Sea otters (Enhydra lutris) spend most of their lives in shallow coastal waters of the North Pacific. They eat, groom, nurse and sleep on the surface, often anchored by leafy kelp. Diving to depths up to 50 meters (165 feet), sea otters forage for urchins, clams and other animal food. Otters break open hard-shelled prey using anvil stones; they are the only marine mammals to use tools.

Key players They may be small, but sea otters play a big ecological role in the North Pacific. Sea otters feed on urchins, which in turn consume kelp. Without otters, sea urchins destroy kelp forests that provide vital habitat for many marine organisms. © F. Stuart Westmorland / Photo Researchers

When diving for food, mothers leave newborns floating on the surface—despite the risk of losing a pup to a predatory bald eagle. Adults fall prey to white sharks and, more recently, killer whales.

CONSERVATION: Luxurious Fur
Unlike most other marine mammals, sea otters are insulated with dense fur instead of blubber. Air trapped between hairs conserves body heat and helps with buoyancy, so otters spend hours grooming their fur to keep it clean and fluffy. Their coats have an astounding 1 million hairs per square inch-more than any other mammal. Sea otters were hunted to near extinction, but they rebounded after the International Fur Seal Treaty of 1911 outlawed the sale of their luxurious pelts.