Time budgets and behavioural synchronization in aggregated and isolated male and female mice

Albino mice (Mus musculus ), initially housed in single sex groups and, subsequently, in social isolation, were used in this study to analyze the influence of social companions on the amount and on the distribution throughout the day of several behaviours. An observational recording technique was employed to record behaviour during the dark phase of the day. Behavioural sex differences in grouped mice were observed in four out of six behavioural categories. Females generally proved to be more active than males. Furthermore, prolonged social housing conditions resulted in an increase in male social interactions, in concomitance with changes in their time budgets. Conversely, females showed a decrease over time in social interactions with only slight effects on their time budget. Isolation seemed to increase slightly both male and female activity levels. Subjects housed together generally showed significantly similar Rest, Feed and General Activity patterns throughout the dark phase of the day. By contrast, the averaged patterns of different groups generally proved to be dissimilar in grouped females, but not in grouped males. When isolated, mice showed a distribution of their activities throughout the day different from what they had displayed under social conditions. These data indicate that social environment has an effect on the individual activity profiles which results in a definite synchronization within female groups and in a tendency towards desynchronization within male groups.