A Behavioral Analysis of Aggression and Coat Color in Social Networks of Domestic Horses (Equus caballus)

Abstract

Research is being conducted to understand the underlying factors that contribute to the variant personality behavior of individuals of the same species, as well as how these behaviors contribute to decision making in a group living environment. Displays of behavior can often be categorized along a shy-bold spectrum. This study examines the possibility that the pattern of decision making and response to novel stimuli of domestic horses with different coat colors are predictable and of significant difference. This study follows two groups of horses in Cranbury, NJ (N=10), and Morningview, KY (N=25) and performs behavioral tests and individual removal experiments of mid-range dominant horses of varying coat colors. To determine the specific interaction of coat color and dominance, aggression networks were created and analyzed using social network analysis (SNA). One short term removal was performed in Cranbury in order to calibrate methodology, and three successful removals were conducted in Morningview for more direct comparison. These short-term removals showed that lighter coat-colored horse removals showed less of a group-wide impact in herds and struggled to reclaim their rank upon reintroduction more than darker colored individuals. On an individual level, lighter colored incurred more in-aggression from other horses. No significant correlations were found between coat color and out-aggression, but there was a significant trend between darker coat color and more dominant ranking. This study also showed a significant difference of the way lighter and darker colored subjects responded to a novel stimulus in investigation time and approaching or retreating. This study provides an animal model for complex behavior and decision making in social systems. Understanding this sheds light on the way herds organize themselves hierarchically with dominance and provides information to herd managers and owners about adding or removing different individuals into a herd based on specific personality traits of horses of varying coat color.