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Walking a woodland trail on a quiet autumn day, I heard a small animal make strange, twittering sounds as it rustled through leaf litter on the forest floor. Surprised at its loudness, I quietly followed the upheaval trail until I caught a glimpse of a shrew. Commonly mistaken for mice, shrews are micro-beasties with pointed noses on streamlined, grayish bodies. Shrews are nature’s elusive, voracious, small mammals. Vocalizations include short staccato squeaks, softer twittering, and whispers.

The shrew family, Soricidae, has 385 species worldwide, including 16 in Canada and at least nine in the Atlantic region. The Cree and Ojibway First Nations called shrews Kin-skee-sha-wah-bee-gah-nore-see which means sharp-nosed, short-tailed field mouse.

Metabolically supercharged, with hearts beating 800 to 1,200 times per minute, high-strung shrews have been timed making as many as 12 body movements per second. Such frenetic activity require an enormous amount of energy, so shrews eat constantly. Some consume their own body weight in food daily. Prey includes insects, spiders, earthworms, mice, voles, frogs, salamanders, nestling birds, vegetable matter, fungi, and even other shrews. I’ve seen dead garter snakes, just emerged from hibernation and too slow to escape a shrew attack. Theodore Roosevelt fed his pet shrew a garter snake.

If a shrew can’t locate food, it probably starves within 24 hours. Sleeping intermittently during both night and day, they wake every few minutes to change position, and use their tongues and hind feet to clean themselves.

Small but mighty hunters
Shrews have poor eyesight and often live and hunt in dense cover. Their pointed snouts house hook-like upper incisor teeth and elongated lower incisors. Those tweezer-like teeth enable them to accurately grapple and cut into their prey, which they detect by touching with constantly moving long, highly sensitive whiskers. They employ hearing and smell as well.

The Smokey shrew, Sorex fumeus, mainly lives and finds food in in tunnels made by other animals (including shrews). These are located near rotting logs and moss-covered rocks in hardwood forests.

Masked shrews, Sorex cinereus, live in a wide variety of habitats across the country, including the tundra and meadows.

Pygmy shrews, Sorex hoyi, also known as Microsorex hoyi, weigh as little as two grams, giving them the title of  our smallest North American mammal. Masked and pygmy shrews are both tree climbers.

Run across my swimming pool?
The American water shrew, Sorex palustris, weighs 10 to 18 grams, making it one of the heavier shrews. I was sitting one evening by the pond below our house when a water shrew ran from an island on the pond across the water to the shore, a distance of about three metres. Water shrews have stiff hairs on the underside of their feet that hold the air bubbles and make this feat possible. Their fur generally holds pockets of air, while absorbing little moisture. This enables them to swim, dive, and patrol along stream bottoms to catch fish and dig eggs out of spawning beds.

A venomous mammal
The short-tailed shrew, Blarina brevicauda, uses venom to immobilize prey. This is a large, common shrew that prefers hardwood forests but can inhabit many other areas, including gardens, swamps and fields. It can weigh up to 21 grams with a body length up to 10 centimetres.

One such shrew has enough venom to immobilize 200 mice. Lacking the hollow fangs of a snake, they use a gland that mixes saliva with the venom instead. Biting the prey introduces venom-loaded saliva into the wound. After a bite, mice can die of respiratory failure within three minutes.

However, while the venom paralyzes some victims, they stay alive. The shrew transports its immobile prey to a cache, hoarding it to eat on a poor hunting day. The American Chemical Society reports that a mealworm bitten this way will last, stiff but alive, for 15 days. Often shrews will eat the first thing they capture and cache the rest. In one laboratory situation, written about by Jean T. Adams in the New York State Conservationist, a short-tailed shrew killed 82 frogs, caching 80.

Robie Tufts’s book, Birds and Their Ways, mentions a rough-legged hawk that died near Oak Point, Man. An autopsy confirmed that it ate five live shrews, and they’d repeatedly bitten the bird’s crop lining, causing the internal hemorrhaging that killed it. A shrew bite may prove painful to humans, but usually the pain disappears after a few days.


Short life span
Most shrews live about 14 months. Their teeth wear out rapidly, but most die from predation, disease, or starvation. Winter is hard. All species remain active in a range of about 0.4 to two hectares over their entire lives, hunting night and day. Short-tailed shrews will burrow below frost level to find earthworms. They also feed on seeds and modify their activities in winter to conserve body heat and lower energy consumption. 

Short-tailed shrew females birth two to 11 young in April or May. It takes about 16 days for newborns to acquire fur coats and become mobile. To travel quickly, female shrews lead their young in single file “caravan,” each juvenile burying its snout in the rump of the one ahead. After 30 to 40 days, the mother leaves the youngsters on their own. If their mother mated after their birth, she may have another litter in August. Shrews live solitary lives, with a great deal of time spent hunting, while taking refuge in deserted mouse nests or under rotten logs. Young water shrews hide in crevices and overhanging ledges beside streams.

Formidable yet tiny, shrews are nevertheless vulnerable. The odour of their musk glands sometimes repels dogs and cats, but foxes, bobcats, lynx, coyotes, weasels, skunks, mink, owls, hawks, and even large fish often tackle them successfully.

Shrews can influence their ecosystems. Masked and Arctic shrews can be significant predators that moderate outbreaks of spruce budworm and larch sawfly populations. These insects can inflict extensive damage on Eastern forests. One researcher found that small mammals consume 40 to 50 per cent of spruce sawfly cocoons, with the masked shrew being the most voracious predator. Shrews also eat engorged female ticks that fall to the ground when they are ready to lay eggs. As tick and forest insect pest consumers, I appreciate the several shrew species that patrol the woodland here.

It you hear a noisy, wee creature loud mouthing its way under an eruption of fallen leaves, stop and listen. You’re being shrewd!

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