Susu and Bhulan: Platanista gangetica gangetica and P. g. minor

Susu Platanista gangetica gangetica and bhulan Platanista gangetica minor are two river dolphin subspecies that are the sole surviving members of a primitive and once widespread taxon of archaic cetaceans. These dolphins have a slightly awkward appearance with an especially long snout particularly in adult females, broad flippers, a tiny dorsal fin appearing as a hump, and an extremely small eye visible as only a pin-like hole. They exhibit specialized adaptations to a riverine environment including a flexible neck for highly maneuverable swimming, a specialized projection on the skull to focus echolocation signals for chasing individual prey, side-swimming behavior where the dolphins sweep their head back and forth in a scanning motion while trailing one flipper along the bottom, and severely reduced optic nerves and absence of a focusing lens since vision is of little value in the generally turbid waters that characterize their habitat. Both subspecies are endangered due to water development, including dams and embankments, which have degraded their habitat and fragmented populations, as well as from fatal entanglements in fishing gears, especially gill nets. These threats are particularly acute for both subspecies due to their general occurrence in countercurrent pools that are eliminated or reduced in size in channels affected by water development and are the primary fishing grounds for local communities.