I think rodents would attack lower down, and I've never seen a squirrel in my garden. (Actually, no rabbits, either - I've gone to some lengths to make the veggie garden rabbit proof, and the cat keeps them out of the rest of the garden for most of the time.)
But I saw the cat chew off some grass at just that height today, so my suspicion is getting stronger... Especially as I've just noticed that now that I've covered the sugarsnap peas with wire mesh again, that same villain has started on my other peas! I'll have to cover everything, I think. And I'll spend the day at the kitchen window staring at my peas, so I can catch the culprit red handed... Or green mouthed

. Whatever it is, it's eating the stuff; there's no debris lying about.
It's nice to know my cat has her greens every day, but can't she stick to grass? Or if it has to be legumes, I've got some nice clover and tares... She's probably just taking revenge because I wormed her the other day. Didn't speak to me all night after that.
Ina