Q: Do you know what would cause this damage to tomato plants?
A: It could be either a squirrel or a chipmunk. In my experience, squirrel damage is usually higher on the plant than chipmunk damage. The chipmunks usually chew close to the ground.
There are no repellents for either of these two creatures. The best course of action is to fence them out. But sometimes they will climb over a fence to get into your tomatoes despite the barrier.