The Ganges River Dolphin is an ancient species and one of the world’s few remaining freshwater dolphin populations. As a top predator, it serves as an indicator of the overall health of its river system. The species is currently classified as endangered, facing immense pressures in one of the world’s most densely populated regions.
Identification of the Ganges River Dolphin
The scientific community recognizes this mammal as Platanista gangetica, a species distinguished by adaptations for life in turbid, sediment-laden waters. Its most notable physical feature is its long, slender snout, which can measure up to 20% of its total body length. This beak-like structure is equipped with long, sharp teeth, used for catching fish and shrimp on the river bottom.
The dolphin is often called the “blind river dolphin” because its eyes are extremely small and lack a lens, preventing image formation. Instead of sight, the animal navigates and hunts entirely through sophisticated echolocation, emitting a constant stream of ultrasonic clicks to detect prey and obstacles. A low, fleshy hump serves as its dorsal fin. Unfused vertebrae grant the dolphin unusual flexibility, allowing it to turn its head from side to side to scan its surroundings.
Geographic Distribution and Habitat
The Ganges River Dolphin’s current range spans over 10,000 kilometers across the vast river systems of the Indian subcontinent. Its distribution is concentrated within the Ganges-Brahmaputra-Meghna and the Karnaphuli-Sangu river systems. This range includes the main river channels and tributaries flowing through Nepal, India, and Bangladesh.
The dolphins prefer specific riverine habitats where food is abundant. They are most commonly found in the deepest sections of the river, often utilizing eddy countercurrents downstream of river confluences and sharp meanders. These areas, particularly near tributary junctions, concentrate prey species and provide refuge from the main flow.
Historically, the species’ range was continuous throughout these large river basins. However, the current population is highly fragmented and isolated into smaller groups. The largest numbers are concentrated in the main stem of the Ganges River in India and the Brahmaputra River in Bangladesh. For instance, fewer than 100 individuals remain in the tributaries within Nepal.
Factors Impacting Their Riverine Home
Human activities severely compromise the viability of the Ganges River Dolphin’s habitat, leading to significant fragmentation and degradation. The construction of dams and barrages is a primary concern, as these structures physically block the dolphins’ movement, isolating populations. This isolation prevents genetic exchange and limits the ability of the dolphins to move to favorable feeding or breeding grounds.
Water extraction for irrigation, often associated with barrages, reduces water volume, particularly during the dry season. Reduced flow shrinks the available habitat, especially the deep pools the dolphins rely on. This altered hydrology also impacts the migration and breeding cycles of fish, which are the dolphin’s main food source.
Widespread contamination from human sources is another major pressure. The waterways are burdened with industrial effluents, untreated sewage, and agricultural runoff containing pesticides and heavy metals. These pollutants accumulate in the dolphins’ tissues, affecting their health and reproductive capacity.
Accidental entanglement in fishing gear, known as bycatch, is a leading cause of direct mortality. The widespread use of gillnets in the deep river sections preferred by the dolphins results in numerous deaths each year.