Small mammals can be found throughout Yellowstone National Park. This post will focus on: Yellow-bellied Marmot, Beaver, Badger, Uinta Ground Squirrel and Pika. These are some of the smaller mammals I had the opportunity to photograph while looking for larger mammals, which are my personal favorite. Other small mammals in the park that can be spotted fairly easily include: Snowshoe Hares (common in Norris Geyser Basin area), River Otters (best viewed around lakes and their tributaries, especially Yellowstone River), Golden Mantle Ground Squirrels and Chipmunks (both in rocky areas), and White-tailed Jackrabbits (lower elevations of the park).
There are several small mammals I have not seen and consider more difficult to find: Marten, Short and Long-tailed Weasels (forests, willows and meadows), the Lynx, Bobcat, Mountain Lion and Wolverines. The animals are solitary, stealthy and very good at remaining out of view.
Yellow-bellied Marmot
The Yellow-bellied Marmot, Marmota flaviventris, can grow up to 28 inches in length and weighs between 3.5-11 pounds, making it one of the largest rodents in Yellowstone. They have a reddish-brown upper body with a yellowish belly, small ears and prominent active tail.
Yellow-bellied Marmot in Yellowstone National Park
Marmots hibernate up to 8 months of the year, emerging from February to May depending on elevation. They may estivate (animals slow their activity for the hot, dry summer months) in June in response to dry conditions and lack of green vegetation and reappear in late summer. Marmots breed within two weeks of emerging from hibernation. Their litters average five young per year. Their colonies consist of one male, several females, plus young of the year. Marmot vocalizations include a loud whistle (early settlers called them “whistle pigs”), a “scream” used for fear or excitement, and a quiet tooth chatter that may be a threat. Males are territorial and display dominance and aggressiveness by waving their tail slowly back and forth.
Marmots are most active in morning, late afternoon, and evening, which are the best times to look for them. They can be found from lowest valleys to alpine tundra, usually in open grassy communities and almost always near rocks. They feed on grasses and forbs in early summer; switch to seeds in late summer, and occasionally will eat insects.
Badger
The badger, Taxidea taxus, is a predator of rodents. They are 22–28 inches long, and weigh 13–25 pounds. They may live up to 14 years. Their bodies are short and stout and well adapted to digging. They have a light colored body with a dark stripe down back and darker feet. Their broad head forms a wedge. The sides of face are white with black patches, white stripe from nose extends towards back.
Badger in meadow near Slough Creek turnoff in Yellowstone
Badgers prefers open areas like grasslands, which is the best place to look for them. Badgers are mostly active at night. I have spotted them in the meadows along the Northeast Entrance Road, with several sightings in the areas around the Slough Creek turnoff and along the beginning of the Slough Creek Hiking Trail.
They have adapted to eat ground squirrels, pocket gophers, and other small rodents. They will also eat ground-nesting birds and their eggs. The average badger needs to eat about two ground squirrels or pocket gophers a day to maintain its weight. Badgers digs burrows in pursuit of prey. Badger adults are preyed on by mountain lions, bears, and wolves. Coyotes and eagles will prey on young badgers.
Badger heads off through sage looking for another burrow to dig for food
Badgers are mostly solitary except in mating season (summer and early fall). They have delayed implantation with active gestation starting around February. They excavate dens which are used for daytime resting sites, food storage and giving birth. The dens typically have one entrance, marked by a mound of soil. Badgers may be inactive in their dens for up to a month in winter, but they are not true hibernators.
Beaver
The beaver (Castor canadensis) is a keystone species that affects habitat structure and dynamics through the damming and diverting of streams, and the felling of trees and other woody vegetation. The resulting ponds and flooding help create an environment favorable to willow and aspen, the beavers’ preferred winter foods and used in building their lodges. The territoriality of beavers probably deters two colonies from locating within 50 meters of each other, and most streams in the park lack either suitable vegetation or a sufficiently low gradient to provide beavers with habitat, but information about the distribution and number of beaver colonies in the park over time adds to our understanding about the long-term effects of changes in vegetation and climate.
Like wolves, beavers live in family groups, which are called colonies. Fewer than 5% of mammals live in an organized fashion like this. Per the Yellowstone National Park website, there were 112 colonies counted in 2011. One colony may support 2–14 beavers that are usually related. Six is considered average. Beavers are 35–40 inches long, including their tail and weigh 30–60 pounds. They have an average life span of 5 years. Male and female beavers look alike, with thick brown fur and a distinctive paddle-shaped tail.
Beaver swimming through a lake
Beavers are crepuscular, meaning they are active in evening and morning. If they are living on rivers, they may build bank dens instead of lodges. The best places to look for beavers:
- Willow Park (between Mammoth and Norris), Beaver Ponds (Mammoth area), Harlequin Lake (Madison area), and the Gallatin River along US 191.
- In the backcountry: upper Yellowstone River (Thorofare region), Bechler River, and Slough Creek. Occasionally seen in the Lamar, Gardner, and Madison rivers.
- Wait in areas near known beaver activity. You may see them swimming or clambering onto the bank to gnaw at trees and willows. Listen for the sound of the beaver slapping its tail on the water before it submerges to seek safety.
Uinta Ground Squirrel
The Uinta Ground Squirrel, Spermophilus armatus, is 11–12 inches long and weighs 7–10 ounces. They have a grayish back and rump with fine white spots on back. Their nose and shoulders are tan to cinnamon and the tail is grayish underneath.
Uinta Ground Squirrel in meadow near Madison Junction
The ground squirrel hibernate as early as mid-July through March. Ground squirrels breed in early spring and have one litter of 6–8 young per year. After the young leave the burrow, they are vulnerable to long-tailed weasels and hawks. During cool spring weather, the Uinta ground squirrels are active at all times of day. As the weather warms activity is more limited to morning, late afternoon, and evening. Ground squirrels are preyed on by long-tailed weasels, hawks, coyotes, badgers, grizzly bears.
Uinta ground squirrels can be found throughout the park in disturbed or heavily grazed grasslands, sagebrush meadows, and mountain meadows up to 11,000 feet. They eat grasses, forbs, mushrooms, insects, and carrion (including road-killed members of its own species). During winter, Uinta ground squirrels are sometimes active near the Albright Visitor Center and the hotel at Mammoth Hot Springs. Perhaps they are aroused from hibernation due to ground temperatures rising as hydrothermal activity increases in the vicinity. No one knows for sure.
Uinta Ground Squirrel comes out of it’s burrow in May to find a spring snowstorm.
Pika
The pika, (Ochotona princeps), is considered an indicator species for detecting ecological effects of climate change. While abundant in the Greater Yellowstone Ecosystem, pika numbers are declining in some areas of lower elevations in response to increased warming, which reduces their suitable habitat. While the recent US Fish and Wildlife Service review of the pika found no current need to list the species as threatened or endangered, pikas will likely disappear from some lower elevation or warmer sites.
Pika gathering a branch to take back to it’s haystack
Currently, pika are considered abundant. They are 7–8.4 inches long, and weigh 5.3–6.2 ounces (about the size of a guinea pig). Pika breed in spring and have two litters per year. They are often heard but not seen and make a distinct shrill whistle call or a short “mew.” They are grey to brown with round ears and no tail. They blend in well with rocks. Pika scent marks by frequently rubbing cheeks on rocks. In late summer they gather mouthfuls of vegetation to build “haystacks” for winter food. They will defend haystacks vigorously. Haystacks are often built in same place year after year and have been known to become three feet in diameter. Like rabbits and hares, pika eat their own feces, which allows additional digestion of food. Predators include coyotes, martens, and hawks.
Pika are active year-round. They agilely dart around on rocks and travel through tunnels under snow. They are found on talus slopes and rock falls at nearly all elevations in the park. Pika eat plant foods such as grasses, sedges, aspen, lichen, and conifer twigs. The best areas to look for them are Tower and Mammoth.
