Sea Otters

March 10, 2022

Q: I recently vacationed in Aptos and found a dead sea otter on the beach. A park ranger said CDFW would collect it because they monitor sea otter causes of death. What typically kills sea otter?

A: CDFW has been monitoring sea otter mortality since 1968 to determine how to best care for injured or oiled sea otters and how to help recover California’s sea otter population. In recent years, the leading cause of death for sea otters has been bites from white sharks. Sharks bite sea otters to determine if they are prey, but sometimes decide they’re not worth eating because they don’t have blubber like other marine mammals. Unfortunately, most sea otters that are bitten die from their wounds.

CDFW recently reviewed data from more than 500 sea otter necropsies and found that other causes of death include parasitic infections (mostly from land-based parasites) and poisoning by domoic acid. Investigation of sea otter mortality is supported in part by the California Sea Otter Voluntary Contribution Fund. The public can help by donating to this fund on line 410 of the California state income tax form! Please visit wildlife.ca.gov/Tax-Donation for more information.

For more information visit CDFW’s Sea Otter Stranding Response webpage (https://wildlife.ca.gov/OSPR/Science/MWVCRC/Sea-Otter-Stranding-Response).