THE EFFECTS OF ENVIRONMENTAL AND SOCIAL FACTORS ON INTRAGROUP COMMUNICATION IN FERAL HORSES (EQUUS CABALLUS)

Abstract

Multi-modal communication in animals has been the focus of many studies in recent years. The inherent cost of communicating information in multiple modalities has led many scientists to wonder what the advantages of such a communication strategy may be. For feral horses, four different modes of communication have been identified: acoustic, olfactory, tactile, and visual. This observational study sought to determine how various social and environmental variables affected the use of these modalities, as well as communication strategy generally. Analyses focused on interactions occurring within harems. We examined agonistic and social interactions for male-female and female-female interactants, as well as sexual interactions for male-female interactants. We found that feral horses produce a higher number of signals simultaneously during agonistic interactions than in other interaction categories. Furthermore, the total number of signals produced during agonistic interactions was higher at watering hole locations than at non-watering hole locations. The length of an interaction and the number of modalities used was higher in sexual interactions between males and females than in other interaction categories. Taken together, these results indicate a high degree of flexibility and adaptability in communication strategy in feral horses. Higher stakes situations, such as when there is a valuable resource at stake or the the potential of mating, yield more complex communication patterns. This suggests that for signaling occurring between horses of the same harem group, complexity of communication is driven by what stands to be gained or lost in each interaction. Horses are more likely to incur the higher cost of communicating in more complex patterns if doing so stands to either help them gain a crucial benefit or avoid a potentially devastating cost.