Scientists believe they may finally know why more than 1,000 sea lion pups turned up sick on Southern California beaches over the last year.
The phenomenon seemed to begin in January 2013 when a large number of pups began washing ashore injured, dehydrated and malnourished.
Scientists looked at environmental factors, such as algae growth and wind pattern changes. But they now believe a dramatic drop in the sardine population was the culprit.
The cold water conditions in the Pacific Ocean have caused a crash in the number of sardines, according to scientists with the National Oceanic and Atmospheric Administration.
Sea lion mothers depend on the oily fish to pack on pounds before giving birth, but the sardine population has been dwindling as a result of cold water and a population increase in predators.
With sea lions no longer able to depend on sardines for nutrition, they may be forced to eat less nutritious prey. That leaves them unable to feed their pups enough milk, scientists believe.