SOUTHERN SEA OTTER
With the densest fur on the planet, sea otters survive in cold waters without the blubber layer that insulates other marine mammals. They also need to eat a lot to keep warm: They consume up to a quarter of their body weight every day. While Northern Sea Otters, found off the West Coast of the U.S. from Alaska to Washington, have a robust population of roughly 77,000, fewer than 3,000 Southern Sea Otters live off the coast of California. Why they're in trouble: The biggest threats to sea otters came in the past, when the fur trade caused their numbers to drop from more than 1 million to fewer than 2,000. Ongoing threats include oil spills, habitat loss, food limitations, disease, entanglement in fishing gear and conflict with shellfish fisheries (since otters like mussels, clams, crabs and other seafood that humans enjoy, too). How to help: Visit Defenders of Wildlife and learn more about otters and adopt your own.