Since rabbits tend to be nocturnal, night time, creatures you will not always see them even though they may be around. How these small trees were eaten is a clue since rabbits tend to eat leaves, although they can chew stems down too. Squirrels will, if there is little else to eat, eat plants but mostly they stick with seeds, which nuts are. If possible make some cages to go around and over the trees to keep both the rabbits and squirrels away and see what happens.

Thanks for the reply. They lowest part of the stem was the only part chewed off. I am not sure if the animal ate it or just chewed for fun. I am fabricating a large net with plastic chicken wire and PVC pipes.

Let me ask you a foolish question. Will the remaining roots in the soil start a new growth? I haven't thrown them away yet just in case.

This doesn't sound like squirrel behavior to me, and there are rabbits in central FL.

Here is a link that might be useful: Florida Wildlife Control