Alot of the antlers that I have found espercially near a water source get chewed up pretty fast and I think the muskrats and beavers do the lions share of the damage to the ones near water.
Yes the rabbitts, squirrels, porkupines, possums etc can eat away at them pretty severely, antlers are a great source of calcium and minerals for the animals especially in the winter when times are lean.
I found ones that have been chewed all the way through the main beams, this matched set would have been a nice 8 point shed set if not for the chew marks now they are antler buttons and assorted antler use products.
Hope you find a good one.