Porcupines are prolific tree climbers; habits benefit others

An older male porcupine raises up on its hind legs.

Story and photos by Scot Stewart

“The spice of life is all about diversity. Even the smallest gem adds great delight to life’s plate.” – Anonymous

Life in heavily forested areas of the U.P. can seem dark and mysterious. The canopies of large sugar maple, American basswood, pine, spruce and birch can block out much of the sunlight and make it difficult to see wildlife, especially animals living in the trees like pine martens, flying squirrels, grouse and owls. Much time is required in these woods to come to know all its characters. Time spent on the floor of the forest – close to the ground on the dirt, and up in the canopy, climbing trees to find the difficult to see, often-missed portions of the life cycle of the forest. The connections big and small are even more challenging to understand.
One of the strands of the mysterious forest is the porcupine. It’s a strange, greatly misunderstood animal, often filling those familiar with the North Woods with many misconceptions. Because of it nocturnal activities and its life in the treetops, it is not seen often, and when it is seen, it is always headed the other direction, not choosing to stick around and chat.
There are eight “new world” porcupines – ones that live in North and South America. A second group of “Old World” porcupines lives in Africa and Asia and is characterized by longer quills organized in clumps instead of singly like the “New World” ones. Only one porcupine lives in the United States, and it’s officially called the North American porcupine. All the rest live in Mexico, Central America and northern South America. Only the beaver is a bigger rodent in the U.S. North American porcupines can be up to two-and-a-half-feet long and weigh up to 30 lbs.
They are built to climb trees. They have stocky bodies, long, curved claws for digging into bark and soft, and leathery cushions instead of first toes to hold onto branches better. They are basically grayish with quills providing white highlights, but black melanistic forms and white albino forms are known. Neither are seen often, but their condition can bring them fame.
In 1911, National Geographic magazine published an article by George Shiras III that included an albino form he photographed along the shore of Whitefish Lake in Alger County. Shiras is well known for his pioneering efforts to photograph wildlife with a flash. His extensive articles in National Geographic in the early 20th century featured white-tailed deer, lynx, raccoons and other animals, but his long-term photographic series of an albino porcupine was one of his more unusual. It was copied in A flashlight story of an albino porcupine and of a cunning but unfortunate coon. Over a number of years, he followed the all-white animal that may have been completely blind or at least of limited vision as is a frequent malady of albino individuals. He watched and photographed it as it came down to the lake at predicted spots where it could be caught with his flash at night. The porcupine became another important part of Shiras’ Upper Peninsula wildlife legacy.
Looking like big mops, porcupines always seem to be moving in slow motion. Great information about their natural history, especially in Michigan is found in Michigan Mammals by Rollin H. Baker. Like sloths, they are not particularly comfortable on the ground and when frightened can move into second gear as they aim for the largest nearby tree. The fur on their backs may become erect, with their whitish, black-tipped quills standing out amid their long, grayish fur.

A close-up view of a porcupine foot. The leathery pad of the foot helps the animals grip and climb trees.

Once into the embrace of a protective sentinel though, they slide around to its backside and steadily make their way up away from danger, usually 30 feet or more above the ground. It is there they spend the greater part of their days in summer and good parts of their nights in winter.
Porcupines have few enemies but many challengers. Wolves, coyotes, mountain lions, bobcats, red and gray foxes have all been known to kill porcupines, and smaller animals like mink, weasels, pine martens and even great-horned owls have been known to eat porcupines, but these smaller animals may have simply eaten dead ones.
All of them, plus domestic dogs, may dive in to attack, only to back away with a snoot full of quills sticking in their cheeks and nose. Unfortunately for them, the quills are not designed to be pulled out easily. Their tips are etched with tiny barbs. Like fishhooks, they are meant to be inserted easily and extracted only with extreme pain and effort, or not at all. Some attackers are fortunate to have the quills come out. For other, unfortunate predators, quills only extend into the skin and muscles more completely with effort and may continue on a path through the body until they reach and penetrate important organs and occasionally kill the animal.
One dog owner in Ontario has a huge jar filled with porcupine quills extracted from a team of huskies with very short memories. The owner, a part-time musher, found the best way to pull a mouthful of quills out was to wedge the dog between his legs, hold the dog’s head, grab a quill firmly with a plyers, and gently push the quill farther into the dog. The dog would wince and pull away, leaving the quill in the grip of the plyers an inch away. He then repeated the process until all the quills were removed.
The one true predator of the porcupine is the fisher, a larger member of the weasel family. The nearly black animals have been reputed to have the dexterity to flip the porcupines quickly on their backs, giving them access to the prey’s quill-less bellies and a chance to make a kill. It seems like a logical strategy, but contemplating diving into a big mop filled with barbed spikes to grab a foot or nose and give a 30 lbs load a quick flip seemed a nearly impossible task, even though porcupines killed in this way are turned on their backs so the fishers can feed on the porcupines internal organs from their bellies.
More extensive observations revealed the fishers were using a different method to subdue their prey by grabbing and biting their heads and necks to kill them. Then the fishers were able to turn them over and eat them. Porcupines will attempt to avoid fatal attacks by pushing their faces against a tree trunk to protect this vulnerable spot and protect themselves with a shield of quills on their back and tail. They are thought by some to throw their quills but the illusion stems from the loose manner their quills are attached to their skin, and the back and forth shaking movement they exhibit when threatened. Loose quills can fly off their back and tail, making it look like they have been shot at their attacker. There is a small muscle attached to each three-inch quill to raise it up and provide some distance between enemy teeth and their own skin. The quills are extremely stiff and sharp, and even predators successfully able to take a porcupine end up with a few quills in their face or paw.
Trapping all but eliminated the fisher from Michigan in the mid-1940s but a correlation between lower porcupine populations and higher numbers of fishers in parts of New York state led wildlife managers to realize reintroducing fishers into Wisconsin and Michigan could lower the numbers of porcupines in both states and reduce the damage to trees in commercially important forests. By the 1960s evidence of the successful reintroduction of the fishers was seen as porcupine numbers decline.
The lives of porcupines in Michigan varies greatly with the seasons. In winter porcupines escape cold conditions by denning in small openings in trees and logs, rock crevices and other openings on the ground or in hollow tree trunks and branches higher up in the canopy. The winter conditions can restrict their travel to just a few large trees where they feed mostly at night on bark and conifer needles. For those who spend a lot of time in the woods and don’t see many porcupines during the winter, this may be the reason why. They can however be located by a pile or vast mound of droppings that may come tumbling out of an opening in a tree hollow where they are roosting during these colder months.

Those who spend a lot of time hiking in the woods may only see porcupines on rare occasions. It could be they’re looking in the wrong directions. Porcupines enjoy climbing, feeding and resting high up in trees.

During winter, their diet is almost entirely bark from a variety of trees and needles of hemlock and spruce. A diet like that is extremely low in sodium. It drives porcupines to search for the element, especially in spring when the snow has melted, and they have more mobility on the ground. In spring their mobility changes and so does everything else for them.
After a slow climb into a hemlock or aspen tree they may remain there several days feeding on new limbs and buds or the inner bark of the tree trunk Like white-tailed deer and moose, they begin to seek out salt to make up the deficit and it often gets them into conflicts with humans. Handles of tools like axes and hammers are doomed if left out. Anything with salt on it – from perspiration, urine, even road salt – is of interest to porcupines. Outhouses are a frequent target, as are the undersides of cars – especially things like brake lines covered in the winter’s road salts – can be chewed.
Much attention has been given to plywood construction in the U.P. Because porcupines are rodents with strong, ever growing teeth and live a life feeding on the bark and branches of trees, they are ever so capable of handling and devouring anything made of wood. It is not difficult to find signs missing corners or even whole sides of signs in places where there are higher densities of porcupines.
It is always a wonder to follow the lives of animals and watch how their lives impact those of others. It is apparent humans still have much to learn about the connections between animals, plants, fungi, bacteria, the geology, hydrology and climate interconnections. Porcupines feeding on leaves high in the trees are out of harm’s way and often are a beneficiary to other mammals in the woods. When feeding on slender branches their chewing can cause twigs to fall away and land below. There, particularly in winter, hungry snowshoe hares, deer and other herbivores benefit from the extra bounty.
As snow depths climb during harsh winters, those small tidbits are welcome morsels, particularly to hungry hares. As winter ends and the porcupines seek out new foods, they move more often. Because they only travel around two mph and mostly in darkness, they become frequent accident victims on highways. Motorists first swerving to miss them may later become the owners of flat tires if the quills puncture tire sidewalls and cause slow leaks.
There have been concerns that porcupines feeding on bark were a commercial danger to trees that might be girdled by the animals feeding on bark. A few trees do have their bark eaten extensively and lose branches and tops above the eaten bark, but this type of feeding usually has little impact on the overall health of the forest. They are also known to damage farm crops like corn and alfalfa.
Porcupines can court all the way to January with both males and females occasionally mating with multiple partners. Their gestation period is exceptionally long at 209 to 213 days. Single young are born in April, May or June and weigh just over a pound. They are extremely precocious, with soft, one-inch quills that dry and harden within a few hours. They are able to walk within a few hours, can climb trees within a couple days, are weaned within two weeks and begin eating solid food – in trees! Young may follow their mothers until they are nearly two.
During their first days of summer, porcupines in the U.P. seem to prefer yellow birch and basswood, and elm if they can still find it. Later in summer they will also feed in maple, hemlock, aspen, northern oak and cherry. During warmer weather they seem to prefer eating during daylight hours and nap in the host trees between meals. They will also feed on plants closer to the ground and some aquatic plants.
Porcupine live up to 10 years in captivity. Their longer lives allow them the luxury of a single youngster, and that young one usually has a low mortality rate due to its early time in trees and the protection of its quills.
Quills have been an important part of the art and crafts of native people in places where porcupines are found. Baskets decorations, ornamentation for pouches, quivers, bonnets, clothing and moccasins have long been part of well-crafted quill work.
Native peoples recognized the unique character of the porcupine and its value to the northern forest. Time spent in the woods today allows all to appreciate how special these mammals are and the unique part they play in the natural world.

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