Behavioral synchrony in ibex groups: Effects of age, sex and habitat

Synchrony of activities is usually high in foraging groups, possibly to mai ntain group cohesion. Individuals with different levels of activity budgets , however, may have a hard time synchronizing their behavior to each other without incurring a cost. We predicted that the age and sex structure of a group would affect synchronization levels within a group because of differi ng individual activity budgets. Individuals in same-sex-age groups were hyp othesized to show higher levels of activity synchrony than individuals in m ixed sex-age groups. We investigated activity synchrony in adult mate, adul t female, subadult, and mixed sex-age groups of Alpine ibex - one of the mo st sexually dimorphic ruminant species. Activity budgets and movement rates were measured to calculate synchrony of activities between group members i n June and July 1999. Adult males were more synchronized with group peers t han either females or subadults of both sexes. However, while adult males w ere synchronized in 81 % when in bachelor (adult mate) groups, they were on ly synchronized in 65% of the time when in mixed sex-age groups. Adult fema les were synchronized 61% of their time when in mixed sex-age groups and 69 % when in female groups. Individual subadult males displayed higher synchro ny when in bachelor or female groups than when in mixed sex-age or subadult mixed-sex groups. Subadult groups and mixed sex-age groups showed the lowe st degree of synchrony of all group types. In general, animals in groups of same body-sized individuals were more synchronized with their group member s than animals in mixed body-size groups. Two and three year-old males did not adjust their time spent lying to the group but their time spent walking , They also tended to change their time spent grazing and standing accordin g to group type. Among subadults, females spent more time foraging than mal es but less time lying and standing. There was no difference in time spent walking. Bachelor and subadult groups had the greatest movement rates while female groups were relatively sedentary within escape terrain. Individuals in escape terrain did only marginally synchronize their behavior to each o ther likely because groups did not move much and synchrony was presumably l ess important. We conclude that habitat type, group movement rates, and a g roup's sex-age composition may affect the extent to which an individual wil l synchronize its activities to the other group members.