Endangered Arabian Sea Humpback Whales Were Isolated for 70,000 Years

Scientists have taken a closer look at the humpback whales inhabiting the Arabian Sea and have found that they're the most genetically distinct humpbacks in the world. The new findings suggest that these whales have remained separate from others for as much as 70,000 years.

The humpback whale is known for its massive size and haunting songs. But it's also known for having the world's longest mammal migration. In fact, individuals have been tracked over a distance of more than 9,000 kilometers between polar feeding areas and tropical breeding areas. That's why this latest finding has puzzled researchers.

"The epic seasonal migrations of humpbacks elsewhere are well known, so this small, non-migratory population presents a wonderful and intriguing enigma," said Tim Collins, the co-author of the new study, in a news release. "They also beg many questions: how and why did the population originate, how does it persist, and how do their behaviors differ from other humpback whales?"

In order to assess the origins of the Arabian Sea humpback whale population, the researchers examined nuclear and mitochondrial DNA extracted from tissue samples collected from the biopsies of 47 individual whales. Then, the scientists compared these samples to data sets from humpback whales in both the Southern Hemisphere and the North Pacific.

In the end, the researchers found that the population itself was genetically distinct. More specifically, it had been separated for about 70,000 years. The scientists believe that this separation may be linked to various glacial episodes in the late Pleistocene Epoch and associated shifts in the strength of the Indian Monsoon. In addition, the separation might be reinforced by breeding cycles that are asynchronous; different populations breed during different seasons.

"The Arabian Sea humpback whales are the world's most isolated population of this species and definitely the most endangered," said Howard Rosenbaum, one of the researchers. "The known and growing risks to this unique population include ship strikes and fishing net entanglement, threats that could be devastating for this diminished population; we need to see increased regional efforts to provide better protection for these whales."

The findings are published in the journal PLOS One.

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