Shrew, a small predatory mammal of the family Soricidae. There are about 250 species. Some animals that are not members of the family Soricidae are also called shrews, but are not discussed here.

ShrewsShrews are among the smallest mammals.

Shrews have long, narrow bodies; thin tails; and heads with long, pointed snouts. The smallest shrew—as well as the smallest mammal in the world—is Savi's pygmy shrew, which is about 2 1/2 inches (6.4 cm) long, including a 1-inch (2.5-cm) tail, and weighs 1/14 ounce (2 g). One of the largest shrews is the African giant shrew, which is about 9 1/2 inches (24 cm) long, including a 4-inch (10-cm) tail. It weighs about 2 ounces (57 g). Shrews have tiny eyes and ears, which are often concealed by fur. They have poor vision. The fur is short, thick, and very soft, and is usually gray or brown.

Shrews are found around the world in temperate and tropical areas except in Australia. There are more than 40 species in North America; one of the most common is the short-tailed shrew. Most shrews are land animals, but several species are aquatic. Aquatic shrews have stiff hairs on the feet that trap air bubbles, allowing the animal to run on the surface of the water. The Tibetan water shrew is the only shrew with webbed feet. Shrews live mostly in moist areas such as swamps and bogs, and on the moist, leaf-covered floors of deciduous forests. They hide under vegetative covering, logs, or large rocks, or in underground burrows.

The shrew is a fast-moving, excitable animal that uses up so much energy that it must eat day and night in order to keep alive. It eats two or three times its own weight in food each day—mostly insects, mice, and other small animals. Some shrews have poisonous saliva that paralyzes their prey. Shrews have a pair of scent glands on their hind legs; the glands secrete an acrid, musky odor that repels predators.

Shrews have a maximum life span of about two years. They reach maturity when they are about a year old. In the tropics, shrews breed throughout the year; in temperate climates the breeding season is usually from March to November. As many as four litters are born a year, with from two to 10 young in a litter.

Why Do Shrews Have Short Lives?

Most small animals such as shrews have short life spans. Some scientists think the reason is that such animals need so much food. Burning all this food for energy may put too much stress on the bodies of the animals.

Shrews that live in captivity live only one or two years. Shrews in the wild face many more dangers that can shorten their lives even further. Animals such as owls, foxes, and weasels prey on them. Shrews also can be killed by parasites or diseases. Sometimes a loud noise such as thunder can scare a shrew to death.

What Are Some of the Smallest Mammals?

Shrews are among the smallest mammals. The pygmy shrew is the smallest mammal in North America. This shrew usually measures less than 3 inches (7.5 centimeters) from its nose to the tip of its tail. It weighs around 0.12 ounce (3.4 grams). That is less than a small coin weighs. Another shrew that size is Savi’s pygmy shrew. It is the smallest mammal in Europe.

Newborn shrews are often smaller than a coffee bean. They also are blind and hairless, and they are completely dependent on their mothers.

Which Shrew Has the Strongest Backbone?

The armored shrew of Africa is one of the largest and strongest shrews. It is also called the hero shrew for a good reason.

The structure of the armored shrew’s backbone is one-of-a-kind among mammals and other vertebrates (VUR tuh brihts), or animals with backbones.

Mammals have backbones made up of interlocking bones called vertebrae. But an armored shrew’s vertebrae interlock more than any other mammal’s do. The strength of this reinforced backbone is truly amazing. It has been reported that an armored shrew can support the weight of an adult human being atop its body.

The shrew family, Soricidae, is in the order Insectivora. Most species belong to the genus Sorex or the genus Crocidura, which includes the African giant shrew, C. flavescens. Savi's pygmy shrew is Suncus etruscus; the short-tailed shrew, Blarina brevicauda; the Tibetan water shrew, Nectogale elegans.