Although stereotypic behaviors are a common problem in captive animals, why certain
individuals are more prone to develop them remains elusive. In horses, individuals show
considerable differences in how they perceive and react to external events, suggesting
that this may partially account for the emergence of stereotypies in this species. In this
study, we focused on crib-biting, the most common stereotypy displayed by horses.
We compared how established crib-biters (“CB” = 19) and normal controls (“C” = 18)
differed in response to a standard “personality” assessment test battery, i.e., reactivity to
humans, tactile sensitivity, social reactivity, locomotor activity, and curiosity vs. fearfulness
(both in novel and suddenness situations). Our analyses showed that crib-biters only
differed from control horses in their tactile sensitivity, suggesting an elevated sensitivity
to tactile stimuli. We suggest that this higher tactile sensitivity could be due to altered
dopamine or endogenous opioid physiology, resulting from chronic stress exposition.
We discuss these findings in relation to the hypothesis that there may be a genetic
predisposition for stereotypic behavior in horses, and in relation to current animal
husbandry and management practices.