Environment | ANIMAL TRACKER

River shrew

by Rowan Hooper

* Japanese name: Nihon kawanezumi
* Scientific name:Chimarrogale platycephala
* Description: Shrews are small mammals and are thought to be similar to the first mammals that evolved. Fur is dark gray-brown with a white-gray underside; the hindquarters are fringed with silvery hairs. They have small eyes and white whiskers. Their feet are fringed with short, stiff hairs. Head and body length ranges from 8-13.5 cm; tails are relatively long in this species, from 6-12.6 cm. Body weight ranges from 25-40 grams. River shrews are slightly larger than their wholly terrestrial cousins.
* Where to find them: Japanese river shrews are endangered, but can still be found in clean mountain streams in Honshu, Shikoku and Kyushu. They have been found at high altitudes, up to 1,500 meters. “Clean” is the key word — pollution is a major reason for the decline in river-shrew numbers. They are semiaquatic and can be found on the river banks, in waterfall plunge pools and in rivers. They are good swimmers and can walk on the bottom of the river. They are solitary except for when they are breeding; the entrances of their burrows are usually under water. They are active during the day.
* Food:River shrews eat insects, aquatic larvae, crustaceans and small fish. They have extremely high metabolisms and must eat every few hours or they will die. They have a mild poison in their saliva which can stun their prey. They also secrete oils from scent glands which they use to mark out their territories and which may also repel potential predators (domestic cats refrain from eating river shrews, even if they don’t refrain from killing them).
* Special features:The shrew might be the basic mammalian type, but river shrews have evolved, adapting to their aquatic life. Like seals, they have dense fur which is highly water repellent (river shrews must groom themselves carefully), and like seals, they are able to close their ears when they submerge: River shrews have flaps which keep out the water. The fringes of stiff hairs on the lateral edges of their toes increase the area for pushing against the water. Likewise, the tail is longer than in other shrews and is helpful for steering underwater.