The Ganges River Dolphin (Platanista gangetica gangetica) is a unique freshwater cetacean adapted to the turbid waters of the Ganges-Brahmaputra-Meghna river system across Nepal, India, and Bangladesh. This species is functionally blind, possessing eyes that can detect light and dark but cannot form clear images, a trait evolved for its low-visibility habitat. It features a long, slender snout and a flexible neck, physical characteristics integral to its survival and hunting. The dolphin’s endangered status underscores the importance of understanding its ecological role within these river ecosystems.
Primary Food Sources
The Ganges River Dolphin primarily consumes a variety of fish and invertebrates. Its diet includes small to medium-sized fish, such as catfish, carp, and gobies, often targeting slow-moving or bottom-dwelling species. It also eats freshwater prawns and other aquatic crustaceans. Due to its limited vision, the dolphin relies on detecting available prey in its immediate surroundings rather than actively pursuing fast-moving targets. Prey items typically measure between 20-30 cm, and larger dolphins can consume approximately 1.3 to 3 kg of food daily.
Unique Foraging Techniques
Ganges River Dolphins navigate and hunt using echolocation, or biosonar, essential for survival in their murky aquatic environment. They emit high-frequency clicks constantly, interpreting returning echoes to construct a detailed sonic map and locate prey up to 20 meters away. The dolphin’s elongated snout, equipped with sharp teeth, is specifically adapted for probing the riverbed and snatching prey. They often employ a characteristic side-swimming behavior, swimming at roughly a 10-degree angle with flippers trailing the bottom to sweep the riverbed for food and navigate shallow waters. This unique swimming posture also positions their eye to potentially sense light, aiding orientation during dives.
Habitat Influence on Diet
The Ganges River Dolphin’s habitat directly shapes its diet and foraging strategies. The turbid, shallow, and sometimes fast-flowing waters dictate the types of prey available and the methods dolphins use to catch them. Seasonal variations, particularly the monsoon floods, influence water levels and the distribution of fish, prompting dolphins to migrate to tributaries and larger river channels. Human activities also impact the dolphin’s food sources; infrastructure like dams and barrages restrict fish migration and reduce prey availability, while pollution and overfishing diminish aquatic life. Toxic chemicals, such as endocrine-disrupting chemicals and heavy metals, accumulate in fish, transferring contaminants to the dolphins through their food chain.