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.