The Indus River dolphin is one of the world's rarest mammals and most endangered cetaceans. Only about 1,000 of this unique species exist today in the lower reaches of the Indus River. It has a long beak and a stocky body. It has a low triangular hump on its back in place of a 'true' dorsal fin. It is gray-brown in color, sometimes with a pinkish belly. It measures between 1.5 and 2.5m (5-8ft) in length and weighs 80-90 kg.
The Indus River dolphin is functionally blind having evolved without a crystalline lens or well-developed light-sensitive organ. However, this is not a disadvantage but an adaptation to living in the silt-laden turbid waters of the Indus where eyes are virtually useless, as very little light penetrates below the surface of the murky water.
This dolphin swims on its side, at times enabling it to swim in water as shallow as 30cm. As it swims on its side, it trails a flipper along the bottom of the river. After 30 to 60 seconds, when it needs to breath, it swims to the surface, rotates upright to take in the air, and then rotates thorough 90 degrees again as it swims back to the bottom.
Numbers have dramatically declined since the construction of the irrigation system in the Indus. Most now remain in a 1,200km stretch of the Indus River.