Prickly Porcupine

North American Porcupine

The prickly, untoward small mammal, the porcupine, is one of the anomalies found within the animal kingdom, mostly due to hairs modified into barbed quills. “Porcupine” means “quill pig” in Latin, though it is not a pig but rather a large rodent.  Two groups of porcupines are known: Old and New World porcupines. New World porcupines climb trees or are arboreal, Old World’s do not.  In North America, there is only a single species, dorsatum, in the genus Erithizon. Native to Canada, United States, and northern Mexico, sightings of live porcupines are relatively rare. South American porcupines have been divided into four genera: Echinoprocta, Sphiggurus, Coendou, Chaetomys with about 13 species.  There still remains some uncertainty within these latter groups by taxonomists.  The genus Coendou is unique as it is known as the prehensile tailed porcupine, meaning it can use its tail similar to monkeys.  

Porcupines are slow, lumbering, somewhat clumsey large rodents. In North America, evidence of their presence is often more likely seen in roadkills than observed alive in nature.

Porcupines prefer northern forests, range lands, and even deserts.  They are arboreal and adapted to graze in upper northern forests.  They are generalist, mostly nocturnal, herbivores, feeding on almost every kind of tree they encounter.  Porcupines are adapted to gnawing.  They have large protruding incisors and strong jaw muscles.  During wintertimes, porcupines feed on tree bark, sapwood and buds.  They will often feed on a single tree for days rather than moving from tree to tree often resulting in complete girdling and death of the tree.  So, control has often been exerted to preserve trees as their most efficient enemy, the fisher, has been depleted by trapping.  The agile fisher attacks the clumsy porcupine’s head and face, biting it until helpless, then feeding on the soft belly tissues.  Other enemies include cougars, martens, bear, wolf, coyotes, wolverines, great horned owls, and other carnivores.  Some learn fast and only attack once.  In the summers, porcupines feed mostly on ground growing shrubs and herbs.  Their intestines are extensive allowing herbaceous materials to more fully decompose and ferment by bacteria before absorption.  Porcupines are attracted to salt containing materials such as boat seats, outhouses, plywood.  My dad, who many years ago worked summers by plowing virgin Idaho sagebrush ground with a team of horses, often had problems with porcupines gnawing and damaging salt impregnated leather harnesses between uses. 

Porcupines defend themselves primarily with their spiney tails.  Their best defensive posture is climbing a tree and swinging their quill-filled tail.  There are reports that quills are not lethal to major predators, though some reports have reported that quills have been lethal to some attackers.  When porcupine barbed quills are lost, new ones grow back.  Porcupines have mediocre vision, but have excellent senses of hearing and smell and are reported to be intelligent and capable of learning rapidly.  They are not territorial and will often coexist with other porcupines in caves, hollow trees or other places of shelter.  Home ranges are normally between 30 to 40 acres.  Porcupines are solitary most of the year.  They may occupy the same territory for years and rarely move much during the winter, but may be more mobile and move more extensively in the summers, up to 300 acres.  Their lifespan is 6 to 11 years.

During mating season, there may be fierce competition among males for receptive females.  Males have been known to fight intense battles during which they bite and drive numerous quills into each other.  Sex ratios in porcupine populations have a higher proportions of females perhaps due to high male mortality rates.  During fall mating season, males mark their presence by urinating and searching for female urination sites, indicating that chemical communication plays a large role.
When receptive females are encountered, male urine distribution, vocal grunts, wrestling, chase resulting in eventual fertilization. 

Porcupines mate during the autumn or early winter, and usually birth only a single young after 205 to 217 days in April – June.  The mother furnishes milk to the precocious young during the summers and invest much energy in rearing offspring.
At birth, eyes are open, with functional quills and mobility, even eating vegetation on their own within a week of birth. Parasites of porcupines include fleas, lice, ticks, mites, roundworms, flatworms and tongue worms, though none apparently adversely affect the host.

Porcupine economic status includes damage to orchards, forest trees, crop damage, gnawed holes in auto tires, plastic tubing used collect maple sap, injury to domestic animals and possible transmission of diseases such as tularemia and tick fever. However, most reports suggest that porcupine damage is not sufficiently significant to warrant poisoning campaigns.

Forsyth, A.  1999.  Firefly Books, Ltd.  Buffalo, NY.  350 p.
Crump, D. J., Ed.  1981.  National Geographic Book of Mammals.  National Geographic Society, Washington, D. C.  Volume I. 304 p. 
Radford, K. H. and J. F. Eisenberg  1992. Mammals of the Neotropics.  University of Chicago Press, Chicago, IL  3 vols.  
Woods, C. A.  1973.  Erethizon dorsatum.  Mammalian Species, No. 29, 6 p.