The research was conducted over two decades. To date, almost 25% of the sea lions that first responders bring to the Marine Mammal Center in Sausalito have died from one aggressive cancer, among the highest prevalence of a single cancer type in any mammal, including humans.
Balmy temperatures can lead to conditions perfect for the spread of infectious diseases, Sanderson said. When sea ice melts too early in the season, seal pups must enter the water before they are ready to be weaned, leaving them weaker and more vulnerable to disease. Vanishing sea ice also means that seals and sea lions in cold regions will have less space to emerge from the water to rest, breed, or escape predators, forcing them to crowd more tightly together.
The center said it sees a surge in the number of sea lions admitted with symptoms of leptospirosis every four to five years. Before the 2017 outbreak, the most recent ones occurred in 2011 and 2008. During the 2011 outbreak, about 200 sea lions infected with leptospirosis were admitted to the center, according to a news release.
“What we currently have on the Columbia River is an ecosystem seriously out of balance,” said Herrera Beutler, who believes the bill is necessary to save fish runs on the brink of extinction.