Largest genetic study of humpback whale populations conducted in Southern Hemisphere

Scientists from the Wildlife Conservation Society, the American Museum of Natural History, and an international coalition of organizations have unveiled the largest genetic study of humpback whale populations ever conducted in the Southern Hemisphere.

By analyzing DNA samples from more than 1,500 whales, researchers can now peer into the population dynamics and relatedness of Southern Hemisphere humpback whales as never before, and help inform management decisions in the sometimes politically charged realm of whale conservation.

"Humpback whales are perhaps the most studied species of great whale in the Northern Hemisphere, but many of the interactions among Southern Hemisphere populations are still poorly understood," said Dr. Howard Rosenbaum, director of the Wildlife Conservation Society's Ocean Giants Program and lead author of the study.

"This research illustrates the vast potential of genetic analyses to uncover the mysteries of how humpbacks travel and form populations in the southern ocean basins," he added.

So little is known about southern ocean basin humpbacks that researchers initially used old whaling records for insights into whale population boundaries.Researchers collected skin samples from 1,527 whales from fourteen sampling sites from the Southwestern and Southeastern Atlantic Ocean, and the Southwestern and Northern Indian Oceans.

The populations are known as Breeding Stocks A (Southwest Atlantic Ocean), B (Southeast Atlantic Ocean), C (Southwest Indian Ocean), and X (Northern Indian Ocean), based on information amassed and designated by the International Whaling Commission, including data from 19th and 20th centuries commercial whaling.

The findings so far have revealed that the highest rate of gene flow between populations is between whales that breed on either side of the African continent (Breeding Stocks B and C), with an estimated one or two reproductively active whales every year swimming from one ocean to join whales in another breeding ground.

Authors of the current study previously identified the same individual whale in both Atlantic and Indian Ocean breeding grounds at different times, the first recorded instance of a humpback whale traveling between these two oceans. While no individual whales have been detected traveling across the Southern Atlantic to both breeding grounds, genetic similarities reveal a slight degree of populations interacting.

Interestingly, an examination of humpback whale songs between the two populations are similar, another hint at interchange between the two groups, most likely in the whales' feeding grounds in Antarctic waters.