After two decades of research, scientists have recognised the Endangered Indus and Ganges river dolphins as separate species. Since the 1990s, the river dolphins have been considered to be a single threatened species but a landmark study published in Marine Mammal Science concludes that the dolphins in the Indus river basin and those in the Ganges-Brahmaputra river basins are sufficiently distinct to be classified as species in their own right.
The work, which took 20 years to complete, was led by Dr Gill Braulik of the Sea Mammal Research Unit at the University of St Andrews, who travelled across India and Pakistan searching for dolphin skulls to measure for the study. The research shows that the two river dolphin species have different numbers of teeth, coloration, growth patterns and skull shapes as well clear genetic differences.
“Recognizing the species-level differences between Indus and Ganges river dolphins is extremely important as only a few thousand individuals of each species remain. They have long been regarded as two of the world’s most threatened mammals,” said Dr Braulik. “My hope is that our findings will bring much-needed attention to these remarkable animals, which will help to prevent them sliding towards extinction.”
The research was a long-term collaboration between the University of St Andrews, WWF-Pakistan, Patna University in India, and the Southwest Fisheries Science Center of the National Oceanic and Atmospheric Administration in the US as well as many other researchers in South Asia.
The Indus and Ganges river dolphins are often referred to as blind dolphins because they live in naturally muddy rivers and, over millions of years of evolution, have lost their eyesight and instead rely on a sophisticated sonar or echolocation system to navigate and catch prey. Both species are threatened by accidental entanglement and drowning in fishing nets, the construction of hydropower dams and irrigation barrages, and pollution of their waterways – and are listed as Endangered on the IUCN Red List.