Source: NIE
Subject: Species in News
Context: A report by the Wildlife Institute of India reveals that a drastic reduction in the Chambal River’s water flow is forcing endangered Ganges river dolphins to shift their habitat downstream toward the Yamuna confluence.
About The Ganges River Dolphin:
What it is?
- Commonly known as the Susu due to the sound it makes when breathing, the Ganges river dolphin is one of the oldest creatures in the world and serves as an indicator species for the health of the entire river ecosystem.
- It was officially discovered in 1801 and is India’s National Aquatic Animal.
IUCN Status: Endangered
Habitat and Distribution:
- Deep Waters: They prefer deep river stretches, particularly in and around the confluence of rivers.
- Range: Found in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh.
- Indian States: Distributed across seven states: Assam, Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar, Jharkhand, and West Bengal.
- Critical Habitats: Key stretches include the Upper Ganga, Chambal, Ghaghra, Gandak, Son, Kosi, and Brahmaputra rivers.
Key Characteristics:
- Physical Stature: Sturdy yet flexible body with large flippers and a low triangular dorsal fin. Females (up to 2.7m) are significantly larger than males (up to 2.12m).
- Smooth Skin: Calves are born chocolate brown, turning grayish-brown in adulthood with hairless skin.
- Blindness and Echolocation: They are essentially blind and navigate or hunt using ultrasonic sound (echolocation). They emit sound waves that bounce off prey, allowing the dolphin to see an image in its mind.
- Reproduction: Females mature at 10–12 years and give birth to a single calf once every 2–3 years after a gestation period of 9–11 months.
- Strictly Freshwater: Unlike many other dolphins, this species lives exclusively in freshwater and cannot survive in the ocean.
Conservation Issues and Implications:
- The construction of dams and barrages water flow and separates dolphin populations, leading to a narrowed gene pool.
- Dolphins require at least 3 meters of water depth to survive. Current extraction for irrigation and industry is reducing the Chambal’s flow to levels that make survival impossible in upper reaches.
- Low water levels create land bridges to river islands, allowing predators like jackals and dogs to destroy the nests of threatened birds like the Indian skimmer and black-bellied tern.
