Western gray whales were tagged seven years ago to monitor migration . The tags are attached by a line that is pulled through the water and then released at regular intervals as they drift toward their winter feeding grounds in Alaska or Canada.
Western gray whales were tagged seven years ago to monitor migration . The then nine-year-old female called Varvara swam from Russia to breeding grounds near Mexico during five-and-a-half months in 2011 . Gray whales typically do n't feed during migration , which has led researchers to believe she did n't eat during the long journey . Previous record was held by a humpback who swam 11,706 miles in 2011 .