Horses are highly social animals for whom isolation causes significant psychological stress, with management approaches that provide social contact being a fundamental welfare requirement.
Isolation is one of the most significant welfare compromises for horses as a species that evolved to live in complex social groups. The anxiety caused by separation from conspecifics is strongly motivated and produces measurable physiological stress. Isolated horses redirect social motivation into stereotypic behavior and human-directed behavior that can become problematic. Even temporary isolation during transport or competition causes acute stress. Ensuring horses have appropriate social contact is a fundamental welfare requirement rather than an optional management consideration. When keeping single horses, companion animals of other species provide partial but meaningful social welfare benefit.