NEW YORK (NYTIMES) - No one can talk to a horse, of course. But a new study set out to find whether horses are trying to tell us something when they snort.
In the study, published Wednesday (July 11) in the journal PLOS ONE, researchers in France determined that the snorting exhale that horses often make may be a sign of a positive emotion.
Mathilde Stomp, a doctoral student at the University of Rennes who led the research, said she set out to understand whether the snort could be used as an measure of the horse's mood.
She and her collaborators recorded 560 snorts among 48 privately owned and riding school horses.
All the horses snorted - as little as once or as often as 13 times an hour.
The horses mainly snorted during calm and relaxing activities, and those that spent more time out of doors snorted the most, the study found.
When a horse was snorting, the researchers also recorded the animal's ear position; forward-pointing ears are a known signal of a positive internal state, Stomp said.
Researchers also developed a composite score of each animal's stress level when snorting, with measurements including how much time a horse spent facing the wall in its stall, as well as its level of interaction with or aggressive behavior toward the researcher.
Stomp said her work was motivated by the desire to help people better understand and meet the needs of their animals.
"We think that with this acoustic indicator, maybe they will be able to test when their horses are in good conditions or not," she said.
Not all horses may be snorting in contentment, however, but rather in discomfort or simply acting on a physical need, akin to humans blowing their noses.
Sue McDonnell, a specialist in equine physiology and behavior at the University of Pennsylvania School of Veterinary Medicine, said not enough is known to draw conclusions about a horse's emotional state from its snorts.
"I think it's a huge overreach, an overinterpretation of their data," she said.
McDonnell, who daily observes her school's herd, takes the more traditional view that snorting is a way of clearing a horse's nasal passages. She has noticed a difference when she lets the horses feed on short blades of grass versus longer ones, which are more likely to tickle their noses. Horses eat shorter grass just as enthusiastically as longer blades, "but they don't do all that snorting," she said.
Horses also snort in negative circumstances, McDonnell said. If they encounter an aggressive or fearful situation, their "fight or flight" response includes a bump in adrenaline, which dries their mouth and nose.
Once the situation resolves and adrenaline levels drop, secretions like saliva and mucus start flowing again, McDonnell said. She has watched stallions snorting as their adrenaline levels fall, suggesting that the flow of mucus caused them to make the noise, she said.
Then again, horses probably do use snorting to somehow communicate to others in the herd, alerting them when danger has passed. But that does not translate into knowing if a horse is happy, she added.
While Karyn Malinowski, professor and director of the Rutgers University Equine Science Center in New Jersey, discouraged the practice of ascribing human emotions to animals, she said the new study's findings made sense to her. The horses she studies display emotions, like sorrow when a close companion dies, so she believes they are certainly capable of happiness. Malinowski said the study also aligns with her physiological research that shows horses are much less stressed when they are allowed to live outside, rather than in stables.
In the new study, horses that lived in more natural conditions snorted more often, and even the stabled horses snorted more when they were outside. "I've been studying stress for 40 years. The worst thing you can do for a horse is to keep it inside," Malinowski said. Outside, "they're happier, healthier, the air is fresher."
Lauren Brubaker, a Ph.D. student at Oregon State University specialising in human-animal interactions, said the study also matches the experience of people in the horseback riding world.
"You hear a lot of riders and instructors and trainers who will say they're looking for horses to do that snorting behavior while they're riding, because they believe the horses are relaxing and releasing adrenaline," she said.
Brubaker said it was too early to conclude that snorting is a form of active communication. She would like to see research into snorting behavior when horses are ridden, are pulling carriages, used for therapy and performing in shows or races.
Stomp said she planned to investigate whether dust levels in stalls affect snorting, to further explore her hypothesis that snorting is about more than nostril-clearing.