
Reuters: California Sea Lions Face 'Unprecedented Rate of Cancer'
- Cancer
- Pollution
California Sea Lions Face 'Unprecedented Rate of Cancer'
Published by Reuters: June 8, 2021
When a female adult sea lion came ashore in San Luis Obispo County in central California recently, responders immediately knew something wasn't right.
She was thin and underweight, swayed her head back and forth, and did not flee as people approached, said Dr. Cara Field, medical director at The Marine Mammal Center in Sausalito.
"All of those things tell us there's something wrong, but we didn't know what it could be until we got her here," Field said.
Once the sea lion was sedated and intubated in a quarantine cell on the Center's grounds for an ultrasound, more worrying signs appeared.
Using three decades of data collection and analysis, the Center’s research has revealed a high prevalence of cancer in California sea lions.
Cancer Research at The Marine Mammal Center
Cancer was first diagnosed in California sea lions at The Marine Mammal Center in 1979. Since then, our veterinarians and scientists have contributed to a number of scientific papers on cancer in marine mammal populations.
{"image":"\/Animals\/Wild\/California sea lion\/cropped-images\/csl-on-a-rock-shutterstock-191-0-3072-2400-1617060454.jpg","alt":"California sea lion on a rock","title":"Unlocking the Role of a Genital Herpesvirus in California Sea Lion Cervical Cancer","link_url":"https:\/\/www.marinemammalcenter.org\/publications\/unlocking-the-role-of-a-genital-herpesvirus-in-california-sea-lion-cervical-cancer","label":"Research Paper","type":"publication"}

Unlocking the Role of a Genital Herpesvirus in California Sea Lion Cervical Cancer
Read More{"image":"\/Animals\/Patients\/California sea lions\/2018\/cropped-images\/csl-leadbelly-by-bill-hunnewell-c-the-marine-mammal-center-664-0-2502-1954-1607626905.jpg","alt":"California sea lion","title":"Contaminant Exposure and Herpesvirus Associated with Cancer in Wild Sea Lions","link_url":"https:\/\/www.marinemammalcenter.org\/publications\/contaminant-exposure-and-herpesvirus-associated-with-cancer-in-wild-sea-lions","label":"Research Paper","type":"publication"}

Contaminant Exposure and Herpesvirus Associated with Cancer in Wild Sea Lions
Read More{"image":"\/Animals\/Patients\/California sea lions\/cropped-images\/csl-resting-c-the-marine-mammal-center-605-0-3523-2751-1603927376.jpg","alt":"California sea lion resting on the pen floor with a young sea lion in the background","title":"Prevalence of Cancer in Stranded California Sea Lions (2005-2015)","link_url":"https:\/\/www.marinemammalcenter.org\/publications\/prevalence-of-cancer-in-stranded-california-sea-lions","label":"Research Paper","type":"publication"}

{"image":"\/Animals\/Patients\/California sea lions\/2020\/cropped-images\/csl-boycrus-by-bill-hunnewell-c-the-marine-mammal-center-0-0-3110-2429-1603927870.jpg","alt":"California sea lion","title":"California Sea Lions as a Model for Studying a Common Cancer","link_url":"https:\/\/www.marinemammalcenter.org\/publications\/california-sea-lions-as-a-model-for-studying-a-common-cancer","label":"Research Paper","type":"publication"}

Yes, I want to save a life!

Yes, I want to save a life!
You’ll be giving sick and injured animals the best possible care at the Center’s state-of-the-art hospital. With your gift today, you are giving a patient a second chance at life in the wild.
See Our Latest News
{"image":"\/Animals\/Patients\/Sea otters\/2025\/cropped-images\/so-mooring-release-2-laurie-miller-c-the-marine-mammal-center-USFWS-permit-MA101713-1-80-0-1270-992-1757003194.jpg","alt":"A southern sea otter rests in the ocean after being released from rehabilitative care.","title":"Entangled in Ocean Trash, Sea Otter Mooring Gets a Second Chance at Life","link_url":"https:\/\/www.marinemammalcenter.org\/news\/entangled-in-ocean-trash-sea-otter-mooring-gets-a-second-chance-at-life","label":"Patient Update","date":"2025-09-05 02:00:00"}

Entangled in Ocean Trash, Sea Otter Mooring Gets a Second Chance at Life
September 5, 2025
Read More{"image":"\/Animals\/Patients\/Harbor seals\/2025\/cropped-images\/denali-hs-photo-by-clive-beavis-c-the-marine-mammal-center-79-0-1270-992-1756314221.jpg","alt":"2026 marine mammal center calendar cover star","title":"Pacific Harbor Seal Denali Chosen as the 2026 Calendar Cover Star","link_url":"https:\/\/www.marinemammalcenter.org\/news\/vote-for-your-favorite-marine-mammal-to-be-the-2026-calendar-cover-star","label":"News Update","date":"2025-08-04 02:00:00"}

Pacific Harbor Seal Denali Chosen as the 2026 Calendar Cover Star
August 4, 2025
Read More{"image":"\/Animals\/Wild\/Gray whale\/stranded-gray-whale-july-2025.jpg","alt":"stranded gray whale","title":"Scientists respond to dead gray whale in San Francisco Bay as species faces population recovery challenges","link_url":"https:\/\/www.marinemammalcenter.org\/news\/scientists-respond-to-dead-gray-whale-in-san-francisco-bay-as-species-faces-population-recovery-challenges","label":"Press Release","date":"2025-07-17 02:00:00"}

Scientists respond to dead gray whale in San Francisco Bay as species faces population recovery challenges
July 17, 2025
Read More{"image":"\/Animals\/Patients\/Harbor seals\/cropped-images\/hs-group-with-hats-photo-by-bill-hunnewell-c-the-marine-mammal-center-34-0-1270-992-1750873865.jpg","alt":"Four harbor seals with small ID tags on their heads swim in a rehabilitation pool.","title":"How Our Patients are Named and Identified","link_url":"https:\/\/www.marinemammalcenter.org\/news\/how-our-patients-are-named-and-identified","label":"Patient Update","date":"2025-06-26 02:00:00"}

pollution
Cara Field
Pádraig Duignan
California Sea Lion