The Rate at Which a Horse Blinks Can Indicate Stress Levels

Step aside, cortisol. Blinking is the new stress indicator in horses.

Researchers at the University of Guelph, in Ontario, Canada conducted a study that found a horse's blinking rate revealed its stress level. Similar studies have previously been done in humans and cows.

Katrina Merkies, PhD, associate professor and equine program coordinator at Guelph, said:

"Horses in our study showed a reduced amount of half and full eye blinks along with an increase in eyelid flutters when exposed to certain stressful situations."

Merkies was assisted by her student, Amelia Garnett, in the observational study. A total of 23 equines were observed during three stress-inducing situations: separation, food restriction, introduction of a sudden scary object.


The horse's blinking patterns were recorded on video for accurate quantification and compared to the blinking rates of horses at rest. Cardiac and behavior monitoring were also carried out with both the test subjects and control to match stress level and eye movement.


Merkies said:

"The eye flutters are reminiscent of what we see in the horse grimace scale (HGS) with regard to what they call a triangular eye. Horses had more worry wrinkles or piqued eye shape when they were in pain in the HGS study, and that's similar to what we saw in our study with the eye flutters—likening the stress to worry or pain."

A non-invasive test like this creates zero stress on the animal, unlike blood draws for cortisol testing that themselves can cause more stress.

What signs indicate your horse is stressed? Share in the comments below.

WATCH NOW: Endo the Blind Horse Is an Inspiration