While Yellowstone National Park is famous for its grizzly bears, wolves, and massive bison herds, you’re actually far more likely to encounter the park’s smallest mammals during your visit.
Six squirrel species inhabit Yellowstone’s diverse ecosystems, from the lodgepole pine forests surrounding Old Faithful to the alpine meadows near the park’s highest peaks.
These energetic rodents play crucial roles in Yellowstone’s ecosystem—dispersing seeds, aerating soil through their burrows, and providing essential food for predators ranging from hawks to grizzly bears.
Understanding squirrels in Yellowstone National Park enhances your wildlife viewing experience and helps you appreciate the intricate web of life thriving in America’s first national park.
You’ll discover which squirrels hibernate through Yellowstone’s brutal winters, which ones vocally defend their territories, and how to distinguish between species that visitors frequently confuse at picnic areas and trailheads.
1. Red Squirrel
The Red squirrel (Tamiasciurus hudsonicus) provides the soundtrack to Yellowstone’s coniferous forests with its loud, persistent chattering calls that echo through the trees.
These small tree squirrels measure 10 to 15 inches total length and weigh just 5 to 9 ounces, making them considerably smaller than most tree squirrels but larger and more robust than chipmunks.
You’ll recognize red squirrels by their distinctive rusty-red to reddish-brown upper body coloration contrasting sharply with white or cream-colored bellies.
During summer months, many individuals display a prominent black lateral line separating their reddish backs from white undersides. Their tails are moderately bushy with reddish fur often tinged with black and edged in white, and their large black eyes give them an alert, inquisitive expression.
Red squirrels inhabit coniferous and mixed forests throughout Yellowstone, particularly abundant in lodgepole pine forests that dominate much of the park.
You’ll frequently encounter them near campgrounds, parking areas, and along forested trails where they’ve become habituated to human presence. These squirrels remain active year-round and don’t hibernate, making them one of the few mammals you can reliably observe during Yellowstone’s winter months.
Pro Tip: Red squirrels are Yellowstone’s most vocal mammals. If you hear loud, rapid chattering or scolding calls while hiking through forests, you’ve entered a red squirrel’s territory. They’ll often perch on branches directly overhead, vigorously defending their space while flicking their tails and producing an impressive variety of sounds from harsh rattles to melodic chirps.
What makes red squirrels particularly interesting in Yellowstone is their dependence on conifer seeds as their primary food source.
They harvest pine cones year-round, creating massive caches called middens where they store thousands of cones in piles that can accumulate over generations. These middens—often several feet high and wide—become so important to red squirrels that they aggressively defend them from all intruders.
Red squirrels also consume fungi, berries, bird eggs, and occasionally small vertebrates, displaying more carnivorous tendencies than other Yellowstone squirrels.
They’re known to tap lodgepole pine and other conifers to drink sap, similar to how eastern red squirrels tap maple trees. Their high-energy lifestyle requires frequent feeding, and you’ll observe them actively foraging throughout daylight hours.
These squirrels breed once or twice annually in Yellowstone, with breeding seasons typically occurring in late winter and early summer. Females produce litters of 3 to 5 young after a gestation period of about 35 days.
The young are raised in tree cavity nests or leaf nests called dreys, usually positioned in dense conifer branches for protection from predators like hawks, owls, martens, and weasels.
2. Uinta Ground Squirrel
The Uinta ground squirrel (Urocitellus armatus) ranks among Yellowstone’s most commonly observed mammals during summer months, frequently seen standing upright like sentinels in meadows and along roadsides throughout the park.
These medium-sized ground squirrels measure 8 to 10 inches in body length with an additional 2 to 4 inch tail, and weigh between 6 to 12 ounces.
Uinta ground squirrels display relatively uniform coloration—grayish-brown backs with fine white or buff spotting, tan to cinnamon-colored faces and shoulders, and lighter grayish undersides.
Their tails are grayish underneath with darker coloring on top. This subtle coloration provides excellent camouflage against Yellowstone’s sagebrush and grassland soils.
You’ll encounter Uinta ground squirrels in open meadows, sagebrush flats, and grasslands throughout Yellowstone, particularly abundant in areas like Hayden Valley, Lamar Valley, and around thermal features where vegetation is sparse.
They prefer well-drained soils suitable for burrow construction and avoid densely forested areas. These ground squirrels are strictly diurnal and most active during morning and midday hours.
What makes Uinta ground squirrels remarkable is their extremely long hibernation period—approximately 8 months each year, one of the longest hibernation periods of any North American mammal.
Adult males enter hibernation first in mid-July, followed by females in early August, and juveniles last in late August. They remain underground until spring snowmelt triggers emergence, typically between late March and May depending on elevation and snow conditions.
Key Insight: Before hibernation, Uinta ground squirrels undergo dramatic physical transformation. Males can more than double their body weight, accumulating so much fat that you can literally see it rolling across their bodies as they move. This fat provides the energy reserves necessary to survive 8 months without eating, drinking, or eliminating waste—a physiological feat that has fascinated researchers studying hibernation.
During their brief active season, Uinta ground squirrels feed intensively on green vegetation, grasses, seeds, flowers, and occasionally insects. Their grazing helps maintain meadow diversity and their burrow systems provide shelter for other small mammals, reptiles, and invertebrates.
These ground squirrels are also a critical food source for Yellowstone’s predators including badgers, coyotes, hawks, eagles, and even grizzly bears emerging from hibernation in spring.
Breeding occurs immediately upon spring emergence, with most mating taking place within the first two weeks after males appear. Females produce a single litter of 4 to 8 young after a 28-day gestation period.
The young emerge from burrows at about 4 weeks old and must grow rapidly to accumulate sufficient fat reserves for their first winter hibernation—a challenge that claims many juvenile lives.
3. Golden-Mantled Ground Squirrel
The Golden-mantled ground squirrel (Callospermophilus lateralis) is Yellowstone’s most frequently misidentified mammal, with visitors commonly mistaking it for an oversized chipmunk due to its prominent stripes. These medium-sized ground squirrels measure 9 to 12 inches total length and weigh 6 to 10 ounces, noticeably larger than any chipmunk species.
Golden-mantled ground squirrels are beautifully marked with distinctive copper-gold coloring on their heads and shoulders—the “golden mantle” that gives them their name.
Two prominent white stripes bordered by black run along each side of their bodies from shoulders to rump, but critically, their faces and heads lack stripes entirely. Their backs are grayish-brown between the stripes, and they possess moderately bushy tails that are less full than tree squirrel tails but bushier than most ground squirrel species.
Common Mistake: Many Yellowstone visitors call these animals “chipmunks,” but the lack of facial stripes is your key identification feature. True chipmunks have distinctive stripes running through their eyes and across their faces. If the animal’s head is solid-colored with no facial stripes, you’re looking at a golden-mantled ground squirrel, not a chipmunk.
You’ll find golden-mantled ground squirrels in diverse habitats across Yellowstone, from lower elevation sagebrush areas up to alpine zones above treeline.
They’re particularly common around developed areas including campgrounds, parking lots, and picnic areas where they’ve become accustomed to human presence. These ground squirrels favor areas with rocks, logs, and other cover providing protection from predators.
Golden-mantled ground squirrels are more solitary than Uinta ground squirrels, though their home ranges may overlap. They’re opportunistic feeders consuming seeds, nuts, berries, fungi, green vegetation, flowers, and insects.
Around campgrounds and picnic areas, they readily approach humans seeking food, though feeding wildlife is strictly prohibited in Yellowstone and harmful to the animals.
| Species | Facial Markings | Body Size | Hibernation Period | Primary Habitat |
|---|---|---|---|---|
| Golden-mantled Ground Squirrel | No facial stripes | 9-12 inches | 7-8 months (Sept-April) | Rocky areas, forests, alpine |
| Least Chipmunk | Distinctive facial stripes | 7-9 inches | Periodic torpor | Forest edges, shrublands |
| Uinta Ground Squirrel | No stripes at all | 10-14 inches | 8 months (July-March) | Open meadows, grasslands |
These ground squirrels hibernate for 7 to 8 months from September or October through April or May, though the exact timing varies with elevation and weather conditions.
They accumulate fat reserves and cache food in their burrows to consume during brief winter arousal periods. Breeding occurs shortly after spring emergence, with females producing single litters of 4 to 6 young.
Golden-mantled ground squirrels serve important ecological roles in Yellowstone by dispersing seeds and fungi spores, creating burrows that improve soil drainage and provide shelter for other species, and serving as prey for numerous predators including hawks, foxes, coyotes, weasels, and snakes.
4. Least Chipmunk
The Least chipmunk (Neotamias minimus) lives up to its name as North America’s smallest chipmunk species and one of Yellowstone’s tiniest mammals.
These diminutive rodents measure just 7 to 9 inches total length including a 3 to 4 inch tail, and weigh a mere 1 to 2 ounces—small enough to fit comfortably in your palm.
Least chipmunks display distinctive striping patterns that make identification straightforward when you know what to observe. Five dark brown to black stripes alternate with four light gray or white stripes running from nose along their backs to the base of their tails.
Critically, their faces show three dark stripes—one through each eye and one down the center of the face—separated by two white stripes above and below the eye stripes. Their overall body color is yellowish-brown to grayish-brown, and their moderately bushy tails are held upright when running.
You’ll encounter least chipmunks in remarkably diverse habitats across Yellowstone, from sagebrush steppes at lower elevations to alpine tundra near the park’s highest peaks.
They’re common along forest edges, in areas with fallen logs and rock piles, around developed areas, and anywhere offering a mix of cover and open foraging areas. These chipmunks are highly adaptable and thrive in disturbed habitats.
Least chipmunks are primarily ground-dwelling but readily climb trees, shrubs, and even buildings when foraging or escaping predators. They’re diurnal and most active during morning and evening hours, spending midday resting in burrows during hot weather.
Their diet includes seeds, nuts, berries, flowers, fungi, green vegetation, and insects, which they transport in expandable cheek pouches.
Important Note: While least chipmunks may appear cute and approachable, especially around picnic areas and campgrounds, feeding them is illegal in Yellowstone and detrimental to their health. Human food lacks proper nutrition and causes chipmunks to become aggressive in seeking more, ultimately harming both the animals and visitor experiences.
Unlike ground squirrels that hibernate deeply, least chipmunks enter periodic torpor during winter—a lighter form of dormancy. They cache substantial food stores in their burrows and wake periodically throughout winter to feed on stored provisions. This strategy requires less dramatic fat accumulation than true hibernation but demands large food caches.
Chipmunk burrow systems are extensive despite the animals’ small size, with tunnels extending 10 to 30 feet and including multiple chambers for food storage, nesting, and waste. Entrance holes are typically well-hidden beneath vegetation, logs, or rocks, and chipmunks scatter excavated dirt away from entrances to conceal their burrows from predators.
Least chipmunks breed twice annually in Yellowstone, with spring breeding in April-May and summer breeding in July-August. Females produce litters of 4 to 6 young after a 30-day gestation period. Young chipmunks emerge from burrows at about 6 weeks old and must rapidly learn foraging skills and predator avoidance to survive. They face predation from hawks, owls, weasels, foxes, coyotes, snakes, and even red squirrels.
5. Wyoming Ground Squirrel
The Wyoming ground squirrel (Urocitellus elegans) represents one of Yellowstone’s less commonly observed ground squirrels, inhabiting specific areas within the park where suitable habitat exists. These medium-sized ground squirrels measure 9 to 11 inches in body length with an additional 2 to 3 inch tail, and weigh 8 to 14 ounces.
Wyoming ground squirrels display relatively plain coloration without the striking patterns of golden-mantled ground squirrels or the fine spotting of Uinta ground squirrels.
Their fur is grayish-brown to buff-brown on the back with slightly lighter undersides, and their short tails are grayish-brown with lighter edges. This subtle coloration provides effective camouflage in the dry grasslands and sagebrush areas they inhabit.
You’ll find Wyoming ground squirrels primarily in the northern sections of Yellowstone, particularly in lower elevation sagebrush grasslands and areas with well-drained soils suitable for burrow construction.
They prefer more arid habitats than Uinta ground squirrels and are less common around thermal features and developed areas. Their distribution in Yellowstone overlaps with Uinta ground squirrels in some areas, but Wyoming ground squirrels typically occupy drier sites.
These ground squirrels follow similar life patterns to Uinta ground squirrels, hibernating for 7 to 8 months from late summer through spring.
Adult males enter hibernation first in late July or early August, followed by females and then juveniles in late August. They emerge in spring between March and May depending on elevation and snow conditions, with lower elevation populations emerging earlier.
Wyoming ground squirrels are strictly diurnal and most active during morning hours. They feed on green vegetation, seeds, flowers, and insects, with their diet shifting seasonally as different plants become available.
During late spring and early summer, they consume primarily fresh green vegetation rich in moisture and protein. As summer progresses, they switch to seeds and flowers while building fat reserves for hibernation.
Their social structure is less colonial than Uinta ground squirrels, with individuals maintaining more solitary territories though multiple animals may inhabit suitable habitat areas. Males establish larger home ranges than females and engage in aggressive interactions to establish dominance hierarchies during breeding season.
Breeding occurs immediately upon spring emergence, concentrated in the first two weeks after males appear above ground. Females produce single litters of 5 to 10 young after a gestation period of about 24 days.
The young develop rapidly and emerge from burrows at 3 to 4 weeks old, facing the challenge of accumulating sufficient fat for their first hibernation—a test that many juveniles fail.
Wyoming ground squirrels play important ecological roles in Yellowstone’s grassland ecosystems by serving as prey for numerous predators including badgers, coyotes, foxes, hawks, eagles, and weasels. Their burrow systems provide shelter for other species, and their grazing influences plant community composition in their habitats.
6. Northern Flying Squirrel
The Northern flying squirrel (Glaucomys sabrinus) ranks among Yellowstone’s most secretive and rarely observed mammals due to its strictly nocturnal lifestyle.
These specialized tree squirrels measure 10 to 12 inches total length including a 4 to 6 inch flattened tail, and weigh just 3 to 6 ounces—remarkably light for their apparent size.
Northern flying squirrels feature soft, silky fur that’s cinnamon-brown to gray-brown on their backs and creamy white on their bellies. Their most distinctive feature is the patagium—a furred membrane of skin stretching from wrist to ankle along each side of their body.
When they leap from trees and extend their legs, this membrane opens to create a gliding surface allowing them to travel distances up to 150 feet through the air. Their large, prominent black eyes are adapted for nighttime vision, and their flattened tails function as rudders during glides.
You’ll find northern flying squirrels in mature coniferous and mixed coniferous-deciduous forests throughout Yellowstone, particularly in areas with standing dead trees (snags) that provide den cavities.
They’re closely associated with old-growth forest characteristics and require large trees with natural cavities, woodpecker holes, or dense canopy cover. These flying squirrels are almost never seen by park visitors due to their nocturnal habits and tree-top lifestyle.
Pro Tip: The best chance to observe northern flying squirrels in Yellowstone comes during evening hours just after sunset when they emerge from den trees to begin nightly foraging. Watch mature forest edges near campgrounds or lodging areas, and listen for soft chirping calls. You might spot their silhouettes gliding between trees against the darkening sky—a memorable wildlife encounter few Yellowstone visitors experience.
Northern flying squirrels don’t actually fly but glide using their patagium as an airfoil. They launch from high in one tree, extend their legs to spread the membrane, and glide downward at angles to land on the trunk of a target tree.
They can adjust direction mid-glide by shifting their legs and using their tail as a rudder. Upon landing, they quickly scamper up the tree to avoid ground predators—a critical survival behavior since they’re vulnerable when on the ground.
Their diet differs significantly from other Yellowstone squirrels, consisting primarily of fungi (including underground fungi), lichens, tree sap, seeds, nuts, insects, and occasionally bird eggs.
The fungi component is particularly important, and flying squirrels play crucial ecological roles by dispersing mycorrhizal fungi spores that form symbiotic relationships with tree roots. They also consume more lichens than other squirrel species, which provides essential nutrients during winter months.
Northern flying squirrels remain active year-round in Yellowstone and don’t hibernate, facing the challenge of surviving brutal mountain winters.
They rely on communal denning behavior, with multiple individuals—sometimes 8 to 10 or more—huddling together in tree cavities to share body heat. This social thermoregulation allows them to survive subzero temperatures that would quickly kill solitary individuals.
Breeding occurs once annually in Yellowstone, typically in late winter or early spring. Females produce litters of 2 to 4 young after a 37 to 42 day gestation period.
The young are born in tree cavity nests lined with shredded bark, lichens, and other soft materials. Young flying squirrels develop slowly and don’t leave the nest until about 6 weeks old, with gliding ability developing over several more weeks of practice.
Yellowstone’s six squirrel species showcase remarkable adaptations to the park’s challenging environment, from red squirrels chattering in lodgepole forests year-round to ground squirrels hibernating through 8-month winters to flying squirrels gliding through darkness.
Each species fills a unique ecological niche—red squirrels harvesting and caching conifer seeds, ground squirrels aerating soils and feeding predators, chipmunks dispersing seeds across elevation gradients, and flying squirrels spreading essential fungi through forest ecosystems.
While wolves and bears capture headlines, these small mammals form the foundation of Yellowstone’s food webs and drive ecosystem processes that maintain the park’s ecological integrity.
Next time you visit Yellowstone, take time to observe and identify the squirrels around you—their behaviors and adaptations reveal as much about wilderness survival as any larger charismatic species, and their ubiquity means you’re virtually guaranteed close encounters with these fascinating mammals throughout your park experience.
