The Indus River dolphin's habitat is shrinking because of irrigation dams that divide up the river into sections, new research suggests.
The findings support conservationists' long-held suspicion that dams along the world's major rivers have been catastrophic for the species that live there.
"It is river habitat fragmentation by dams, and removal of river water for irrigation, that has caused the massive range decline of the Indus River freshwater dolphin," Gill Braulik, a cetacean specialist at the Wildlife Conservation Society in Tanzania and lead author of the new study, said in a statement. "This increased understanding of species decline in fragmented river systems is especially important because hundreds of new dams and water developments are planned, or are under construction, in many of the world's rivers, and large losses of aquatic biodiversity can be expected." [In Photos: The World's Most Endangered Wildlife]
River dolphins evolved from ancestors that swam the seas but adapted to their inland homes after being edged out of the oceans by other marine dolphins. Around the world, there are several species of river dolphins, which evolved similar features independently, according to a 2012 paper in the journal Proceedings of the National Academy of Sciences. River dolphins have longer snouts than those of their ocean-dwelling counterparts, but they can't see as well as marine dolphins, probably because good eyesight wasn't needed in the dim, cloudy river water where they live, according to the World Wild Fund for Nature.
Unlike their marine counterparts, many river-dwelling cetaceans are listed as endangered or critically endangered, according to the International Union for Conservation of Nature. For instance, the Yangtze River dolphin hasn't been seen for years and has likely been extinct since the mid-2000s, the researchers wrote in the paper.
The Indus River dolphin, Platanista gangetica minor, lives in the Indus River, which originates high in the Tibetan Plateau, winds through Pakistan and empties into the Arabian Sea. Due to high demand for hydroelectric power and irrigation, dams now dot the river and break up the river dolphin's native habitat.