This is the time of year when my thoughts invariably turn to…porcupines. Yes, that’s right, this time of year, the phone calls pick up about interactions between humans and porcupines.
Porcupines are the second largest rodent in North America, the beaver being the largest. A full grown adult 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 kind of porcupine-the North American Porcupine. The North American porcupine is unique among these subspecies because they are the only ones 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, and don’t worry-the quills don’t harden until after the baby has been born.
Porcupines have a very good sense of smell, and 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 skin’s 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.
Porcupines are also known for gnawing on plywood and siding. 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, 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 solution.
Anti-cribbing solution, like Carbolineum, is a chemical that horse owners put on the top rails of horse stalls to keep horses from chewing on them. We have found that this same solution discourages porcupines from chewing on some of our plywood signs and structures. Porcupines also 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.
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.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR in Rhinelander, and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.