Wolves In Our Ecosystem

Scientific name: Canis lupus
Type: Mammal
Diet: Carnivore
Average life span: In the wild, they live 8-13 years while in captivity they can live up to 15 years
Size: Head and body, 36 to 63 in (91 to 160 cm); Tail, 13 to 20 in (33 to 51 cm)
Weight: 40 to 175 lbs (18 to 79 kg). Females tend to be smaller in size than the males
Group name: Wolves are social animals that live in groups, called packs, which typically include a breeding pair (the alpha pair), their offspring, and other non-breeding adults.
Protection status: Gray wolves were listed as an endangered species in 1974 and delisted from the Endangered Species act on 2011.
Habitat: Wolves can thrive in a diversity of habitats from the tundra to woodlands, forests, grasslands and deserts.
Breeding: Wolves breed only once a year, typically between January and March so the pups will be born in the spring, when food is plentiful and the weather less severe where mating only occurs between the alpha pair leaders of the pack, who form a lifelong bond.
Gestation and Birth: Wolves gestation period is 63 to 68 days. On average, five pups are born in early spring and are cared for by the entire pack. For the first six weeks, pups are reared in dens. Dens are often used year after year, but wolves may also dig new ones or use some other type of shelter, such as a cave.

Pups depend on their mother’s milk for the first month, then are gradually weaned and fed regurgitated meat brought by pack members. By the time pups are seven to eight months old they are almost fully grown and begin traveling with the adults. After a year or two, young wolves may leave to try to find a mate and form a pack. Lone, dispersing wolves have traveled as far as 600 miles in search of a mate or territory.


Over hundreds of years, wolves once roamed across most of North America, side by side with their prey and filled an important role in the ecosystem. Opportunistic hunters, wolves preyed on deer, elk and beaver, killing and eating the young, the sick, the weak and the old and leaving the fittest to survive and reproduce. Wolf kills provided a source of food for numerous other species such as bears, foxes, eagles and ravens. Wolves even contributed to forest health by keeping deer and elk populations in check, thus preventing overgrazing and soil erosion. Not surprisingly, the cultures which inhabited North America before the time of European exploration revered the wolf and its role in nature. Many indigenous groups relied on hunting as their major source of food and goods and were keenly attuned to their environment. The elements of the natural world, including the wolf, were important to their everyday lives and spirituality. In the America’s early years there were two top predators, wolves and man. By the 1850s, with the loss of prey like buffalo, which it was eradicated by the early European settlers, the wolf had two options for survival: eat livestock or starve. By 1894 farmers were losing most of their calves to hungry wolves, and people were calling for complete eradication of wolves. Wealthy stock growers associations had enough resources to legislate Canis lupus out of existence. The last wolves were killed in Yellowstone in 1926. After that time, sporadic reports of wolves still occurred, but scientists confirmed that sustainable wolf populations had been extirpated and were absent from Yellowstone during the mid 1900s. It wasn’t until 1973 that the Gray Wolf, Canis Lupus was listed as an endangered species as part of the Endangered Species Protection Act.

Ecological impacts after wolves were eradicated

Once the wolves were gone the elk began to take over. Over the next few years conditions of Yellowstone National Park declined drastically. A team of scientists visiting Yellowstone in 1929 and 1933 reported, "The range was in deplorable conditions when we first saw it, and its deterioration has been progressing steadily since then." By this time many biologists were worried about eroding land and plants dying off. The elk were multiplying inside the park and deciduous, woody species such as aspen and cottonwood suffered from overgrazing. The park service started trapping and moving the elk and, when that was not effective, killing them. This killing continued for more than 30 years. This method helped the land quality from worsening, but didn't improve the conditions. The destruction of the landscape affected many other animals. With the wolves gone, the population of coyotes increased dramatically, which led to an extreme decrease in the number of pronghorn antelope. However, the increase in the elk population caused the most profound change in the ecosystem of Yellowstone after the wolves were gone.

Wolves Reintroduction to Yellowstone National Park

In 1995 and under a high level of controversy, 14 wolves from separate Canadian packs were captured and after the acclimatization period released into Yellowstone National Park. Various wolves were equipped with radio collars to allow scientist monitor the packs and study their development, packs count, wolf-prey predation and impact to the Yellowstone ecosystem. By 1996, an additional count of 17 wolves were released into Yellowstone National Park; thus, marking a new chapter in Yellowstone's ecology.

Positive impact of wolves in the ecosystem

Studies at Yellowstone National Park are finding that the effect of wolves cascades throughout the park's ecosystems. Ravens, foxes, wolverines, coyotes, bald eagles, and even bears benefit because they feed on carcasses of animals killed by wolves. Coyotes have declined because wolves view them as competition and keep them out of their territories; which may be responsible, in part, for an increase in small rodents. Elk changed their behavior to avoid wolf predation, which allowed willow, aspen, and cottonwood regrowth. This, in turn, provided food for beavers and habitat for songbirds. The ecosystem changes and cascading effects continue and are expected to do so for some time.