Shrews may resemble mice but they are different

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Shrews resemble a mouse but they have a pointed snout, small ears and tiny eyes.

—Photo by ROADY OUTDOOR PHOTOGRAPHY

Editor's note: This is the third of a three-part series.

Shrews are one of the smallest mammals in North America and the smallest one

resides in North Idaho--the pygmy shrew. The pygmy shrew weighs between two and

four grams, roughly the weight of a pencil. Other shrews that reside in North Idaho

include the American water shrew, masked shrew, montane shrew and vagrant shrew.

Shrews may look like mice but they are significantly different because they

belong to a different order containing insectivores and they have pointed noses, small

ears and tiny eyes. Like voles, identifying a shrew on the species level is difficult.

One unique aspect of a shrew, if you can catch one or find one dead, is that they

all have reddish tips to their teeth. Shrews can also be identified by five toes on all feet

whereas mice have four toes on the front feet and five toes on the hind feet.

All insectivores use senses besides sight to find food, mainly hearing, touch and

smell. Shrews have many characteristics that allow them to forage for insects.

Shrews have tiny eyes because they don’t rely on sight to find their food. Their

pointed snout helps them burrow through soil to reach grubs including earthworms,

insects, spiders and other small animals such as young mice, salamanders, snails and

slugs. Some shrews even use echolocation like bats to find insects.

Since their sense of smell is extremely important for finding food, a larger portion

of their brain is devoted to their sense of smell. Once shrews find an insect, they catch

the insect with their two enlarged, pincer-like upper front incisors that protrude forward.

As big eaters, shrews eat at least their body weight in food each day. If they don’t

eat frequently they may die of starvation so shrews store food in their nest. This

voracious appetite doesn’t keep shrews from being picky eaters. Shrews prefer fresh

food, even fresh stored food.

With a diet of insects, storing fresh food may seem unlikely but shrews keep their

catch fresh by crushing the prey’s skull and biting off the legs. This keeps the insect

alive until the shrew eats it. Shrews have sharp, pointed teeth adapted just for

crunching on insect exoskeletons.

While shrews may have a voracious appetite and a unique way of storing food,

they are not on the top of many predators food list. Many shrews emit a musky odor

from scent glands that resembles a skunk odor and effectively deters most predators

except for owls.

Like some mice, voles and lemmings, shrews are mainly nocturnal but will also

be sporadically active during the day. They burrow in the leaf litter or humus layer to

travel or travel in the burrows or runways made by voles and moles (also an

insectivore).

Like the water vole, the water shrew readily takes to water and lives around

streams and ponds. The water shrew can even run on water because of the long, stiff

hairs between its toes and along the sides of feet that trap air bubbles.

Many of the shrews, mice, voles and lemmings survive the cold winter

temperatures by living in the subnivian zone. This zone stays within one to two degrees

of freezing regardless of the air temperature if there is adequate snow cover.

Occasionally, tracks of these small mammals can be seen on the surface of the

snow scurrying between trees or clumps of grass. However, the small mammals don’t

stay on the surface long because they are more prone to predation, even if they

possess a musky odor.