Yellowstone has been described as North America's Serengeti for its rich wildlife resources. And with wolves, bison, bears, elk, moose, mountain lions, Canada lynx and more, it's easy to understand how that tag became attached to the park. For families, there's no better place to indulge in a game or three of wildlife bingo.

Yellowstone overflows with wildlife.

Visit the Hayden Valley and you're sure to encounter bison. Head over to the Lamar Valley in early summer (mid-June) and you'll find elk, coyotes, bison, wolves, and possibly even grizzly bears if you train your eyes on distance ridgelines.

Bighorn sheep at times can be found on the hillsides in the Lamar Valley, though in spring you're almost certain to encounter them on a hike up Mount Washburn.

Wolves, once native to this landscape, were eradicated from the park by the 1950s, in part over concerns they would prey too heavily on other wildlife. Fortunately, officials realized Yellowstone's natural kingdom was missing a key predator and a recovery plan was launched in 1995, one that has established a stable population of the predators.

Mountain lions are another predator native to the park, though they're solitary, low in number (perhaps two dozen live in the park) and, as a result, hard to spot.

Both grizzly and black bears roam Yellowstone. Grizzlies are usually seen in the open areas, according to park officials, while you might spot black bears along the edges of trees in the Lamar and Hayden valleys, or among the trees near Mammoth and Tower.

BLACK BEAR (Ursus americanus)

Color: Varies from pure black to brown, cinnamon, or blonde; in the Rocky Mountains, approximately 50% are black with a light brown muzzle.

Height: About 3 ft (0.9 m) at the shoulder.

Weight: Male: 210-315 lbs (95-143 kg); Female: 135-160 lbs (61-73 kg)

Annual Home Range Size: Males: 194 km2 (75 mi2); Females: 44 mi2 (17 mi2)

Life Expectancy: 15 - 20 years in the wild; 30+ years in captivity.

GRIZZLY BEAR (Ursus arctos horribilis)

Color: Varies from black to blonde; frequently with white-tipped fur giving a grizzled, "silver-tipped" appearance. In the Yellowstone ecosystem, many grizzly bears have a light brown girth band.

Height: About 3-1/2 ft (1.0 m) at the shoulder.

Weight: Male: 216-717 lbs (98-325 kg); Female: 200-428 lbs (91-194 kg)

Home Range Size: Males: 874 km2 (x km2); Females: 281 km2 ( mi2)

Life Expectancy: 15 - 20 years in the wild; 30+ years in captivity.

These days there perhaps is no more controversial animal in Yellowstone than bison. These shaggy ungulates, the largest land mammal in North America, has a mind of its own and goes where it wants to when it wants to. And that's what creates the controversy.

Come winter many bison in the northern part of Yellowstone prefer to head north out of the park to lower elevations where the season is not so harsh. Montana livestock interests in general are opposed to bison, as they can transmit brucellosis, a disease that causes abortions, to cattle.

Efforts to quell the controversy arrived in the spring of 2011, when an agreement was reached to give Yellowstone bison access to 75,000 acres of land in Montana during winters. However, the agreement doesn't preclude the iconic animals from being hunted or shot for going too far north of the park.

Trumpeter swans often can be found on the Firehole or Yellowstone rivers. The 167 trumpeter swans counted during the winter of 2010-2011 represented a 600 percent increase from the 23 tallied during the winter of 2009-10 and marked the highest count in the park since 2007, according to U.S. Fish and Wildlife Service records.

Mergansers and ducks also enjoy these streams, and at times you can spot bald eagles here, too, looking for either a meal of fish or fowl.

Sandhill cranes like marshy areas, such as those near the head of Yellowstone Lake where the Yellowstone River arrives, though you'll need to canoe, kayak, or take a long hike to reach this area.

Moose can be tricky to spot, due in part to their solitary nature. To spy them you'll have to search willow thickets and riparian areas. Park officials say moose are commonly observed in the park's southwestern corner along the Bechler and Falls rivers, in the riparian zones around Yellowstone Lake, in the Soda Butte Creek, Pelican Creek, Lewis River, and Gallatin river drainages, and in the Willow Park area between Mammoth and Norris.

When is a good time to spot animals in Yellowstone? Well, practically anytime you're in the park and awake! That's not hyperbole, either, thanks to the many wildlife species in the park. But here are some pointers.

Visit Yellowstone in fall and you'll find that animals are on the move, with the elk heading into their rut, bison slowly migrating to river bottoms, bears foraging to bulk up, and wolves following the bison and elk.

Spring, which arrives in June, is another good season to look for wildlife, particularly in the Lamar Valley, as noted above.

But seriously, wildlife is visible any and all seasons in Yellowstone. To see what animals, birds, fish, amphibians, and reptiles you might encounter in the park, search the list on this page.