In the past two years, high numbers of starving sea lion pups have washed onto California’s beaches and this year may set a record. More than 470 young sea lions have been admitted to rehab centers in the state, and what is considered to be peak stranding season is likely still on the way.
Not only are these young California sea lions sometimes found weighing half of what they should, they are often at an age when they should still be with their mothers—and depending on their milk. "They're extremely emaciated, basically starving to death," veterinarian Shawn Johnson told National Geographic.
Marine biologists aren’t exactly sure what’s led to the surge of strandings, which began in 2013 when some 1,600 sea lion pups came ashore. That year, NOAA described the situation as an “Unusual Mortality Event” and researchers began looking for a cause. According to The Marine Mammal Center, a rescue facility in Sausalito, “so far there is no evidence of underlying primary infectious disease or toxic insult to suggest what has caused these sea lion pups to strand.”
One theory is that a drop in fish populations may be leading mother sea lions to ween their pups a few months earlier than normal. A related theory is that fewer fish are causing mothers to venture further away from their young in search of food, and the pups—who usually stay on the shores of the Channel Islands—are jumping in the water after them, but are too weak to swim in strong currents.
In an interview with the San Francisco Chronicle, Justin Viezbicke, stranding network coordinator for NOAA Fisheries in California, speculated that the population might have hit a plateau that the environment can support.
California sea lions (Zalophus californianus) are not considered a threatened species by the International Union for Conservation of Nature, although Stellar sea lions, another sea lion species found in California, are considered “Near Threatened.” That said, the California sea lion is protected by the Marine Mammal Protection Act, which prohibits them from being hunted or captured except by certain Native American groups.
Whatever the cause of the strandings may be, rescue workers are on alert and are doing their best to keep the young animals from dying, with the hope that they can eventually be returned to the wild. The Marine Mammal Center is collecting donations for food and treatment for the pups; you can learn more about how to help here.