Wildlife in Yellowstone National Park

Bald Eagle

America's official bird is a nesting resident of Yellowstone National Park, and one of 330 species that have been documented in the park to date. While it's no longer on the federal list of endangered species, the noble raptor -- along with the peregrine falcon and the osprey -- receive special monitoring by the park. The extra attention has paid off, but the news isn't good. Research has revealed a recent decline in successful bald eagle nest sites in and around Yellowstone. Researchers think that the downturn is linked to a decline  in the park's population of cutthroat trout, which are a vital part of the bald eagle diet.

American Bison

Bison on the hill by the water
Although poaching reduced herd numbers to about two dozen animals by 1902, Yellowstone is the only place in North America where there has been a continuous free-roaming bison population since prehistoric times. Today, Yellowstone lays claim to a population of more than 3,000 American bison, the largest land mammal in North America. Bison prefer the park's grasslands during the summer, and can be seen near thermals along the Madison River in wintertime. The park's Hayden and Lamar Valleys are year-round habitats for the buffalo. If you encounter one in the wild, it's recommended to remain at least 25 yards away. Every year, more people are injured by bison than bears in Yellowstone. Mostly, this happens when people get too close to them. Despite their size, these animals, which can weigh a ton, are surprisingly agile.

Grizzly Bear

Threatened grizzly bear (Ursus arctos horribilis), Yellowstone National Park
Yellowstone is one of the few places in the United States that Grizzly Bears can be found in the wild. While black bears, also present in the park, tend to inhabit forested areas where they climb tress to access food, grizzlies prefer open meadows and valley areas. It is not uncommon to encounter a grizzly bear in Yellowstone's open backcountry, but due to the bear's characteristic aggression, it's wise to give them a wide berth. In fact, the park enforces seasonal restrictions that prohibit human entry to different areas. This is to protect visitors and allow bears space to "pursue natural behavior patterns free from human disturbance." If you do happen upon a grizzly, make sure to keep your distance -- at least 100 yards away. Familiarize yourself with Yellowstone's bear precautions to prevent incidents and minimize your risk of encountering a bear.


Yellowstone Elk
Elk are the most abundant large mammal visitors will encounter in Yellowstone, and they've maintained a presence in the area for at least the past 1,000 years. There are seven or eight major herds of free-roaming elk in the park, numbering more than 30,000 during summer months. Reintroduction of predators such as wolves to the park and hunting of the animals during their winter migration into Montana may have contributed to an apparent reduction in the Northern Yellowstone elk herd. However, some experts say that a diminished elk population isn't a bad thing, since a smaller herd leaves more room for the animals to thrive.

Cutthroat Trout

Yellowstone Lake is the epicenter of the largest inland population of cutthroat trout in the world. Known by their distinct orange, red or pink linear markings behind their gill plates, cutthroat trout are native to the Great Basin, and Rocky and Cascade mountain ranges of the American West, where geographic isolation has given rise to a number of distinct subspecies. Yellowstone is, as one might expect, the hub of its own subspecies' ecosystem, where a number of larger animals (like bears and birds of prey) depend on the trout for food. Unfortunately, invasive species -- such as other kinds of trout -- and other factors threaten this vital link in Yellowstone's food chain. The park's fisheries program is countering these threats through direct, aggressive intervention, but it's important for anglers to cooperate.