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Dealing with Danger

Feral horse mares are focused on an external stimulus (in this case, a foal distress vocalization in the distance) and are showing “standing attentive behavior”. Note the directionally pointed ears, rigid body position, and focused eyes characteristic of this expression.1

The herd or band provides the horses in it with many benefits.

  • Each horse is superbly endowed to detect a predator at a distance. But when two horses are on the alert for predators, their chances at early detection improve even further.
  • If the herd chooses to flee, then when it is running, a predator in pursuit wastes valuable time trying to select a victim and trying to track it as the horses run away.
  • If the herd chooses to fight to protect foals, a foal has many defenders, and has a much better chance of survival than if he is defended by only one mare.

Attention. Here a band has paused because they noticed the photographer in the distance.2 A telephoto lens was used to capture this scene — the immobile horses would be harder to detect by a distant predator not armed with a camera.

A horse can detect danger through sound, sight, or smell. An interesting study3 suggests that his reactions to danger or novelty may depend on how it was sensed. Reactions to novel visual, auditory and olfactory stimuli were examined in 24 stallions at the age of 2. In all conditions, eating dropped off, suggesting that each stimulus was arousing and perhaps of concern. But there were differences between these senses in how the young stallions responded to these three kinds of novel stimuli.

  • During the olfactory test, total eaten diminished and the horses had an increased number of eating bouts and became more vigilant towards their surroundings, but the unusual scent had no effect on heart rate.
  • The novel visual and auditory stimuli elicited significantly increased heart rate and delayed eating, reducing the amount eaten.
  • The horses took significantly more steps backwards in response to the auditory test.

It would appear that horses sense danger primarily with their eyes and ears. In this study, at least, the auditory signal seemed to have the biggest effect on fear, followed by the visual signal. Olfaction affected the horses, but in very different ways than sound and sight.4 From the chapter on The Mind of Your Horse, we might wonder if most of this sensing is done by the right side of the brain — meaning left eye and ear.

Why would a horse have a stronger response to scary sights and sounds than to scary smells? Researchers5 in Sweden and Denmark seem to have found the answer. They note that “there is a general belief among riders that horses are innately frightened by certain odours.” The title of their study suggests that these riders may need to reconsider this belief: “Predator odour per se does not frighten domestic horses”. In three experiments, they exposed 45 2-year-old horses to three scents: (1) urine from wolves and lions, (2) blood from slaughtered horses that had been mixed with fur-derived wolf scent, and (3) a sudden auditory stimulus in either presence or absence of fur-derived wolf scent.

In the first experiment, where the horses were only exposed to scent of predator urine, the horses showed more sniffing, but no change in other variables measured, such as heart rate.

In the second experiment (horse blood and wolf scent), they found more sniffing, more vigilance, and less eating, but still no increase in heart rate.

In the third experiment, some horses were presented with a sudden sound (a moving plastic bag) alone, and some were presented with that sound combined with wolf odor. The researchers found that the combination of sound and odor left the horses with a longer delay before resuming eating, and significantly increased their heart rates.

The researchers draw this conclusion: “The results indicate that predator odour per se does not frighten horses but it may cause an increased level of vigilance. The presence of predator odour may, however, cause an increased heart rate response if horses are presented to an additional fear-eliciting stimulus. This strategy may be adaptive in the wild where equids share habitats with their predators, and have to trade-off time and energy spent on anti-predation responses against time allocated to essential non-defensive activities.” A disturbing scent may increase a horse’s alertness for danger, but it may not be enough to trigger flight.

Sounding the Alarm

When a horse experiences an unexpected sound, sight, or smell, he may freeze and direct his head in the direction of the surprise. Turning his head automatically directs ears, eyes, and nose in the best direction for gathering more information. Ears turn toward the apparent source of the sound, to hear it better and locate it more precisely. The horse freezes in place, useful to hear better and useful to avoid detection (a distant predator can track a moving object more easily than one that is not moving.)

When a horse focuses on something with eyes and ears, others in the herd may do so as well. By doing so, an alarm passes through the herd, reaching those that might not otherwise responded immediately to the surprise.

Humans who have detected a predator are likely to shout, to try to drive it off. “Bear! Bear!” But horses who have detected a predator are likely to remain completely silent. Their nonverbal communication is perfectly adequate for all to understand each other. And both freezing and remaining silent reduce the number of clues a distant predator can use to confirm what she has detected. (I am not suggesting that you remain silent at the next bear. Horses might detect the bear half a mile away, whereas you might detect it when you nearly step on it. So consider remaining silent if it is at a great distance, but make plenty of noise, as the park rangers will advise, when you find it much closer.)

Mares take an alert position when guarding a sleeping foal, or whenever a predator approaches.

What’s Underneath?

Exposure to novelty may trigger fear, which we might measure by seeing changes in a horse’s behavior, and researchers might measure by changes in heart rate and neuroendocrine system changes. The first reaction to a sudden, novel stimulus is the immediate reaction of the sympathetic nervous system, which increases both the rate and force of heart contractions, preparing the horse for flight (or fight). Changes in the endocrine system take a second longer, but involve the secretion of cortisol, which brings a feeling of anxiety.6

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1 image source: Ransom, Jason I., and Brian S. Cade. “Quantifying Equid Behavior–A Research Ethogram for Free-Roaming Feral Horses.” U.S. Geological Survey Techniques and Methods 2-A9, 23 p. (2009) http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1018&context=usgspubs

2 image source: Ransom, Jason I., and Brian S. Cade. “Quantifying Equid Behavior–A Research Ethogram for Free-Roaming Feral Horses.” U.S. Geological Survey Techniques and Methods 2-A9, 23 p. (2009) http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1018&context=usgspubs

3 Christensen, Janne Winther, Linda Jane Keeling, and Birte Lindstrøm Nielsen. “Responses of horses to novel visual, olfactory and auditory stimuli.” Applied Animal Behaviour Science 93, no. 1 (2005): 53-65.

4 Unfortunately for us, many of the studies of fear have relied on fear tests which may have methodological problems and may not have adequate reliability or validity. See Forkman, Björn, Alain Boissy, M-C. Meunier-Salaün, E. Canali, and R. B. Jones. “A critical review of fear tests used on cattle, pigs, sheep, poultry and horses.” Physiology & Behavior 92, no. 3 (2007): 340-374. As they say, “more research is needed”, particularly research done with well-designed testing procedures.

5 Christensen, Janne Winther, and Margareta Rundgren. “Predator odour per se does not frighten domestic horses.” Applied Animal Behaviour Science 112.1 (2008): 136-145.

6 Guyton, A.C., Hall, J.E., 1997. Human Physiology and Mechanisms of Disease, sixth ed. W.B. Saunders

Company, pp. 501–502, 620–621.

 

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