Sea otter grooming fur, Monterey Bay, California, United States

Life between fur and sea. Sea otter, Monterey Bay, California, United States

Few animals are both expert groomers and guardians of underwater forests. In today's image, a sea otter grooms its fur in Monterey Bay, California—a daily ritual essential to its survival. Sea otters have the densest fur of any animal, with up to one million hairs per square inch. Unlike seals and whales, they have little blubber, so their thick, air-trapping coat provides insulation against the cold Pacific.

Their clever adaptations do not stop there. Loose folds of skin beneath their forearms act like pockets, where they can stash food or a favourite rock. They may then use that rock as a tool, smashing open hard-shelled prey such as mussels and clams.

Sea otters also have a huge appetite, eating roughly a quarter of their body weight each day. By feeding on sea urchins, they help protect kelp forests from overgrazing, making these playful-looking mammals vital guardians of coastal ecosystems.