Friendship improves fitness of feral mares

Friendship is more than just having someone to laugh with or a shoulder to lean on in tough times. A friend can also make you more fit. Just ask the feral horses of New Zealand.

Scientists spent hundreds of hours looking at the social behavior of these wild horses in the south western Kaimanawa ranges as part of a detailed study of social structure and parental care. They found that female horses that integrated better socially with their fellow mares had greater reproductive success.

This is one of the first studies to look at the role of female friendship in non-primates as an influence on individual fitness. The researchers suspect that the social bonding helps mares avoid harassment from aggressive stallions and this in turn reduces stress levels.

The scientist arrived at the results by spending hours in the field watching the behavior of individual mares as they interacted with other horses. The recorded behaviors such as mutual grooming, aggressiveness, and other indicators to arrive at composite index of social integration. They looked at 4 years of behavioral data and found that social integration between unrelated females increases both foal birth rates and survival, independent of maternal habitat quality, social group type, dominance status, and age.

Source:	Proceedings of the National Academy of Sciences
Title:	Social bonds between unrelated females increases reproductive success in feral horses
Authors:	ab) Elissa Cameron, a) Trine Setsaas, and bc) Wayne Linklater
	a) University of Pretoria, South Africa b) Massey University, New Zealand c) Victoria University of Welington, New Zealand