I’m going to be a dissenting voice: Although most likely boredom, not necessarily so.
My young gelding is on either 12 or 24 hour turnout, depending on the weather, gets worked regularly, and is a mellow dude – and still nibbles on fences, both ridden and when out to pasture. He doesn’t nibble the wood in his stall. He’s not a beaver by any means, and he’s not cribbing or windsucking. He just likes to take little nibbles out of fences.
Personally, I think it’s a little stereotype behavior (like stall weaving or cribbing), that started as a mimic behavior – he developed the habit while pastured with a couple of equine beavers. It became an ingrained habit over time, and now any time we stop at a fence, he has to take a little bite out of it. He’s not obsessive, so if I ask him to step back from the fence, he won’t try to reach out to it.
Again, I agree with the group that it is most likely boredom (or at least started out as boredom), just wanted to offer this slightly counter example, because there can be other reasons for wood chewing.
If it is boredom from being in a stall, I’d suggest a stall toy of some sort, especially one with a reward, like an Licky Thing.
Proud Partner of Yankee Allstar,
Rocky Mountain Gaited Horse