Mammals
Ganges River Dolphin
Platanista gangetica · also called Ganges river dolphins, susu
Gliding on its side just above the riverbed of a heavily trafficked South Asian river, a Ganges river dolphin hunts entirely by sound, its eyes no longer capable of forming images at all, a functionally blind species that has turned echolocation into its only reliable way of seeing the world.
Overview
The Ganges river dolphin, Platanista gangetica, is a functionally blind freshwater dolphin native to major river systems across South Asia, including the Ganges, Brahmaputra, and their tributaries. Its complete reliance on echolocation, distinctive sideways swimming posture, and survival within some of the most heavily used rivers in the world make it one of the more physically remarkable and conservation-urgent freshwater cetaceans found anywhere on Earth.
A species that gave up seeing entirely
Rather than retaining even limited vision, the Ganges river dolphin has evolved past sight altogether, betting its entire survival on a sense of hearing refined enough to replace eyes completely within its murky river home.
Status
Endangered and decreasing, present across major South Asian river systems, with declines driven by dam construction, water extraction, pollution, and fishing gear entanglement.
Ganges River Dolphin: common questions
Is the Ganges river dolphin really blind?
This species has lost the ability to form images and is considered functionally blind, a significant sensory adaptation that reflects how little vision matters within the murky, sediment-heavy river water it inhabits, where echolocation provides far more reliable information than sight ever could.
Why does the Ganges river dolphin swim on its side?
This species has been observed swimming on its side while foraging near the riverbed, a distinctive posture thought to help it search for prey along the bottom more effectively, possibly by positioning its sensory apparatus advantageously relative to the substrate.
How is the Ganges river dolphin related to the Indus river dolphin?
This species is closely related to the Indus river dolphin, with the two sometimes considered subspecies of the same overall species, separated primarily by the different river systems each inhabits rather than by dramatic physical differences between them.
Why is the Ganges river dolphin endangered?
This species inhabits river systems that are among the most intensively used by people anywhere in the world, exposing it to significant pressure from dam construction, water extraction, pollution, and heavy boat traffic, pressures that together have driven a significant population decline.