I see more Porcupines in the average month around my home in the Adirondacks than I saw in a year and a half of trekking the Eastern and Western Wildways, though on those long conservation journeys I hiked through thousands of miles of forest that looked plenty inviting for bark-eaters. My fellow rambler Jerry Jenkins, author of the Northern Forest Atlas Project, has half-seriously proposed that here in the Adirondacks, at least, Porcupines — not quite the largest, but surely the pointiest of North American rodents — may be a keystone species.
What is a Keystone Species?
Keystone species are those that play roles in their ecosystems greater than their modest numbers would suggest. Examples are Beavers here in forested areas and prairie dogs in western grasslands, both of which enhance natural habitats through their building and feeding habits; and Wolves and Cougars, which serve as regulators on herbivore behavior and abundance.
North American Porcupines (Erethizon dorsatum; relatives of several similar quilled species of South America and Africa) may indeed play major herbivory roles here in the Adirondacks, where our forests grow much hemlock and hardwood. Porcupines feed heavily on hemlock branches and deciduous tree bark. Almost like climbing Beavers, Porcupines sometimes eat so much of a hardwood tree’s bark that they effectively girdle and eventually kill the tree. An individual Porcupine may have a favorite hemlock that she climbs most days for weeks, eventually pruning it into a new, more compact shape. Dead trees, of course, provide food and become homes for woodpeckers and cavity nesters, from chickadees to Fishers — the main predator of Porcupines.
High Numbers of Porcupines in the Adirondacks
Why do we seem to have so many Porcupines in the Adirondacks? I suspect this quilled rodent may be more abundant now than it was in earlier centuries because, unfortunately, our forebears exterminated Cougars and greatly reduced Fishers and Bobcats, the animals that eat Porcupines. These days, the main killer of Porcupines is the automobile, with many of the dark slow rodents meeting a tragic demise crossing a road or licking salt from the side of the road at night.
I sometimes puzzle when I see partially debarked trees, often American Beeches, high on a slope or ridge. The gnawing can look much like that typically done by Beavers; and sometimes for a moment I think: how came a Beaver way up here so far from water?! Then I realize (from the shallower chewing and the higher location) that the sculptor was the Beaver’s distant cousin the Porcupine, adding lighter colors to the grays and browns of tree trunks and branches. Sometimes, Porcupines, unlike other browsers, climb all the way to the tops of tall trees, especially hemlocks, but sometimes also hardwoods, to eat the more succulent tree branches or bark, sculpting more diversity into the forest.
Coexisting with Quills
I personally enjoy seeing Porcupines, and always chuckle when they show that embarrassed look, at unsuspectingly being spotted half-way up a tree. Some of my neighbors don’t look upon Porcupines so favorably, however, because of their penchant for chewing wood — occasionally including wood that people have fashioned for their own purposes. Having your porch supports gnawed by a Porcupine is annoying, I’ll grant; but there are benign ways (like wire mesh, hot pepper, or ammonia) to discourage rodents from chewing wood. Having your dog quilled by a Porcupine is unhappy for all, and there the solution is simply restraint. Quills are Porcupines’ self-defense, and we can’t reasonably blame the slow vegetarians for protecting themselves.
I hope we will welcome Porcupines as being important members of our region’s forest communities. I urge we also protect their mid-size natural predators, Fisher and Bobcat; and welcome home their largest native predator, the Cougar. Collectively, these predators can keep Porcupine numbers in check, while allowing them to continue their arboreal sculpting.
[Special thanks to Lake Placid-based nature conservation photographer Larry Master (www.masterimages.org) for permission to feature several of his photographs in this post.]