Ground squirrel tunnels typically run 5 to 30 feet in total length and sit 2 to 3 feet below the surface, though some sections can reach 6 feet deep. These aren’t just simple holes in the ground. They’re branching underground networks with separate chambers for sleeping, hibernating, raising young, and storing food.
Size and Structure of the Burrow System
A ground squirrel burrow entrance is about 4 inches in diameter, roughly the size of a baseball. Older, well-used entrances can be noticeably wider from repeated traffic. Below the surface, the system ranges from a single straight tunnel to a complex web of branching passages. The overall layout depends on how long the squirrels have occupied the site: they expand their burrow systems every year, adding new tunnels and creating additional entrances. A burrow that’s been in use for several seasons will be far more extensive than a freshly dug one.
Most of the tunnel network sits within 2 to 3 feet of the surface, which is deep enough to provide insulation from heat and cold but shallow enough to cause real problems for anything built on top. Some sections, particularly nesting chambers and hibernation areas, can extend to 6 feet or more. Inside, the squirrels maintain distinct chambers: one area for sleeping and hibernation, another for rearing pups, and storage pockets where they cache seeds and other food.
How to Identify Ground Squirrel Holes
The easiest way to tell a ground squirrel burrow from other animal holes is the entrance size and the surrounding soil. That 4-inch opening is larger than what voles or chipmunks produce but smaller than a rabbit burrow. You’ll often see a fan-shaped mound of kicked-out dirt near the entrance, and well-worn paths or runways radiating outward through the grass. Multiple entrances clustered in the same area are a strong sign of an established colony, since ground squirrels add new openings each year.
Gopher mounds, by comparison, tend to be crescent-shaped with a plugged hole, while mole activity produces raised ridges of soil across the surface. Ground squirrel entrances stay open and visible.
When Ground Squirrels Are Most Active Underground
Ground squirrels use their tunnels year-round, but their activity level shifts dramatically with the seasons. In inland areas with hot summers and cold winters, adults go through two dormant periods. They hibernate through winter, typically emerging around January when temperatures start warming. Then, when summer heat peaks and food dries up, adults enter a second dormant phase called estivation, retreating underground in late summer.
Young squirrels tend to stay active all summer regardless of heat. In milder coastal climates, particularly in Southern California, ground squirrels can be active throughout the entire year without any true hibernation. In the southern San Joaquin Valley, they slow down considerably in winter but rarely enter full hibernation.
The practical takeaway: the tunnels are occupied in some capacity nearly all year. Peak digging and expansion happens in spring and early summer, when squirrels are most active above and below ground, foraging, mating, and rearing young.
Damage Ground Squirrel Tunnels Cause
The real concern with ground squirrel tunnels isn’t the holes themselves. It’s what happens to the soil around them over time. As tunnel networks expand year after year, they hollow out significant volumes of earth. This creates several problems.
Soil erosion accelerates because water follows the path of least resistance. During heavy rain, water channels into open burrow entrances and flows through the tunnel system, washing away soil from the inside and potentially causing surface collapse. On slopes, hillsides, and embankments, this can undermine structural integrity. Levees and earthen dams are particularly vulnerable, and land managers in agricultural regions treat ground squirrel colonies on levees as a serious infrastructure risk.
Tunnels beneath foundations and concrete slabs are another concern. When burrows run under a house, garage, or patio slab, the voids they create can lead to uneven settling or cracking as the soil loses its ability to support weight evenly. Oregon State University Extension specifically flags burrows under slab or foundation walls as a situation worth addressing. Pastures and lawns develop trip hazards where tunnel ceilings collapse into shallow depressions, which is a real concern for livestock and anyone mowing or walking the property.
Managing Existing Tunnel Systems
Simply filling burrow entrances with dirt rarely works. Ground squirrels are persistent diggers and will reopen blocked entrances quickly, sometimes overnight. If squirrels are still actively using the tunnels, any physical closure is temporary at best.
The more effective approach starts with reducing the squirrel population first, then addressing the tunnels. Trapping is one of the most reliable methods for small properties. For larger infestations, some landowners use bait stations placed at burrow entrances during the seasons when squirrels are actively foraging. Once you’re confident the tunnels are unoccupied, you can collapse them by tamping the soil down firmly or filling entrances with compacted earth and gravel. For burrows near foundations, packing the tunnels with a soil and gravel mix helps restore structural support.
Exclusion barriers can protect specific areas. Hardware cloth or wire mesh buried at least 2 feet deep around garden beds, building foundations, or other sensitive zones prevents squirrels from tunneling into those spaces. The mesh needs to extend a few inches above the surface as well, since squirrels will try to dig right at the base of a barrier.
Habitat modification also helps over the long term. Ground squirrels prefer open areas with short vegetation where they can spot predators. Allowing taller, denser ground cover around the perimeter of your property makes the area less attractive for new colonies. Removing brush piles and debris near existing burrows eliminates the cover squirrels use while foraging near their tunnels.
Why Tunnels Keep Coming Back
Ground squirrels are colonial animals, and abandoned burrow systems act as magnets for new occupants. Other squirrels, and sometimes other species entirely, will move into vacant tunnels rather than dig their own. A property with a history of ground squirrel activity will tend to attract new squirrels unless the old tunnel systems are thoroughly collapsed and the habitat is made less inviting. Monitoring for fresh digging each spring, when dispersing juveniles are looking for new territory, catches recolonization early before a small problem becomes an entrenched one.