Third-party interventions keep social partners from exchanging affiliative interactions with others
Highlights
► Female horses primarily intervened in affiliative interactions of group mates. ► Higher ranking, socially active group members display such regulatory behaviours. ► Interveners target nonbonded horses and support socially bonded horses. ► Affiliative interventions may prevent competition for partners in costly fights.
Section snippets
Animals
We observed four feral horse harems comprising 84 animals out of 300 free-ranging Esperia ponies in the Italian Abruzzi Mountains. The social groups’ age and sex composition and their social behaviours were comparable to those of other feral horse populations (Berger, 1977, Schilder, 1990, VanDierendonck et al., 2009). Mature adult members of feral horse groups are usually unrelated (Rutberg & Keiper 1993). The horses’ ages ranged between 1 and 28 years, but precise ages were known for only half
Results
Horses intervened significantly more often in affiliative than in agonistic interactions (interventions in total: N = 75; agonistic interventions: N = 8; affiliative interventions: N = 67; binomial test: P < 0.001; Table 1, Table 2). We continued analysing the interventions in affiliative encounters. They were performed by 21 of the 59 female horses and addressed 20 different supported and 31 different targeted horses. Five females performed 55% of all affiliative interventions (Table 2). Whether mares
Discussion
In the present study female horses intervened significantly more often in affiliative than in agonistic interactions of group mates. Whether they had a foal at foot had no effect on their frequency of intervening. Intervening horses were significantly higher ranking than their group members in groups 2 and 3. In group 1 this was only the case when males were excluded from the analysis.
Males never intervened, but were high ranking and therefore affected the outcome of rank comparisons between
Acknowledgments
We thank Juergen Heinze, Klaus Fischer, Thomas Bugnyar and Birgit Flauger for helpful discussions, Korinna Kappeler and Sabine Huber for help with the feral horse observations, Knut Krüger for help with statistics, Kate Farmer for language corrections, as well as Maria and Amerigo Nota for providing us with test horses. The study was supported by an HWP II grant of the University of Regensburg, and a habilitation grant by the Dr Peter Deubner Stiftung.
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