Chipmunks are small, striped rodents and members of the squirrel family, instantly recognizable across the North American landscape. These ground-dwelling animals are active during the day, often seen scurrying to gather seeds and nuts in their cheek pouches. The species found within the United States present a fascinating geographical division, broadly separated into distinct Eastern and Western populations.
Regional Presence: Eastern vs. Western Species
The geography of chipmunks in the US is defined by a single, widespread species in the East and numerous species in the West. The Eastern Chipmunk (Tamias striatus) is the sole representative in its region. It inhabits a massive area from southern Canada down to the Gulf of Mexico, extending west into the Great Plains, reaching states like Oklahoma and North Dakota. This highly adaptable species dominates the eastern half of the country.
In contrast, the western half of the United States is home to the genus Neotamias, which includes over 20 distinct species. Western chipmunks, such as the Least Chipmunk (Neotamias minimus), generally occupy the mountainous terrain of the Rockies, the Sierra Nevada, and the Pacific Coast states. These species tend to have smaller, more localized ranges, often restricted by specific elevation bands or isolated mountain ranges. For example, the Townsend’s Chipmunk (Neotamias townsendii) is found in the moist forests of the Pacific Northwest, including western Washington and Oregon.
Specific Habitat Preferences
Chipmunks seek out specific environmental features that provide cover and food regardless of the region. The Eastern Chipmunk prefers open deciduous and mixed forests, often where mature hardwoods like maple and beech trees are present. They thrive in areas with an open understory and readily available ground cover, such as logs, rocky outcrops, and stumps. They are also commonly found in suburban environments, utilizing parks and gardens for shelter in woodpiles or stone walls.
Western species, while more varied, also rely on structure and vegetation for survival. Many Western chipmunks inhabit coniferous forests at higher elevations, mountain meadows, and rocky slopes. The Cliff Chipmunk (Neotamias dorsalis), for instance, is associated with steep, rocky terrain in arid woodlands dominated by juniper and pinyon pine. They need dense shrubs or brush to provide quick escape routes from predators like hawks, foxes, and snakes.
The Underground Home
A chipmunk’s home is a complex burrow system excavated underground. These elaborate dwellings, which can extend up to 30 feet long and three feet deep, serve as their main refuge. The entrances to these burrows are typically small, measuring only two to three inches wide, and are deliberately hidden.
Chipmunks carry the excavated soil away in their cheek pouches, which prevents a visible mound of dirt from forming at the entrance. This technique effectively conceals the burrow from predators, making the entrance look like a simple hole in the ground. Inside, the burrow features a network of tunnels with specialized chambers. A central nesting chamber, often lined with leaves for warmth, is used for sleeping and raising young. Other side pockets are designated for storing caches of seeds and nuts, which they rely on to survive the winter months.