If you’ve ever seen videos of horses opening locked gates and doors, sometimes even to let their friends out with them, you’ve seen scientific history in the making.

Compiling hundreds of anecdotes and reliable video clips, German researchers have recently provided a scientific stamp of approval on what we’ve been watching for years: Yes, horses can figure out how to open doors.

“We can’t say it’s common, but it definitely does happen, and they definitely do seem to just figure out how to do it on their own,” said Konstanze Krueger, PhD, of the University of Regensburg, in Germany.

Krueger and her fellow researchers investigated claims from owners that their horses were opening various kinds of latches and locks, she said. They carefully scrutinized the information they received from English-, French-, and German-speaking internet users and interviewed the horse owners directly. “We needed to ensure that the claims were valid and that the videos were unedited in order to consider them scientifically reliable,” said Krueger.

The team identified 408 horses capable of opening nearly 600 kinds of closing mechanisms, she said. Specifically, they managed to break through 43 twist locks, 40 carabiners (rock climbing clips), and even two locks with keys. They released 260 horizontal bars, 155 vertical bars, 42 door handles, and 34 electric fence handles. About half the horses could open at least two kinds of mechanisms, and some could open as many as five at up to four different locations.

“We clearly have some very clever horses,” said Krueger.

Owners had not taught these horses any door-opening tricks. On the contrary, they were annoyed by this “clever” skill—as amusing as it might be, said Krueger. “These people were really faced with the problem of keeping their horses locked in, for their safety and the safety of others,” she said.

While some farms had two or more “Houdini horses” able to open locks, most farms had only one. “From what we could tell, this was not the result of social learning (learning by watching other horses),” said Krueger. “They figured this out on their own, maybe by watching humans do it, but still having to adapt to their own methods of using their mouths and tongues to manipulate the mechanisms.”

Welfare conditions appeared to be one motivator behind this skill development, she added. “It was interesting to see that if management or housing conditions weren’t ideal, horses would show few innovations (like figuring out how to open various locks), but they’d do them at a high frequency,” Krueger said. “They’d find a solution and then repeat it regularly, suggesting they’d developed this innovation to enhance their living situation because it was not satisfying to them.

“But we also saw these innovations in horses with very good living conditions and welfare, living in groups at pasture with unlimited access to forage,” she continued. “In that kind of environment we’d see some horses showing many different innovations, but on a lower frequency. It was like they were always switching to some other clever behavior. And these animals are, for us, the really clever ones, always on the lookout to discover and try new things and clearly finding some sort of pleasure in meeting the challenge, because they’d keep doing it, keep developing new innovations.”

Ensuring these lock-breakers stay safely in their enclosures requires first studying their motivations and meeting their welfare needs, said Krueger. If all needs are met, the horses might need additional stimulation in their training or husbandry that allow them to explore new innovations without putting them at risk of danger.

The study, “Animal behavior in a human world: A crowdsourcing study on horses that open door and gate mechanisms,”was published on PLOS ONE.

Krueger K, Esch L, Byrne R (2019) Animal behaviour in a human world: A crowdsourcing study on horses that open door and gate mechanisms. PLoS ONE 14(6): e0218954.