Mountain beaver

It is a member of the Mammalia class, Rodentia order, and the family Paramysidae. It is a primitive semi-subterranean rodent found widely in the coniferous forests of the west coast of North America, and is thought to be close to the fossil mammal Paramys, which is said to be the ancestor of rodents. It has no direct relationship to beavers, but is considered to be part of the Paramysidae family. It has a sturdy, round body, a large head, and a short neck. Its limbs and tail are short, and its ears and eyes are small. It has long, hard, white tentacles. Its body color is gray-brown or reddish brown. Its body length is 30-46 cm, its tail length 1-2.5 cm, and it weighs 800 g. It lives alone or in pairs in moist forests or near water in dry areas, digging complex, winding tunnels, and is herbivorous, eating the leaves, roots, and stems of plants. It stores food underground for the winter. They have a low reproductive rate for a rodent, breeding once a year from February to April, with a gestation period of 30 days and two to three young. The young are weaned at six to eight weeks, and in the fall, both males and females leave their parents and become independent. Their natural enemies are owls, hawks, and coyotes. They chew on tree bark for food and nesting material, which can cause serious damage to forestry.

[Yoshiharu Imaizumi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

哺乳(ほにゅう)綱齧歯(げっし)目ヤマビーバー科の動物。北アメリカ西海岸の針葉樹林地帯に広く分布するなかば地下生の原始的な齧歯類で、齧歯類の祖先とされる化石哺乳類パラミスに近いと考えられる。ビーバーとは直接の類縁関係はなく、ヤマビーバー科とされる。体つきはがっしりして丸く、頭が大きく、頸(くび)が短い。四肢と尾は短く、耳、目は小さい。長くて硬質の白い触毛をもつ。体色は灰褐色ないし赤褐色。体長30～46センチメートル、尾長1～2.5センチメートル、体重800グラム。湿潤な森林か、乾燥地では水辺近くに、複雑に曲がりくねったトンネルを掘って単独あるいはつがいですみ、植物の葉、根、茎を食べる植物食性。冬に備えて地下に食物を貯蔵する。齧歯類としては繁殖率が低く、繁殖期は年に1回で2～4月、妊娠期間30日で2～3子を産む。子は6～8週間で離乳し、秋に雌雄とも親のもとを離れて独立する。天敵はフクロウ、タカ、コヨーテなどである。食物あるいは巣材として樹皮をかじり、林業に大きな被害をもたらすことがある。

［今泉吉晴］

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