Zebra finches are bolder in an asocial, rather than social, context.

Despite an expanding interest in animal personalities, the influence of social interactions and sex differences on individual differences in behaviour remains poorly understood. Using the social zebra finch (Taeniopygia guttata), we tested for behavioural differences in exploration of a novel environment and objects, between individuals of both sexes in relation to a social context; the presence of three male companions, three female companions or no companion birds. We predicted that the presence of conspecific companions should result in focal birds reacting to novelty by exploring more extensively because the companion birds contribute to anti-predator vigilance behaviour and because social isolation often causes behavioural inhibition in social species. We found that exploratory behaviour of focal individuals was significantly reduced in the presence of conspecific companions, irrespective of the companion's sex. Moreover, we found a weak trend towards females being more exploratory than males, irrespective of the social context. These results demonstrate the importance of considering the social context in animal personality studies and of exploring sex differences in personalities.