In the last few weeks, many sick and dying California Sea Lions began showing up on central California beaches, even hauling out at Pier 39 in San Francisco. They were victims of Amnesic Shellfish Poisoning, aka Domoic Acid Toxicosis. What is domoic acid, where does it come from, and why is it affecting so many marine mammals? For answers we turn to Dr. Pádraig Duignan, Director of Pathology at the Marine Mammal Center in Sausalito. He is at the front lines in the response to this outbreak, in addition to many other novel diseases affecting marine mammals, and explains what is happening and why.