In 1980s, scientists moved 140 sea otters to a California island as an insurance policy; most disappeared, but the population eventually rebounded

In the late 1980s, wildlife officials made an unusual decision to protect one of California’s most important marine mammals: They moved 140 southern sea otters to San Nicolas Island, one of the Channel Islands off the Southern California coast.

The relocation was designed as an insurance policy.

Southern sea otters had once occupied much of the Pacific Coast, but centuries of hunting for their valuable fur had dramatically reduced their numbers. By the time California’s remaining population received federal protection in the 1970s, sea otters had disappeared from much of their historic range.


Scientists were concerned that a major disaster, such as an oil spill, could wipe out a significant portion of the remaining population. Establishing a second colony away from the main population could potentially provide a safeguard.

San Nicolas Island appeared to offer a promising location.

Beginning in 1987, researchers captured and transported 140 southern sea otters to the island. The plan was to establish a new breeding population that would remain geographically separated from the larger population along California's central coast.

But the experiment did not unfold as expected.

Many of the relocated otters did not stay on San Nicolas Island. Sea otters are highly mobile animals, and a large number of them left the island and returned to the mainland. Others died.

The population fell dramatically, eventually reaching only about a dozen animals.

At first, the relocation appeared to be a failure.

Yet the small colony did not disappear.

Over time, the sea otters that remained on San Nicolas Island began reproducing. The population slowly recovered, demonstrating that the island could support a resident group despite the rocky beginning.

By 2019, the San Nicolas Island population had grown to roughly 100 animals, according to the U.S. Fish and Wildlife Service.

The story illustrates one of the challenges involved in restoring wildlife populations: moving animals to a new location does not necessarily mean they will remain there or establish a successful colony immediately.

Sea otters also play an important role in coastal ecosystems. They consume animals such as sea urchins and can help keep populations of these grazers under control. In areas where sea otters are present, their feeding can influence kelp forests and the broader nearshore ecosystem.

The San Nicolas Island experiment therefore became more than simply an attempt to create a backup population. It also provided scientists with information about how southern sea otters respond to relocation and how they might eventually be restored to portions of their former range.

The population remains small compared with the much larger southern sea otter population along California's coast. The U.S. Fish and Wildlife Service continues to study the possibility of expanding the species' range while addressing threats such as disease, food availability, human activity and oil spills.

The original goal of the 1980s relocation was straightforward: create a second population that could serve as protection against a catastrophe affecting California's main sea otter population.

It took decades, and the early results looked discouraging. But the animals that stayed eventually established a growing colony on San Nicolas Island — turning an initially troubled relocation into an important chapter in the conservation of California's southern sea otters.