**Ground Squirrels** (*Spermophilus* and *Otospermophilus* genera) is a broad term for various squirrel species that live primarily in burrows in the ground, unlike tree squirrels. They are small to medium-sized rodents found in open areas across North America and Eurasia. They are regarded as major agricultural pests and nuisance animals due to the extensive burrow systems they dig, which damage crop roots, compromise irrigation systems, and pose a tripping hazard to livestock and people.
Taxonomy and Classification
Ground Squirrels belong to the family Sciuridae. They undergo complete life stages. Unlike Grey Squirrels, most Ground Squirrel species (e.g., California Ground Squirrel, *O. beecheyi*, and Richardson’s Ground Squirrel, *S. richardsonii*) are true **hibernators**, spending several months of the year in deep dormancy underground to survive winter or periods of drought/heat (aestivation).
Physical Description
Ground Squirrels are stocky, medium-sized rodents, ranging from $6$ to $18$ inches long with short, less bushy tails than tree squirrels.
- **Appearance:** Coloration varies widely by species (speckled, striped, solid gray/brown).
- **Burrow System:** They live in extensive, complex underground burrow systems, often with multiple entrances. The burrow entrance is typically marked by a visible mound of excavated dirt.
- **Behavior:** They are highly social, often living in colonies. They stand upright on their hind legs to scan for danger and emit alarm calls when predators (hawks, coyotes) are sighted.
Distribution and Habitat
Ground Squirrels are widespread across plains, prairies, rangelands, pastures, and agricultural fields globally. Their habitat is open, well-drained soil that is easy to dig, often preferring areas with good visibility to avoid predators. They are common on golf courses, levees, and freeway embankments.
Behavior and Conflict
Ground Squirrels are diurnal and herbivorous, feeding on grasses, seeds, roots, and cultivated crops.
- **Structural Damage:** Their primary damage comes from their burrowing activities. Extensive burrowing compromises the structural integrity of foundations, roads, earthen dams, and irrigation canals, leading to expensive repairs.
- **Crop/Forage Loss:** They consume significant amounts of hay, pasture forage, and grain crops, often feeding close to their burrows.
- **Safety Hazard:** Burrows in pastureland pose a severe risk to livestock (horses, cattle) that can break legs when stepping into a collapsed tunnel.
- **Disease Vector:** Certain species (e.g., California Ground Squirrel) are known reservoirs for the fleas that transmit **plague** (Yersinia pestis), requiring public health monitoring.
Management and Prevention
Control is often necessary for safety and crop protection and requires persistent effort.
- **Habitat Modification:** Eliminate unnecessary ground cover and reduce food sources around high-value areas to discourage colonization.
- **Exclusion:** For small, sensitive areas, ground squirrels can be excluded by burying wire mesh (hardware cloth) $12$ inches deep with the top foot extending above ground.
- **Fumigation/Baiting:** In agricultural settings, professional pest control often uses restricted-use **toxic baits** or **burrow fumigants** (such as aluminum phosphide) to eliminate large colonies, with strict precautions due to their toxicity.
- **Trapping:** Various live and lethal traps are used, often requiring immediate disposal or relocation according to local regulations.
Conservation and Research
Ground Squirrels are managed as significant agricultural and public health pests. Research focuses on safe, non-toxic population control methods (such as reproductive inhibitors) and monitoring their role in zoonotic disease transmission.