Other than poaching, what are the possible reasons for the decline in the population of Ganges River Dolphins?
- Construction of dams and barrages on rivers
- Increase in the population of crocodiles in rivers
- Getting trapped in fishing nets accidentally
- Use of synthetic fertilizers and other agricultural chemicals in crop-fields in the vicinity of rivers
Smart Elimination
The question asks for reasons for the "decline". Usually, human interference is the cause of decline. Option 2 (Crocodiles) is a natural relationship that has existed for millions of years without wiping out dolphins. Options 1, 3, and 4 are human-made threats (dams, nets, chemicals). Eliminate Option 2.
Potential Trap
Plausible Distractor: Statement 2 (Crocodiles) sounds like a natural threat. While crocodiles eat aquatic life, they coexist with dolphins. The decline is driven by *anthropogenic* (human) factors, not natural predation.
Answer Key & Explanation
Answer: CThe correct answer is Option C.
Explanation:
- Dams and Barrages: Correct. They fragment the habitat, isolating dolphin populations and preventing migration (essential for breeding).
- Crocodiles: Incorrect. The increase in crocodile population is not a significant documented cause of the drastic decline of River Dolphins. The main threats are human-induced.
- Fishing Nets: Correct. Accidental entanglement (bycatch) is a major cause of mortality.
- Pollution (Fertilizers): Correct. Agricultural runoff and industrial effluents degrade water quality and biomagnify in the food chain.
Value Addition
- Status: Ganges River Dolphin (Platanista gangetica) is the National Aquatic Animal of India.
- Blindness: They are essentially blind and use echolocation (ultrasonic sound) to navigate and hunt (known as 'Susu').
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Foundational question based on core concepts.