Dog Meets Porcupine

By Ran Courant-Morgan, M.S., BCBA, CCUI, ADT-IAABC, LFPE

In September 2012, my wife and I took our dogs and went up to New Hampshire for our anniversary weekend. It was our second wedding anniversary; on the first, we had adopted a puppy, and we brought her and our other dog with us for this year’s adventure. The cabin is on a dead end dirt road with the houses of families who have been going there for a hundred years (at that point, it was only 90 years, but you get the idea), and the general culture is that dogs are loose: they run around off leash, sleep on the docks, and visit the other dogs and families of the neighborhood. 

Unfortunately for me, this was the first time I learned that we had porcupines in the area.

Shortly after we arrived and let the dogs out to run around, our one-year old dog, Lenny, came stumbling around the corner, pawing at her face. “What is she doing?” I asked, confused - until she got close enough for me to see that she was trying to remove the many porcupine quills sticking out from her muzzle. Our neighbor offered to help pull them out, and Lenny sat there stoically while he used tweezers to pull out about 15 of them. That was enough for us both to realize that 15 was just a tiny fraction of how many there were and that veterinary support was needed.

We drove her to the emergency vet in town. They sedated her, removed all the quills, and we brought her home a couple hours later, somewhat amused and somewhat dismayed at the way our anniversary was kicking off. (And we wonder why my wife has a mild aversion to all the dogs I want to bring home!).

“Well,” we told ourselves. “At least we know that won’t happen again. It was such an uncomfortable situation that we know she’ll never do it again!”

Imagine our surprise when a year later we went back to the cabin (our third anniversary!), let the dogs out, said hi to the neighbors, and saw Lenny running towards us, ears pinned back, stopping only to paw at her face. “Again!?” I exclaimed.

Back to the vet, where they commented about how it was almost exactly a year to the day since our prior porcupine-quill-related visit! Of course it was. Happy anniversary, honey.

According to the vet, September is porcupine breeding season, which is when the porcupines are more likely to be down on the ground - increasing the chances of their interacting with other ground creatures, like my dogs. We are now very careful to keep all the dogs leashed in September. 

Unfortunately, this had not  generalized for me into early August, which is when, in 2023, Beacon had her first porcupine encounter. She had over 250 quills removed from her face, tongue, gums, and legs.

Why does this keep happening?

When I was talking to someone about what had happened they said, “Well, at least she will have learned not to approach porcupines!” and this got me thinking. Lenny certainly hadn’t learned to avoid porcupines, and the vet mentioned that they often had “repeat offenders.” One would think that biting a porcupine would be aversive, giving the obvious discomfort the quills inflict and the intensive care that immediately follows. The more I thought about it, though, the more it made sense. One reason dogs may not learn to avoid porcupine after an incident like this is not necessarily because it’s not punishing, but as a direct result of  the side effects of punishment.

Let’s assume that biting the porcupine - which it seems she tried to do, given the quills in her mouth - was punishing. The presence of a porcupine now predicts pain and discomfort, and therefore escaping or avoiding the porcupine is more valuable than it likely was in the first encounter. One way that a dog might escape or avoid a porcupine is to move away upon seeing it, which is what many of us might expect would happen.

However, it’s also very possible that, rather than moving away, the dog will attempt to make the porcupine move away. This aligns with one of the documented side effects of punishment: aggressive and emotional responses (Cooper, Heron, and Heward 2020). Whether or not the dog is attempting to make the porcupine move away or responding aggressively or emotionally, they could emerge as a topographically similar response: aggression towards the porcupine. In other words, the aversiveness of the porcupine quills has been learned - but this results in increased approaching and biting, rather than avoidance.

For some dogs, an interaction with a porcupine could be a one-time learning event, after which the dog avoids porcupines and anything that appears similar to a porcupine. However, for many other dogs, the experience will have the opposite effect, resulting in multiple porcupine events.

What the research says

When I looked into the research on dogs and porcupines, I found that the fall does seem to be the most common time for dogs to encounter porcupines; but there is definitely still evidence of encounters during the rest of the year. Johnson et al (2006) found the following distribution of quill injuries by season: 38.2% in fall, 28% in spring, 24.3% in summer, and 9.5% in winter. 

Johnson et al reviewed hospital records of 296 porcupine injuries to dogs from 1998 to 2002. A total of 215 dogs were included in the study. They found that 31 dogs (14%) had repeated injuries; of these, most of the dogs only had two episodes of quill injuries, but 9 of the dogs (4%) had more than 2 episodes, with four of the dogs having 3-6 episodes of quill injuries. Johnson et al note that while “fifty-four cases of repeat incidents of porcupine encounters were documented… other patients may have been treated for additional porcupine encounters elsewhere. Owners should be warned that dogs do not “learn from their mistake” and that repeat quill injury episodes are common.”

Things to know if your dog is quilled

When we picked up Beacon this summer, the person who discharged us told us that any quills they missed would work their way out. However, multiple articles in veterinary journals indicate that this is not the case, and that they will, in fact, work their way in and can cause serious damage. There are reports of dogs with complications due to quills migrating into the joints, eyes, lungs, heart, brain, and more (Johnson et al, 2006; Sevy et al, 2023; Shank et al, 2021). There is evidence that waiting longer to bring the dog to the vet is associated with increased complications, and that, if there are complications from quills that are missed, they are most likely to become apparent within three weeks after the event; therefore, the dog should be closely monitored during that time (Johnson et al 2006).

So what next?

Porcupine encounters are, for many dogs, uncomfortable and intense - and of course this does not translate to a great experience for their humans, either! After Beacon’s first quill removal at the emergency vet, we found that they had missed a few quills in her face. Due to the risk of migrating quills, we went to another emergency vet, where Beacon was sedated and they attempted to remove the quills they could find. However, they were only able to get to one quill, where we had seen at least 3. It is recommended for us, at this time, that we just monitor her, and if we see any unusual symptoms arise in the next 5 years, to remind the vet of this quilling event.

While someone might be inclined to let their dog “learn from their mistakes,” the evidence suggests that this is not an appropriate approach with dogs and porcupines. But not all hope is lost! In some parts of the United States where venomous snakes pose a risk to dogs, there are “snake avoidance” training programs. Many of these rely on punishment, which could result in many of the same behavioral outcomes discussed here. However, there is a movement to use positive reinforcement-based methods to teach dogs to avoid snakes (here’s a course through Karen Pryor Academy, and this video about the protocol is available for purchase), and these same methods could be utilized to teach dogs a specific behavior they should engage in when encountering a porcupine. If you have a dog who might be inclined towards chasing wildlife, this is probably worth exploring! In the meantime, stay safe out there, especially in the late summer and early fall.

References

Cooper, J. O., Heron, T. E., & Heward, W. L. (2020). Applied Behavior Analysis (3rd Edition). Hoboken, NJ: Pearson Education.

​​Johnson MD, Magnusson KD, Shmon CL, Waldner C. Porcupine quill injuries in dogs: a retrospective of 296 cases (1998-2002). Can Vet J. 2006 Jul;47(7):677-82. PMID: 16898110; PMCID: PMC1482438.

Sevy, J., Gottlieb, L., Vaught, M., & Rozanski, E. Porcupine quilling–associated pneumothorax in dogs: 25 cases (2001–2022). AVMA, 2023 Jan; 261 (4).

Shank AMM,  Teixeira LBC,  Dubielzig RR.  Ocular porcupine quilling in dogs: Gross, clinical and histopathologic findings in 17 cases (1986-2018). Vet Ophthalmol. 2021; 24: 114–124. https://doi.org/10.1111/vop.12851