Endearingly slow moving creatures, at least when on the ground. They can move surprisingly fast up a tree. Porcupines are mostly arboreal, often sleeping on tree branches high above the ground (though they do fall off and one biologist studying this species, said that they suffer a number of broken bones because of this). They den up in large tree cavities, in hollow stumps, log, inside caves, rock piles, and even use culverts in winter, to rest in.