單齒鼠科山河狸科 Aplodontiidae (Sub-family of Rodentia)

山河狸科（Aplodontiidae）來自希臘文ἁπλόος（haplóos, 「單一、簡單」）和希臘文 ὀδούς （odoús, 「牙齒」）,意思是「簡單的牙齒」,指的是這個家族的所有成員每個頰牙都有一個主要的單一的凹槽.

Aplodontiidae, from Greek ἁπλόος (haplóos, “single, simple”) and Greek ὀδούς (odoús, “tooth”), means “simple tooth”, in reference to the fact that all the members of this family have a single large basin comprising the bulk of each cheek tooth.

種的俗名 Common names of members

山河狸.

Mountain beaver.

分佈 Distribution

北美洲.

North America.

體型 Size

成體通常重 500 到 900 克,尾長 1 到 4 公分,全長 30 到 50 公分.

Adults typically weigh between 500 and 900 g. With a tail length of 1-4 cm, the overall length is between 30 and 50 cm.

形態描述 Morphology

牠們的外型很像海狸,通常是深灰色或棕色,但依亞種不同,毛色也會有所不同,有的偏紅,有的偏黑.兩隻耳朵下方各有一塊淺色的斑塊.這種動物的尾巴很短.個別成年個體的體重超過 1,000 克.

They resemble beavers in appearance and are typically dark gray or brown, though depending on the subspecies, their fur can vary from being somewhat more reddish to being more blackish. They also have a light patch under each ear. The animals' tails are notably short. A few adults weigh more than 1,000 g.

生態與棲息地 Habitat & Ecology

海平面到樹線是牠們的活動範圍.雖然針葉林和落葉林都有牠們的蹤跡,但在大部分的範圍內,牠們似乎偏好針葉林多於落葉林.

Sea level to the tree line is their range. Although they are found in both coniferous and deciduous woods, they seem to favor the former over the latter over most of their range.

食性 Diet

牠們似乎是專門以植物為食;牠們的主要食物來源很可能是蕨類植物,以及一些木本植物的新芽和軟質草本植物.為了獲取更多營養,牠們會有食糞行為,吃下軟質的糞塊;而硬質的糞塊則會被移動到牠們巢穴系統內的糞屑室.

They seem to be exclusively herbivorous; the majority of their diets most likely consist of ferns, along with new shoots from more woody plants and mushy herbs. To get the most nutrition, they practice coprophagy and consume soft fecal pellets; hard fecal pellets, however, are moved to fecal chambers found inside the burrow system.

繁殖 Reproduction

一次繁殖季節（一至三月）會使兩或三隻幼崽在二至四月出生.其中一個月用於懷孕,幾週的時間用於排卵.幼崽出生時是粉紅色、無毛且眼睛沒有視覺的.經過6到8周的哺乳期後,幼崽就會斷奶並很快離開洞穴.這種囓齒動物的壽命很長,從 5 到 10 年不等.牠們的家園範圍可能會重疊,但牠們不是並非群居動物.不過儘管牠們主要是獨居動物,但當食物來源和足夠的棲息地都集中在有限的區域時,山河狸就會組成群體；因此,族群數量會有很大的差異.

Two or three young are born in February and April during the breeding season, which runs from January to March. A month is dedicated to gestation and a few weeks to ovulation. The young are pink, hairless, and blind at birth. After six or eight weeks, they are weaned and soon after depart the burrow. Rodents have fairly lengthy life spans, ranging from 5 to 10 years. Their home ranges may overlap, but they are not gregarious beings. Although they are primarily solitary animals, mountain beavers have been known to form groups when food sources and adequate habitat are concentrated in a limited region; as a result, population numbers vary greatly.