The Monterey Bay Aquarium's Sea Otter Program has been studying the threatened southern sea otter since 1984 with the aim of understanding threats to the population and promoting its recovery. We rescue, treat and release injured otters; raise and release stranded pups through our surrogate program; seek homes for sea otters that can't return to the wild; and conduct scientific research.
Southern sea otters once ranged from Baja California to the Pacific Northwest. But, by the 1920s, they were considered extinct due to intensive hunting. They were listed as "threatened with extinction" under the Endangered Species Act in 1977. But despite decades of federal and state protection, the California population of southern sea otters (Enhydra lutris nereis) is still only a fraction of its historic numbers, estimated at 16,000 to 20,000 animals.
Recent research by the U.S. Geological Survey and the Aquarium suggests that the sea otter population growth rate is limited by food availability. In the meanwhile, the risk of a major oil spill remains a serious threat.
Sea otters are an iconic species, representing the beauty and diversity of life in Monterey Bay. They're also a keystone species, determining the kinds and health of species in nearshore environments. They eat sea urchins and other invertebrates that graze on giant kelp. Without sea otters, urchins prevent kelp forests from forming important habitats for many animals.
Sea otters are also good indicators of ocean health. Since they are the top predator of invertebrates along the California coast, changes in their health can make scientists aware of variations in the ocean environment itself.
By 1911, when sea otters gained protection under international treaty, a small group of perhaps 50 otters survived along the remote Big Sur coast. Since then, they've slowly expanded their range and grown in number to nearly 3,000. As of 2014, their range extends from south of Half Moon Bay in the north to south of Point Conception in the south—only a small part of their historic range.