Canadian porcupine, Common porcupine
The North American porcupine (Erethizon dorsatum) is the second largest rodent in North America, after the North American beaver. In addition, the range of this species is the northernmost of all porcupines. Its ancestors crossed the Atlantic from Africa to Brazil 30 million years ago, and then migrated to North America during the Great American Interchange after the Isthmus of Panama rose 3 million years ago.
Porcupines are usually dark brown or black in color, with white highlights. They have a stocky body, a small face, short legs, and a short, thick tail. The most distinguishing feature of the porcupine is its coat of quills. An adult porcupine has about 30,000 quills that cover all of its body except its underbelly, face, and feet. Quills are modified hairs formed into sharp, barbed, hollow spines. They are used primarily for defense but also serve to insulate their bodies during winter. The quills are normally flattened against the body and in this position are less easily dislodged. Porcupines do not throw their quills, but when threatened contract superficial muscles which cause the quills to stand up and out from their bodies. In this position, they become easier to detach from the body, especially when the tail is swung toward an attacker. The barbs at the end of the spines lodge in the flesh of a victim and are difficult and painful to remove. The North American porcupine has a strong odor to warn away predators, which it can increase when agitated. The smell has been described as similar to strong human body odor, goats, or some cheeses. The odor is generated by a patch of skin called the rosette, on the lower back where modified quills serve as osmetrichia to broadcast the smell.
Having the northernmost range of all porcupines, these rodents occur throughout much of North America, from the Arctic Ocean to northern Mexico. They inhabit most of Alaska and Canada, the northern part of the Great Lakes region as well as the western and northeast regions of the United States. North American porcupines live in coniferous and mixed forested areas but have adapted to harsh environments such as shrublands and tundra. They make their dens in hollow trees or in rocky areas.[
North American porcupines don't tend to display social behavior and are mainly found solitarily, although they do have a social structure. During the winter months, up to 8 individuals may live in the same den. During this period they are also known to forage in groups of up to 20 animals. They choose to forage in these groups in order to protect themselves from predators. However, some may prefer living and foraging alone. Each individual has its own territory, which it defends. Meanwhile, males of this species are more territorial, fiercely defending their home range. These nocturnal animals rarely go beyond their territories. They communicate with conspecifics through a system of acoustic, chemical, visual, and tactile signals. North American porcupines have specific behaviors to warn or defend against predators. They have a strong warning odor which they can increase when agitated. When threatened, an adult porcupine can bristle its quills, displaying a white stripe down its back, and use its teeth to make a warning, clacking sound. If the olfactory, visual, and auditory warnings fail, then it can rely on its quills. An adult porcupine when attacked turns its rear to the predator. When approached, the porcupine can swing its tail at an attacker's face. The porcupine's last line of defense is to climb a tree.
The winter diet of these herbivorous animals mainly consists of tree bark. During the rest of the year, they feed upon green vegetation such as leaves, twigs, and fruits, supplementing their diet by gnawing on occasional bones and antlers that are rich in mineral nutrition.
North American porcupines have a polygynous mating system, where a dominant male breeds with multiple females. Breeding occurs only if a female wants to breed. The latter tries to get pregnant by the 'best' male. North American porcupines breed between October and November. A single young is born after a gestation of 210 days. The baby is nursed for 127 days, during which period the mother provides it with the required food. During the first 6 weeks, females are constantly nearby their young, meeting the babies only during the night. Mothers spend their daytime hours sleeping, while their young are hidden in a secluded place on the ground. Independence is reached at 5 months old, while the age of reproductive maturity is 29 months old for males and 25 months old for females.
Currently, there are no serious threats to the population of this species as a whole, although the animals are often hunted and trapped as pests due to damaging trees, crops, car tires, and other property. The population in Mexico is on the verge of extinction as a result of excessive hunting. In addition, North American porcupines suffer from collisions with automobiles.
According to IUCN, the North American porcupine is common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) and its numbers are stable.
