Cats are pretty awesome animals. Of course, they have a few irritating habits as most pets do, such as clawing at your favorite leather sofa or seductively rubbing all over you while you’re trying to work. But perhaps their most annoying and thoroughly disgusting habit is their fondness for bringing a bloody bedraggled carcass to your doorstep, presenting it as if it were an early Christmas present wrapped in a big red bow.

Incredibly, a study published just last year in Nature Communications suggested that cats in the US kill between 1.3 and 4 billion birds and between 6.3 and 22.3 billion small mammals per year. That’s a pretty impressive figure. So why do they do this? Are they just cold-blooded killers that love nothing more than juggling an innocent little fluffy shrew between their sharp claws, just for kicks? Or is there a deeper, evolutionary reason? I’m sure you’ve already worked out that it’s the latter.

Cats evolved to become highly efficient predators- they have sharp teeth and retractable claws, cushioned paws to silently creep up on prey, night vision, and they’re incredibly swift and agile. While the domestication of cats from wild ancestors to human companions started taking place some 10,000 years ago, cats have retained their feral hunting instincts as well as their ability to digest raw meat. No matter how much you coddle them and dress them up in bows and sunglasses, you can’t take their predatory instincts away.

Cats learn through experience and traditionally they are raised by their mothers. This involves teaching the kittens how to look after themselves, including how to catch prey. The mother educates her young gradually, starting off by bringing back dead prey for the kittens to eat. Next she will bring back live (but rather disheveled) prey for the offspring to kill themselves, and eventually when they’re ready, she will take her young out and show them how to hunt. There have also been documented examples of female cats doing this for young that do not belong to them.

Given that female cats are most likely to bring back animal presents, the most likely explanation for this behavior is that they are trying to teach you the hunting skills that you clearly lack. It is also possible that the animals are merely bringing it back to you as a gift, but it seems more likely that this relates to their hunting instincts that have been suppressed and dulled by domestication.

So next time Misty decides to leave a disgusting, bleeding, twitching corpse on your doormat, try to remember that she loves you and she is just trying to bring out your inner predator.