Zora chews wood. I thought when she was a baby that she did it to relieve teething pain, but she kind of kept it up. It is 100% a boredom issue. Given enough space and something to do (ie: grazing, slow feed, active pasture mates) she doesn't do it at all. She LOVES those Lik-it things, and she doesn't chew much in the barn IF there are other horses around. If she's by herself, she starts to "make her own fun." This horse also learned that if she "plucked" the tensile wire fence with her hoof, it made a fun noise. This could entertain her for HOURS. Usually until she pulled out some staples.

The others haven't picked up the wood chewing, but they are considerably older. And seem content with their activity levels in life.

One thing they do all REALLY like is stripping the bark off trees. When they were in a smaller pen, we often had to fell big poplars on the property (up north, they grow to a certain height, then pop out of the muskeg and fall on things...like your house.) We'd stick the trees in the horse pen for a while, and they all quite liked liked that activity. I was told by an older horseman that this is called "barking" and apparently used to be quite a common practice.