Do Squirrels Nest in the Ground? A Look at Their Burrows

Many squirrel species nest exclusively in the ground, building elaborate underground tunnel systems that serve as homes, hibernation shelters, food pantries, and nurseries. The squirrel family (Sciuridae) includes roughly 300 species, and a large share of them are ground-dwellers that dig burrows rather than build leaf nests in trees. If you picture a squirrel scurrying up an oak tree, you are thinking of tree squirrels, which represent only one branch of a much bigger family. Prairie dogs, chipmunks, marmots, and dozens of species called “ground squirrels” all dig burrows that can stretch several meters underground, and the architecture of those burrows is far more sophisticated than a simple hole in the dirt.

Tree Squirrels vs. Ground Squirrels

The split between tree-nesting and ground-nesting squirrels is not a minor lifestyle difference. It reflects deep evolutionary divergence. Ground squirrels belong mostly to the tribe Marmotini, a lineage that adapted to open grasslands, prairies, tundra, and arid scrublands where trees are scarce or absent. Tree squirrels, by contrast, evolved in forested habitats and build dreys (leaf nests) or den in tree cavities. Some overlap exists: chipmunks, for instance, spend a lot of time in trees foraging but sleep and hibernate in underground burrows. The eastern chipmunk digs an extensive burrow system and defends an individual territory around it, while the Siberian chipmunk builds a simpler burrow and does not hold territory the same way.

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If you live in North America, the squirrels raiding your bird feeder are almost certainly eastern gray squirrels or fox squirrels, both tree species. But the continent also hosts a remarkable diversity of ground-dwelling squirrels: thirteen-lined ground squirrels across the Great Plains, California ground squirrels on the West Coast, Richardson’s ground squirrels (often called “gophers” by ranchers) in the northern prairies, Arctic ground squirrels in Alaska and northern Canada, and Columbian ground squirrels in the mountain West. Each of these builds and maintains burrow systems.

What a Ground Squirrel Burrow Looks Like

A ground squirrel burrow is not just a tube in the dirt. Most species dig systems with multiple entrances, branching tunnels, dedicated sleeping chambers, food-storage rooms, and even separate latrine areas. The overall size of the system depends heavily on the species. A review of North American ground-dwelling squirrel burrows found that body size is the single best predictor of burrow length and depth: bigger species dig longer, deeper systems. Burrow length scales with body mass in a way that suggests ventilation is a limiting factor. Underground air does not circulate well, so there is a metabolic ceiling on how far a squirrel can extend a tunnel before the air quality becomes a problem.

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Social species dig longer burrows than solitary ones, because multiple residents need more room. Cape ground squirrels in southern Africa, for example, live in social groups and dig large clusters of interconnected burrows. They sleep together in shared chambers at night.

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Interestingly, the review found that temperature stress at the surface did not predict how deep a burrow went. That sounds counterintuitive, but it makes sense once you account for the insulating properties of soil and snow cover. Even a shallow burrow under a layer of snow can maintain relatively stable temperatures. Arctic ground squirrels are the extreme case: soil temperatures near their burrows averaged around −9°C over the winter in Alaska, with lows dipping below −18°C, yet the squirrels survived months of hibernation underground by generating their own body heat.

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Food Storage Underground

Some ground squirrels use their burrows as pantries, caching food in dedicated side chambers to sustain themselves through winter or periods of scarcity. Arctic ground squirrels in the Yukon Territory build food caches alongside their nest chambers. Researchers who excavated burrows at two sites found that the caches consist of seeds, fruits, and plant material from a dozen or more species, stored in small round chambers along the main tunnels. At one site, the caches were dominated by wild rose hips and seeds, which made up over 95% of stored food by weight. At a second site, berries from a different plant dominated, accounting for about 83% of cached material.

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This food-caching behavior is not unique to Arctic species. European ground squirrels also store food underground. In one case, a construction crew in central Europe unearthed a burrow cavity containing 380 grams of plant tubers just 30 centimeters below the surface. A second burrow at the same site held 290 grams of tubers in a blind-ending tunnel about 90 centimeters deep. That burrow had no nesting material at all, suggesting it was used purely as a food hideout where the squirrel could eat without being exposed to predators.

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Hibernation and Surviving Extreme Cold

For many ground squirrel species, the burrow is not just a home but a hibernation chamber. Hibernation in ground squirrels is among the most dramatic in the animal kingdom. Arctic ground squirrels hold the distinction of being the only known mammal whose body temperature drops below freezing during torpor bouts, reaching around −3°C in their tissues. They accomplish this by supercooling their body fluids. But the burrow itself gets far colder than that. Over three winters in Alaska, soil temperatures recorded near Arctic ground squirrel hibernation chambers averaged about −9°C, with some readings as low as −19°C. The squirrels spent more than five months in conditions below −3°C, during which they periodically aroused from torpor and burned stored body fat to warm themselves back up before dropping into torpor again.

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This cycle of torpor and arousal is metabolically expensive. The food caches described earlier help, but most ground squirrels rely primarily on fat reserves built up during a frantic summer feeding season. Some species enter hibernation having nearly doubled their body weight. The burrow’s insulation from wind and direct cold exposure is what makes survival possible: without the underground shelter, even the fattest squirrel would not last an Alaskan winter.

How Burrows Protect Against Predators

A burrow’s most obvious function is shelter from predators, and ground squirrels have evolved a suite of behaviors that revolve around their tunnel entrances. Columbian ground squirrels do most of their vigilance behavior, including scanning and standing upright, near their burrow openings. When they hear alarm calls, they prefer to climb onto rocks near their burrows to get a better vantage point, favoring high rocks that are close to an entrance they can dive into if a threat appears.

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California ground squirrels have an even more remarkable anti-predator trick. When confronting rattlesnakes, they flag their tails back and forth. This tail-flagging deters snakes from striking, apparently by advertising that the squirrel is alert and ready to dodge. Adult squirrels that tail-flag also increase the chance that the snake will abandon its ambush position entirely, because the display raises the vigilance of other squirrels in the area, making the ambush site less profitable for the snake.

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The tail-flagging system goes a step further. California ground squirrels can heat their tails and add an infrared signal to the display when they are facing a rattlesnake, which has heat-sensing pit organs. They do not bother with the infrared component when confronting gopher snakes, which lack heat-sensing ability. Researchers confirmed this by presenting rattlesnakes with robotic squirrel models: when the robot’s tail included an infrared signal, the snakes shifted more strongly from predatory to defensive postures.

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All of these defensive behaviors orbit around the burrow. A ground squirrel caught in the open far from any entrance is in real danger. The burrow network effectively sets the boundaries of their daily world.

Where Ground Squirrels Choose to Dig

Not all soil is equally suitable for burrow construction. Ground squirrels show clear preferences for certain soil types, and those preferences shape where colonies establish themselves. A study of Anatolian ground squirrels found that the species strongly favored loamy clay soils, appearing in about 82% of sampled areas with that soil type. The presence of stones in the soil actually helped: nest density was highest where stoniness levels fell in a sweet spot around 9 to 9.5%, and dropped off when the ground was either less stony or more stony than that. Sandy soils, on the other hand, had a negative effect on nest site selection, likely because sand is less structurally stable and prone to tunnel collapse.

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This soil selectivity has practical consequences for anyone dealing with ground squirrels on their property. If your land has firm, loamy soil with moderate stoniness and good drainage, it is prime real estate for a ground squirrel colony. Sandy, loose soils or heavy pure clay are less attractive. Colonies also tend to establish in open areas with short vegetation and good sight lines, because ground squirrels depend on visual detection of predators. Tall, dense vegetation limits their ability to spot danger, making them less likely to settle there.

What Burrowing Does to the Landscape

Ground squirrel burrows are not just structures for the squirrels. They reshape the soil around them in ways that affect entire grassland ecosystems. European ground squirrels, by digging and maintaining their tunnel systems, create patches of disturbed soil that differ in fertility, aeration, and microbial activity from undisturbed ground. The mounds of excavated soil around burrow entrances become hotspots for decomposition and nutrient cycling, effectively creating a mosaic of soil conditions across the grassland.

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This role as “ecosystem engineers” is a big part of why ground squirrels matter ecologically, even in places where ranchers and farmers consider them pests. Their burrows provide shelter not just for squirrels but for insects, spiders, snakes, burrowing owls, and other animals that take over abandoned tunnels. Their digging turns over soil, brings nutrients to the surface, and improves water infiltration. Remove a ground squirrel colony from a grassland, and you lose a surprising amount of the habitat heterogeneity that supports biodiversity.

Fleas, Disease, and Burrow Microclimates

One less welcome aspect of ground squirrel burrows is their role in disease ecology, particularly plague. Ground squirrel burrows harbor flea populations, and fleas are the primary vectors that transmit the plague bacterium (Yersinia pestis) between rodents and occasionally to humans. The microclimate inside a burrow, specifically the temperature and humidity at different depths, strongly influences which flea species thrive and when they reproduce. Research on California ground squirrels found that artificially keeping the soil moist to a depth of one meter dramatically altered flea population dynamics: summer-breeding flea species were suppressed, while a winter-breeding species became much more reproductively active during the summer.

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This connection between burrow conditions and flea dynamics is one reason public health agencies in the western United States monitor ground squirrel colonies for plague activity. A colony of burrows is, in effect, an incubator for the fleas that carry the disease. Drought years, wet years, and changes in soil moisture all shift the flea community inside the burrows, which in turn affects the risk of plague outbreaks in surrounding wildlife and, rarely, in nearby humans.

Evolutionary Roots of Burrowing

The squirrel family’s common ancestor was likely an arboreal animal. Ground-dwelling squirrels evolved from tree-dwelling predecessors, and the transition to a fossorial (burrowing) lifestyle left marks on their anatomy. A study of skull morphology across ground squirrel lineages found that ground-dwelling species share certain structural features in their skulls that represent genuine adaptations for digging, rather than simply the loss of traits their tree-climbing ancestors needed. These include changes in muscle attachment points and skull proportions that favor the forceful, repetitive head and jaw movements involved in loosening soil.

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The transition from trees to ground happened multiple times across squirrel evolution, which is why ground-dwelling species are found on multiple continents and in very different habitats. Whether you are looking at an Arctic ground squirrel on the Alaskan tundra, a Cape ground squirrel in the Kalahari, or an Anatolian ground squirrel on a Turkish steppe, you are seeing animals whose ancestors independently gave up the canopy and committed to a life of digging.

Managing Ground Squirrel Burrows on Your Property

For homeowners, ranchers, and park managers, ground squirrel burrows can be a genuine problem. Burrows undermine foundations, damage irrigation systems, create ankle-breaking hazards for livestock, and leave mounds of dirt across lawns and fields. Traditional control methods have included poisoning, trapping, and shooting, but recent research has explored less lethal alternatives.

One approach is burrow deterrence: physically blocking burrow entrances and applying scent deterrents. Researchers in a Canadian national park tested blocking Columbian ground squirrel burrows using foam noodles, wooden stakes, and hardware cloth, sometimes combined with coyote urine spray. Results were mixed. In one study, the likelihood of squirrels re-entering a blocked burrow decreased over time, suggesting the animals gradually accepted the closure and moved on.

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However, a related study at the same sites found that neither the type of blocking material nor the use of coyote urine spray predicted whether squirrels would re-enter.

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The takeaway is that simple burrow blocking can help, but it is not a silver bullet. The first study’s authors suggested that reducing the overall attractiveness of the habitat, encouraging squirrels to disperse to adjacent suitable areas, and gradually reducing population sizes through fertility control might be more effective long-term strategies than blocking individual holes.

Another avenue is chemical repellents applied to physical barriers. A lab study found that treating structural barriers with anthraquinone, a naturally occurring compound that causes gastrointestinal discomfort when ingested, reduced barrier defeat by Richardson’s ground squirrels by 50 to 55% compared to untreated barriers. The squirrels also ate less food near treated barriers, suggesting they learned to associate the area with the unpleasant compound.

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If you are dealing with ground squirrels and trying to decide on an approach, persistence matters more than any single technique. Ground squirrels are tenacious diggers, they have strong site fidelity, and a colony occupying good habitat will resist displacement. Combining physical exclusion, habitat modification (letting vegetation grow taller, removing brush piles that provide cover), and professional pest management advice tends to yield better results than any one method alone. And it is worth checking local regulations first: several ground squirrel species are protected or subject to specific trapping and control rules depending on your state or province.