Herbivores including Arctic hare, lemming, muskox and caribou, famous predator like Arctic fox and wolf and polar bear wolverines, ermines and Arctic ground squirrels, marine mammals such as seals, walrus and several species of cetacean- baleen whale, narwhals, killer whales and belugas and some endemic bird and marine species are together composed the Arctic food chain.(wikipedia)
Animals have to adapt to the extreme environment in the Arctic. Most marine mammals have a thick layer of fat to defend to freezing weather like whales and seals, and in winter, some of them slow their heartbeat down and hibernate in order to reduce the energy consumption like polar bear. Some sea birds spend their summer in the Arctic but leave when the weather get colder in order to get enough food.
Animals in the cold reduced their energy consumption in many ways, including changing thermoregulation by good insulation and nasal heat exchange and by reducing their activity, and reducing the basal level of heat production themselves. Those small reduction can contribute to save large energy.( Arnoldus Schytte Blix, 2005) Arctic animals not only need to reduce their heat loss to adapt to the cold environment, but also they have cope with a more important problem, their food. This is a problem through the whole food chain in the Arctic and this problem became worse due to the climate changes.