Unlike most other marine mammals, sea otters don't have a layer of blubber to keep them warm and bouyant. Instead, they have a dense, two-layer fur coat with more than a million hairs per square inch! That's ten times more than on your entire head!
Once thought to be extinct, the population was estimated at only around 50 members in 1914 by the Californian Department of Fish and Wildlife. But thanks to the efforts of organizations like Monterey Bay Aquarium, there are now and estimated 3,000 Southern Sea Otters in the wild! This is still far below their historical numbers, however. Sea otters used to spread all the way up the Oregon coast and down into Mexico, but today they can only be found on the Californian coast from Santa Barbara up to Santa Cruz.
Like wolves in Yellowstone, otters are a keystone species in their ecosystem. They live in kelp forests and river estuaries, and are vital to keeping these local ecosystems under control. Sea urchins, infamous for destroying kelp forests and creating areas known as "urchin barrens" where nothing else can survive, would go unchecked without sea otters to keep them at bay. Similarly, crabs would wreck havoc on eelgrass estuaries if not for otters. This is one of the many reasons why otters need to be protected.
Once thriving across the Northern Pacific Rim, Southern Sea Otters were nearly hunted to extinction by fur traders. By the 1900s sea otters were thought to be extinct, until a raft of approximately 50 otters was found near Big Sur in 1914. The population slowly recovered by tiny, incremental amounts up till 1973, when the U.S. Congress passed the Endangered Species Act. Since then, with the support of more legal protections and programs like the one at Monterey Bay Aquarium, the Southern Sea Otter population has grown to around 3,000 individuals! However, otters are still an endangered species, so places like Monterey Bay Aquarium are there to ensure their numbers do not drop so low again.
Sea otters have evolved a high metabolism to keep themselves warm in cold ocean waters. They can eat between 6kg (13lb) to 8kg (18lb) of food every day — that's a quarter of their own body weight! A person weighing 70kg (154lb) would have to eat 17.5kg (38.5lb) just to keep up with an otter!