The porcupine well armed, long distance traveller

For such a common mammal, the North American porcupine has been the subject very little scientific research, says biologist Tom Jung. It has been cursed by dog owners more often than studied by experts right across the continent.

by Erling Friis-Baastad

For such a common mammal, the North American porcupine has been the subject very little scientific research, says biologist Tom Jung. It has been cursed by dog owners more often than studied by experts right across the continent. It’s also a familiar highway hazard wherever it waddles, especially during the spring.

Beyond that, however, the porcupine’s effect on the environment is relatively benign in the Yukon, says Jung, of the Yukon’s Department of Environment. Though sometimes eaten, it’s not a major food source for humans or other mammals. Nor is it a great obstacle to economic growth, especially in a region with no tree plantations.

What we do know about Erethizon dorsatum is intriguing, however. For one major thing, these large rodents are distinguished from their mammalian forest neighbours by how far they have had to travel to reach the Yukon, says Jung. “We don’t have many animals in North America that evolved in South America,” he adds.

“Most of the animals we have here evolved here or arrived by way of the Bering Land Bridge from Eurasia.” In fact, the far-more-common Western Hemisphere animal-travel story tells of North American mammals going south and replacing South American mammals.

The porcupines dispersed into the North, all the way to the tree line, following the last ice age. And, despite speed not being a quality anyone would associate with these lumbering characters, they moved north quickly. Many other familiar Yukon mammals, such as coyotes, are more-recent arrivals – four-legged cheechakos.

So what brought porcupines north?

“I think they were just occupying available habitat,” says Jung. They found room to move, plants to eat in summer and conifer bark to eat in winter. And few effective predators lurked between them and the boreal promised land. Those sharp, stiff quills – a modification of hair – have served porcupines well. And each porky is well supplied, with as many as 30,000!

Meanwhile, as they moved north, they apparently grew larger, in keeping with Bergmann’s Rule. This rule posits that mammals in cool regions tend to be larger than their counterparts in warm regions. South American porcupines run about two to 12 pounds (.9 to 5.4 kg). North American relatives can reach 40 pounds (18 kg). That fat is essential for keeping them warm in the boreal winter, though they may also climb trees to bask in the late-morning northern sun.

Bergmann’s rule doesn’t always hold, says Jung. Coyotes and red foxes, for instance, don’t appear to vary in size drastically from south to north. And shrews tend to be much larger to the south. But porcupines continue to serve the 19th-century biologist Carl Bergmann’s reputation well.

Unlike some rodents, porcupines don’t appear to reproduce rapidly, certainly not in the North. There have been rare cases of twins, but it’s more likely there will be one baby per year. Even that could really depend on how much nourishment the adults are getting, says Jung.

Bark is not all that nutritious and a long winter can leave the animals undernourished, he says. That’s why the bare roads of spring attract them, and why so many end up as road kill. Like caribou, which also feed on less-nutritious winter fare (lichen), porcupines lick needed minerals, like sodium, from the road.

Old World porcupines, which occur in Africa, not in Europe, are smaller species. They are also vulnerable to fast, determined predators like leopards.

“Almost anything will try a porcupine once,” says Jung. That’s why dogs, wolves and sometimes even wolverines can end up with quills in their muzzles.

Some people think fishers, who are of the weasel family, are porcupine specialists. Fishers are fast, strong and patient. They will repeatedly circle around to the vulnerable nose of the porcupine, where there are no quills. They wear the prey down, says Jung. Though he believes fishers are more opportunistic than they are actual porcupine specialists. At any rate, there are few of these small carnivores in the Yukon.

When threatened, porcupines may stick their heads in a crevasse, den or hole in the rock leaving only their well-protected back ends exposed, says Jung. And he stresses, there is no truth to the rumour that porcupines throw quills. They may swing their tails and their would-be predators may press their own faces into the quills, but quills are not Mother Nature’s prototype missile-defence system.

 

Close encounters of the painful kind

 

For most of us porcupines wander out of sight and out of mind – at least until we’re reminded of them by our overly curious dogs. I contacted Alpine Veterinary Medical Centre Ltd. seeking practical advice for anyone suddenly faced by a somewhat stunned-looking pet whose muzzle is full of quills.

Porcupines “are fascinating animals,” said veterinarian Dr. Jess Heath in an emailed response. “But they are definitely dangerous to dogs and the source of one of the most common veterinary emergencies we see.”

Removing quills from a stressed dog is not a recommended do-it-yourself project.

“The main advantage of bringing a dog with porcupine quills to a veterinary hospital is that a veterinarian will have the knowledge, and medication, to sedate or anesthetize a dog, so quills can be removed safely and without pain,” she wrote. The big problem is that quills can migrate under the skin if they break, as they do while a dog is thrashing around.

Alpine clinic vets have treated dogs suffering from quills that migrated to joints, eyes and body cavities, Heath wrote.

If a dog owner is far from a clinic and must treat a quill-riddled pet, Heath recommended “using a Leatherman or similar tool to grasp the quill as close to the skin surface as possible, and to pull it out on the same plane that it entered…”. Do not clip a quill, as it will be harder to grasp. And do not bend the quill when pulling it out.

If a muzzle is an option, it could prevent a serious bite. For those driving a dog to the vet, a cone may prevent more broken quills.

This column is co-ordinated by the Yukon Research Centre at Yukon College with major financial support from Environment Yukon and Yukon College. The articles are archived at http://www.yukoncollege.yk.ca/research/publications/your_yukon. 

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