Wolves in Yellowstone

Magpies and ravels fly above a bloody carcass in snow approached by a moving wolf
Yellowstone National Park ensures the long-term viability of wolves in Greater Yellowstone and provides a place for research on how wolves may affect many aspects of the ecosystem.

NPS / Jim Peaco


Although wolf packs once roamed from the Arctic tundra to Mexico, loss of habitat and extermination programs led to their demise throughout most of the United States by early in the 1900s. In 1973, the US Fish and Wildlife Service listed the northern Rocky Mountain wolf (Canis lupus) as an endangered species and designated Greater Yellowstone as one of three recovery areas. From 1995 to 1997, 41 wild wolves from Canada and northwest Montana were released in Yellowstone National Park. As expected, wolves from the growing population dispersed to establish territories outside the park where they are less protected from human-caused mortalities. The park helps ensure the species’ long-term viability in Greater Yellowstone and has provided a place for research on how wolves may affect many aspects of the ecosystem. Continue: Description and Population


Quick Facts

Number in Yellowstone

  • As of January 2016, there were at least 98 wolves in 10 packs living primarily in Yellowstone and 528 wolves living within the Greater Yellowstone Ecosystem.
  • In general, wolf numbers within YNP have fluctuated between 83-104 wolves from 2009 to 2015.

Where to See

  • They inhabit most of the park. The best time to look is at dawn and dusk, which is when they are the most active.
  • The northern range of Yellowstone is one of the best places in the world to watch wolves.

Size and Behavior

  • 26-36 inches tall at the shoulder, 4-6 feet in length from nose to tail tip;males weigh 100-130 pounds, females weigh 80-110 pounds.
  • Home range within the park is 185-310 square miles (300-500 km2) and varies with pack size, season, and availability of vulnerable prey.
  • Average lifespan within YNP is 4-5 years, average lifespan outside of YNP is 2-3 years.
  • Oldest known wolf to live in YNP was 12.5 years.
  • Leading cause of death for wolves within the park is death by other wolves;leading cause of death for wolves outside the park is human-caused.
  • Two main color variations exist in YNP: black and gray in approximately equal proportions.
  • Prey primarily on hoofed animals. In Yellowstone, 90% of winter diet is elk;summer prey consist of more deer and smaller mammals.
  • Breeding season is in early February and average gestation period is about 63 days.
  • Pups are born in early April and average litter size is 4-5 pups. They emerge from den at 10-14 days and the pack remains at the den for 3-10 weeks unless disturbed.

More Information

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Mailing Address:

P.O. Box 168
Yellowstone National Park, WY 82190-0168


(307) 344-7381

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