Why cats wiggle
before they pounce

The full narration of the video.

Why does a cat wiggle its butt before it pounces? Drag a wand toy across the floor and it drops low, eyes locked on, back end raised, swaying left, then right. Then, whoosh, it launches.

It looks like the cat is just being cute, but tigers and lions do the same wiggle before they pounce on prey. Big cats and little cats both kept this move, so it's probably an old family skill. What is it for? Try something yourself first. Stand up straight, feet together, ready for a standing long jump.

Before you jump, don't you bend your knees and shuffle your feet a little, looking for a spot that won't slip? A cat is about to do much the same thing. When it walks, its back legs take turns, left, right, left.

But for the pounce, both back legs push off at the same moment, and all its force lands on the soles of its feet. If a foot slips just then, or the ground wobbles, the pounce goes soft: the prey gets away, and the cat might even take a tumble. So those few wiggles are most likely the cat planting its back feet, one at a time.

Butt swings left, the left foot presses down; swings right, the right foot presses down. Only when both feet feel solid does it dare to go. Sprinters do the same before a race: they wedge their feet into the starting blocks, push back a couple of times, and only crouch once they know the blocks will hold. A cat has no starting blocks, so it uses the wiggle to press the pads of its back feet into the ground.

The force that keeps a foot from slipping is called friction, or grip. Run across a tile floor in socks and you slide, because there's too little friction. The blocks give a sprinter friction, and the wiggle earns the cat friction too. A sprinter has to be coached, but a cat is born with it. Kittens start practicing pounces at six or seven weeks old, wobbling all over at first and getting smooth only with practice.

The wiggle also works as a warm-up, getting the leg muscles moving, while the eyes use those seconds to judge the distance and pick a landing spot. And there's the simplest possibility of all: it's fun. Hunting gets a cat excited, and the wiggle may just be that excitement spilling over. To be honest, though, almost no experiments have studied this wiggle. Everything here is experts' best guess from watching cats move, and some cats never wiggle at all.

How many wiggles make the best pounce, and whether a longer wiggle means a steadier one: nobody has measured that yet. Does your cat wiggle twice and go, or wiggle forever before it charges?