Mutual grooming is a fundamental social behavior in horses that provides physiological and psychological welfare benefits — and its absence in singly-housed horses represents a welfare gap that companionship addresses.
Mutual grooming in horses is welfare-significant beyond its obvious social function. The physiological calming effect — measurable heart rate reduction and endorphin release — makes it a genuine comfort behavior with health implications. Horses kept without companions cannot access this behavioral pathway to stress reduction. Human grooming provides partial benefit through the physical contact and cardiovascular calming it induces, but does not replicate the social relationship dimension that grooming with a conspecific partner expresses. This provides additional welfare evidence — beyond behavioral needs generally — for the importance of equine companionship in horse husbandry.