The narwhal, a whale with a long spiral tusk that inspired the myth of the unicorn, has the ranking of most potentially vulnerable in a climate change risk analysis of Arctic marine mammals. The narwhal, which is also known as the "corpse whale", is now considered the most at risk as the Earth warms. The study, conducted by a journal called Ecological Applications, looked at nine different variables that help determine ability to withstand future climate changes. Those factors included population size, habitat uniqueness, diet diversity and ability to cope with sea ice changes. The narwhal, which dives about 6,000 feet to feed on Greenland halibut, evolved specifically to live in small cracks in parts of the Arctic where it is 99 percent heavy ice. As the ice melts, not only is the narwhal habitat changed, predators such as killer whales will likely intrude more often.