The North American porcupine, Erethizon dorsatum, is thought to be generally solitary except for brief mating associations in autumn and mother-baby pairs in spring and summer. However, I believe I have some video footage of porcupines playing together in winter.

Some background: After getting several photos of two porcupines together during winter at two different Massachusetts sites, I realized there can be some interaction during winter at least in my neck of the woods. To learn more about their interactions, I set out two trail cameras programmed to record video last winter. I put one on a cliff near a cluster of porcupine dens in rock crevices, and the other facing a hemlock tree bearing abundant sign of porcupine browsing with a carpet of nipped twigs and a sprinkling of porcupine scat on the ground beneath.

Spilling from the mouths of the dens was fresh porcupine scat on a bed of old decomposed droppings, suggesting generations of porcupine occupancy. As for the hemlock tree – it had been well pollarded, suggesting generations of porcupine feeding. With their stout branches and dense sprouting of twigs at pruned ends, such trees become more desirable over time, because a porcupine can perch on the thick branches while feeding on tender young twigs without risk of breaking the branch under its weight.

Results? The camera at the dens never got a clip with more than one porcupine, but the camera at the feeding tree got several. In fact, there were seven separate instances of two porcupines together, each of which is labeled in the video below.

Here is a summary of what was seen in the video:

Interaction 1 – Two porcupines walking in tandem, the leader turns to face the follower and they wrestle for several seconds before resuming tandem travel.

Interaction 2 – Both porcupines walk toward the camera; the leader paws at it.

Interaction 3 – Rough and tumble behavior that goes on for about 8 minutes. (The camera was set to rest for 1 minute after each video clip so I did not get the entire 8 minutes on film.) This was the most aggressive interaction. At times you can see raised quills, tail slaps, and some spinning behavior, all of which are employed in defense against threats.

Interaction 4 – About 3 minutes of wrestling. You can see raised quills during this episode as well but it doesn’t look quite as aggressive as the previous interaction and notice that at one point one of the animals lies down and exposes his belly. I think that suggests he is not really concerned about being harmed by his partner.

Interaction 5 – Two porcupines walking in tandem, and the leader turns and faces the follower. The video clip stopped at this point, but if they had wrestled for more than a minute, another clip would have been recorded. So either they did not wrestle at all, or they did so briefly before moving on.

Interaction 6 – One climbs the hemlock tree while the other sits and watches.

Interaction 7 – One descends from the hemlock tree while the other waits to tackle. The two wrestle for 3-4 minutes. There does not appear to be much quill raising or tail slapping, and there is no spinning.

I suspect these two animals were traveling together quite often during the winter. It is remarkable that they appeared together 7 different times over a 4 month period in the same spot. What are the chances of that happening if they weren’t spending a lot of time together? And while some of the wrestling appeared aggressive, they nevertheless resolved their disputes (if they were, in fact, disputes) and continued to associate with one another.

Could the wrestling have been playful? Captive porcupines, especially those under two years of age, are known to play, and wrestling is one of their favorite forms of play. Porcupine expert Uldis Roze (see sources below) suspects that this behavior is rare in the wild, since porcupines do not have litter mates. However, I have footage of play between mother and baby, as can be seen in the video below, suggesting that play may be a normal part of a young porcupette’s experience.

So what is going on in the video at the pollarded hemlock tree? I don’t know for sure, but I think it is mostly play. It’s possible that their more aggressive looking interactions were competitive, since they took place at a highly desirable feeding tree, but some of the interactions were clearly not aggressive. I hope to get more footage next winter.

Drawing upon observations by Roze of porcupines in the northeastern US, I suspect the two animals are genetically related males, brothers with the same mother and possibly the same father, (but born in different years because, as I mentioned, they don’t have littermates). Why males? Because North American porcupines are unusual among mammals in that juvenile females disperse in fall while males stay in their mother’s home range and eventually establish their own home ranges near hers. This means that neighboring males are often genetically related. They are said to tolerate each other, but according to my reading, “tolerate” means they can feed in neighboring trees without doing battle. They are not known travel together on a regular basis. Of course my assumption that it’s the same two porcupines in each interaction is just that – an assumption….But…Occam’s razor….

Sources

Roze, U. Porcupines: The Animal Answer Guide. Baltimore: The Johns Hopkins University Press, 2012.

Roze, U. The North American Porcupine. Washington DC: Smithsonian Institution Press, 1989.

Shadle, A. R. “The Play of American Porcupines (Erethizon dorsatum epixanthum).” Journal of Comparative Physiology. 37 (1944): 145-150.

Interested in porcupines? See footage of a porcupine grooming and napping.