It's probably a vole. Voles will eat the bark, roots, figs and sometimes even the wood. I had a couple of whole tree completely disappear from them. Now I set traps, and put mothballs and chopped garlic around the trees. Last was the first year with no damage so I'm going to do it again.
I was told you can also buy a product called "Scoot" but I haven't found it around here to give it try.
I hope you get them under control because once those critters find a food source they invite the whole family over for dinner and you're picking up the tab.