American pronghorn, mule deer, jackrabbits, cottontail rabbits, least chipmunks, and Richardson's ground squirrels are probably the only mammals the average visitor is likely to see during a casual summer visit, although 44 mammal species have been recorded in the monument. The majority of the mammals are small, active only at night, confined to small isolated habitats or are so wary of humans that they are only rarely seen.

Check out our fossil mammals.

White-tailed prairie dog - Cynomys leucurus

The white-tailed prairie dog can be found in western and central Wyoming, southern Montana, eastern Utah, and northern Colorado. They are typically found at elevations between 5600 ft and 8500 ft (1700 m and 2600 m) but can be found over 10,000 ft (3030 m). White-tailed prairie dogs live in large colonies, or “towns,” made of a network of connecting burrows. They are prey for badgers, coyotes, and many species of raptors. They hibernate from October or November through March. Albino prairie dogs have been spotted in Fossil Butte’s prairie dog towns in at least 5 years since 2009.

Pronghorn - Antilocapra americana

Pronghorn are the fastest land animals in North America, traveling at speeds up to 60 mph (97 kph). They are sometimes called antelope, but there are no true antelopes in North America. Pronghorn have the longest land migration in the continental United States, traveling 150 miles from the Upper Green River Basin to Grand Teton National Park. Pronghorn's horns are neither true antlers or true horns. True antlers are made of bone and shed every year. True horns are made of keratin and are not shed. Pronghorn horns have a bony core covered by a keratin sheath that is shed every year. Pronghorn are usually somewhere on the monument from late spring through late fall or early winter. They migrate to wintering areas outside the monument as snow accumulates.

Mule Deer - Odocoileus hemionus

Mule deer browse on a mixture of herbaceous plants and the leaves and stems of woody shrubs. New growth provides more nutrition. Mule deer will scrape their antlers across trees in order to remove the velvet from their antlers when it starts to shed. They are most often seen at dawn or dusk. Some mule deer may reside in the park throughout the year, but most migrate in late fall to winter to range located elsewhere.

Moose - Alces alces

Moose are the largest of Fossil Butte’s residents. They prefer wetter habitats than the sagebrush grasslands that make up most of the park. The best place to see them is in the aspen groves of the Nature Trail where springs have made a wetter environment. Moose will eat the stems, bark, and leaves of many trees including aspen. Remember, these large animals can be dangerous, especially mothers with young. If one is seen, observe it quietly and from a safe distance (at least 25 yards/23 m or two bus lengths).

Elk - Cervus canadenses

Elk are the largest members of the deer family after moose. Like most deer species, only the males have antlers. They are well-known for their distinctive high-pitched calls during the mating season, known as bugling. Autumn through early spring is the best time to see a herd of elk on the side of Fossil Butte. They are most commonly seen in the evening from the back porch of the visitor center. Read about elk research at Fossil Butte (PDF 1.06 MB) and about the observations made (PDF 2.50 MB).

American Badger - Taxidea taxus

This burrowing predator is excellent at digging up its prey that also lives in burrows such as prairie dogs and ground squirrels. Badgers are opportunistic hunters and will eat other small animals such as birds and amphibians. Coyotes and badgers sometimes hunt together. Coyotes can chase down prey that badgers have scared away and badgers can dig after prey that coyotes have scared underground. It is uncommon to see badgers as they are primarily nocturnal, but you may see large holes in the ground dug by badgers as homes or to find food. Badgers have very sharp claws and are aggressive, so leave their burrows alone and watch them from afar.

Coyote - Canis latrans

Coyotes are highly adaptable animals that can live in a wide range of ecosystems. They are omnivores and will eat plants as well as animals and carrion. They are smaller than wolves, which are not found near Fossil Butte. You may hear coyotes’ calls or see them trotting through the sagebrush at dusk. Coyotes have more vocalizations than any other species of dog. Sometimes they are called song dogs.

Yellow-bellied marmot - Marmota flaviventris

The yellow-bellied marmot is a member of the squirrel family, closely related to groundhogs. They weigh 5-11 lbs/2-5 kg. Marmots will hibernate for 6-8 months, but will wake up for short periods of time. They are sometimes called whistle pigs for the sharp high-pitched warning call they make. They are also known as rock chucks because they are found near rock outcrops. They are sometimes seen on the rocky slopes at the top of the Nature Trail.

Richardson’s ground squirrel - Urocitellus richardsonii

Like all ground squirrels, Richardson’s ground squirrels are burrowers. They will stan on their hind legs when looking for predators, much like prairie dogs. They can be distinguished from prairie dogs by their longer tail and smaller body size. They do not live in large colonies like prairie dogs. They hibernate for up to 8 months of the year. Males go into hibernation first, then females, then first year juveniles.

Bobcat - Lynx rufus

Bobcats are about twice the size of house cats. They are recognizable by their very short tails and tufted ears. They are primarily nocturnal but may be seen at all hours of the day. They are solitary hunters that prefer rodents and rabbits, but they will eat other meat including carrion.

Mountain lion - Puma concolor

Solitary and elusive, the mountain lion is the top predator in the park’s ecosystem. They are very uncommon at Fossil Butte, but their tracks can sometime be seen in the northern areas of the park. Their prey includes everything from elk to squirrels. If one is seen, leave the area. If one approaches, shout, make noise, and spread your arms to appear larger. Do not run.

Least chipmunk - Neotamias minimus

The least chipmunk has a wide range from the eastern mountains of Pacific Coast states, continuing east through the Rocky Mountains, and from New Mexico north into Canada. They live in a variety of ecosystems from sagebrush shrub to the understory of pines and pinyon-juniper. They are well adapted for arid habitats while other chipmunks are not. They eat seeds, berries, and sometimes invertebrates. They will cache food.

Golden-mantled ground squirrel - Callospermophilus lateralis

Golden-mantled ground squirrels look similar to least chipmunks. Chipmunks have stripes on their face, while golden-mantled ground squirrels have them on their backs only. Their range is similar to least chipmunks. Golden-mantled ground squirrels are omnivores and eat seeds, fruits, insects, meat, and carrion. They store food in their burrows in preparation for winter. They hibernate from late fall to early spring.

White-tailed jackrabbit - Lepus townsendii

The jackrabbit is the largest member of the rabbit and hare family weighing between 6-10 lbs./2.7-4.5 kg. They are a hare, not a rabbit, as hares have longer feet and generally longer ears. Jackrabbits have a brown coat in summer that turns white in winter to provide camouflage with the snow. They are most commonly seen on the park road early in the morning around sunrise.

Mountain cottontail - Sylvilagus nuttallii

The mountain cottontail has a large range in the western United States. They usually live above 6,000 ft/1828 m in elevation. They weigh less than 3 lbs./1.4 kg. The top of their tail is a similar gray-brown color to the back, but the underside is white, giving it the name cottontail. Sagebrush makes up a large portion of their diet as well as grasses.

References

“American Badger.” Washington Department of Fish and Wildlife. Accessed May 28, 2024. https://wdfw.wa.gov/species-habitats/species/taxidea-taxus

“Antler Growth Cycle.” Deer Ecology and Management Lab. Mississippi State University. Accessed on May 28, 2024. https://www.msudeer.msstate.edu/growth-cycle.php

“Bobcat – Lynx rufus.” Montana Field Guide. Montana Natural Heritage Program and Montana Fish, Wildlife and Parks. Accessed on December 17, 2024. https://fieldguide.mt.gov/speciesDetail.aspx?elcode=AMAJH03020

Callospermophilus lateralis-Utah Natural Heritage Program Field Guide. Utah Division of Wildlife Resources. State of Utah. 2019. Accessed December 19, 2024. https://fieldguide.wildlife.utah.gov/?species=callospermophilus%20lateralis

Dell'Amore, Christine. “Why This Coyote and Badger ‘Friendship’ Has Excited Scientists.” National Geographic. February 5, 2020. Accessed May 28, 2024.

“Elk.” Missouri Department of Conservation. Conservation Commission of Missouri. 2024. Accessed December 18, 2024. https://mdc.mo.gov/discover-nature/field-guide/elk

Least Chipmunk — Neotamias minimus. Montana Field Guide. Montana Natural Heritage Program and Montana Fish, Wildlife and Parks. Accessed on December 19, 2024. https://FieldGuide.mt.gov/speciesDetail.aspx?elcode=AMAFB02020

Lue, Julie. “Marmota flaviventris Yellow-bellied marmot.” Montana Outdoors. Montana Fish, Wildlife, and Parks. September-October 2021. Accessed December 17, 2024. https://fwp.mt.gov/binaries/content/assets/fwp/montana-outdoors/outdoor-portraits/2021/yellowbelliedmarmot.pdf

“Moose – Alces alces.” Montana Field Guide. Montana Natural Heritage Program and Montana Fish, Wildlife and Parks. Accessed on December 17, 2024. https://FieldGuide.mt.gov/speciesDetail.aspx?elcode=AMALC03020

Mountain Cottontail — Sylvilagus nuttallii. Montana Field Guide. Montana Natural Heritage Program and Montana Fish, Wildlife and Parks. Accessed on December 20, 2024. https://FieldGuide.mt.gov/speciesDetail.aspx?elcode=AMAEB01060

“Mountain Lion Safety.” U.S. Fish & Wildlife Service. Accessed December 18, 2024. https://www.fws.gov/story/mountain-lion-safety

“Mule Deer.” National Wildlife Federation. Accessed on May 28, 2024. https://www.nwf.org/Educational-Resources/Wildlife-Guide/Mammals/Mule-Deer

Pauli, Jonathan N. et al. “White-tailed Prairie Dog (Cynomys leucurus): A Technical Conservation Assessment.” Department of Zoology and Physiology. University of Wyoming. November 13, 2006. Accessed May 28, 2024. https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fseprd502560.pdf.

“Pronghorn.” San Diego Zoo Animals and Plants. San Diego Zoo Wildlife Alliance. Accessed on May 2, 2024. https://animals.sandiegozoo.org/animals/pronghorn

“Safety.” Yellowstone National Park. Accessed December 17, 2024. https://www.nps.gov/yell/planyourvisit/safety.htm

Sylvilagus nuttallii-Utah Natural Heritage Program Field Guide. Utah Division of Wildlife Resources. State of Utah. 2019. Accessed December 20, 2024. https://fieldguide.wildlife.utah.gov/?species=sylvilagus%20nuttallii

“Urocitellus richardsonii: Richardson’s Ground Squirrel. Rare Species Guide. Minnesota Department of Natural Resources. Accessed Dec. 17, 2024. https://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=AMAFB05040

White-tailed jackrabbit. Minnesota Department of Natural Resources. Accessed December 19, 2024. https://www.dnr.state.mn.us/mammals/whitetailedjackrabbit.html

Wojda SJ, McGee-Lawrence ME, Gridley RA, Auger J, Black HL, Donahue SW. Yellow-bellied marmots (Marmota flaviventris) preserve bone strength and microstructure during hibernation. Bone. 2012 Jan;50(1):182-8. doi: 10.1016/j.bone.2011.10.013. Epub 2011 Oct 20. PMID: 22037004; PMCID: PMC3489026.

Zeveloff, Samuel I. and Collett, Farrell R. Mammals of the Intermountain West. Salt Lake City: University of Utah Press, 1988.