A baby boom of gray whales migrated through California waters this spring. There were twice as many calves born this season over last, according to NOAA.

More than 1,100 gray whale calves completed their first-ever 5,000-mile northward migration, from the warm water lagoons of Mexico to the Arctic Circle. That's twice as many calves as last year, according to Wayne Perryman, biologist with NOAA’s Southwest Fisheries Science Center.

Perryman helped count the cow/calf pairs along their journey.

"We’re counting them as they migrate northbound past a little point of land near San Simeon California, and that’s a site that cows and calves pass very very close to the beach," he said.

Perryman said the boom occurred because the Arctic ice cover melted early last spring, which enabled pregnant females early access to vital feeding areas.

"So if a female is pregnant and she’s going back up north, if ice is slow to melt, then she can’t get to the feeding ground and I think the odds of that pregnancy going to term are diminished."

Pregnant females fast during the four-month round-trip migration, so it’s important for them to fatten up quickly upon their return in May to the North Pacific, added Perryman.

"Cause if you’re going to reproduce and you’re a gray whale, you want to be a fat girl, because the next season you’re going to give birth to the calf, and you’re going to fast and lactate at the same time," he said.

Mature gray whales eat small crustaceans and tube worms found in sediments along the sea floor. Calves drink 50 to 80 gallons of their mother's milk per day.

Perryman said when the whales returned to their feeding grounds this year, the ice was extensive and slow to melt in the Bering Sea.

"So I’m predicting that next year we’ll see a dramatic drop in calf production."

The whales begin their annual southern migration in October as the northern Arctic ice pushes southward.

The Pacific gray whale population stands at about 20,000. Once hunted to the brink of extinction, gray whales were removed from the endangered species list in 1994.

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