Baby sea lions in California beaching themselves in record numbers

A record number of baby sea lions - many too weak to swim - are stranding themselves on the California coast.

It remains unclear why they are turning up emaciated in such large numbers. But the surge in stranded sea lions has kept animal rescue teams busy.

"This is the highest number I've had in all my career -- my 29 year career," Peter Wallerstein, director, Marine Animal Rescue, told CBS News Correspondent Bigad Shaban.

Rescuers have saved more than 275 sea lions so far this year -- more than double the number rescued in the same time period during a similar crisis two years ago. Many of the sick sea lions have compromised immune systems, and also suffer from pneumonia, parasite infections, and other illnesses.

"There's no body fat on them. You can see the ribs and their hips and their spine," said Wallerstein, as he tended to sick seal lions in San Diego. "That's why they get hypothermic. That's why they spend a lot of time out of water."

Some scientists blame warmer water - which is driving baitfish into deeper waters so the pups can't find food.

"This guy for instance, he should be almost 50 percent heavier than what he is now," said Todd Schmitt, a senior veterinarian with SeaWorld San Diego.

Schmitt and his team at Seaworld San Diego are nursing the pups back to health. He says it takes up to six week before they're strong enough to be released back into the ocean.

"We're trying to give them enough reserves so that they can swim far enough and also dive deep enough to find that food," he said.