Why do tigers and cats both hiss and puff up?

The full narration of the video.

A tiger and a house cat look exactly the same when they're angry. The mouth opens with a hiss; the fur on the back puffs up, and the ears flatten. A tiger weighs around two hundred kilos, about fifty times a house cat.

They've never lived together, and a house cat will never meet a tiger. So who taught them this routine? Start with the hiss. A hiss isn't a call: it's air forced out of a wide-open mouth, with the teeth on show.

Its meaning is simple: don't come any closer. When a cat hisses at you, it usually isn't hate, it's fear. In a real fight, even the winner gets hurt; if a scare works, nobody has to fight.

A tiger pushed too far also hisses and growls first, baring its teeth. Now the puffed-up fur. At the root of every hair sits a tiny muscle. A scare sends an alarm signal through the body, the tiny muscles all pull at once, and the hairs stand up one by one.

The cat can't control this; it doesn't puff up on purpose. With the fur up, it looks a size bigger, and the other side hesitates. Tigers have these tiny muscles too, but with short fur and a huge body, their puff is much harder to see from afar.

Something you can't even control can't be learned. The answer lies much further back. About ten million years ago, today's cats were still one family, with one shared ancestor. It most likely could already hiss and puff up.

Then the family split up: one branch became tigers and lions, another became house cats. Like siblings moving out, each took the same family rule with them: when danger comes, scare first, don't fight. Except this rule needs no teaching. It's built into the body.

That tiny muscle has a name: the arrector pili. You have them too. When you're cold or startled, the goosebumps on your arm are your arrector pili pulling. Our hair is just too thin to puff up, so all we get are little bumps.

What made your cat hiss at you the first time?