In North America, the coat colors of wolves follow Gloger’s rule: wolves in the Canadian arctic being white and those in southern Canada, the U.S., and Mexico being predominantly gray.
Wolves in Cold Weather
The winter fur of a wolf is highly resistant to the cold. Wolves in northern climates can rest comfortably in open areas at −40 °C (−40 °F) by placing their muzzles between the rear legs and covering their faces with their tail. Wolf fur provides better insulation than dog fur and does not collect ice when warm breath is condensed against it.
In cold climates, the wolf can reduce the flow of blood near its skin to conserve body heat. The warmth of the foot pads is regulated independently from the rest of the body and is maintained at just above tissue-freezing point where the pads come in contact with ice and snow. In warm climates, the fur is coarser and scarcer than in northern wolves.
Wolves typically dominate other canid species in areas where they both occur. In North America, incidents of wolves killing coyotes are common, particularly in winter, when coyotes feed on wolf kills. Wolves may attack coyote den sites, digging out and killing their pups, though rarely eating them. There are no records of coyotes killing wolves, though coyotes may chase wolves if they outnumber them.
Lone Wolves and Pack Wolves
The wolf is a social animal. Its populations consist of packs and lone wolves, most lone wolves being temporarily alone while they disperse from packs to form their own or join another one. The wolf’s basic social unit is the nuclear family consisting of a mated pair accompanied by their offspring. The average pack size in North America is eight wolves
Offspring typically stay in the pack for 10–54 months before dispersing. Triggers for dispersal include the onset of sexual maturity and competition within the pack for food. The distance travelled by dispersing wolves varies widely; some stay in the vicinity of the parental group, while other individuals may travel great distances.
Wolves are Territorial
Wolves are territorial and generally establish territories far larger than they require to survive assuring a steady supply of prey. Territory size depends largely on the amount of prey available and the age of the pack’s pups. They tend to increase in size in areas with low prey populations, or when the pups reach the age of six months when they have the same nutritional needs as adults. Wolf packs travel constantly in search of prey, covering roughly 9% of their territory per day, on average 25 km/d (16 mi/d). The core of their territory is on average 35 km2 (14 sq mi) where they spend 50% of their time.
Wolves advertise their territories to other packs through howling and scent marking. Scent marking involves urine, feces, and anal gland scents. This is more effective at advertising territory than howling and is often used in combination with scratch marks. Wolves increase their rate of scent marking when they encounter the marks of wolves from other packs. Lone wolves will rarely mark, but newly bonded pairs will scent mark the most.
Wolf Size and Weight
The mean body mass of the wolf is 40 kg (88 lb), the smallest specimen recorded at 12 kg (26 lb) and the largest at 79.4 kg (175 lb). On average, North American wolves weigh 36 kg (79 lb). Females in any given wolf population typically weigh 2.3–4.5 kg (5–10 lb) less than males. Wolves weighing over 54 kg (119 lb) are uncommon, though exceptionally large individuals have been recorded in Alaska and Canada.
On average, adult wolves measure 105–160 cm (41–63 in) in length and 80–85 cm (31–33 in) at shoulder height. The tail measures 29–50 cm (11–20 in) in length, the ears 90–110 mm (3 1⁄2–4 3⁄8 in) in height, and the hind feet are 220–250 mm (8 5⁄8–9 7⁄8 in). The size and weight of the modern wolf increases proportionally with latitude in accordance with Bergmann’s rule.