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Stereotypic behaviours such as crib-biting, weaving and box-walking are among the most recognisable signs of compromised welfare in horses. These repetitive behaviours appear to serve no obvious purpose and are most seen in horses kept under restrictive management conditions, where opportunities for natural behaviours such as continuous grazing, free movement and social interaction are limited.
Although stereotypies are widely regarded as indicators of reduced welfare, scientists are increasingly recognising that not all stereotypic behaviours arise for the same reasons. Understanding these differences could help develop more effective management strategies for affected horses.
Stereotypies are generally divided into two broad categories. Oral stereotypies involve repetitive movements of the mouth, with crib-biting being the best-known example. Locomotor stereotypies involve repeated movement of part or all of the body, such as weaving or box-walking.
As part of her PhD research at the Centre for Comparative and Evolutionary Psychology, University of Portsmouth, Kate Lewis and colleagues investigated whether horses displaying different forms of stereotypic behaviour also differed in their responses to a potential source of social enrichment: a stable mirror.
Mirrors have previously been shown to provide some horses with the illusion of another horse being present, potentially helping to reduce stress associated with social isolation. The researchers wanted to determine whether horses exhibiting locomotor stereotypies might be more socially motivated than those showing oral stereotypies.
The study involved 16 horses: six horses that regularly box-walked, five that crib-bit, and five control horses with no stereotypic behaviour. Each horse underwent a 24-hour baseline observation period, followed by 24 hours with a large stable mirror measuring one by 1.5 metres installed in the stable. Behaviour was then monitored for a further 24 hours after the mirror was removed.
The results revealed clear differences between the groups. Horses that box-walked showed a noticeable reduction in the behaviour while the mirror was present, and this reduction persisted even after the mirror had been removed. In contrast, crib-biting behaviour was unaffected by the presence of the mirror.
The horses also differed in how much attention they paid to the mirror. Both the box-walking horses and the control horses spent more time orientated towards it than the crib-biters, suggesting that the locomotor stereotypy group may have been more interested in the apparent social companion.
However, the findings also showed that the picture is more complex than simple social attraction. Box-walking horses did not display more ear or head movements associated with affiliative social behaviour towards the mirror, nor did they show greater signs of frustration after the mirror was removed. This suggests that although mirrors appeared to reduce box-walking, the underlying reasons remain unclear.
The researchers conclude that the study provides preliminary evidence that horses displaying different stereotypies respond differently to environmental enrichment. In particular, locomotor stereotypies such as box-walking may have stronger links with social factors than oral stereotypies like crib-biting.
Because the study involved relatively small numbers of horses, the authors emphasise that larger, well-controlled studies are needed before firm conclusions can be drawn. Nevertheless, the findings add to growing evidence that stereotypic behaviours should not be viewed as a single condition, but rather as behaviours with potentially different underlying causes that may require different approaches to management and welfare improvement.
For more details, see:
Lewis, K., McBride, S. D., Parker, M. O., Faithfull, R., & Proops, L.
Differences between horses (Equus caballus) displaying oral and locomotor stereotypies in their responses to a stable mirror.
Behavioural processes, (2026). 241, 105415.
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