Time budgets and synchrony of activities in muskoxen: the influence of sex, age, and season

Synchrony of activities and time budgets of age-sex classes of muskoxen (Ovibos moschatus) was studied on Victoria Island in the Canadian High Arctic during late winter (April - late May), spring (late May - early June) and summer (mid-June - July). As revealed by the kappa (kappa) coefficient of agreement, herd members exhibited significant synchrony in 79 of 82 groups. The degree of synchrony was not related to group size in mixed herds but decreased with group size in bachelor herds. Diversity in age-sex classes, group type (mixed versus bachelor), and season did not affect synchrony. However, synchrony was less among adult males than among other age-sex classes. Muskoxen were more synchronised at the start of activity bouts than at the end. As revealed by principal components analysis, calves tended to spend more time lying and standing and less time feeding than other age-sex classes. In addition, males in bachelor groups tended to feed more and rest less than males in mixed herds. Duration of active and lying bouts was not affected by age-sex class. Length of active bouts did not change with season, but lying bouts decreased in length significantly from late winter to spring and from spring to summer. We suggest that synchrony of activities maintains group cohesion but constrains the time budget of some group members, especially adult males.