Dozens of blue whales swim off California coast in rare sighting
{{#rendered}} {{/rendered}}Blue whales, the world's largest animal, are being seen in droves off the California coast.
The ocean giants are being lured by an increase this year in their favorite food -- shrimp-like creatures known as krill, biologists said.
In Monterey Bay, whale watching tour operators have reported seeing dozens of blue whales and droves of humpbacks.
{{#rendered}} {{/rendered}}"I tell people it's a once-in-a-lifetime chance," marine biologist Nancy Black told the Santa Cruz Sentinel newspaper.
Blue whale sightings close to shore are generally rare.
The animals, which were nearly hunted to extinction a century ago and remain endangered, tend to stay further out to sea while migrating north. They can also stay under water for more than 20 minutes.
{{#rendered}} {{/rendered}}There are only about 10,000 blue whales left worldwide, with 2,000 in the northeastern Pacific Ocean.
Marine biologists say a biological chain reaction is likely behind the whale boom.
Strong northwest winds have brought to the surface more of the cold, nutrient-rich waters from the deep. This brings phytoplankton up to the surface, which multiply in the sunnier environment, and are in turn feasted on by krill.
{{#rendered}} {{/rendered}}Blue whales can eat about four tons of krill every day.
"We are seeing every single day humpbacks feeding on krill, and most days, blues feeding," Mike Sack, co-owner of Sanctuary Cruises in Moss Landing, told the Monterey County Herald newspaper.