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Researchers Predict Dramatic Drop In Gray Whale Births

A gray whale calf travels alongside an adult gray whale to their summer feedi...

Credit: NOAA Fisheries Northwest

Above: A gray whale calf travels alongside an adult gray whale to their summer feeding grounds in the Arctic.

More than 20,000 gray whales are starting to leave their Alaskan feeding grounds to travel 5,000 miles to the warm lagoons in Mexico. Pregnant females are the first to make the trek in order to give birth in Baja and protect their calves in the warm water.

But a significant drop in calf production is expected this year, according to Wayne Perryman, a biologist with NOAA’s Southwest Fisheries Science Center. He said when the whales returned to their feeding grounds in the Arctic Circle last spring, the ice was extensive and slow to melt, preventing newly pregnant females from getting enough to eat.

"We had more ice in the spring than has ever been recorded in the satellite record, and that goes back about 35 years," said Perryman. "And I think the odds of their pregnancies going to term are reduced.”

The 10,000 mile round-trip journey is the longest known migration undertaken by any mammal, and pregnant females fast during the entire trek.

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

Calves drink 50 to 80 gallons of their mother's milk per day.

Perryman said the past year's unusual weather could also impact the size of the overall population as well as the timing of the migration.

Gray whale sightings off San Diego’s coast typically peak around mid-January and again in March.

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