Sick, starving and dying sea lion pups are washing up on the shores of California in record numbers this year. In 2015, 940 young sea lions have turned up, officials with the National Oceanic and Atmospheric Administration (NOAA) said last week — four times the number California would normally see. But why?

Experts say it’s the warm water. Scientists believe warmer coastal waters force the prey of sea lions — squid and sardines, for example — deeper beneath the ocean’s surface. Then nursing sea lion mothers must look further afield for food, leaving their pups for longer than normal. Deprived of sustenance and weakened, the pups limply wash ashore.

“The prey source is just too far away for the mothers to go out, get food and come back and wean the pups,” Jim Milbury of the National Marine Fisheries Service told Yahoo News. Peter Wallerstein, director of Marine Animal Rescue in Los Angeles County, said the pups are unable to dive down to get food for themselves.

The ocean is up to five degrees warmer in the northeast Pacific and off the West Coast — probably a record, NOAA climatologist Nate Mantua told the Associated Press. He said its due to the same high-pressure system that has the state in a four-year drought.

“By the time they reach the mainland, they are so starved that they are basically shutting down,” Michael Remski, marine mammal rehabilitation manager for the California Wildlife Center told Yahoo News. According to the Associated Press, 300,000 sea lions live between the Mexican border and Washington state, and this is the third year straight that a high number of pups have died or become stranded. The deaths were so high in 2013 that experts declared an “unusual mortality event” for the species.

The influx of stranded sea lions has put a strain on animal shelters, some seeing record numbers of rescues.“It’s the highest number I’ve had in 29 years of rescues. … We get like 50 calls a day on sea lions,” Wallerstein said. “We rescued four today [even though] we are limited to three a day because the rehab center is so full. We had to leave some adults on the beach. It’s like a paramedic not having a hospital to bring a patient.”

On Tuesday, Getty photographer Justin Sullivan spent a day at the Marine Mammal Center in Sausalito. The center said it’s in the middle of the crisis.

“During the first 10 days of February, we responded to 100 more California sea lions — most of them starving pups,” it wrote in a press release. Currently, the center cares for more than 160 of the emaciated sea lions.