Abstract: Third-party intervention is the interruption of a dyadic interaction by a third animal. We observed such interventions in affiliative interactions in free-ranging Esperia-ponies (Equus caballus). It is known that horses intervene in affiliative contexts especially when a preferred partner is involved, probably to protect their social bond to this preferred partner. To prove this hypothesis the present study investigated whether the preferred partner was targeted, i.e. challenged, or supported by the intervener or both randomly. Therefore we examined the social relationship between the intervener and both dyadic interacting individuals. We found that interveners usually supported individuals to which they have stronger social bonds than to other group mates, while they have no particular relationship to the targeted animals. This indicates that interveners in stable horse groups protect their social bonds to the supported animals by challenging their interaction partners. Of all observed horses only some mares showed intervention behaviour. Their social position, reflected by their position in the dominance hierarchy, social networks, and the spatial group structure were investigated. We found that interveners occupy no unique position, but they are involved in a high amount of affiliative interactions, high-ranking, and relatively aggressive. KW -