Can cows starve to death?

Can cows starve to death?

I had been keeping four cows in a shallow pit two blocks deep, four wide,
and ten long, open to the sky, but surrounded by fences (the idea being to
let me in without allowing them to wander out through the fence gate). I
left them for an extended deep digging session.
On my return I find I have only one cow remaining. While staring
disconsolately at my now-defunct leather farm, I noticed that a) the
remaining cow eats grass from time to time (like a sheep), and b) most of
the floor is actually stone, not grass, so there isn't much available.
I have sheep and chickens in identical adjacent pens. They appear to be
fine (no losses). The sheep did have more grass.
I am wondering if my other cows might have starved to death, or succumbed
somehow to overcrowding. Is that possible? If not, how else might they
have disappeared?