Since the beginning of the year more than 500 sea lion pups have been found washed ashore and on the verge of death in Southern California, Wired reports.
The number of weakened, emaciated pups has been steadily increasing; only three months into the year the number of pups found already exceeds the yearly totals of some previous years.
Marine scientists and researchers are at a loss to explain why this is happenings.
Most of the 517 pups are nine months old and weigh just half of what they should by that age, Wired reported.
The pups show signs of dehydration and malnourishment.
Some scientists suspect the pups are leaving the rookeries early, though just why they would choose to do so remains a mystery.
So far, the 517 pups that have been accounted for since March 13 have been taken in by one of five animal rescue centers in southern California. Hundreds of the pups will spend time in rehabilitative care in the hope that they may return to the sea in good health.
Many others were not so lucky and had to euthanized because they were beyond help.
Sadly, more strandings are expected as the peak season for sea lions to become stranded has not happened yet. Historically sea lion pups that are weaned from their mothers in April and May become stranded after not being able to make it on their own.
"We anticipate it will only get worse in the coming months," said Sharon Melin, a wildlife biologist with the National Fisheries Service, according to Wired.
It's possible that something is awry with the ecosystem, as sea lions are often studied as a gauge of the marine ecosystem. Warmer water temperatures and diseases have been suspected as causes of the strandings.
"Sea lions are usually pretty good at adapting," Melin said. "If the system starts changing or becomes out of whack, they're the one that are going to show the signs."