Dolphins: Intelligence, Social Behaviour & Conservation in India

Subject: GS 3: Environment

Context: A viral video of a dolphin carrying its dead calf has renewed global attention on dolphins’ intelligence, social behaviour, and conservation.

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About Dolphins

• Dolphins are highly intelligent aquatic mammals belonging to the order Cetacea and suborder Odontoceti (toothed whales), with more than 40 species distributed across marine and freshwater ecosystems.
• Distribution
• • Marine Habitat: Most dolphin species inhabit tropical, subtropical and temperate oceans, while some occur in cold subpolar waters.
  • Freshwater Habitat: A few specialised species are restricted to major river systems such as the Ganga, Indus, Amazon, Orinoco, Mekong and Ayeyarwady.
• Key Features
  • Physical Characteristics: Dolphins possess streamlined bodies, horizontal tail flukes, pectoral flippers, a dorsal fin and a blowhole, enabling efficient swimming and air breathing, while the melon helps focus echolocation signals.
  • Diet: Dolphins are carnivorous predators feeding mainly on fish and squid, while some coastal and riverine species also consume crustaceans, molluscs and other aquatic organisms.
  • Communication: Dolphins communicate through whistles, clicks and body movements, and use echolocation to navigate, locate prey and identify objects in murky or deep waters.
  • Social Behaviour: Dolphins live in cooperative social groups called pods, displaying complex behaviours such as coordinated hunting, calf care, defence against predators and evidence of empathy and grief.
• Conservation Status: Depending on the specific species, a dolphin’s conservation status on the IUCN Red List ranges from Least Concern to Critically Endangered.

Types of Dolphins (UPSC prelims 2019, 2015)

• Marine Dolphins
• • Coastal/Inshore Dolphins: Inhabit coastal waters, estuaries and bays; examples include the Common Bottlenose Dolphin (Least Concern) and Indo-Pacific Humpback Dolphin (Vulnerable).

• • Pelagic Dolphins: Occupy the open ocean and often form large groups; examples include the Spinner Dolphin (Least Concern), Striped Dolphin (Least Concern), and Pantropical Spotted Dolphin (Least Concern).
  • Blackfish (Large Delphinids): Large-bodied dolphins include the Orca/Killer Whale (Least Concern), Pilot Whales (Near Threatened), and False Killer Whale (Near Threatened).
• River Dolphins
  • Ganges River Dolphin: Found in the  Ganga–Brahmaputra–Meghna River System and Chambal river of India, Nepal and Bangladesh.
    • It is also the national aquatic animal of India
    • Protection Status: 
      • IUCN Status: Endangered
      • Wildlife (Protection) Act, 1972: Schedule I 
      • CITES: Appendix 
  • Indus River Dolphin: Occurs in the Indus River basin of Pakistan and the Beas River in India; IUCN Status: Endangered.
  • Amazon River Dolphin (Boto): Distributed in the Amazon and Orinoco river basins of South America; IUCN Status: Endangered.
  • Irrawaddy Dolphin: Found in the Ayeyarwady, Mekong and Mahakam river systems and estuarine waters; IUCN Status: Endangered.
  • Tucuxi: A freshwater dolphin of the Amazon River basin belonging to the marine dolphin family; IUCN Status: Endangered.
  • Franciscana (La Plata Dolphin): Occurs in the coastal waters and estuaries of Brazil, Uruguay and Argentina; IUCN Status: Vulnerable.
  • Baiji (Chinese River Dolphin): Formerly endemic to the Yangtze River in China and now considered Extinct (functionally extinct; IUCN lists it as Critically Endangered–Possibly Extinct

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