Arabian Sea humpback whale unique subspecies

MUSCAT, OCT 8
Arabian Sea humpback whales represent a distinct evolutionary lineage and could potentially be recognised as a fourth subspecies of humpback whale, according to a new genetic study.
The research, led by the Wildlife Conservation Society (WCS) in collaboration with the Environment Society of Oman (ESO), the Environment Authority and other local and international partners, marks a significant milestone in more than 25 years of research on the Arabian Sea humpback whale population.
Published in Frontiers in Marine Science, the study suggests that Arabian Sea humpback whales are genetically distinct from the three currently recognised humpback whale subspecies and have followed an independent evolutionary trajectory for tens of thousands of years.
Researchers analysed mitochondrial DNA from 2,285 humpback whales sampled across the species' global range. The findings revealed high levels of genetic differentiation between the Arabian Sea population and humpback whale populations in the North Atlantic, North Pacific and Southern Hemisphere, indicating very limited gene flow between them.
“Arabian Sea humpback whales have long been an enigma to the scientific community. Their ecology is unlike that of any other known humpback whale population, and this new genetic work represents an important milestone in understanding how that uniqueness developed,” said lead author Dr Rita Amaral, who coordinated the genetic analysis with WCS.
“The results clearly indicate the Arabian humpback whales have followed their own evolutionary trajectory for tens of thousands of years and support their recognition as a distinct subspecies,” she added.
The findings add to previous evidence that Arabian Sea humpback whales are unique among studied humpback populations. Genetic analyses estimated that the whale lineages diverged tens of thousands of years ago, with different groups showing estimated divergence times ranging from about 43,000 to 113,000 years ago.
Suaad al Harthi, Executive Director of the Environment Society of Oman (ESO) and a co-author of the study, said the findings resulted from more than 25 years of dedicated research in Oman.
“What began with small-boat surveys to photograph individual whales and collect tiny tissue samples has developed into a much broader programme using satellite tracking, acoustic monitoring, health assessments and other techniques,” she said.
“It is enormously rewarding to see samples collected during those early years now contributing to findings of such international scientific importance.”
The study also highlights the vulnerability of the population because of its isolation. Arabian Sea humpback whales face threats including entanglement in fishing gear, vessel strikes, underwater noise and pollution, as well as natural pressures such as disease.
Climate-driven changes to monsoons and ocean upwelling could also affect the availability of sardines and other prey. The study notes that the population remains small, with no evidence of an increase over the past two decades, and warns that it could face local extinction without concerted efforts to address these threats.
Aida al Jabri of the Environment Authority of Oman said the growing body of research had provided a clearer understanding of both the importance of the population and the pressures it faces.
“This evidence is now helping us move from scientific understanding towards practical conservation action, including regional cooperation through the International Whaling Commission and Oman’s work to explore greater protection for important marine habitats through international mechanisms such as the International Maritime Organisation’s special protection provided by Particularly Sensitive Sea Areas,” she said.
Dr Howard C Rosenbaum, Executive Director of the WCS New York Bight Programme and Senior Conservationist with the WCS Global Conservation Programme, said the latest research further highlighted the genetic distinctiveness of Arabian Sea humpback whales.
“Generating robust science about its unique evolutionary history, isolated nature, and small population size strengthens the case for protecting these humpback whales throughout their range,” he said.