Social facilitation in the horse ( Equus caballus)

Abstract

The concept of “social facilitation” is approached by observing two types of behavioral synchrony: “group synchrony” and “materno-filial synchrony”. The former supplies information as to whether the group as a whole (complete synchrony) or 50% plus one of its members (partial synchrony) carry out the same behavior. Observations were carried out on a complete social group consisting of 12 individuals of the Asturcón horse living in wilderness in the mountains of Asturias. The group is composed of 1 male adult, 4 mares, 2 adults, 1 juvenile and 4 offspring. Recordings were made during the month of September throughout an entire day selected at random and utilizing “instantaneous samples” in 2-min periods. The following behaviors were identified: grazing, walking, standing, standing up, lying up, lying down, suckling and mutual grooming. A total of 303 data were obtained for group synchrony and 1212 for materno-filial synchrony. The results show 10% complete synchrony, 81% partial synchrony and 64% materno-filial synchrony. With regard to the behavior carried out by the individuals that show synchrony and to the materno-filial distance, we have found the following statistical significant differences: (1) materno-filial synchrony is more frequent and the materno-filial distance is larger when the mother is grazing than when she is resting; (2) complete synchrony of the group is also more frequent when the group is grazing than during any other behavior; (3) the stallion of the harem synchronizes with the group more frequently in active behaviors (grazing and walking) than in passive behaviors (lying up or down). We conclude that behavioral synchrony and the materno-filial distance are influenced by the behavior which gives the highest efficiency in the mother's task of watching over her offspring and that of the stallion watching over the harem.