The North American least shrew (Cryptotis parva) is one of the smallest mammals, growing to be only up to 3 inches long.

The North American least shrew's eyes are small and its ears are completely concealed within its short fur, giving it very poor eyesight and hearing.

[4] This species can be found in meadows, fields, and weedy areas, where the vegetation attracts its insect diet.

Hunting by smell and touch, the North American least shrew digs through loose soil and leaf litter for its prey along the surface of the ground.

The behavior of captive individuals suggests it can also tunnel through moist soil in search of food much like moles do.

[4] Its diet consists of mostly small invertebrates, such as caterpillars, beetle larvae, earthworms, centipedes, slugs, and sow bugs.

[4][7] The North American least shrew makes its home in burrows or shallow runways under flat stones or fallen logs.

Evolutionary analysis seems to show the shrews evolved from the ancestor Crocidosorex in Europe and crossed over into the Nearctic, consisting of North and Central America, via the Bering Strait (above sea level at the time).

Once the descendants of the Crocidosorex crossed into North America, this subfamily of Soricidae gave rise to the genus Antesorex during the Miocene.

However, the olfactory lobes are well developed, revealing the significance of the ability to smell in the shrew's survival.

The reproductive and urinary systems are joined in one external opening, called the cloaca, which is a primitive character not found in higher mammals.