There are more than 300 species of shrews, according to the University of Michigan Museum of Zoology. Shrews are mammals and belong to the same order, Insectivora, as moles. Shrews live in all parts of the world except the polar regions, southern South America and Australia. While shrews can help eliminate pests like insects and small animals, they can be pests for homeowners and landscapers. Shrews dig underground tunnels to build nests and construct runways. They may establish their habitats in vegetable and flower gardens and move into cellars and barns in winter.
Size, Behavior and Lifespan
Shrews are very small, reaching an adult weight of only 2 to 3 grams. Their small size prohibits hibernation since they are always looking for food. Shrews are active day and night, are territorial, solitary and often live in moist habitats above and below ground. Some shrews construct elaborate systems of runways and tunnels. The normal lifespan of a shrew is a year.
Shrews are constantly eating to compensate for their small size. Each day, they eat and metabolize three times their weight in food and they store food for the winter. Shrews eat plants, small animals and non-insect arthropods. Their diet may include plants, snails, salamanders, beetles, snakes, mice, frogs, birds and other shrews.
Defense and Aggression
Shrews are aggressive and have been known to attack larger animals. Shrews mark their territories with scent and threaten intruders. Venomous saliva enables some shrews to subdue and eat prey equal to their size. Humans who are bitten by shrews experience allergic reactions similar to that caused by bee stings. Shrews emit musky odors that may repel predators. They make sounds like chirps and twitters as a sign of aggression.
Senses and Communication
Shrews have very tiny eyes and use their other senses-smell, hearing and touch-to experience the world. Some shrews use echolocation like bats and whales. They emit sounds that are ultrasonic clicks and interpret the returning echoes to perceive the environment without sight.