Canis lupus Linnaeus, 1758

Taxonomic Classification

The wolf (Canis lupus Linnaeus, 1758) is the largest living member of the Canidae family. It can be distinguished from coyotes and jackals by a broader snout, shorter ears, a shorter torso, and a longer tail.

Body Build

It has a slender, powerful build with a large, deeply descending rib cage, a sloping back, and a heavily muscled neck. Its legs are moderately longer than those of other canids, which allows faster movement and easier travel through deep winter snow across most of its range, though some wolf populations have shorter-legged ecomorphs.

Head Features

Its ears are relatively small and triangular. The wolf has a large, heavy head with a wide forehead, strong jaws, and a long, blunt muzzle.

Skull Measurements

Its skull measures 230–280 mm (9.1–11.0 in) long and 130–150 mm (5.1–5.9 in) wide.

Dental Traits

The wolf's heavy, large teeth are better suited to crushing bone than those of other canids, though they are not as specialized as hyenas' teeth. Its molars have a flat chewing surface, but this flatness is less pronounced than in coyotes, which eat more vegetable matter.

Sexual Dimorphism

Females typically have narrower muzzles and foreheads, thinner necks, slightly shorter legs, and less massive shoulders than males.

Body Length and Height

Adult wolves are 105–160 cm (41–63 in) in total length and 80–85 cm (31–33 in) tall at the shoulder. Their tails measure 29–50 cm (11–20 in), their ears 90–110 mm (3.5–4.3 in) in height, and their hind feet 220–250 mm (8.7–9.8 in).

Size Geographical Variation

Following Bergmann's rule, the size and weight of modern wolves increases proportionally with increasing latitude.

Weight Ranges

The average mean body mass of the wolf is 40 kg (88 lb), with recorded specimens ranging from 12 kg (26 lb) to 79.4 kg (175 lb). On average, European wolves weigh 38.5 kg (85 lb), North American wolves 36 kg (79 lb), and Indian and Arabian wolves 25 kg (55 lb).

Sexual Weight Dimorphism

Females in any wolf population usually weigh 2.3–4.5 kg (5–10 lb) less than males.

Exceptionally Large Individuals

Wolves weighing over 54 kg (119 lb) are uncommon, though exceptionally large individuals have been recorded in Alaska and Canada. In central Russia, exceptionally large males can reach 69–79 kg (152–174 lb) in weight.

Historic Distribution

Wolves are distributed across Eurasia and North America.

Distribution Reduction Causes

Deliberate human persecution, driven by livestock predation concerns and fear of wolf attacks on humans, has reduced the wolf's current range to roughly one-third of its historic range.

Local Extinction Areas

The wolf is now locally extinct across much of its former range in Western Europe, the United States, and Mexico, and is completely extirpated from the British Isles and Japan.

Current Habitat Range

In modern times, wolves occur primarily in wilderness and remote areas. They can be found from sea level up to 3,000 m (9,800 ft) elevation, and inhabit forests, inland wetlands, shrublands, grasslands including Arctic tundra, pastures, deserts, and rocky mountain peaks.

Habitat Use Drivers

Wolf habitat use depends on prey abundance, snow conditions, livestock density, road density, human presence, and topography.

Home Range Size

When adjusted for body mass, grey wolf home ranges are 275–362.9 hectares per kilogram. This is comparable to the body mass-adjusted home ranges of cheetahs (310.1 hectares/kg) and African wild dogs (242.1 hectares/kg), and much larger than those of spotted hyenas (8.3 hectares/kg) and lions (5.5 hectares/kg).

Mating System

Wolves are monogamous, and mated pairs typically stay together for life. If one partner dies, the other will quickly find a new mate.

Inbreeding Avoidance

In wild wolf populations, inbreeding does not occur when outbreeding is possible.

Reproductive Maturity

Wolves reach physical maturity at two years of age, and sexual maturity at three years of age.

First Breeding Age Factors

The age of first breeding depends mostly on environmental conditions: when food is abundant, or when wolf populations are heavily managed, wolves can raise pups at younger ages to better take advantage of plentiful resources.

Breeding Frequency

Females are capable of producing pups every year, with an average of one litter per year.

Breeding Season

Oestrus and rut occur in the second half of winter and last two weeks.

Den Purpose

Dens are usually built for pups during the summer.

Den Natural Shelter Sources

When constructing dens, females use natural shelters such as rock fissures, overhanging cliffs along riverbanks, and holes densely covered by vegetation.

Appropriated Dens

Sometimes wolves take over burrows dug by smaller animals like foxes, badgers, or marmots, and these appropriated dens are usually widened and partially remade.

Self-Dug Dens

On rare occasions, female wolves dig their own burrows, which are typically small and short with one to three openings.

Den Placement

Dens are usually built no more than 500 m (1,600 ft) from a water source, and most often face south to receive more sunlight for warming and faster snow melt.

Den Surroundings

Resting spots, play areas for pups, and food remains are commonly found around wolf dens. The smell of urine and rotting food from the den area often attracts scavenging birds such as magpies and ravens.

Den Proximity to Humans

Though wolves mostly avoid areas visible to humans, they have been recorded nesting near human homes, paved roads, and railways.

Pregnancy Den Placement

During pregnancy, female wolves stay in a den located away from the peripheral areas of their territory, where violent encounters with other wolf packs are less likely.

Gestation and Birth Timing

Gestation lasts 62–75 days, and pups are usually born in spring, or early summer in very cold regions such as the tundra.

Litter Size

Young females give birth to four to five pups, while older females have six to eight, and can have up to 14. Pup mortality rates are 60–80%.

Newborn Pup Appearance

Newborn wolf pups resemble German Shepherd Dog pups. They are born blind and deaf, and covered in short, soft greyish-brown fur.

Newborn Pup Development

They weigh 300–500 g (11–18 oz) at birth, and begin to see after nine to 12 days. Their milk canines erupt after one month.

Early Pup Activity

Pups first leave the den after three weeks. By one and a half months of age, they are agile enough to flee from danger.

Pup First Weeks Care

Mother wolves do not leave the den for the first few weeks, relying on the father to provide food for the mother and pups. Pups start eating solid food at three to four weeks of age.

Pup Growth Rate

They grow very quickly during their first four months of life, during which a pup's weight can increase by nearly 30 times.

Pup Play Behavior

Wolf pups begin play-fighting at three weeks old; unlike young coyotes and foxes, their bites are gentle and controlled. Actual fights to establish social hierarchy usually happen at five to eight weeks of age.

Hierarchy Establishment Comparison

This differs from young coyotes and foxes, which may start fighting even before they begin play behavior.

Pup Hunting Participation

By autumn, pups are mature enough to join adult wolves on hunts for large prey.