Social Networks and Herding Behavior of Feral Horses (Equus Caballus) in Captivity

Abstract

The feral horse (Equus caballus) has a rather complicated management history in the United States. While they are legally protected, some of the management practices have been reported to interfere with the natural social structure of the horses. Insufficient research has been completed to demonstrate the structural changes or the consequences of such changes. We examined three populations of feral horses that had been managed to different degrees throughout their history in order to better understand the social changes that result from management. None of the three populations behaved like feral horses in the wild, as they each spent a large portion of their time gathered into a tight herd. While we were unable to discern precise reasons for the herding behavior, we suggest that the ecology of their current maintenance setup, including supplemental feeding and biting fly pressures, contributed to this behavior. We also examined the variation within and between populations in which harems spent more time outside the herd. We did not find that either internal harem structure or specific time budgets was a predictor of how much time was spent out. We also did not find a difference in bachelor harassment between the two populations. However, there was a difference in that one of the populations had lowered levels of internal aggression (p < .01) that was matched by increased female-­‐female affiliation (p <.001), which may be a response to inexperienced stallion leadership or to an unstable social situation. We then examined the stallion-­‐bachelor social network, and found that the most managed population had a younger age structure (p<.05), and formed less selective social relationships than the populations that were less managed. This suggests that the management technique used upon this population altered the social structure of the population. More research would have to be conducted in order to ascertain the consequences of these changes.