Animals of Yellowstone: Wildlife to See and Where to Find It

Yellowstone’s wildlife at a glance

Yellowstone, created in 1872 as the world’s first national park, covers nearly 9,000 km² (3,470 sq mi), mostly in Wyoming. It sits at the heart of the Greater Yellowstone Ecosystem, one of the largest nearly intact temperate ecosystems on Earth.

Numbers come from National Park Service counts and change from year to year.

Bison: Yellowstone’s living legacy

Yellowstone is the only place in the lower 48 states where bison have lived free-ranging since prehistoric times. Poachers had cut the park’s herd to about two dozen animals by 1902; protection, plus animals brought in from ranch herds, saved them. Today the herd is the largest public bison population in the United States, with recent counts between 3,500 and nearly 6,000. Read why the species came so close to disappearing in why did bison almost go extinct?

Bulls weigh up to about 900 kg (2,000 lb) and cows up to 450 kg (1,000 lb), and both can run at up to 48 km/h (30 mph). Calves, nicknamed “red dogs” for their orange coats, are born in late April and May. The rut, in late July and August, is noisy and dramatic, with bulls bellowing, wallowing in dust and clashing heads. Bison look slow and calm but are agile and unpredictable, and they injure visitors who get too close almost every year. See our American bison profile.

Elk: the most abundant large mammal

Elk are the most numerous large animals in Yellowstone. An estimated 10,000–20,000 elk from six or seven herds spend the summer in the park, but most move to lower ground outside it for the winter. Bulls weigh about 320 kg (700 lb) and stand about 1.5 m (5 ft) at the shoulder; their antlers can span almost 1.8 m (6 ft).

In September and early October, bull elk gather groups of cows and fill the valleys with their high, whistling bugle. The lawns of Mammoth Hot Springs and the meadows along the Madison River are famous rut-viewing spots. Rutting bulls are aggressive, so keep well back. Learn more in our elk profile.

Gray wolves and the 1995 reintroduction

Wolves were deliberately exterminated in Yellowstone, and the last known wolves in the park were killed in 1926. After decades of debate, wolves returned in 1995: from 1995 to 1997, 41 wild wolves from Canada and northwest Montana were released. They thrived, and in early 2025 at least 108 wolves lived mainly in the park, in packs averaging about 12 animals.

Elk make up about 90% of their winter prey. Many scientists think the return of wolves changed elk behavior and numbers enough to help willows and aspen recover in some places, a chain reaction called a trophic cascade, although how strong this effect really is remains debated. Wolves in Yellowstone may be gray, black or nearly white. Our gray wolf profile covers their family life.

Grizzly and black bears

An estimated 1,030 grizzly bears lived in the Greater Yellowstone Ecosystem in 2024, about 150 of them wholly or partly inside the park. Grizzlies were listed as threatened in the lower 48 states in 1975, and the Yellowstone population has grown greatly since then. In spring, bears emerge from their dens and search for winter-killed bison and elk; in summer they dig for roots, eat army cutworm moths high on talus slopes and, in autumn, feed on whitebark pine seeds.

Black bears are common in the forests of the northern range and the park’s southwest corner. Yellowstone is one of the few places in the US where both species live side by side. Color is no help in telling them apart, because many black bears are brown or cinnamon; see grizzly bear vs black bear for the reliable clues, such as the grizzly’s shoulder hump.

Pronghorn, moose and bighorn sheep

Pronghorn are the fastest land mammals in North America and can sprint at 72–80 km/h (45–50 mph). About 500–600 live on Yellowstone’s northern range, around Gardiner and the Lamar Valley. Despite the common name “antelope,” they belong to a family of their own that evolved in North America.

Moose are rare, with fewer than 200 in the park, and their numbers have declined over the past 40 years because of the loss of old-growth forest around the park, the great fires of 1988 and predation. Look for them in willow flats in the south and northeast. Bighorn sheep live on the steep cliffs of the upper Yellowstone River; in 2018, 345 were counted in the northern Yellowstone area, 131 of them inside the park.

Other mammals include coyotes, red foxes, river otters, badgers, cougars, the rarely seen Canada lynx and wolverine, and mountain goats, which colonized the park from introduced herds nearby.

Birds: bald eagles and trumpeter swans

Bald eagles nest along the Yellowstone, Madison and Snake rivers and around Yellowstone Lake; park staff monitored 31 bald eagle territories in 2023. Ospreys also nest in the Grand Canyon of the Yellowstone, often on rock pinnacles.

Trumpeter swans, the largest waterfowl native to North America, almost disappeared from the lower 48 states by the 1930s, and the Greater Yellowstone region was one of their last strongholds. Inside the park their numbers have fallen since the 1960s: park biologists counted 29 resident swans, including five breeding pairs, in 2023. Look for them on quiet rivers and ponds such as the Madison and Yellowstone rivers. Sandhill cranes, American white pelicans, harlequin ducks and common ravens are other highlights.

How Yellowstone’s animals survive winter

Most of the park lies above 2,100 m (7,000 ft), and winter brings deep snow and temperatures that can fall far below freezing for weeks. Animals cope in different ways. Most elk, pronghorn and many bison move to lower valleys in and beyond the northern edge of the park, where snow is shallower. Bison that stay swing their huge heads from side to side to sweep snow away from the grass below, and many gather in the geyser basins, where heat from the ground melts the snow and keeps some plants within reach.

Grizzly and black bears sleep through the coldest months in dens, usually from about November to March or April, and ground squirrels and marmots hibernate. Wolves, coyotes, foxes and ravens often do well in winter, because deep snow slows down elk and bison and leaves more carcasses for scavengers to share.

Best places and seasons to see Yellowstone wildlife

• Lamar Valley: often called “America’s Serengeti,” with bison, pronghorn, elk, wolves, grizzlies and coyotes. The road from the North Entrance to the Northeast Entrance is open all year.
• Hayden Valley: bison herds, grizzlies, wolves, waterbirds and trumpeter swans along the Yellowstone River.
• Mammoth Hot Springs: elk graze the lawns year-round, and the autumn rut is spectacular.
• Madison River: elk, bison, bald eagles and trumpeter swans.
• Dunraven Pass and Mount Washburn: bighorn sheep and summer grizzlies on open slopes.

Late spring, from May to June, is the best all-round season, with newborn bison and elk calves and bears active in the open. Summer brings the bison rut, autumn the elk rut, and winter the best chances of seeing wolves on the snow in the Lamar Valley. Wildlife is most active around dawn and dusk.

Distance rules and staying safe

Yellowstone’s rules require visitors to stay at least 100 yards (91 m) from bears, wolves and cougars and at least 25 yards (23 m) from all other animals, including bison and elk. If an animal approaches, move away to keep that distance. Use pullouts instead of stopping in the road, watch from your car when animals are near, and never feed wildlife. Hikers are safest in groups of three or more and should make noise on trails. In an emergency, call 911.