When eyeing a predator, horses keep a poker face as their hearts race

Horses know a predator when they see one – even if it’s only on a video screen they’re watching in a stall, with no sounds, smells or previous experience providing context to what they’re viewing, a new study suggests.

And though sensors indicated the horses’ heart rates increased when they were looking at wolves on the screen, they otherwise kept a poker face. They didn’t bob their heads or swish their tails, and their gaze wasn’t fixed in a way that would indicate their brain was processing a threat, results showed.

“Rather than just spooking, horses show remarkable cognitive restraint when evaluating a potential threat,” said lead author Zeynep Benderlioglu, a senior lecturer in evolution, ecology and organismal biology at The Ohio State University. “And not all fear or stress will result in overt behavior. They’re not in fight-or-flight mode, but they’re assessing, and they’re doing it in a remarkably fast way. But their hearts are racing at the same time.”

The findings are relevant to horse and human welfare, Benderlioglu said: Riders and handlers may not be able to tell when a horse is agitated.

“This visual recognition means horses may be experiencing an internal state of agitation while remaining physically still,” she said. “Understanding this disconnect is vital for ensuring both rider safety and the welfare of a horse that is processing a threat, especially if that threat is a canid – any dog.”

The research was published today (July 15, 2026) in the journal PLOS One.

Eighteen horses of both sexes and a range of ages were involved in the study. The animals watched a brief silent video in a standard stall while wearing an equine heart monitor and being recorded on a video camera.

Benderlioglu said that to the best of her knowledge, this research represents a novel approach in testing equine predator recognition by isolating visual cues from other sensory inputs like scent or sound.

The video showed three scenes for 20 seconds each: A control stimulus featuring free-ranging wombats grazing, followed by videos of groups of wolves either interacting aggressively or grooming. Half of the horses saw wolves fighting first and then grooming, and the wolf sequence was reversed for the other half.

Separately, researchers collected data from handlers on the animals’ age, sex, social status in the herd, social dependency and temperament – such as social anxiety or fearfulness.

Heart rates remained at baseline when the horses were viewing the wombats, but significantly increased when they were viewing the wolves, no matter which behavior the predators were engaged in, fighting or grooming – a surprising finding.

“I expected the horses would differentiate the fighting videos from the grooming videos, but they didn’t. They had high alertness and a higher heart rate, compared to baseline and wombats, when looking at both grooming and fighting wolves,” said Benderlioglu, also director of the Undergraduate Research Lab in Ohio State’s Department of Evolution, Ecology and Organismal Biology.

Heart rate increases were more pronounced in male horses and in horses with higher social status.

“Males had the same baseline heart rates compared to females, but males reacted more. They had heightened heart rate responses, higher arousal,” she said. “High-status horses showed heightened heart rate responses during predator stimuli, likely because they play an important role in collective decision-making and leading the herd. High-status horses are often followed by others because the herd places increased trust in them to make collective decisions, especially when it comes to safety.”

The gaze-related findings were of particular interest to the team, and could help explain why the horses didn’t show their hypervigilance cards by displaying any physical behavior.

Previous research has suggested that horses and most vertebrates use left-eye gazing to assess a threat because that function is based in the right side of the brain. A right-eye gaze suggests animals are engaged in a cognitive assessment, more of a left-brain task.

In this study, the horses showed no gaze preference while viewing the wolves, and when they were viewing wombats, they watched intently with binocular vision – both eyes, straight on.

“They were investigating, it seems, the point being they’re immediately, within 20 seconds, they’re assessing,” Benderlioglu said. “You cannot be in the head of the horse, but the gaze and their hearts, those are giving something away. It’s like the horse thinks, ‘Here is a wolf.’ Wait a minute, the horse thinks again, ‘What is that fluffy thing?’”

Horses evolved as prey animals, which is why this level of discernment was unexpected, she said.

“People don’t necessarily attribute a high level of cognition to prey animals,” she said. “But the horses are engaging in a really unexpectedly high level of cognitive processing. They are on high alert, and then the threat didn’t materialize, so behavioral manifestations are not occurring because they’re cognitively assessing.

“So if they’re not showing any overt stress signs, you don’t realize they might be in a high-alert state.”

The study took place at the Ohio State Equine Center operated by the Department of Animal Sciences.

Co-authors, all from Ohio State, were Rachel Hofacker, Natalie Sebunia (now at Cornell University) and Jessica Pihlblad (now at the University of Arizona).