Relations of affinity are essential within harems of Przewalski horses (Equus ferus przewalskii). They exist between the mares and their foals to allow the adoption of the newborns by their mothers, but also between siblings, the different mares, and even the mares and the stallion. The horses with affinities spend more time together, do the same things simultaneously, share food resources, groom each other, rub their heads against each other, chase each other's insects, etc.