Context: The first-ever comprehensive survey of river dolphins has revealed a population estimate of 6,327 dolphins mainly in the Ganga, Brahmaputra and Indus river basins across eight Indian states.
Relevance of the Topic: Prelims: Key Facts about Gangetic Dolphin; Project Dolphin; Echolocation.
Major Highlights of the Report
- There were 6,324 Ganges river dolphins, and three Indus river dolphins (a related species).
- The Gangetic dolphins were spread in river Ganga, tributaries of Ganga, Brahmaputra, tributaries of Brahmaputra and Beas river.
- The first-ever survey was led by the Wildlife Institute of India and state forest departments of certain states.
- It was conducted under Project Dolphin launched in 2020.
- The next survey will likely take place after four years.
- The highest number of dolphins were reported in Uttar Pradesh (highest concentration in Chambal River), followed by Bihar, West Bengal, and Assam.
- Acoustic Survey: For their survey, the researchers travelled by boat at a constant speed using acoustic hydrophones (essentially underwater microphones) that pick up sounds emitted by the dolphins.
About Gangetic Dolphin and Indus Dolphin
- India is home to two species (out of five species of river Dolphin globally) of freshwater dolphins — Gangetic Dolphin and Indus river Dolphin.
- Found mainly in the Indian subcontinent, particularly in Ganga-Brahmaputra-Meghna and Karnaphuli-Sangu River systems.
- Key Characteristics:
- An adult gangetic dolphin could weigh between 70 kg and 90 kg.
- Male dolphins as being about 2-2.2 metres long
- Females are a little longer at 2.4-2.6 m.
- The breeding season extends from January to June.
- The species is shy (avoids human contact) and feeds on several species of fishes, invertebrates etc.
- Dolphins stay under water and surface only sporadically to breathe.
- An adult gangetic dolphin could weigh between 70 kg and 90 kg.
- Significance:
- Dolphins act as an umbrella species and their conservation has direct impacts on their habitat and biodiversity.
- They serve as bio-indicators of healthy river ecosystems.
- Conservation Status (Both dolphins):
- IUCN Status: Endangered
- CITES: Appendix I
- Wildlife Protection Act, 1972: Schedule I
- Threats:
- Getting entangled in fishermen’s nets
- River Pollution
- Habitat loss due to construction of dams and barrages
- Poaching
Dolphin Conservation Efforts
- Conservation Action Plan for the Ganges River Dolphin (2010-2020).
- Project Dolphin (2020) to promote awareness and involve local communities in conservation efforts.
- Comprehensive Action Plan (2022-2047) to ensure well being of the river dolphin and aquatic habitats.
- Recognition of Ganges river dolphin as the National Aquatic Animal of India.
- MoEFCC has included Ganges river dolphin as one of the 22 critically endangered species for providing financial assistance to States under the Centrally sponsored scheme ‘Development of Wildlife Habitats’.
- Important habitats of Gangetic river dolphins along the Ganges river have been notified as Protected Areas, such as Vikramshila Dolphin Sanctuary, Bihar.
Echolocation:
- Echolocation is the use of sound as a form of navigation.
- Echolocation (bio sonar) is a biological active sonar used by several animal groups, both in the air and underwater.
- Echolocating animals emit calls and listen to the echoes of those calls that return from various objects near them.
- They use these echoes to locate and identify the objects.
- Echolocation is used for navigation, foraging, and hunting prey.
Ganges Dolphin and Echolocation:
- Ganges river dolphin most typically makes echolocation sounds such as clicks, bursts, and twitters.
- As the dolphin is blind, it produces an ultrasonic sound that is echoed off other fish and water species which allows it to identify prey.
- Echolocation is used for population counts by using acoustic surveying.