Water Shrews: American & Eurasian

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Don't let its size fool you, because the water shrew is an impressive little creature. In this lesson, we'll talk about two specific water shrews, the American water shrew and the Eurasian water shrew. And you might be surprised at what you learn!

What Is a Water Shrew?

Shrews are some of the tiniest mammals on Earth. There are over 350 different species of shrew, an animal that is recognizable by its snout covered with long, sensitive whiskers. At first glance, you might think shrews look like mice. But while mice have large eyes and ears, shrews have smaller eyes and ears that are tucked into their fur.

Water shrews has small eyes and ears, but long, sensitive whiskers for finding prey
Eurasian water shrew

Some shrews, such as the water shrews, will also be found in places that mice won't dare go. And as the name implies, that's aquatic environments. Water shrews are amphibious animals, meaning they do well on both land and in water. The water is where water shrews forage, or look for food. Their whiskers are important here because they allow the shrew to seek food underwater just by their sensitive touch. Because of those small eyes and ears, water shrews don't hunt with sight, hearing, or even smell.

There are different kinds of water shrews, but in this lesson we're going to focus on two specific ones: American and Eurasian.

American Water Shrew

Let's start with the American water shrew, Sorex palustris. Since the American water shrew is found in Alaska, Canada, and the northern mountainous areas of the United States, this guy is also known as the northern water shrew and North American water shrew.

Though very tiny, the American water shrew is relatively large in the shrew world, ranging from five to six inches in length and weighing no more than half an ounce. Their tails are also impressive, and can be as long as two to three inches themselves. This shrew has dense, blackish fur, the hairs of which are grooved (the hairs of terrestrial shrews are smooth). This unique feature not only traps heat and insulates the shrew underwater, but also acts to repel water.

The American water shrew with babies
American water shrew

Their hind feet are larger than their front feet, anywhere from 0.7 - 0.8 inches, and they are covered in stiff hairs. Both the size of their hind feet and those hairs help to propel the shrew through the water. The American shrew has also been seen to walk on water, as it can also use those feet and hairs to trap air bubbles on the surface.

The American water shrew likes to forage in rivers and streams that are surrounded by dense vegetation, logs, and rocks. Being an insectivore, its favorite snacks include things such as the larvae and nymphs of mayflies, caddisflies, and stone flies. It also eats small fish, earthworms, snails, and fungi. Because American shrews are so small, they need to eat almost constantly. They can only survive about three hours without food! So, as you can imagine, they are pretty active all the time. In particular, the American water shrew forages both during the day and at night.

The American water shrew is a solitary fellow but also an aggressive one. Fighting is common between individuals, and they will stand on their hind feet and slash at each other with their teeth when in a spat. They also have to watch out for predators, such as snakes, hawks, owls, and weasels, all of which would love to make a meal out of this water shrew. If they can avoid all of this, their typical lifespan is about 18 months.

Eurasian Water Shrew

Next, we move on to the Eurasian water shrew, Neomys fodiens, the largest of the British shrews. As its name implies, this water shrew is found in Europe and Asia, most commonly throughout the British Islands, Russia, China, parts of Siberia, the Mediterranean, and North Korea. With a black backside and white underside, it ranges from two and a half to three and a half inches in length, with a tail about two to three inches, and weighing less than one ounce! They have a similar lifespan as the American water shrew, living to 19 months on average.

The range of the Eurasian water shrew
range of eurasian water shrew

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