DNA study of humpback whales reveals mating habits

SYDNEY (Reuters Life!) - A 15-year genetic study of Southern Hemisphere humpback whales has opened a window into the little known mating habits of the giant cetaceans, revealing some whales travel between the Atlantic and Indian Oceans to mate.

Analyzing DNA skin samples from 1,527 whales in the South Atlantic and Indian Oceans, an international group of scientists mapped how different whale populations interact, their mating habits and distribution across oceans.

"Many of the interactions among Southern Hemisphere populations are still poorly understood," said Howard Rosenbaum, director of the U.S.-based 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," Rosenbaum said in a statement Wednesday announcing the study, published on PLoS ONE, an online scientific journal (www.plosone.org)

So little was known about Southern Ocean humpback whales that the researchers used whaling records dating back to 1761 for initial insights.

The whaling logbooks tried to determine whale population boundaries and breeding stock, but studying humpbacks in the wild, even in modern times, is difficult due to the wild oceans they inhabit and the vast distances they travel.

"We're still trying to answer the same question with molecular technology in concert with whaling logbook records," said Rosenbaum.

The slow-swimming humpback was hunted commercially until the International Whaling Commission protected the species in 1966. Humpback numbers are recovering, but their total population may still be only a small percent of the original population.

The study found that the highest rate of gene flow between Southern Hemisphere humpbacks occurred with whales breeding on either side of Africa, with one or two whales swimming between the Atlantic and Indian Oceans each year to mate.

This was the first time a humpback had been recorded traveling between the two oceans, said the study.

Whale populations on either side of the South Atlantic did not seem to mate, but similarities in their "songs" revealed a degree of interaction between the two groups, most likely in the feeding grounds in Antarctic waters.

The small humpback population of less than 200 in the Indian Ocean, off the Arabian Peninsula, was distinct genetically and unlike other populations did not migrate and therefore was a "conservation priority," said the study.

"Molecular technology gives us a window into the lives of whales that can help us understand the ecological forces shaping their movements and distribution," said Rosenbaum.

"We can also use our findings to inform management decisions for a species that is only now beginning to recover from centuries of commercial whaling," he said.

(Editing by Sugita Katyal)