questions about how animals differ in how they engage with strangers. The Chilean degu offers an opportune case study to investigate novel social situations, as females form relationships relatively rapidly with unrelated peers. We presented degu dyads with a series of 20 min ‘reunion’ sessions and found that session-to-session variability in stranger females is, in fact, lower than in cagemates, and lower than stranger or cagemate males. Reduced variability was observed only after an initial social exposure, suggesting it was a feature of new relationships rather than novelty. There was no evidence that groups differed in predictability of behaviours within a reunion. It is known that in the wild, female degus differ from males by readily forming cooperative relationships with unrelated individuals. The data therefore raise the possibility that animals predisposed to cooperation might also show reduced behavioural variability across encounters with new individuals. This work offers new results and methods for considering strategies animals use to cope with social uncertainty.