The role of space availability and affiliation in shaping equine social distances and dynamics

Horses confined to enclosures with limited opportunities for spatial avoidance and escape experience heightened social stress and conflict. While forced proximity can pose welfare risks, voluntary social proximity is considered a positive indicator of well-being. To investigate the effects of space availability on spatiotemporal dynamics, social network structure and agonistic interactions, this study used ultra-wideband sensors to continuously (1 Hz) measure interindividual distances in 34 horses across three groups under paddock and field conditions. Interindividual distances increased in larger enclosures (paddock: median 8.3 m, field: 19 m), but closest associates remained nearer to each other than other dyads (paddock: 3.6 m vs. 8.3 m, field: 13.6 m vs. 19 m) and spent more time within 3 m (paddock: 42.34% vs. 20.59%, field: 9.81% vs. 1.85%). However, horses did not disperse maximally in larger spaces, staying within range of even their least frequent associates, suggesting a threshold distance for group cohesion. Network analysis revealed higher closeness centrality in the paddock, indicating a more integrated social network. Agonistic interactions were more frequent between close associates, occurred more often in the paddock than the field, and correlated negatively with absolute interindividual distances. These findings highlight the complex interplay between space availability and social dynamics and their importance for equine welfare.