Chipmunks are small, striped rodents inhabiting forests and shrublands, primarily across North America. These familiar creatures are part of the squirrel family (Sciuridae) and are classified within the genus Tamias. The name Tamias is derived from a Greek word meaning “storer” or “treasurer,” referencing their habit of collecting and hoarding food for colder months. The genus contains a surprising level of biological diversity.
The Official Species Count and Global Range
The current scientific consensus places the total number of living chipmunk species at approximately 25. This figure reflects decades of research consolidating various forms into a unified classification under the genus Tamias. The species are distributed across the globe in a highly uneven pattern.
Only a single species, the Siberian Chipmunk (Tamias sibiricus), is found outside of the New World, ranging across northern Asia. The remaining 24 species are native to North America. Only one North American species, the Eastern Chipmunk (Tamias striatus), is found in the eastern half of the continent, while the remaining 23 species are restricted to western North America.
Understanding Taxonomic Subgroups
All chipmunks are categorized under the genus Tamias, but scientists divide the group into three distinct subgenera to reflect evolutionary distance. This structure helps organize the diversity and trace their distinct origins.
The first subgenus, Tamias, is monotypic, containing only the Eastern Chipmunk (T. striatus). The second subgenus, Eutamias, is also monotypic and contains the Siberian Chipmunk (T. sibiricus), the sole Eurasian species.
The final and largest category is the subgenus Neotamias, which contains the remaining 23 species of North American chipmunks. These species are polytypic, reflecting the extensive number of distinct forms that evolved in the complex western landscapes. Genetic studies support this taxonomic division despite the morphological similarities among all chipmunks.
Examples of Species Diversity Across North America
The Eastern Chipmunk (Tamias striatus) serves as a baseline for comparison, as it is the largest species and the only one in the East. Its range extends across the eastern half of the continent, and it typically weighs around 3 ounces (90 grams). The vast number of species in the western subgenus, Neotamias, demonstrates a remarkable degree of adaptation.
The Least Chipmunk (Tamias minimus) is the most widespread western species and the smallest in the entire genus. This species weighs between 1 and 2 ounces (35 to 70 grams) and is found across varied habitats, from sagebrush deserts to high mountain forests.
Other western species have developed specialized ecological niches, such as the Lodgepole Chipmunk (Tamias speciosus). This species is restricted to the high-elevation coniferous forests of the Sierra Nevada and other mountain ranges. This specialization in habitat and size is why the species count is concentrated in the western mountains.