Shrews, which are insectivores rather than rodents, are intriguing little animals. They are voracious nocturnal predators with a high metabolic rates—in fact so high that they must hunt and eat frequently or face the real possibility of quickly dying of starvation. When sleeping, however, shrews sometimes conserve energy by falling into a torpor, which lowers their body temperature.

Scientists have discovered that some shrew species use echolocation to find their prey, giving the animals an added advantage on their hunting forays. Though shrews are seldom seen, they are actually fairly common in many habitats, including arid regions of the Southwest.

Sonoran Desert species:

desert shrew (Notiosorex crawfordi)

Order: Insectivora
Family: Soricidae

Distinguishing Features

The desert shrew vies with the pipistrelle bat as the smallest desert mammal. An adult desert shrew weighs from 3 grams (the weight of a penny) to 5 grams (the weight of a nickel). It has short legs, a pointed snout, tiny eyes, pale grey fur, and a short tail. The body is a little over 2 inches (5 cm) long.

Range

The desert shrew is found throughout the southwestern United States and northern Mexico.

Habitat

Desert shrews do not appear to be restricted to any particular habitat, so long as there is sufficient cover. They are often found in packrat houses, or under dead agaves, old logs, or other debris.

Feeding

• Diet: The desert shrew eats a variety of arthropods as well as lizards and even small mice. It eats scorpions and seems to be immune to their sting.

• Behavior: Shrews store food items in their nests. To keep food fresh, shrews crush their victims’ heads and bite off their legs, but do not kill them. Shrews eat up to 75 percent of their body weight in food every day.

Life History

The desert shrew prowls and searches for its prey at night, so it often falls victim to nocturnal hunters such as owls and snakes. The shrew has scent glands on its sides, however, that emit a strong musky odor; this scent appears to make it less palatable to mammalian predators. Even so, most shrews probably only survive a year or so in the wild.

The desert shrew is well adapted to desert life, surviving without free water and obtaining what moisture it needs from its prey. It also conserves water by concentrating its urine and remaining in its nest during the heat of the day.