If it very low near the ground could be rabbits...........if it is above a ft.or so..........deer......they chew & rub their antlers on them........use spectracide tree repair spray......I bought mine at Walmart but Lowe's & Home Depot should have it. You might need to put a wire fence around it and support it with 2....2 by 6 banged into the ground & tie the fence to it. Also deer do not like Irish Spring original soap, I cut it into 4 cuts and use old onion bags and hang on the fence near the tree...........they don't like the smell. when it rains it refreshes the smell.