Moose (North America) or elk (Eurasia), a member of the New World deer subfamily, is the largest and heaviest surviving species of deer in the deer family. Moose are known for their broad, palm-shaped (open-handed) antlers; the antlers of other members of the family are dendritic ("dendritic"). Moose usually inhabit northern forests and temperate broad-leaved forests and mixed forests in temperate to subarctic climates in the Northern Hemisphere. Over time, hunting and other human activities have led to a reduction in the elk's range. Moose have been reintroduced into some of their former habitats. Currently, most elk are found in Canada, Alaska, New England (Maine has most of the 48 states), Finnos Kandia, the Baltic States, and Russia. Their diet includes terrestrial and aquatic vegetation. The most common moose predators are gray wolves, bears, and humans. Unlike most other deer species, moose are herds and are solitary, except for calves that stay with cows before estrus (usually 18 months after they are born), who chase away calves during estrus. Although moose are usually slow and sedentary, they become aggressive and quick to move if they are angry or frightened. During the autumn mating season, the males fight fiercely for the females. Moose need to have enough habitat for edible plants, such as pond grasses, young trees, and shrubs, to protect them from predators and from extreme heat or cold weather. To meet these needs, moose migrate between habitats with the seasons. Moose is a cold-adapted mammal with thickened skin, dense fur, thermal insulation, low surface volume ratio, good cold tolerance, but poor heat tolerance. Moose survive in hot weather by cooling, cooling or soaking in cold water. On hot days, moose are often spotted wading or swimming in lakes or ponds. Under high temperature stress, moose may not be able to adequately forage during the summer months and may not be able to obtain enough body fat to survive the winter. In addition, if the summer weight is not sufficiently gained, the moose cow may not give birth to calves. Moose need to enter both young forests for browsing and mature forests for shelter and covering. Forests disturbed by fire and logging promote the growth of elk feed. Moose also need access to mineral licks, safe calves and aquatic feeding sites. Moose avoid areas with little or no snow, as this increases the risk of wolves preying, and avoid areas with deep snow, as this impairs mobility. Therefore, moose habitat selection is based on trade-offs between predatory risk, food availability, and snow depth. As bison are reintroduced into the northern forests, there are fears that bison will compete with moose for winter habitat, exacerbating the decline in moose populations. However, this does not seem to be a problem. In early winter, moose prefer subalpine scrub, while bison prefer moist sedge valley meadows. In late winter, moose prefer alpine terrain above deciduous forest-covered river valleys or tree lines, while bison prefer moist sedge meadows or sunny southern grassy slopes.