The U.S. National Park Service calls him P-22. The resident mountain lion of Griffith Park is at the top of the food chain there, but it was something near the bottom of the food chain that got him sick.
When officials trapped the 4-year-old cougar last month to change the batteries in his GPS tracking collar, they found that he was underweight and suffering from mange, a parasitic disease of the hair and skin. Blood tests determined rat poison was the cause.
The National Park Service says a rodent ate the poison, and then a coyote ate the rodent, and then P-22 ate the coyote.
"We do know that P-22 has eaten at least two coyotes. For the most part, mountain lions in this area eat mule deer, but occasionally they will eat something else as it becomes available. We have documented that he's eaten at least two coyotes, and so it's likely that is where he got the poisoning from," said Kate Kuykendall with the National Park Service.
P-22 was treated and returned to the 4,300-acre Griffith Park, where it continues to successfully hunt its natural prey. Biologists say it's unclear whether the cat will fully recover.
Because of the threat to wildlife, California's pesticide regulatory agency decided to ban the sale of over-the-counter rat poison to consumers. The ban goes into effect in July.
The Associated Press contributed to this report.