Fission–fusion dynamics in sheep: the influence of resource distribution and temporal activity patterns

Abstract

Fission–fusion events, i.e. changes to the size and composition of animal social groups, are a mechanism to adjust the social environment in response to short-term changes in the cost–benefit ratio of group living. Furthermore, the time and location of fission–fusion events provide insight into the underlying drivers of these dynamics. Here, we describe a method for identifying group membership over time and for extracting fission–fusion events from animal tracking data. We applied this method to high-resolution GPS data of free-ranging sheep ( Ovis aries ). Group size was highest during times when sheep typically rest (midday and at night), and when anti-predator benefits of grouping are high while costs of competition are low. Consistent with this, fission and fusion frequencies were highest during early morning and late evening, suggesting that social restructuring occurs during periods of high activity. However, fission and fusion events were not more frequent near food patches and water resources when adjusted for overall space use. This suggests a limited role of resource competition. Our results elucidate the dynamics of grouping in response to social and ecological drivers, and we provide a tool for investigating these dynamics in other species.

Heat stress conditions affect the social network structure of free‐ranging sheep

“…Networks with high modularity are characterised by many and strong connections within the group or cluster, while connections between groups are sparser (Tetzlaff et al., 2023 ). Fission–fusion societies, such as sheep (Della Libera et al., 2023 ), are structured into sub‐groups and modularity measures are higher compared to cohesive groups (Sosa et al., 2021 ). If divergent shade use results in greater internal network structure, and stronger subgroup clustering, we would expect higher modularity measures.…”

“…Fission-fusion societies, such as sheep (Della Libera et al, 2023), are structured into sub-groups and modularity measures are higher compared to cohesive groups (Sosa et al, 2021). If divergent shade use results in greater internal network structure, and stronger subgroup clustering, we would expect higher modularity measures.…”

Whole group tracking reveals that relatedness drives consistent subgrouping patterns in white-nosed coatis

“…Given that the frequency of fission-fusion events and the composition of subgroups may vary across the landscape, traditional methods may lead to biases in which subgroups and events are observed. Tracking technologies such as GPS tags offer the potential to monitor the movements of multiple individuals simultaneously (Della Libera et al, 2023; Kays et al, 2015; Strandburg-Peshkin et al, 2015). This approach can give us greater insight into the decision-making processes of group members by allowing us to determine which subgroups individuals choose to join as well as those they reject.…”