Squirrel In Action

Predatory behavior by various species of ground squirrels, particularly the thirteen-lined ground squirrel, has been noted. For example, Bailey, a scientist in the 1920s, observed a thirteen-lined ground squirrel preying upon a young chicken. Wistrand reported seeing this same species eating a freshly killed snake. Whitaker examined the stomachs of 139 thirteen-lined ground squirrels, and found bird flesh in four of the specimens and the remains of a short-tailed shrew in one; Bradley, examining white-tailed antelope squirrels' stomachs, found at least 10% of his 609 specimens' stomachs contained some type of vertebrate, mostly lizards and rodents. Morgart (1985) observed a white-tailed antelope squirrel capturing and eating a silky pocket mouse.
Taxonomy
The living squirrels are divided into five subfamilies, with about 50 genera and nearly 280 species. The oldest squirrel fossil, Hesperopetes, dates back to the Chadronian (Late Eocene, about 40–35 million years ago), and is similar to modern flying squirrels.