Gray whale travels 13,987 miles, breaking world record

What a trip.

A western North Pacific gray whale traveled nearly 14,000 miles from Russia to Mexico and back again, breaking the known world record for mammal migration, researchers say.

The 13,987-mile journey took 172 days and was tracked in a study published in the journal Biology Letters.Previously, the world record for mammal migration belonged to the humpback whale, which migrates up to 10,190 miles, according to Guinness World Records.

The new title holder is a gray whale named Varvara, meaning Barbara in Russian, according to Oregon State University biologist Bruce Mate, the lead author of the study and chair of the school's Marine Mammal Institute.

Researchers monitored the journey by attaching satellite-monitored tags to seven western North Pacific gray whales in their feeding grounds off the Russian coast. The gray whales were once considered extinct and are currently critically endangered with only 150 left in the wild, according to Mate.

Before the study, little was known about the migratory routes and reproductive areas of the whales.

"The expectation was western gray whales migrated down (the) Asian Coast and many suspected that the winter breeding area was the South China Sea," Mate told USA TODAY Network.

But Varvara didn't go that route.

He says she crossed the Bering Sea, the Gulf of Alaska and the length of the North American continent to get to Baja breeding areas that are used by eastern North Pacific animals. Two other gray whales, Agent and Flex, also made similar migration routes, though their tags fell off before reaching the breeding grounds.

Researchers were surprised by several aspects of Varvara's journey. She appeared to have taken a different route to and from the breeding grounds in Mexico, suggesting she knew the migration route well, Mate said.

"By coming all the way to Mexico it reveals that Varvara was born there," Mate says. "Calfs inherit their mothers' foraging area, so she would have closely followed her mother from the breeding area where she was born to the feeding area."

During the nearly six-month-long journey, Varvara did not stop to eat. While that sounds like a long way to go on an empty stomach, Mate says it's normal for gray whales not to eat during the journey.

Western or eastern gray whales?

Eastern gray whales are closely related to western gray whales, and typically breed near the Baja Peninsula. Mate says it's possible that the western gray whales the team was tracking were actually Eastern gray whales that migrated west to Russia.

Mate says the research also raises the question of whether the western population is genetically distinct from the eastern population, or whether the whales are actually a single species.

If that's the case, the eastern whales may have expanded their range when the western whales numbers dwindled.

Mate says the researchers are hoping to successfully tag more whales and identify whether the population of eastern whales is smaller than originally thought.

"If there is a more impoverished population of western gray whales than originally thought, there is more reason to ensure the conservation of their genetic diversity," Mate says.

Follow @MaryBowerman on Twitter