How big is a Shrew?

Shrews are small mammals with long, pointed snouts that eat mainly insects, worms, spiders and other small animals without backbones. The shrew in the explorer is 10 centimeters (4 inches) long from the tip of its nose to the tip of its tail. That is about the length of a common shrew of Europe or a masked shrew of North America. The more than 300 species of shrew live across most of the world, but not in Australia, the polar regions or the far south of South America.

Size

Guides usually give a shrew's head-and-body length and its tail length separately. The Mammal Society, in Britain, gives the common shrew a body 5–8 centimeters (2–3 inches) long, a tail 2–4 centimeters long and a weight of 5–14 grams. From nose to tail tip, that makes it 7–12 centimeters (3–5 inches) long.

North America's masked shrew averages 99 millimeters from nose to tail tip, and its tail makes up more than 40 percent of that. It weighs 2.5–4.0 grams. Shrews as a group vary much more. The Etruscan shrew, one of the smallest known mammals, weighs 1.8–3 grams, while a male Asian house shrew can weigh as much as 147 grams.

Size comparisons

• The explorer's hummingbird is also 10 centimeters long. An Anna's hummingbird of that length weighs 4–4.5 grams, a little more than a masked shrew.
• The largest hailstone on record by diameter, 20.3 centimeters (8.0 inches) across, was about twice the length of the explorer's shrew.
• A common shrew's body, without its tail, is about as long as a large chicken egg, which is about 6 centimeters long.
• Three shrews 10 centimeters long, lined up nose to tail, would stretch about the length of a 12-inch (30-centimeter) ruler.
• A common shrew eats 80–90 percent of its body weight in food every day. For a person weighing 50 kilograms (110 pounds), that would be 40–45 kilograms (88–99 pounds) of food a day.

Living fast

Shrews lose heat quickly, because a small body has a lot of surface for the amount of body inside it. To stay warm, shrews burn food very fast. A common shrew's heart can beat 500–1,000 times a minute, and the animal is active day and night, taking only short naps.

A common shrew has to eat every two to three hours to survive. Some of the earthworms it eats are 10 centimeters long, longer than its own body. The smaller pygmy shrew can eat more than 250 prey animals in a day, up to 125 percent of its body weight. Common shrews also live short lives, rarely longer than a year.

Venom and echolocation

Shrews have tiny eyes and probably rely mostly on touch, hearing and smell. Some also use sound. The northern short-tailed shrew of North America sends out ultrasonic clicks, too high for people to hear, and listens for the echoes to sense what is around it. Common shrews also make ultrasonic sounds, but use them much less than bats do.

A few shrews are venomous. The northern short-tailed shrew makes toxic saliva that helps it overpower animals much larger than itself, including frogs, mice and other shrews. The water shrew of Europe also has venom in its saliva.

Not a rodent

Shrews look like mice, but they are not rodents. Scientists sort mammals into large groups called orders. Mice belong to the rodent order, Rodentia. Shrews belong to a different order, Eulipotyphla, along with moles and hedgehogs.

Sources

• Common shrew. Mammal Society.
• Pygmy shrew. Mammal Society.
• Mole. Mammal Society.
• European hedgehog. Mammal Society.
• House mouse. Mammal Society.
• Soricidae: shrews. Animal Diversity Web, University of Michigan Museum of Zoology, 2002.
• Cinereus shrew. Animal Diversity Web, University of Michigan Museum of Zoology, 2001.
• White-toothed pygmy shrew. Animal Diversity Web, University of Michigan Museum of Zoology, 2005.
• Asian house shrew. Animal Diversity Web, University of Michigan Museum of Zoology, 2004.
• Northern short-tailed shrew. Animal Diversity Web, University of Michigan Museum of Zoology, 2011.
• Anna's hummingbird. Animal Diversity Web, University of Michigan Museum of Zoology, 2001.
• Official Documentation of the Verification of the Vivian, SD Record Setting Hailstone of 2010. NOAA National Climatic Data Center, 2010.
• Shell Characteristics of Eggs from Historic Strains of Single Comb White Leghorn Chickens and the Relationship of Egg Shape to Shell Strength. Anderson et al., International Journal of Poultry Science, 2004.