Porcupines: Pests or Pets?
A common resident of the Northwoods, the porcupine is often the source of much frustration and consternation for forest managers and homeowners. The Masked Biologist wants to help you get to know the porcupine and maybe share some tips or tricks to reduce porcupine damage in this week’s Wildlife Matters.
On a recent family outing, we noticed that wildlife is on the move taking advantage of what’s shaped up to be an early spring. We also noticed that one animal that seemed to be bad at safely crossing roads was the porcupine.
Porcupines are the second largest rodent in North America, the beaver being the largest. A full grown adult porcupine can reach 30 inches long and weigh 30 pounds. There are 27 varieties of porcupine located around the world. In Wisconsin, we only have one porcupine species—the North American Porcupine. The North American porcupine is unique among these subspecies because it is the only one in the world adapted to cold winter temperatures. In the wild, a porcupine might live six years, which is actually quite long for a rodent; in captivity, they can live up to 18 years. The female porcupine gives birth to one offspring a year, called a porcupette, born headfirst, with soft quills that don’t harden until after the baby is born.
Porcupines have a very good sense of smell, but very poor vision. They are mostly nocturnal; this is primarily because they feed on leaves, twigs, and bark, and the best materials and nutrients are available at night when the tree is not actively photosynthesizing. They also like to eat green plants like skunk cabbage, clover, and lupine during the growing season.
Porcupines are best known for their quills, actually a kind of modified hair with tiny scaly hooks at the tip and base. The shaft of the quill is spongy and somewhat hollow. When the porcupine feels threatened, it turns its back and rump toward its attackers and tightens a special muscle under the skin. This loosens the skins grip on the quills, making them easier to pull off. In fact, some might even fall off if the animal shakes or jumps, giving the illusion that the quill was thrown. However, the quills are not thrown or ejected by the porcupine. When an animal touches a quill, the tip sticks in the skin, the tiny scales grab on and hold it there, and the spongy air-filled shaft swells with the added body heat of the victim. The result is a painful distraction that allows the porcupine to move away from its attacker. There are still some predators that focus on eating porcupine. The fisher is well-known for its ability to slowly and painfully kill a porcupine, flip it over, and eat it from the stomach, where there are no quills. Bobcats also eat them, as do owls and a couple other predators, but sometimes these predators are mortally injured by their prey. Quills are an effective deterrent for most porky predators, with the exception of vehicles, which seem to have no trouble killing them as they bumble across roads at night.
Porcupines like to pick a favorite tree, called a loafing tree, and slowly kill it by munching off the bark. If you see this happening to a tree you want to save, you can try putting an exclosure around the tree, like some smooth tin wrapped around the trunk. Because they have to gnaw constantly to keep their front teeth short, and because they really like salt, porkies will chew animal bones, shed deer antlers, tool handles, footwear, clothing, paint, mineral licks, road salt, soaps, plywood, siding or anything else that has salt in it, or has been soaked with sweat or urine containing salt.
While it is fairly easy to trap, fence out, or shoot porcupines to protect plywood and siding, it may not be desirable. Applying an anti-cribbing solution may be a better option. Anti-cribbing solution, like Carbolineum, is a chemical that horse owners put on the top stall rails to keep horses from chewing on them. You may be able to ask the local farm supply store to order some in for you, or you might order it online and have it shipped. While it may not be the cleanest or easiest solution, it is definitely more humane and less messy than shooting one in your yard. Porcupines are not a game animal; in fact, they are an unregulated animal in Wisconsin. This means they can be shot when causing damage, they can legally be live trapped and relocated, and they can be legally captured and kept as pets if you wanted to do that for some reason.
If you haven’t had them chew on a favorite tree or your deck, siding or deer stand, you may not have given porcupines much thought before now. They are fascinating animals and add variety and complexity to our Northwoods landscape.