Northern short-tailed shrew facts for kids
Quick facts for kids Northern short-tailed shrew |
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Blarina
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brevicauda
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The northern short-tailed shrew (Blarina brevicauda) is a small, busy mammal found in northeastern North America. It's the biggest shrew in its group, called Blarina. These shrews are very active and love to eat insects. They live in many places, like forests, bushy areas, and even near rivers. What makes them special is that they are one of the few venomous mammals! Their name, brevicauda, comes from Latin words meaning "short tail".
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About the Northern Short-tailed Shrew
What is a Red-Toothed Shrew?
The northern short-tailed shrew is part of a group called "red-toothed shrews." There are about three or four different kinds of shrews in this group. Scientists used to think this shrew was a close relative of the southern short-tailed shrew. Now, they divide the northern short-tailed shrew into 11 smaller groups, or subspecies. These groups might have been separated by ancient glaciers.
How to Identify a Northern Short-tailed Shrew
This shrew is about 10.8 to 14 centimeters (4.3 to 5.5 inches) long. Its tail is short, only about 1.8 to 3.2 centimeters (0.7 to 1.3 inches). It weighs between 15 and 30 grams (0.5 to 1.1 ounces), which is about the weight of a few quarters. Males are usually a little bigger than females.
Their fur is thick and soft, like velvet. It can be black, brownish-black, or silvery-gray. The fur on their belly is a bit lighter. They change their fur twice a year. In October and November, they get a longer, darker winter coat. In spring and summer, they have a shorter, paler coat.
These shrews have three special scent glands. They might use these glands to mark their territory.
Where Northern Short-tailed Shrews Live
Ancient History of the Shrew
Most of what we know about B. brevicauda from the past comes from the Pleistocene Ice Age. Some very old records suggest they might have been around even earlier, in the late Pliocene period. Scientists believe this shrew species first appeared in the middle or late Pliocene.
Geographic Range of the Shrew
You can find this shrew across central and eastern North America. Their range stretches from southern Saskatchewan in Canada all the way to Atlantic Canada. In the United States, they live as far south as northern Arkansas and Georgia. They are very common in the Great Lakes area.
Usually, there are about 5 to 30 shrews living in an area the size of a soccer field. Each shrew usually has a home range of about 2.5 hectares (6.2 acres). These home ranges might overlap a little with other shrews.
Preferred Habitats for Shrews
Northern short-tailed shrews can live in many different places. This includes grassy fields, marshy areas, and both deciduous (trees that lose leaves) and coniferous (evergreen) forests. They also like household gardens. However, they prefer moist places with lots of fallen leaves or thick plant cover. They don't like forests that have been burned or areas where all the trees have been cut down.
What Northern Short-tailed Shrews Eat
This shrew is a very hungry animal! It can eat up to three times its own weight in food every day. While it eats small amounts of fungi and seeds, it mostly eats meat. Its favorite foods include insects, earthworms, voles, snails, and other shrews. They also eat salamanders and mice. These shrews eat more vertebrates (animals with backbones) than other shrew species.
They mostly hunt a few hours after sunset. However, they are also active on cloudy days. Shrews need a lot of water because they lose it quickly. They get some water from their food. They also often hide food, especially in the fall and winter. One study found that they hide 87% of the prey they catch!
The Shrew's Venomous Bite
The northern short-tailed shrew has special saliva that contains a toxin. This toxin helps them paralyze and control their prey. The venom is strong enough to kill small animals, even ones bigger than the shrew itself. If a human is bitten, it can be quite painful.
This venomous saliva comes from glands under their jaw. It flows through a small tube that opens near their lower front teeth. The saliva then travels along a groove in these teeth and into their prey. Interestingly, this toxin is very similar to the one found in the Mexican beaded lizard. Both animals developed their toxins in a similar way, even though they are not closely related. This is an example of Convergent evolution.
How Shrews Sense and Survive
Shrew Senses and Echolocation
Northern short-tailed shrews don't have a great sense of smell. Their eyes are not well developed, and they can probably only tell the difference between light and dark. But they make up for this with amazing senses of touch and hearing. They use echolocation, like bats, to find their way around and hunt. They send out high-pitched sounds and listen for the echoes to create a picture of their surroundings.
How Shrews Stay Warm
The shrew's ability to eat almost anything helps it survive cold winters. They need to keep their body temperature around 38 to 38.5 degrees Celsius (100.4 to 101.3 degrees Fahrenheit). When the temperature outside is between 25 and 33 degrees Celsius (77 to 91.4 degrees Fahrenheit), they don't need extra energy to stay warm.
In winter, they eat 43% more food than in summer. This extra food helps them speed up their metabolic rate to stay warm in the cold. Temperatures above 35 degrees Celsius (95 degrees Fahrenheit) can be deadly for them.
Shrews are mostly active at night. But in winter, they come out earlier in the evening. In summer, they are active later at night. This helps them save energy by avoiding the coldest or hottest parts of the day. Other ways they stay warm in winter include building warm nests, hiding food, and hunting under leaves or snow where it's warmer. They also have special fat that helps them create body heat.
Shrew Behavior
Northern short-tailed shrews spend more time underground than other shrews. They prefer to dig tunnels under the ground, through fallen leaves, or under the snow. They have bursts of very fast activity, lasting about five minutes. These active periods are followed by longer rests. Overall, they are only active for about 16% of a 24-hour day. They can dig very fast, about 2.5 centimeters (1 inch) per minute!
The shrew builds a nest up to 20 centimeters (8 inches) wide. It's usually underground or under a log. They line their nests with leaves or fur from other animals, like the meadow vole. They keep their nests very clean, leaving their waste in a special "latrine" area outside the nest. Other parts of their tunnels are used to store food.
These shrews are usually solitary, meaning they live alone. If two shrews meet, they might make aggressive sounds or movements to scare each other away. If new shrews are put together in a cage, one will often kill the other within a few hours.
Reproduction and Life Cycle
Northern short-tailed shrews mate from March to September. Most babies are born early or late in this period. When males court females, they sometimes make clicking sounds. During mating, the male and female stay connected, and the female might drag the male along.
Pregnancy lasts about 21 to 24 days. After birth, the female nurses six to eight babies for up to 25 days. A female usually has two litters of babies each season, but sometimes three. When the young are nursing, the mother makes the nest stronger and hunts more to get enough food.
Baby shrews are born without hair and are blind. They weigh less than a gram. They can become ready to have their own babies in as little as two to three months. Shrews born in the spring grow up faster and might even have babies in the same year they were born. Young shrews have pale fur that looks like the adults' summer coat. They change this fur when they reach adult size.
Predators of the Shrew
Northern short-tailed shrews have a high chance of dying young. They try to stay safe by hiding under plants, soil, leaves, or snow. Only about 6% of shrews live to the next year. In winter, up to 90% of them might die, probably because of the cold.
Many animals hunt these shrews, including trout, snakes, raptors (like hawks and owls), canids (like foxes and coyotes), cats, mustelids (like weasels), skunks, raccoons, and opossums. However, many meat-eating mammals seem to avoid them because of the musky smell from the shrew's scent glands.
Conservation Status
The northern short-tailed shrew is listed as a species of "least concern" on the IUCN Red List. This means it is widespread, there are many of them, and their population is not decreasing.
Shrews and Humans
Northern short-tailed shrews cannot be domesticated or kept as pets.
See also
In Spanish: Blarina brevicauda para niños
