By E.B. Solomont, MNN
Researchers in California are struggling to explain why California sea lions are getting sick with cancer.
Fourteen years after veterinary experts first noticed sea lions becoming ill, scientists are studying 300 sea lions and examining three prime suspects: viruses, PCBs in the water and genetics. “Years of study have led researchers to think the answer lies not with any one culprit, but with several,” reports The New York Times.
“It’s such an aggressive cancer, and it’s so unusual to see such a high prevalence of cancer in a wild population,” said Dr. Frances Gulland, director of veterinary science at the Marine Mammal Center. In 1996, Gulland and colleagues at the University of California, Davis, found that 18 percent of deaths among stranded adult sea lions were related to cancerous tumors.
“That suggests that there’s some carcinogen in the ocean that could be affecting these animals,” Gulland said.
The first reports of sea lion cancer came 14 years ago, among rescued California sea lions. Today, the Marine Mammal Center sees 15 to 20 California sea lions with cancer each year.
“It’s pretty distressing to see,” Gulland said. During post-mortem examinations of the sick sea lions, doctors have found tumors in the animals’ genitals, lymph nodes, lower spine, kidneys, liver and lungs.
Next: What’s causing the cancer