May 12, 2023 
Recognizing signs of stress in our horses is important for both their welfare and our safety. Unfortunately, this can be a tricky task, because their behavior doesn’t always match their stress levels.
Take a look at this video of my horse and my pony at a transit stable last summer, for example:
On first glance, you might assume that my horse is more stressed than my pony. He is showing clear behavioral signs of stress, like weaving, while the pony looks calm.
In fact, they’re likely experiencing similar levels of stress. At the time of the video they had been on the road for several days, they were in an unfamiliar location with lots of unfamiliar horses, and they were confined to a stable 24/7.
All of these are good reasons for horses to be stressed.
They behave so differently because they have different coping styles: my horse is a more proactive coper while my pony is a more reactive coper1. (These are the scientific terms, but as “reactive” means the opposite in equestrian lingo I often use active and passive coper instead.)
Proactive/active copers are more likely to deal with something unpleasant by trying to get themselves out of the situation, while reactive/passive copers are more likely to deal by trying to adapt to the situation.
In real life, proactivity manifests as rearing, bucking, balking, bolting, biting, kicking, weaving, etc.
Reactivity manifests as…standing still.
This is what makes passive copers so difficult to spot, and easy to abuse.
Horses that are labeled “stubborn” or “lazy” are often displaying a passive stress response. Take for example a horse that refuses to load by planting its feet on the ramp and not budging: this horse finds the trailer frightening, but because of its personality it doesn’t pull away—it freezes.
Furthermore, research indicates that stress levels don’t necessarily correlate with coping styles. Passive copers may be more stressed than their proactive counterparts, in spite of appearing outwardly calm.
In their study Poker Face: discrepancies in behaviour and affective states in horses during stressful handling procedures (2018), Squibb et al. investigated correlations between physiological signs of stress and refusal behaviors in horses confronted with a novel obstacle.
They assessed 46 privately owned horses in two handling tests: crossing a tarpaulin and walking through a curtain of plastic streamers. For each horse, they recorded eye temperature, heart rate, and heart rate variability—reliable indicators of a stress response—before and after each test.
They also recorded the time it took for each horse to cross the obstacles, as well as their behavior during the test. Any refusals to cross that lasted for longer than 10 seconds were categorized as either a proactive/active stress response (if the horse moved) or a reactive/passive stress response (if the horse stood still).
Interestingly, when they compared the physiological measurements with the latency to cross the obstacles, they found no correlations. More compliant horses did not necessarily have lower stress levels than the ones that refused. Furthermore, there were no correlations between the physiological measurements and proactive/active behaviors.
The authors note that some horses were “crossing the obstacles despite (…) exhibiting physiological signs of stress.” They discuss that these horses may be more responsive to cues such as pressure from the halter and comply regardless of their level of stress.
Squibb et al. conclude: “the results of this study suggest that the magnitude of stress response is not associated with a coping strategy in horses.”
In simple terms, it means two things:
- A horse that appears outwardly calm can still be very stressed on the inside.
- Compliance is not a good indicator of how a horse feels about a situation.
This is an important insight for anyone who works with horses. Just because a horse is standing still or doing what we ask does not mean they are comfortable and relaxed.
It also gives pause for thought about how we train our horses. An obedient horse may do what we ask even though they’re afraid. Is that something we want? Proponents may argue that having our aids overshadow a flight response makes for a safer horse, but is that really the case?
And what are the ethical implications of making horses do things they find stressful or frightening?
To end on a more hopeful note: reactive/passive coping strategies can be hard to spot, but there are some clues we can look for. Go back to the video of my horses at the transit stable and watch the pony’s facial expression closely.
What do you see?
Some clues that tell me he’s not too happy with the situation are:
- frequent blinking
- slight “worry wrinkle” above eye
- general alertness
- dilated nostrils
- neighing
- not eating his hay (for a hungry pony this is a big warning sign!)
The title of both this post and the study reference a poker face, but in fact a horse’s facial expression will often give the earliest indication of how they feel. It’s worth learning how to read subtle clues such as tension in the eye muscles, wrinkles around the nostrils, and changes in blink rate.
With that said, there will always be individual variations in how horses respond to stressful situations, both in terms of how active or passive they are, but also in terms of the subtle behaviors and facial expressions they display.
While some will be more open, some will have a poker face.
Footnote:
1. Proactive and reactive coping styles are fundamental aspects of personality in all animals, including us humans. Like with everything in biology coping strategies are not a binary state of either-or but rather a continuum, and every individual sits somewhere on the spectrum. Think about how you respond in stressful situations—are you a more proactive coper or a more reactive coper?
This article was originally published on theequineethologist.substack.com and reprinted here with permission.
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