What sort of influence do adult horses exert on youngsters?
Résumé
Experienced adults of many animal species are known to influence the behaviour of young individuals. However, wether one- and two-years-old youngsters could still use the influence of adults to improve their social skills and wether this influence varied according to their proportion in groups remain unknown. We tackled this question by conducting parallel experiments on two subspecies of horses, Equus f. caballus and Equus f. przewalskii, with comparable social structures. Temporary introductions of foreign adults in same age - same sex groups of domestic horses led to an increase of preferential associations and positive interactions along with a decrease of aggression rates compared controls without similar introductions. Observations run on same-age Przewalski horses in natural families revealed variations of social behaviours related to adult-young ratios: the lower this ratio, the more the young were aggressive, the more young and adult segregated, the tighter the young bonded to other young. These findings highlight the major role adults play in regulating the behaviour of youngsters and suggest that their influence depends on their relative numbers.