look for douglas fir 8 to 10 inch in diameter, the picture showing the vertical marks are what you are looking for, once they get the bark off they drag their front teeth down the trunk to get at the soft cambium layer. the whiter the the wood the fresher the peel, they will start to color up right away, look at the darker pic for reference of one that is turning. i hunted for a timber company in the late eighties where we had them peeling 50 trees a week.