chewing up arbrovitae
Hello, and thank you for the question.'
It is likely, that the animal chewing on your arborvitae is a squirrel. In the winter, when they are hungry, they chew the bark for food and nip off the ends of branches to use in a nest or for whatever reason they can think of. I'm attaching more information about squirrel damage. Unfortunately, there is little that you can do to control them, as you can read in these articles. You may spray the area below the trees with Liquid Fence or a capsicum (red pepper) spray which may deter them but there are a lot of squirrels out there and they do live in trees. Please read these articles for more information. https://www.canr.msu.edu/news/tree_damage_from_squirrels_can_be_severe_during_winter_months and https://www.canr.msu.edu/news/red_squirrel_injury_to_spruce_trees_in_winter
You may also consult with a certified arborist to ask their opinion on what is causing the damage and how to deal with it. Contact an arborist in your area at www.treesaregood.org, the website of the International Society of Aboriculture.