At least in the northern portion of its range, the North American porcupine (Erethizon dorsatum) uses dens in winter for protection from wind and weather. They choose spots near good feeding trees, but they are flexible in terms of den type. Rock crevices, hollow logs, abandoned beaver bank lodges, space under upturned trees and space under outbuildings are all examples I have seen. These dens make interesting trail camera targets for studying porcupine behavior as well as for capturing visits by porcupine predators and by other animals which might also want to use the den. They are usually easy to identify, for reasons described below. This post will include how to identify porcupine winter dens, photos of several dens I have found, and videos of interesting behaviors at a couple of different dens.
Identifying Porcupine Winter Dens
Porcupine dens are often conspicuous because porcupine scat accumulates at the entry, so the key to finding one of these dens is to learn to recognize the scat. Like many herbivores, these prickly rodents void pellets. They are usually curved and elongated, measuring about 1 inch long and 3/8 inch wide. They have been likened to cashew nuts in size and shape, but often in a pile there will be some that are nearly straight, and some that are small and oval, kind of like deer pellets.
Apparently porcupines push the droppings out the doorway as they accumulate, creating piles just outside the den, which you will see in the photos below. Station your camera in late fall or winter after you have found evidence of fresh scat. You can certainly set a camera on one with only old scat, but the chances of capturing porcupine activity are greater with evidence of recent occupancy.
Examples
Dens among rocks
In Massachusetts where I spend a lot of time tracking, most porcupine winter dens are associated with rocks: They are under rock overhangs, in cracks, and between boulders, especially if these resources are in close proximity to hemlock trees, a favorite winter food source. My experience is similar to that of porcupine expert Uldis Roze, who found that 70% of porcupine dens in the Catskill Mountains were in rock outcrops. Check out the following examples of Massachusetts porcupine dens.
Dens in tree cavities
Another den type is the tree cavity. Porcupines will den in a cavity of a tree trunk, from ground level to at least 10 feet above ground. They probably den higher than that, as long as the cavity is large enough. The next photo shows one in a hollow at the base of a large tree. To see one in a tree cavity about 10 feet above ground level, scroll down to the Videos.
Dens in old beaver lodges
I have seen the occasional porcupine den in old beaver bank lodges but it probably doesn’t have to be a bank lodge. They’d probably use an old pond lodge after the pond drains.
Trail Camera Videos at Porcupine Winter Dens
This video of the action at a porcupine den in a tree cavity about 10 feet above ground level, reveals so much interesting behavior. Turn the volume up and listen to the noisy competition for the cavity. Notice the porcupine’s surprisingly clumsy butt-first descent, in comparison to the raccoon’s and the squirrel’s rather graceful head-first descent. Watch the tail action as the porcupine comes down – it appears to be used to help find the way, as well as for stability.
The next video features more noisy squawking, as one animal approaches an occupied den. With my cameras I am finding that competition for a den is fairly common. Roze has found that each individual typically uses a given den for a few weeks, then finds another. My videos suggest that “finders keepers” is the rule. Perhaps they would use the same den all winter if it was always available. Roze also says that they occasionally share winter dens, though often begrudgingly.
Finally, here’s one featuring a fisher, the most effective porcupine predator, nosing around a den. Notice also the nervousness of the porcupine who emerges from the den 6 hours later.
Bobcats and raccoons also show up at porcupine dens fairly frequently, particularly those among rocks. It appears that both species scent mark under rock overhangs and along rock faces, and both species also use rock crevices for shelter. This post features a video of a raccoon and a bobcat at a porcupine den: Raccoon Scent Marking and Comparison with Bobcat.
