You will probably have heard that the ice-caps are melting at a higher rate than before. A large part of one of Antarctica's ice shelves has broken away recently. The Arctic ice-cap is also decreasing in size, which is threatening the polar bears numbers. There are currently about 25,000 polar bears in the Arctic. Polar bear cubs spend weeks in ice dens, as they are believe it or not smaller than a human baby at birth and are blind similar to other mammalian babies. Increased numbers of bears are dying when the ice and snow melts causing collapse of their dens. Every Summer the pack ice is decreasing in size, which is problematic, as polar bears live mainly on the pack ice, and are not adapted to living on the land itself. They swim in the sea/ice holes off the pack-ice to catch their main food which is ring seals. The break-up of the pack-ice means shipping lanes may be able to open between Siberia and the Arctic, good news for human trading but bad news for the polar bear.