SAN FRANCISCO, Feb. 6 (UPI) -- For the third winter in a row, wildlife officials and animal rescue volunteers are seeing an influx of sick and starving sea lion pups stranded on the beaches of California. In January, more than 250 emaciated sea lion pups were rescued.
In 2013, more than 1,500 sea lion pups were found washed ashore, a record that prompted officials with NOAA's National Marine Fisheries Service to declare the phenomenon an Unusual Mortality Event, or UME. Last year was nearly as bad, and now 2015 is off to an ominous start.
"Looking at the data over the past 10 years, this is the busiest January on record, as far as strandings go," Justin Viezbicke, who is in charge of monitoring animal strandings in California for the National Marine Fisheries Service, told the Press Democrat.
Researchers aren't exactly sure what's causing so many distressed pups to arrive on shore, but some biologists suggest unusually warm waters off the coast may be playing a role -- forcing mothers to leave their pups alone for longer periods of time as they search for food. Sea lion pups are dependent on their mothers for most of the first year of their lives.
"The pups are desperate and starving, so they just jump in the water and swim and get pulled to the coastline," Shawn Johnson, director of veterinary medicine at the Marine Mammal Center in Sausalito, told the San Francisco Chronicle. "They're just too small and too weak to dive and catch fish."
Other explanations for the worrisome phenomenon include the possible accumulation of biotoxins in sea lions' prey populations as a result of algae blooms. Some scientists say overbreeding could be at play, and the population is at carrying capacity.
"This is the third year that we've seen these mass die-offs, but this is the worst so far," Johnson said. "If this continues, there will be some long-term effects on the sea lion population."
"I hope that we have some answers soon," Johnson told the Los Angeles Times, "so that we can prepare for the future."
Regardless of the underlying causes, rescue centers from San Diego to San Francisco are doing their best to keep up with the influx of sick pups, feeding them ground herring and treating them with antibiotics. It will be several more months before most of them can be released back into the wild.