The effect of the chilling, merciless intensity in a cat’s eyes right before it pounces on an unsuspecting bird is somewhat ruined by how cute its little butt looks wiggling in the air behind it.

There’s no single explanation for this habit (in part because there’s not exactly a massive demand for research on the topic). But, as is the case with kneading, relaxing in sinks, and dozens of other perplexing feline behaviors, experts have some theories.

As Live Science reports, it’s possible that cats are trying to establish traction between their back legs and the ground in order to strengthen their pounce. Feeling steady is especially important since they’re jumping from two paws simultaneously.

“Basically, when cats pounce, they need to propel themselves using both hind limbs for full takeoff. Usually when cats walk, they alternate their back legs, but when jumping or pouncing they use both together,” veterinarian Katie Grzyb told PetMD.

It could also be less about their legs and more about the ground itself. Shifting their weight from back paw to back paw a few times may help them verify that the surface they’re on is firm enough to pounce from. Or cats might just be making the same type of small adjustments that humans do before some grand muscular endeavor.

“It seems they are preparing their muscles for a big movement as they strategize—with tiny movements of their feet and hind limbs—much like a golfer does when setting up at a tee or a batter up to bat,” veterinarian Meghan E. Herron told PetMD.

Excitement could be a factor, too. Cats enjoy hunting, and wiggling a little may be their way of letting off some of that extra energy before going in for the kill. As for whether the pre-pounce shake has any bearing on their success rate, your guess is as good as ours.

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