Animals that live in polar regions must withstand extremely cold temperatures. No land animals except ice worms and a few kinds of insects live in the parts of polar regions that have ice and snow all year round. However, the seas in the Arctic and Antarctic have large numbers of wildlife, including fish, Giant sponges and tiny shrimp like creatures called krill. Krill provides food for many other sea animals, including numerous fish and some whales. Various animals live on the coasts of polar seas. Polar bears, sea lions and walruses spend much of their time on floating sheets of ice in the Arctic. Penguins and seals live on the Antarctic coast. Many animals inhabit the vast Arctic tundra, the cold, treeless plains of northern Asia, North America and Europe. They include Caribou, ermine, Musk oxen, reindeer, lemmings, snowy owls and wolves. Shallow ponds in this region provide a place for mosquitoes and many other insects to lay their eggs. These insects serve as food for the birds that migrate to the tundra each summer to nest. Animals that live in polar regions have developed bodies and ways of life that enable them to deal with the frigid polar weather. Caribou, muskoxen and polar bears have thick fur, which helps them stay warm. The Arctic Fox and Arctic hare have short ears and tails, which keep them from losing too much body heat. Arctic ground squirrels, hibernate or sleep through the long polar winter. They curl up in a Burrow and their body temperature drops, saving energy during their sleep.