California’s beloved sea otters in mysterious population decline

Southern sea otters, among the furriest and most beloved critters in the animal kingdom, have declined in number for the second year in a row, according to scientists who are trying to pinpoint possible causes.

Once hunted to the brink of extinction and currently listed federally as a threatened species, the charismatic otters often seen frolicking off Central California have dwindled to just 2,711 animals.

That figure, based on counts made by the U.S. Geological Survey, represents a 3.6% drop from the 2009 estimate. More alarming, scientists say the number of otter pups has decreased by 11%.

Additionally, their geographic range — about 200 miles from Pigeon Point to Gaviota State Park — appears to be shrinking at both ends.

“We have seen a decrease in sea otter numbers throughout most of their range, particularly in those areas where most of their reproduction occurs, while pup counts have dropped to 2003 levels,” Tim Tinker, a scientist for the USGS Western Ecological Research Center, said in a news release.

“A number of human and natural factors may be influencing this trend, and we are working to better understand what those are.”

Studies suggest that breeding-age otters are succumbing to shark attacks, infectious diseases, exposure to toxins, heart failure and malnutrition. Being coastal predators, they’re more susceptible to pollution and other stress factors.

“Recovery will clearly depend on our understanding the factors contributing to slow population growth in recent years and the current downturn,” said Lilian Carswell, who leads the otter recovery program for the U.S. Fish and Wildlife Service. “Research is fundamental to recovery efforts because we need to understand which stressors are most strongly affecting survival rates in order to develop targeted measures to address them.”

The southern sea otter population will have to grow to at least 3,090 before the animals are considered for removal from the the list of threatened species.

Sea otters prey on sea urchins and other invertebrates and their existence is critical for maintaining the health of kelp forests, which are vulnerable to urchin predation.

Otter numbers might have numbered as many as 300,000 before hunting from the mid-1700s until the early 1900s nearly wiped out the entire population.

The mammals are a tourist attraction in coastal communities such as Monterey. In fact, a 16-week-old otter pup, rescued after being found stranded in poor health recently on a nearby beach, is one of two southern sea otters on display at the Monterey Bay Aquarium (see video).


The pup is named “502” for the number of stranded sea otters delivered to the aquarium’s Sea Otter Research and Conservation program since 1984.

The pup has developed a close bond with “Joy,” the adult otter who is 12 years old and now has served as surrogate mother for 12 otter pups.

“Her calm presence and nurturing maternal instincts should be just what this young animal needs to move forward,” said Chris DeAngelo, associate curator of animals at the waterfront facility.

The pup is being kept because experts believe she would perish in the wild. The aquarium is reporting on her progress periodically on its blog, and has set up an “otter cam” that streams live daily from 7-7.

— Top photo courtesy of Monterey Bay Aquarium / Randy Wilder; video of rescued otter pup courtesy of Monterey Bay Aquarium