Ecology of Wolves

Large predators like wolves and cougar play an important role in maintaining the health of natural ecosystems. Wolves prey primarily on animals that are young or elderly, sick or injured, and weak or unfit, thus keep prey populations healthy.

Wolf kills create an abundant and dependable food source for many other species. Researchers have documented wolf kills benefiting coyotes, bald eagles, golden eagles, grizzly bears, black bears, ravens, magpies, red foxes and at least 20 other species.

By preventing large herbivores, such as deer and elk, from becoming overpopulated wolves help maintain native biodiversity. Deer and elk can overgraze their habitat when populations outgrow the carrying capacity of an ecosystem. Overgrazing destroys the plant base, making the habitat less suitable for other species. When gray wolves were reintroduced into Yellowstone National Park in1995 after a 70-year absence, they began to restore ecosystems that had been degraded in their absence.

Habitat

The gray wolf is a habitat generalist, and can occur in deserts, grasslands, forests and arctic tundras. Habitat use by gray wolves is strongly correlated with the abundance of prey, snow conditions, absence or low livestock densities, road densities, human presence and topography. In cold climates, the gray wolf can reduce the flow of blood near its skin to conserve body heat. The warmth of the footpads is regulated independently of the rest of the body, and is maintained at just above tissue-freezing point where the pads come in contact with ice and snow. Gray wolves use different places for their diurnal rest: places with cover are preferred during cold, damp and windy weather, while wolves in dry, calm and warm weather readily rest in the open. During the autumn-spring period, when wolves are more active, they willingly lie out in the open, whatever their location. Actual dens are usually constructed for pups during the summer period. When building dens, females make use of natural shelters such as fissures in rocks, cliffs overhanging riverbanks and holes thickly covered by vegetation. Sometimes, the den is the appropriated burrow of smaller animals such as foxes, badgers or marmots. An appropriated den is often widened and partly remade. On rare occasions, female wolves dig burrows themselves, which are usually small and short with 1–3 openings. The den is usually constructed not more than 500 m (550 yd) away from a water source, and typically faces southwards, thus ensuring enough sunlight exposure, keeping the denning area relatively snow free. Resting places, play areas for the pups and food remains are commonly found around wolf dens. The odour of urine and rotting food emanating from the denning area often attracts scavenging birds such as magpies and ravens. As there are few convenient places for burrows, wolf dens are usually occupied by animals of the same family. Though they mostly avoid areas within human sight, wolves have been known to nest near domiciles, paved roads and railways.

Diet

Globally, gray wolf diet is predominantly composed of large (240–650 kg (530–1,430 lb)) and medium-sized (23–130 kg (51–287 lb)) wild ungulates, with local population variations due to the mix of wild ungulates, smaller prey and domestic species consumed. All terrestrial mammalian social predators feed predominantly on terrestrial herbivorous mammals that have a body mass similar to that of the combined mass of the social group members. The gray wolf generally specializes in predating on the vulnerable individuals of large prey, with pack of timber wolves capable of bringing down a 500 kg (1,100 lb) moose. Digestion only takes a few hours, thus wolves can feed several times in one day, making quick use of large quantities of meat.

Wolves supplement their diet with fruit and vegetable matter. They willingly eat the berries of mountain ash, lily of the valley, bilberries, blueberries and cowberry. Other fruits include nightshade, apples and pears. They readily visit melon fields during the summer months. A well-fed wolf stores fat under the skin, around the heart, intestines, kidneys, and bone marrow, particularly during the autumn and winter.

Enemies and Competitors

Gray wolves typically dominate other canid species in areas where they both occur. In North America, incidents of gray 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. Near identical interactions have been observed in Eurasia between gray wolves and golden jackals, with the latter's numbers being comparatively small in areas with high wolf densities. Gray wolves are the most important predator of raccoon dogs, killing large numbers of them in the spring and summer periods. Wolves also kill red, arctic and corsac foxes, usually in disputes over carcasses, sometimes eating them. In Asia, they may compete with dholes, though there is at least one record of a lone wolf associating with a pair of dholes in Debrigarh Wildlife Sanctuary

Brown bears typically dominate wolf packs in disputes over carcasses, while wolf packs mostly prevail against bears when defending their den sites. Both species kill each other's young. Wolves eat the brown bears they kill, while brown bears seem to only eat young wolves. Wolf interactions with American black bears are much rarer than with brown bears, because of differences in habitat preferences. The majority of black bear encounters with wolves occur in the species' northern range, with no interactions being recorded in Mexico. Wolves have been recorded on numerous occasions to actively seek out black bears in their dens and kill them without eating them. Unlike brown bears, black bears frequently lose against wolves in disputes over kills. While encounters with brown and black bears appear to be common, polar bears are rarely encountered by wolves, though there are two records of wolf packs killing polar bear cubs. Wolves also kill the cubs of Asian black bears.

Large wolf populations limit the numbers of small to medium-sized felines. Wolves encounter cougars along portions of the Rocky Mountains and adjacent mountain ranges. Wolves and cougars typically avoid encountering each other by hunting on different elevations. In winter, however, when snow accumulation forces their prey into valleys, interactions between the two species become more likely. Wolves in packs usually dominate cougars and can steal kills. They have been reported killing mothers and their kittens. Wolves hunt steppe cats, and may scavenge from snow leopard kills. Wolves may also reduce Eurasian lynx populations. Wolves may kill lynxes by running them down, or killing them before they can escape into trees. Similar reports of encounters between wolves and bobcats have been documented.

Leftovers of wolf kills are sometimes scavenged by wolverines. Wolverines usually wait until the wolves are done feeding, but have been known to drive away wolves from kills. However, there have been confirmed reports of wolf packs killing wolverines.