If you haven’t been to a farm with fainting goats, you might have witnessed their signature move online: When startled, the farm animals will seize up and topple over, sticking their limbs straight out like cartoon corpses. Some people think the apparent over-dramatic behavior is hilarious (as evidenced by countless viral videos), but once you learn the real reason for the response, it doesn’t seem so cute.

Fainting goats are a small domestic goat breed native to North America. Technically called myotonic goats, they don’t really faint at all. Fainting involves losing consciousness briefly due to lack of oxygen in the brain. When a myotonic goat falls over, it’s because of problems with their muscles, not their brain, and they remain completely conscious for the whole episode.

Myotonic goats suffer from a condition called myotonia congenita, which causes their muscles to stiffen involuntarily and stay that way for brief periods. Regular goats, along with most animals, respond one of two ways when confronted with a perceived threat: fight or flight. What this looks like in the body is a sudden tensing of the skeleton muscles—the brain's cue to get ready to move—followed by an immediate relaxing of the muscles, allowing the body to either rush forward or flee the scene.

When a fainting goat's body tenses up in fear it has a much harder time getting back to normal. The goat’s muscles continue to contract for about 10 to 20 seconds after it’s startled, which is where the fainting part of its name comes in. “You can imagine if you’re stiff, you’re going to fall over,” Susan Schoenian, a goat specialist at the University of Maryland's Western Maryland Research and Education Center, tells Mental Floss. “And that’s where the name comes from.”

There’s a reason you don’t see this type of defect too often in nature. Falling to the ground at times when you’re most vulnerable isn’t exactly a desirable trait to have, and in the wild, natural selection would have quickly removed the condition from the gene pool. But when these goats first appeared in Tennessee in the 1880s, breeders had an incentive to keep them the way they were. Myotonia congenita is associated with dense, meaty muscles, and as a result myotonic goats have one of the highest meat-to-bone ratios of any goat breed.

In the 21st century, fainting goats have gained popularity as quirky, internet-friendly pets. Sneaking up on them has become a pastime among some goat owners, but don’t feel too bad next time a fainting goat compilation pops up in your feed: The reaction isn’t supposed to be harmful or painful for goats—it’s likely just annoying.

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