The Real Reason Cats Eat Grass

Cats do some weird things. Maybe not as weird as dogs, but weird. One of the strangest things they do is eat grass — a habit they actually share with dogs — but for cats it's a bit stranger still because cats are true carnivores, while dogs lean omnivore on most days. Also, grass makes them barf, and we humans have a hard time getting our heads around the idea of eating stuff that makes you barf. On purpose.

For a while, experts believed that cats probably eat grass expressly because it makes them barf — perhaps a cat with an upset stomach eats grass in order to purge, which would presumably make the animal feel better afterward.

According to Cole and Marmalade, science decided to look into the whole cats-eating-grass thing (because science isn't busy enough with global warming and curing cancer), and here's what they found. As it turns out, most cats will eat grass when given the opportunity — in the UC Davis study, 1,021 cat owners observed their cats' behavior around grass, and only 11 percent of the animals appeared to have no interest in eating it. And prior to eating the grass, 91 percent of those animals did not display any of the characteristic signs of illness, like excessive thirst, poor appetite, or changes in behavior.

So now we're left with having to come up with more theories. The UC Davis researchers think grass-eating might be leftover behavior from before cats were domesticated. When you live off a diet of rodents, you pick up intestinal parasites. Eating grass makes you barf, so therefore if you want to purge the parasites from your innards, eating grass is a good way to do that. 

But a problem with that theory is that cats don't always barf when they eat grass, in fact, barfing only seems to happen roughly 25 percent of the time. So the other theory is a much simpler one: Maybe cats just like to eat grass. Hey, some people enjoy those awful spinach smoothies with wheatgrass, so there's no accounting for tastes.