和名ヘラジカ（箆鹿、Alces alces）は、哺乳綱偶蹄目シカ科ヘラジカ属に分類される世界最大のシカ。本種のみでヘラジカ属を形成する。別名オオジカ。
中国東北部、アメリカ合衆国北部、エストニア、カナダ、スウェーデン、ノルウェー、フィンランド、ラトビア、リトアニア、ロシア。更新世における分布は現在よりも広範囲に及び、例えば日本列島の中部まで南下していたとされる。
英語ではユーラシア大陸のヘラジカをエルク（elk）、北アメリカのヘラジカをムース（moose）と呼ぶ。エルクはゲルマン語の単語であり、学名になっているラテン語 alces もおそらくゲルマン語からの借用である（『ガリア戦記』6.27 に「alces という動物がいる」と記す）。ムースの語源はマリシート族（英語版）の言語で同種を指すムス（mus）である。なお、北アメリカではシカ属のアメリカアカシカ（ワピチ）がエルクと呼ばれている。

The moose in North America or elk in Eurasia, (Alces alces), is a member of the New World deer subfamily and is the largest and heaviest extant species in the deer family. Most adult male moose have distinctive broad, palmate ("open-hand shaped") antlers; most other members of the deer family have antlers with a dendritic ("twig-like") configuration. Moose typically inhabit boreal forests and temperate broadleaf and mixed forests of the Northern Hemisphere in temperate to subarctic climates. Hunting and other human activities have caused a reduction in the size of the moose's range over time. It has been reintroduced to some of its former habitats. Currently, most moose occur in Canada, Alaska, New England (with Maine having the most of the lower 48 states), New York State, Fennoscandia, the Baltic states, and Russia
Its diet consists of both terrestrial and aquatic vegetation. The most common predators of the moose are wolves, bears, and humans. Unlike most other deer species, moose do not form herds and are solitary animals, aside from calves who remain with their mother until the cow begins estrus (typically at 18 months after birth of the calf), at which point the cow chases them away. Although generally slow-moving and sedentary, moose can become aggressive, and move quickly if angered or startled. Their mating season in the autumn features energetic fights between males competing for a female.

引用元：Wikipedia