How often a horse blinks or twitches his eyelids may be indicative of its stress level. A study team out of the University of Guelph made up of of Katrina Merkies, Chloe Ready, Leanne Farkas and Abigail Hodder, noted that eye blink rates have long been used as stress indictors in humans. They hypothesized that the same could be applied to horses, which exhibit blinks, half blinks and eyelid twitches.
The researchers used 33 horses for their study and exposed them to three stressful situations, like removing them from the herd, throwing a ball at them and denying them food at their typical feeding time. The horse’s heart rates, behavior and eyelid activity were monitored via video. Analysis of the video showed that horses eyelid movements decreased in the stressful scenarios compared to when the horses were in their traditional environment.
The most stressful of the situations for the horses was the restriction of food. The horses held their heads high, were restless and had increased heart rates. The horses had decreased eye blinks, but an increase in eye twitches.
Unstressed horses blinked an average of eight to nine times per minute; when stressed, the horses decreased their blinking rate to about five blinks per minute. Horse’s eyes twitched more when they were exposed to stressful situations–up to six times per minute from twice per minute when not stressed.
The research team says additional studies could show if specific eyelid movements in relation to arousal level might provide clues into horse’s emotional responses.
Read the full study here.
Read more at HorseTalk.
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