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Friday, March 15, 2002


Harvest mouse

* Japanese name: Kayanezumi
* Scientific name: Micromys minutus
* Description: This is Japan's smallest mouse, growing 5-8 cm long and weighing only 5 grams. Harvest mice have long, prehensile tails which they use for gripping the stems of grass when climbing. They have stubby noses and hairy ears; their fur is russet-orange in color except for underneath, where it is white. Harvest mice have poor vision but an exceptional sense of hearing. If they hear a rustle from as far as 7 meters away, they'll freeze or dive for cover.
* Where to find them: Honshu (apart from the central regions) and Kyushu. Harvest mice inhabit grasslands, farmland, fields and marshes. The Japanese name refers to the kaya, or pampas grass, they often live in. But changes in land use have made the harvest mouse rare. They are active year-round, but in winter spend most of their time in tunnels in hay bales, or in shallow burrows in the ground.
* Food: Harvest mice have very high metabolic rates and eat seeds, berries and insects. They'll also take moss, roots, fungi and wild strawberries. Harvest mice have short lives of about 1 1/2 years -- that's if they're not eaten by weasels, stoats, foxes, cats, owls, hawks or crows. But cold weather is the main cause of mortality.
* Special features: Harvest mice are excellent climbers. Pregnant females build nests at night. Resting on a plant stem, with their long tail wrapped around the stem for support, females strip lengths of pampas grass and weave the outer frame of the nest. The lining is made by poking other types of grass through the frame. A nest for raising young is about 10 cm in diameter, roughly the size of a tennis ball (see photo, though this is not their preferred home); everyday nests are 5 cm. Females give birth to about five young and may have three broods a year. The young are blind and helpless at birth but grow exceptionally quickly. By 11 days the babies begin to explore outside the nest; and by 16 days their mother abandons them to build a new nest. From then on, the babies must fend for themselves.

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