Rare whale swims up West Coast toward Russian home

Varvara is the first western Pacific gray whale documented all the way to Baja Mexico, where most California gray whales breed and give birth. Scientists know Varvara did not give birth because she would have stayed in one place for four to eight weeks as the calf gained strength.

She was, however, tracked to all three major breeding and calving areas for eastern gray whales, and she may have found a partner. The whale's gestation period is about one year.

"In good years, females are alternately calving and breeding," Mate said. "Every-other-year-calving is a normal calving interval for healthy adult females when the environment is doing well for them."

The satellite tags average 123 days on a gray whale and the longest documented is more than 380 days. Varvara's has been in place for 200 days. Mate hopes it will last for the crossing of the Pacific.

The Sea of Okhotsk is frozen and scientists would like to see if Varvara heads for the Kamchatka Peninsula or for waters off Japan to approach Sakhalin Island from the south, Mate said.

Either way, he marvels at the voyage.

"Keep in mind that Varvara hasn't fed since she basically left Russia," Mate said. "So several months crossing to get over here, a month in the reproductive areas, several months back — she'll be five months without food, so she's having to do all this on whatever she put in her gas tank, so to speak, before she left Russia."