the indo-pacific humpback dolphin is threatened by both habitat loss and pollution. conservationists warn that hong kong may lose its rare indo-pacific humpback dolphins, also known as pink dolphins for their unique colour, unless china takes urgent action against pollution and other threats. their numbers in hong kong waters have fallen from an estimated 158 in 2003 to just 78 in 2011, with a further decline expected by the hong kong dolphin conservation society. a tour guide from hong kong dolphinwatch spotted a group of pink dolphins helping a mother support the body of her dead calf above the water in an attempt to revive it. the scene, captured on video and widely shared on facebook, has raised fresh concerns about the dwindling population in a city where dolphin watching is a tourist attraction. "we’re 99 percent certain the calf died from toxins in the mother’s milk, accumulated from polluted seawater," said hong kong dolphinwatch spokeswoman janet walker, who added it was the third such incident reported in april alone. fewer than 2,500 of the mammals survive in the pearl river delta, the body of water between macau and hong kong, with the majority found in chinese waters and the rest in hong kong.