Ganges and Indus river dolphins have developed an unusual method of swimming on their side with their tail held slightly higher than their head. The dolphins' range has been reduced, and populations have been fragmented or separated from each other by the construction of dams and water control projects, especially along the Ganges River. These rivers flow through western India, Nepal, Bhutan, and Bangladesh. Ganges river dolphins live in the Ganges, Meghna, Brahmaputra, and Karnaphuli Rivers, and their tributaries (streams that flow into these rivers). Their distribution is limited by two dams built in the 1930s. Indus river dolphins live in about a 100-mile (160-kilometer) stretch of the Indus River where it flows through the Sind and Punjab provinces of Pakistan. The Ganges and Indus river dolphin is found only on the Indian subcontinent. Ganges and Indus river dolphins also use sound to communicate with each other. This process is so sensitive, that they can 'see' an object the size of a kernel of corn at a distance of 50 feet (15 meters), and can find their way around muddy waters as well as clear waters. From the time it takes to collect the echoes, their strength, and their direction, dolphins construct a 'sound picture' of their environment. When the sounds bounce back, the echo is passed through special tissue in the lower jaw to the inner ear. Dolphins make sounds (scientists disagree about how this is done) that seem to be focused through the melon, a lump of fatty tissue in the dolphin's forehead, and skull and then sent out into the environment. Instead of relying on sight to find food, they use a system called echolocation (eck-oh-loh-KAY-shun). They are able to see only light and dark patterns, which is why they are sometimes called blind river dolphins. Ganges and Indus river dolphins have poorly developed eyes. Unlike other dolphins, the opening to their ear is below their eyes. Their flippers are broad and paddle-shaped, and their blowhole is a single slit, set off-center on the top of their head. Ganges and Indus river dolphins have a small hump behind the center of their back instead of a dorsal (back) fin. They use these teeth to catch their prey, animals they hunt for food, mainly fish. These dolphins have a long beak, or snout, and when they close their mouth, their sharp front teeth are still visible. Adults measure between 5 and 8 feet (1.5 to 2.5 meters) and weigh between 150 and 200 pounds (70 to 90 kilograms). Ganges and Indus river dolphins are small, gray-brown dolphins. Native people call these dolphins 'susu,' which sounds like the noise they make when they breathe. However, recent genetic testing shows that even though these groups are separated geographically, they are the same species.

At one time, scientists thought that there were two species in this family, the Indus river dolphin and the Ganges river dolphin. The single member of this family is a dolphin that lives in freshwater rivers on the Indian subcontinent. GANGES AND INDUS DOLPHIN: Platanistidae PHYSICAL CHARACTERISTICS

River dolphin sounds