For many, the primary reason for a visit to these parks is the wildlife: bears, bighorn sheep, bison, elk, bald eagles, river otters, and moose all wandering free, often near roadsides. Yellowstone (and Grand Teton) are home to the largest concentration of free-roaming wildlife in the lower 48. This includes one of the largest herds of elk in North America, the largest free-roaming herd of bison in the U.S., and the only significant population of grizzly bears south of Canada.

Also in the parks are pronghorns, mountain goats, and two species of deer (totaling eight species of ungulates, or hoofed mammals); black bears; three species of wildcats; coyotes; wolverines; pine martens; about 60 smaller species of mammals; and 322 species of birds. Add to that the gray wolves reintroduced in 1995—they now number about 530 in the entire ecosystem—and you have a rich array of wildlife. Most of these creatures steer clear of humans. But humans want to get ever closer to the animals, and that can cause problems. Unlike the critters that inhabit petting zoos, the animals in the Greater Yellowstone Ecosystem are wild and pose an unpredictable threat to the safety of visitors.
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Death is a day-to-day affair in the parks. In the spring, you’ll see carcasses of elk and bison that died during the long winter, attracting bears and other carnivores looking for a free lunch. That’s part of the picture when you vow to interfere as little as possible with nature’s way.

Park naturalists generally agree that every major vertebrate wildlife species that was present during the most recent ice age (more than 10,000 years ago) is a resident of the parks today, as are several rare or endangered species, the most notable being the grizzly bear and the bald eagle.
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Ready for Their Close-Ups

Photographers need a telephoto lens, preferably a zoom, to get good shots of wildlife. Even the biggest animals in the park present minimal risks to humans, unless you move in for a close-up. Invest in a 300-millimeter lens, or 100- to 300-millimeter zoom, and you should get some good shots without disturbing the wildlife or putting yourself at risk.

Mammals

Bear (Black & Grizzly): In recent years, grizzly bears have enjoyed a comeback, in part because of the reintroduction of gray wolves, which create plenty of carcasses for bears to scavenge. But unless you have the patience to spend weeks outdoors in bear country, such as the Lamar and Hayden Valleys, your chances of seeing a grizzly in Yellowstone isn't all that good—you might have to go to the zoo in West Yellowstone.
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Estimates vary, but there are probably about 700 grizzly bears in the Greater Yellowstone Ecosystem today, and an equal or greater number of black bears. Rangers say you’re more likely to spot the black bears, especially during the spring months after they emerge with new cubs from their winter dens. However, the black bears are probably more visible because they are more likely to venture near human development than are grizzlies, meaning that an encounter with a grizzly is most likely to occur in the backcountry. Bears that get a taste for human food, or get too comfortable around human campsites, are relocated to the depths of the wilderness. Black bears are most commonly sighted in the Canyon-Tower and Madison–Old Faithful areas, where they feed on green grass, herbs, berries, ants, and carrion.
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Grizzly bears are most commonly seen in the northeast area of the park, in the meadows on the hillsides of the Lamar Valley, or wandering the Hayden Valley north of Yellowstone Lake. They also feed on trout spawning in Yellowstone Lake tributaries during the late spring (campgrounds by these streams are closed during spawning). They are most active in spring, when they emerge from hibernation hungry, and in the fall, when they busy themselves fattening up for winter.

Grizzly bears can do you the most damage, particularly when their cubs are around or when they think you’re after their food.
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Black Bear or Grizzly Bear?

Because a black bear can be black, brown, or cinnamon, here are some identifiers. The grizzly is the larger of the two: typically 3 1/2 feet at the shoulder with a dish-face profile and a pronounced hump between the shoulders. The black bear’s ears are rounder. The grizzly’s color is typically yellowish brown, but the coat is sometimes recognized by its cinnamon color, often highlighted by silver tips. In terms of tracks, the black bear’s toes follow an arc around the foot pad while the grizzly’s toes are arranged in a nearly straight line. The grizzly’s claws are also considerably longer.
 
Caution: Park rangers attempt to keep track of grizzlies to prevent human/bear encounters. However, it is best to assume that they are always around; make noise when traveling in isolated spots.
 
Bighorn Sheep: If there’s a hint of a foothold, a bighorn sheep will find it. Its hooves are hard and durable on the outside but soft and clamplike underneath—perfect for steep, rocky terrain. You’ll often hear them clattering before you spot their stocky, gray-brown bodies and white rumps. Six feet long, the males weigh up to 300 pounds. Their horns are coiled; the females’ are straight. Look for them on Mount Washburn, along Specimen Ridge, and in the Gallatin Range in Yellowstone; they are also seen occasionally in the Heart Mountain area in southern Yellowstone. 
 
Bison: Bison (commonly, but incorrectly, called buffalo) appear indifferent to humans as they wander the roads and go about their grazing, but don’t think for a minute that they’re docile. Their prodigious size, cute calves and fearless nature ensure that bison are very visible symbols of Yellowstone. On ballerina-thin ankles, these burly brown animals carry as much as 2,000 pounds, concentrated in thick shoulders and massive chests. Those big heads help them clear snow for winter grazing, but during harsh winters they instinctively migrate to lower elevations (some biologists insist that both grizzlies and bison were driven up on the plateau from their natural home on the prairie). Bison are very easy to spot in the summer; you’ll see them munching grass and wallowing in dust pits in Hayden Valley, Pelican Valley, the Madison River area, and the geyser areas near the Firehole River. In the winter, snowmobilers often have to make way for the shaggy beasts because bison take advantage of the snow-packed roads to travel around.
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Coyote: The wily coyote is the predator most often spotted by park visitors. Looking like lanky shepherd dogs with grizzled, gray-brown coats, coyotes make their homes in burrows and caves. Numbers have dropped some since the gray wolf reintroduction, but coyotes are very adaptable. Active hunters year-round, they feast on small animals, such as squirrels and rabbits, as well as the carcasses of animals that died naturally or were killed by larger carnivores. They are seen near park roads, in the meadows, and in the sagebrush. Coyote pups are considered a delicacy by great horned owls, eagles, mountain lions, and bears.

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Gray Wolf: In a controversial move, gray wolves were reintroduced to Yellowstone in 1995 for the first time since the 1920s, when they were eliminated by hunters operating under a federal predator control program designed to protect cattle herds. The population of Canadian gray wolves is thriving in its new environment, though numbers are still down after a bout with deadly distemper virus in 2008 (the population was estimated at about 100 in 2016). They are high-profile occupants of the Lamar Valley, under constant observation by visitors with binoculars or spotting scopes.

Wolf or Coyote?
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Wolves and coyotes both bear a striking resemblance to large dogs. Here are some ways to distinguish them.
  • Coyotes grow to a height of 20 inches; wolves often grow to 34 inches and are far more massive.
  • Coyotes have long, pointed ears; wolf ears are rounded and relatively short.
  • Coyotes have thin, delicate legs, similar to those of a fox; wolves’ legs are thick and long.
Elk: It is estimated that the Yellowstone herd has 10,000 to 20,000 elk (also called wapiti) in summer and 5,000 in winter, and other herds spend time in the park as well. The most common large animal in both parks, elk are rather sociable and travel in small groups. Males are easily identifiable by a massive set of antlers. Although they shed them every spring, by early summer, bulls are beginning to display prodigious racks that, by year’s end, are the envy of their cousins in the deer family. The elk’s grayish brown body, which typically weighs as much as 900 pounds, is accented by a chestnut brown head and neck, a shaggy mane, a short tail, and a distinctive tan patch on the rump.
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One herd can often be located in the vicinity of Mammoth Hot Springs, often on the lawn of the main square. Others are found throughout each park. During winter months, the northern Yellowstone herd heads to a winter grazing area near Gardiner.
 
Moose: Perhaps because of their size, their homely appearance, or their broad antler racks that can grow to 6 feet across, moose elicit unequaled excitement from park visitors. A typical adult male moose weighs 1,000 pounds and is most easily recognizable by a pendulous muzzle and fleshy dewlap that hangs beneath its neck like a bell.
 
Sightings are most frequent on the edges of ponds and in damp, lush valley bottoms, where moose feed on willows and water plants.

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The plodding, nibbling moose in a meadow is not to be approached. Cows will charge any perceived threat to a calf, and bulls become particularly ornery in the fall, so give both a wide berth.

Mountain Lion: After their near-eradication in the early 1900s, today there are probably up to 40 mountain lions (also known as cougars, panthers, or pumas) in Yellowstone. Adults weigh 100 to 150 pounds, making them the largest feline in the parks and the Rocky Mountains. Largely opportunistic predators, the parks' mountain lions hunt deer, elk, and porcupine. They are seldom seen in Yellowstone but more often heard: Listeners often mistake their high-pitched wails for those of a human.
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Mule Deer: Not to be outnumbered by their larger cousins, an estimated 1,900 mule deer live within park borders in summer. They are most often spotted near forest boundaries or in areas covered with grass and sagebrush. Their most distinguishing characteristics are their huge ears and a black tip on their tail that contrasts with their white rump. When they run, they bounce, with all four legs in the air. Fawns are typically born in late spring, often in pairs.

Pronghorn: The often-sighted pronghorns graze near the north entrance to Yellowstone, but they are shy and difficult to approach or photograph because of their excellent vision and speed. Often mistakenly referred to as antelope—they’re actually The pronghorn is identified by its short, black horns, tan-and-white body, and black accent stripes. They can run 45 mph, but they can’t clear fences. Yellowstone’s pronghorn population reached about 450 in 2015, its highest since 1992. 
 
Antlers or Horns?
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Most of the larger, four-legged animals roaming the parks have lavish headpieces that are either horns or antlers. But what’s the difference? Antlers are shed every year; horns last a lifetime. Male deer, elk, and moose shed their antlers every spring, so they’re as bald as cue balls when the parks open. By early June, though, new velvet-covered protuberances are making their appearance. In comparison, both sexes of bison and pronghorn grow only one set of horns during their lifetimes.

Birds in the Parks
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The skies above the parks are filled with predators on the wing, including eagles and 27 species of hawks, not to mention ospreys, falcons, and owls.

Bald Eagle: The bald eagle holds a position in the pecking order that parallels that of the grizzly. Of all the birds in the park, visitors are most interested in spotting this photogenic species, once almost wiped out by the pesticide DDT. The Yellowstone is now home to one of largest populations of eagles in the continental United States; in Yellowstone alone, there are at least 19 active nests, and 18 young were born in 2015. Bald eagles are most recognizable by a striking white head, tail feathers, and wingspans up to 7 feet. The Yellowstone Plateau, Snake River, Yellowstone Lake, and headwaters of the Madison River are prime spotting areas for this spectacular bird.
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Golden Eagle: The bald eagle’s cousin, the golden eagle, is similar in appearance, although it is smaller and does not have a white cowl. The golden eagle goes after small mammals, such as jack rabbits and prairie dogs. They hunt in open country; sometimes you’ll find one feeding on roadkill.
 
Osprey: The osprey, nicknamed the “fish eagle” on account of its diet, is the eagle’s smaller relative, growing from 21 to 24 inches and with a white underbody and a brown topside. Ospreys tend to create large nests made of twigs and branches on the tops of trees and power poles. Look for this handsome, interesting bird in the Snake River area and the Grand Canyon of the Yellowstone River, a popular nesting area.
 
Raven: Sporting a 50- to 60-inch wingspan, the raven is jet black and markedly larger than the crow. The most intelligent bird in the parks, the raven plays an interesting role in the Greater Yellowstone Ecosystem: Biologists have observed ravens communicating with wolves, leading them to carcasses, and even playing with pups. Ravens benefit from wolf kills because they are scavengers, so this relationship is symbiotic. They can be seen just about everywhere in both parks.
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Trumpeter Swan: The trumpeter swan, one of the largest birds on the continent, has made the Greater Yellowstone Ecosystem a sanctuary. Easily recognizable by its long, curved neck, snowy white body, and black bill, it is found in marshes and on lakes and rivers, namely the Madison River in Yellowstone.
  
Other Aquatic Birds: The great blue heron, a skinny, long-legged wading bird, is found in wetlands and rocky outcrops, especially near the end of Jackson Lake. Yellowstone Lake is a prime viewing area for the best fishers in the park, the American white pelicans that capture fish in their long, yellow-pouched bill. The American dipper, the only aquatic songbird in North America, revels in cold, fast-flowing mountain streams. The slate-gray dipper is tiny, only 7 to 8 inches tall, and is recognized by its long bill and stubby tail.
 
 

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.