water shrew
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What is a water shrew?
A water shrew is an amphibious shrew with adaptations for aquatic life, including a broad muzzle, large chest, and long hind legs. They are typically found in montane habitats, foraging in clear, cold streams, using their sensitive whiskers to locate prey underwater by touch, rather than relying on sight, smell, or hearing.
Their dense fur, equipped with water-repellent properties, helps them stay insulated while submerged. The elegant water shrew is the most specialized for aquatic life, while the North American water shrew is the smallest and least specialized. They are classified in the family Soricidae of the order Soricimorpha.
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Where do water shrews live?
Water shrews are amphibious mammals that belong to several genera, including Neomys, Sorex, Chimarrogale, and Nectogale. They mostly live in montane habitats and forage in clear, cold streams and small rivers.
The North American water shrew (Sorex palustris) lives throughout much of the western United States and Canada, from the plains to the mountains. The elegant water shrew (Nectogale elegans) lives in continental Southeast Asia. Several species of Oriental water shrews (Chimarrogale) and Old World water shrews (Neomys) also exist.
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What do water shrews eat?
Water shrews are amphibious mammals that forage in clear, cold streams, using sensitive whiskers to locate prey underwater by touch. The elegant water shrew eats only aquatic insect larvae and nymphs. The North American water shrew's diet consists of about half aquatic insects and the other half terrestrial insects, earthworms, snails, slugs, vegetation, mice, fish, and salamanders.
Some shrews, like the Old World water shrews, produce toxic saliva to immobilize prey. Otter shrews eat freshwater crabs, aquatic mollusks, aquatic insect larvae and nymphs, fish, and frogs.
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How are water shrews adapted for living in water?
Water shrews are well-adapted for their amphibious lifestyle through several key features. They possess a broad, fleshy muzzle, a large chest, and long hind legs and digits, using all four feet to swim, with most of the propulsion coming from the hind feet. Their sensitive whiskers help them locate prey by touch underwater, compensating for their reduced reliance on smell, sight, and hearing.
Their dense fur is water-repellent and provides insulation, with grooved hairs that trap air. The elegant water shrew, highly specialized for aquatic life, has additional adaptations such as the absence of external ears, skin-covered eyes, closable nostrils, scaled feet sides, webbed digits, and rudder-like tail.
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How do water shrews contribute to their ecosystem?
Water shrews, a type of amphibious shrew, play a role in their ecosystems as both predators and prey. They primarily consume insects and other invertebrates, but they also eat small vertebrates, seeds, and fungi. In turn, they themselves become food for larger predators. Water shrews are active year-round, contributing to the food chain in various habitats, from tundra to forests. They use their sensitive whiskers to locate prey underwater, and some species produce toxic saliva to immobilize their prey.
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water shrew, any of 12 species of amphibious shrews that have a broad, fleshy muzzle, large chest, and long hind legs and digits. Most water shrews live in montane habitats and forage in clear, cold streams and small rivers. They use all four feet to swim, but most of the propulsive force comes from the hind feet. Their relatively large brain is associated with enlarged nerves leading to the shrews’ abundant and sensitive whiskers, which are used to locate prey underwater by touch. Water shrews do not hunt by using smell, sight, or hearing, as their olfactory regions of the brain are reduced, their eyes small, and their ears hidden in fur.
Their soft, very dense fur is blackish but slightly paler or white on the underparts. The longer hairs in its coat, instead of being rounded, as in terrestrial shrews, are grooved on each side (H-shaped in cross section), and the grooves contain numerous ridges. This configuration helps trap air, providing the coat with water-repellent properties and increased insulation to counter heat loss while submerged. The long tail is finely furred.
The elegant water shrew (Nectogale elegans) of continental Southeast Asia is the most specialized for aquatic life. Only occasionally emerging from the water, it eats only aquatic insect larvae and nymphs. This species lacks external ears entirely and is blind, its eyes covered by skin. Its nostrils are located behind a nosepad that is closed by flaps to keep out water. The sides of the feet have small scales, and the digits are fringed with stiff hairs; all four feet are webbed. Fringes and webbing expand the surface area of the feet for pushing through the water. The palms have large disklike pads that enhance agility on wet, slippery surfaces. Along the tail are four rows of fringes that coalesce toward the tip into a rudderlike shape. The elegant water shrew weighs up to 45 grams (1.6 ounces), with a body 10 to 14 cm (4 to 5.5 inches) long and a tail nearly as long as the body.
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Two of the 72 species in the genus Sorex are water shrews. The North American water shrew (S. palustris) is found throughout much of the western United States and Canada, from the plains to the mountains. It is the smallest and least specialized species of water shrew, weighing up to 18 grams, with a body 6 to 9 cm long and a slightly shorter tail. It forages on land and enters water to seek food and escape predators. It can remain underwater for 45 seconds or more at a time and is able to skitter across the surface supported by air bubbles trapped in the feet and toe fringes. Half of its diet consists of aquatic insects, the other half of terrestrial insects, earthworms, snails, and slugs as well as vegetation, mice, fish, and salamanders.
In addition to the North American and elegant water shrews, there are several species of Oriental water shrews (genus Chimarrogale) and three species of Old World water shrews (genus Neomys). All are classified in the family Soricidae of the order Soricimorpha, which belongs to a larger group of mammals referred to as insectivores.