What should you do if you see an endangered animal eating an endangered plant?
Leave him to his lunch and mind my own business.
The animal may well be improving the the plant species' chances of survival by eating it and its seeds and then passing them in its shit, thus spreading them about in a ready-made package of fertiliser. Eco systems work like that.
I should especially not assume that just because I'm human I know what's best for either of them.