Sickness in horses – what to look for when you have few clues.

Sickness alters the way horses “see the world”. Although studies don’t always have a clear quantitative approach, observations generally agree that sickness modifies the way horses perceive and react to environmental stimuli.

Alertness, interaction & aggression

Alertness (responsiveness to environmental stimuli) and interactive behaviours could be non-specific but major indicators of sickness.

There are two main ways horses express their poor well-being:

  1. they may, especially in cases of chronic repeated pain, become unresponsive to environmental stimuli, motionless and lethargic or
  2. become aggressive and hostile.

Healthy horses are regularly observed to be attentive to the environment, ready to react to stimuli and to be positive towards other living beings. Therefore an absence of responses may indicate a possible discomfort that, if untreated may transform into pain.

Sickness associated with pain and discomfort can lead to horses’ self-attention and thus withdrawal from the environment with all senses:

  • Auditory (ears back, lowered reaction to sounds)
  • Visual (facing the wall, “empty gaze”)
  • Tactile
  • Gustatory and olfactory responses – untested but sick horses show fewer reactions towards positive stimuli (Pritchett et al., 2003), including sucrose (Fureix et al., 2015).
  • Mobility (of body, ears, etc.) remains to be investigated.

Because the indicators above are non-specific, they are easily misinterpreted. Apathetic equids can be considered “lazy”, or “unwilling” to perform their work (Swann, 2006), while aggressive horses are “badly behaved” and get punished or even culled for this reason, especially as it is believed that it is a temperament trait.

Knowing “laziness” and increased aggressiveness to be early signals of sickness would aid the detection of problems before they have transformed into more severe situations.

Long bouts of immobility in the stall (or paddock) are often interpreted as resting, probably because of the absence of awareness of the associated body posture (quite different between resting and being inactive, Fureix et al., 2012a).

Don’t be fooled by yawning & play behavior

Some behaviours may be mistakenly considered as indicators of health. Thus, anecdotally, but also in many scientific reports, play behaviour is considered as a clear indicator of well-being. Yes, in young horses, play behaviour is a normal part of the behavioural development, and is impaired in cases of disease (e.g. Waring, 2003; Henry et al., 2009, 2012). However, adult play is almost absent from the repertoire of horses living in natural conditions as well as in domestic naturalistic settings, even though it’s regularly reported by owners.

It is suggested that play behaviour in adults may serve as a way of “evacuating stress, hence toxins and getting oxygenation” (Blois-Heulin et al., 2015). Adult play is therefore an ambiguous behaviour that indicates that the animals are temporarily in a better situation, while being a potential signal of sickness.

Another ambiguous behaviour is yawning, which is generally considered to be associated with relaxed states, possibly leading to sleep. Fureix et al. (2011) investigated the potential link between yawning and stereotypic behaviours in horses. One hundred and forty horses were observed in their individual stalls. Yawning and stereotypic behaviour frequencies both increased in the period prior to the meal when all horses did not get fed at the same time (frustrating situation). Yawners were also more prone to be stereotypic than non-yawners. High frequencies of yawning outside of asleep/rest context may therefore be a potential signal that the horse is experiencing some discomfort, and in any case, does not appear to be a reliable indicator of good health.

In summary

Much work is still needed before an agreement can be achieved on the indicators of sickness in horses. However, there are signs that should attract the attention on the horses’ well-being:

  • Flattened backs and immobile postures – described as a despair state when persistent. May also result from learned helplessness (where animals learn that they have no chance of escaping the pain or the repeated painful actions of riders, e.g. Hall et al., 2008).
  • Ears’ postures (when measured in an appropriate calm context) may reveal a range of sickness including back disorders (Hausberger et al., submitted for publication).
  • Aggressiveness and restlessness may be other ways of expressing discomfort and pain.
  • Play or yawning are ambiguous behaviors that can be mistaken for good health.
  • Aggressive horses are not necessarily just nasty animals.


Hausberger, M., Fureix, C. and Lesimple, C., 2016. Detecting horses’ sickness: in search of visible signs. Applied Animal Behaviour Science175, pp.41-49.


Blois-Heulin, C., Rochais, C., Camus, S., Fureix, C., Lemasson, A., Lunel, C., Hausberger, M., 2015. Animal welfare: could adult play be a false friend? Anim. Behav. Cog. 2, 156–185,

Fureix, C., Gorecka-Bruzda, A., Gautier, E. and Hausberger, M., 2011. Co-occurrence of yawning and stereotypic behaviour in horses (Equus caballus). ISRN Zoology2011.

Fureix, C., Jego, P., Henry, S., Lansade, L. and Hausberger, M., 2012. Towards an ethological animal model of depression? A study on horses. PLoS One, 7(6), p.e39280.

Fureix, C., Beaulieu, C., Argaud, S., Rochais, C., Quinton, M., Henry, S., Hausberger, M.,  2015. Investigating anhedonia in a non-conventional species: do riding school horses Equus caballus display symptoms of depression? Appl. Anim. Behav. Sci. 162, 26–36.

Hall, C., Goodwin, D., Heleski, C., Randle, H., Waran, N., 2008. Is there evidence of learned helplessness in horses? J. Appl. Anim. Welf. Sci. 11, 249–266,

Henry, S., Richard-Yris, M.A., Tordjman, S. and Hausberger, M., 2009. Neonatal handling affects durably bonding and social development. PloS one4(4), p.e5216.

Henry, S., Zanella, A.J., Sankey, C., Richard-Yris, M.A., Marko, A., Hausberger, M., 2012. Adults may be used to alleviate weaning stress in domestic foals (Equus caballus). Physiol. Behav. 106 (4),428–438.

Pritchett, L.C., Ulibarri, C., Roberts, M.C., Schneider, R.K., Sellon, D.C., 2003. Identification of potential physiological and behavioural indicators of postoperative pain in horses after exploratory celiotomy for colic. Appl. Anim. Behav. Sci. 80, 31–43.

Swann, W.J., 2006. Improving the welfare of working equine animals in developing countries. Appl. Anim. Behav. Sci. 100, 148–151.

Waring, G., 2003. Horse Behavior, 2nd ed. Noyes Publications/William Andrew Publishing, Norwich, New York.