Mammals
American Water Shrew
Sorex palustris · also called american water shrews
Skittering briefly across the surface of a cold forest stream, an American water shrew relies on air bubbles trapped beneath fringed feet to stay afloat just long enough to escape danger or reach the opposite bank.
Overview
The American water shrew, Sorex palustris, is a semi-aquatic insectivore native to wetland and forest habitat across parts of Canada and the northern United States. Its remarkable ability to briefly run across water using trapped air bubbles for buoyancy, fringed hind feet adapted for swimming, and waterproof insulating fur make it one of the most physically specialised small mammals found anywhere in North America.
A shrew that can walk on water
Few small mammals can claim the ability to run across open water, even briefly, but the American water shrew manages exactly that, using trapped air bubbles beneath its fringed feet to stay afloat just long enough to make the difference between escape and capture.
Status
Least Concern, remaining present across suitable wetland and forest habitat throughout Canada and the northern United States.
American Water Shrew: common questions
How can the American water shrew run across water?
This species can briefly run across the surface of water, with air bubbles trapped by fringes of stiff hair on its feet providing enough buoyancy to prevent it from sinking for a few crucial seconds, an ability that can help it escape predators or cross short stretches of open water.
What does the American water shrew eat?
This species feeds on aquatic insects, small fish, and other small invertebrates, hunting both underwater by diving after prey and along stream banks and forest floor, giving it access to a wider range of food sources than purely terrestrial shrew species.
How does the American water shrew stay warm in cold water?
This species has dense, waterproof fur that traps a layer of air against the skin, helping to keep it insulated and buoyant while swimming in the cold streams and wetlands that make up much of its habitat.
Where does the American water shrew live?
This species is native to wetland and forest habitat across parts of Canada and the northern United States, typically found along clear, cold streams and ponds within forested landscapes.