My cats beg constantly to go outside, and I occasionally let them roam under my supervision. One cat couldn’t care less, but the other seems to enjoy chewing on plants and grass, and he will bolt right to certain types of plants the second I open the door to let him out. He never actually swallows the plant, and usually seems to gag after ever bite like he’s trying to throw up. Why would he put himself through such torture? (on a side note, I once saw an alligator chew on some water plants for an hour, could this be for a similar reason?)
Some references via Google say “the desire to munch on plants is actually not driven by hunger. Experts aren’t certain what precisely motivates a cat to chew plants.” So, does anyone have a guess?
WAGs:
Dogs: Dogs are just stupid and will eat dam near anything.
Cats: Cats through grooming accumulate a lot of fur in their innards (hairballs). This is probably uncomfortable. When they eat some grass, it causes them to vomit, thereby alleviating the discomfort. Not suggesting that they consciously put cause and effect together, or that they know why they are doing it. But imagine a gazillion cats, some that have this behavior and some that don’t. The grass-chewers, being less “stuffed” with indigestible matter, may digest food better, or hunt better, and thus have a very slight edge. More of them might survive to pass on this behavior.
Another reason is that when cats eat mice/birds/antelope they get some previously digested plant matter from the prey’s innards that they still need in their diet.
Our tame tigers still need to get that from somewhere. I used to grow grass for mine, or buy it but haven’t in ages. (I’m a bad mom). I’m not sure if most cat foods do provide these nutrients, but the better high-quality ones should.