A small, non-migratory population of humpback whales in the Arabian Sea are currently on the endangered list, according to the IUCN Red List of Threatened Species. This whale population may also remained isolated from interbreeding with other humpback whales from geographically distinct locations for tens of thousands of years.

Researchers with the Wildlife Conservation Society (WCS) of the American Museum of Natural History reported on December 3 in the journal PLOS ONE that their comparison of both mitochondrial and nuclear DNA samples taken from close to 70 Arabian Sea humpback whales with DNA sequences from other whale populations of the North Pacific and Southern Hemisphere showed strong distinctions. The differences are strongly suggestive of an unusual, long-term isolation.

“The epic seasonal migrations of humpbacks elsewhere are well known, so this small, non-migratory population presents a wonderful and intriguing enigma,” said WCS researcher and study co-author Tim Collins. “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?”

Estimates of gene flow and divergence suggest that the current population may have originated in the Southern Indian Ocean some 70,000 years ago. The genetic diversity values for these whales are significantly below those of humpbacks residing in the Southern Hemisphere. If the results are accurate, the humpback whales of the Arabian Sea are the most isolated population of its kind worldwide.

The authors of the study add that the Arabian Sea humpback faces low reproductive prospects and threats from humankind and therefore, ought to be moved to “Critically Endangered” status on the IUCN’s Red List.