Shark Attacks on California Otters May Threaten Recovery
February 27, 2012
According to a recent report by the U.S. Geological Survey, attacks on California sea otters by white sharks have spiked in the past several years, leading sea otter biologists to question both the reason for the increase as well as how it will affect the threatened species’ recovery.
Co-lead of the California Sea Otter Stranding Network and USGS researcher, Tim Tinker says that reports of shark attacks on otters has been been rising steadily since the early 1990’s when a mere 8 percent of recovered or stranded otters were bite victims.
“Shark bite deaths accounted for 15 percent of recovered carcasses by the late 1990’s, and this has risen to approximately 30 percent of recovered carcasses in 2010 and 2011,” Tinker says.
With a record high 335 sea otters stranded in 2011 and a population hovering around 2,711 the California sea otter is still below the 3,090 threshold that could see it delisted from the federal threatened species list. Toss in the fact that 35 percent of all shark-bitten otters found in 2011 were female and it's no wonder the attacks are a major concern to sea otter biologists.
Many researchers believe sharks don’t actively feed on sea otters because they lack the thick, fatty blubber that make seals and sea lions preferred prey. These conjectures are reinforced by the fact that most otter carcasses found to be shark attack victims have slight wounds, with no sign of tissue removed from the bodies.
Michael Harris, a CDFG sea otter biologist believes the sharks are confusing sea otters with their usual prey, which explains the “taste-test” type bites found on stranded otters. “Unfortunately, even a taste test by a white shark usually proves fatal for a sea otter,” Harris says.
Not all perish, however.
One little survivor of shark violence has recently made news on the Central Coast. Otter 572 went on display at the Monterey Bay Aquarium on Feb. 14 and is the youngest otter ever taken in by the Sea Otter Research and Conservation program. At just two weeks old the baby otter was found alone on a beach in Cayucos with visible scars from a shark attack that biologists believe killed its mother.