A cross between an Antarctic minke whale and a northern minke whale was recently discovered during a DNA analysis of whales caught by Norwegian hunters.
Normally the two whale speciesâ€”both of which can reach 35 feet (11 meters) in lengthâ€”undertake seasonal migrations that separate them by many miles of ocean.
Northern minkes head toward the North Pole in spring and ply waters up to the edge of Arctic ice during the summer. In autumn these whales head south, nearly as far as the Equator, to spend the winter. (See whale pictures.)
Antarctic whales follow a similar pattern, moving between Antarctic ice and warmer mid-latitudes with the seasons.
But because the two hemispheres’ seasons are opposite, the minke species don’t share near-equatorial waters at the same time. Thus, they were never thought to meetâ€”until now.
Whale of a Shocker
Minkes have been hunted extensively since the 1930s, and the few nations that still practice whalingâ€”including Norway, Greenland, and Japanâ€”target them today.
Soon after Norwegians resumed commercial whale hunting in 1993â€”following a brief moratoriumâ€”the country established a DNA registry to analyze whale kills and help ensure that whale products come from legal sources.
Geneticist Kevin Glover was recently analyzing whale DNA when he came across a surpriseâ€”a whale hunted in the northeastern Atlantic in 2007 had the genetic blueprint of a hybrid, with an Antarctic minke mother.
Glover’s colleague then told him an interesting story relayed by a whaling vessel’s scientific observer nearly 15 years ago.
“He said there was a very strange-looking individual taken back in 1996â€”it didn’t have the white patch on its pectoral flippers like the [northern minke whales do],” said Glover, of the Institute of Marine Research in Bergen, Norway. “I wonder if it could be the same sort.”
So Glover analyzed the DNA of the 1996 whale captured in the North Atlantic, and found a shocker: It was a pure Antarctic whale. The sample had been overlooked because the DNA archive was in its infancy when the whale was captured.
This Antarctic whale in the Arctic provided further evidence that Antarctic minkes can migrate to the home waters of their northern relatives andâ€”as the hybrid showsâ€”even mate with them, according to the study, published December 22 in the journal PLoS ONE.
Drop in Food Driving Whale Migration?
Still, the genes leave a lot of unanswered questionsâ€”Is the hybrid whale a fluke, or the beginning of a trend? No one knows, but Glover said that his whale biologist colleague Nils Ã˜ien has an interesting theory.
Japanese studies showed that the numbers of Antarctic minke in the Southern Hemisphere appeared to drop significantly between the 1980s and 1990s. Other studies show that supplies of the krillâ€”tiny marine crustaceansâ€”that fuel the Antarctic food chain also dropped during this period.
“Japanese research has even shown that the fat layer on whales down there has decreasedâ€”not to the point of malnutrition, but suggesting a decreased access to food,” Glover said.
“So we speculate that the amount of krill and available food has decreased, and maybe as a result the whales are starting to go scouting for food.
“It could be that these individuals are straying away from their territory in the search for food, and a few of them may have found their way to the Arctic Circle.”