Sea otter (Enhydra lutris); Bering Sea, Arctic Ocean, Arctic

© Kevin Schafer / WWF-Canon

From a distance, the line of black bobbing forms in the waters just off the coast of Alaska look like flotsam, or driftwood entangled in kelp. But upon closer inspection, the almost comically adorable faces of a raft of playful sea otters pop up from behind cresting waves, their hind feet pointing toward the sky.

Sea otters are commonly spotted on World Wildlife Fund’s and Nat Hab’s Alaska tours. For one of the smallest marine mammals on Earth (yet the largest member of the weasel family), the sea otter has racked up quite a few superlatives:

10. The sea otter can live its entire life without leaving the water.

9. Its fur is the densest of any animal on Earth—an estimated 1 million hairs per square inch. That’s because, unlike its fellow marine mammals, it has no blubber to keep it warm.

8. The sea otter is one of the few mammal species on Earth to use a tool to help it hunt and feed. It wedges a rock between its chest and the “armpit” of a foreleg and pounds shells against it to open them up. The sea otter also hammers rocks against strongly gripping abalone shells to pry them off of rocks and feed on their tasty insides.

7. Another underwater superlative: The sea otter is the only marine mammal capable of flipping over boulders on the sea floor—in this case to search out food. And the only marine mammal to catch fish with its forepaws and not its mouth.

6. The sea otter must consume between 25 and 40 percent of its body weight daily, just to keep warm. They gorge on more than 100 different prey species.

5. If a sea otter’s fur becomes dirty, it has trouble absorbing the air needed to keep it warm. Therefore, sea otters are obsessive about keeping their fur clean, and groom themselves practically non-stop when they’re not eating or sleeping. Oil spills, therefore, can affect sea otters perhaps more so than any other marine mammal; oil coating their fur can lead to death by hypothermia.

4. Sea otters do not migrate far. Their rafts—usually comprised of a single sex—can range from as few as 10 individuals to as high as 1,000.

3. With populations once estimated at close to 300,000, sea otters were hunted extensively for their pelts. Following an international ban on hunting, their numbers rebounded significantly in the 20th century, particularly in Bering Sea and Alaskan waters, their main stomping ground. Still, they remain classified by the International Union for the Conservation of Nature (IUCN) as “endangered.”

2. To keep from drifting apart while they snooze, sea otters often sleep holding paws.

1. Like polar bears in the Arctic, sea otters are considered keystone species in their ecosystems, because they affect great influence on their environments. For instance, they plentifully eat sea urchins, which eat kelp in great abundance. When the sea urchins’ populations are controlled by sea otters, vital kelp forests can flourish.

Look for sea otters on tour with WWF and Nat Hab in Alaska.