Sociality increases juvenile survival after a catastrophic event in the feral horse (Equus caballus)

Abstract

In several social species, adult associations have been linked to individual fitness. Less is known about offspring associations and the mechanisms by which they may influence fitness. We investigate the effects of sociality on juvenile survival in feral horses ( Equus caballus ). We use foal degree (number of associates) and foal weight (number of interactions) to assess sociality’s importance to foal survival of a catastrophic event, the gathering and removal of 40% of the horse population. We found that 1) foal degree was a better predictor of foal survival than was foal weight; 2) following the gather, foals with access to at least one parent and some members of their natal groups were more likely to survive than were foals left with no such access; 3) foals with a higher degree both pre- and postgather were more likely to survive; 4) the influence of pregather degree appeared to be more pronounced among foals without access to parent(s) and natal group members; and 5) the influence of foal degree postgather was important to the survival of all foals, regardless of parental and natal group access. These results add to our understanding of the benefits afforded by juvenile social networks. Moreover, our study is unique in that foals were separated from parental support at a crucial point in development. We were therefore able to separate the effects of parental behavior on juvenile response, allowing us to more directly ask the question: do the behaviors exhibited by young mammals confer immediate and/or future benefits?