Which of the following is not correct regarding the Ganges river dolph...
- The Gangetic river system is home to a vast variety of aquatic life, including the Gangetic dolphin (Platanista gangetica). The Gangetic dolphin is one of five species of river dolphin found around the world. It is found mainly in the Indian subcontinent, particularly in Ganga-Brahmaputra-Meghna and Karnaphuli-Sangu river systems.
- There are currently two species of river dolphins inhabiting India, the Ganges River Dolphin (Platanista gangetica) and the Indus River Dolphin (Platanista minor). Hence, option (d) is not correct.
- Ganges river dolphins once lived in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh. But the species is extinct from most of its early distribution ranges.
- The Ganges river dolphin can only live in freshwater and is essentially blind. They hunt by emitting ultrasonic sounds, which bounces off of fish and other prey, enabling them to “see” an image in their mind. It was found “no sighting record for Gangetic dolphin in waterways wherever the salinity level crosses 10 parts per trillion (ppt)”. The researchers believe that rise in salinity in the eastern and central region of Sundarbans has affected the habitat of species.
- They are frequently found alone or in small groups, and generally a mother and calf travel together. Females are larger than males and give birth once every two to three years to only one calf.
Which of the following is not correct regarding the Ganges river dolph...
The correct answer is option 'D': It is not correct to say that the Ganges river dolphin is the only species of river dolphin found in India.
Here is an explanation of each option:
a) Ganges river dolphins primarily live in freshwater: This statement is correct. The Ganges river dolphin, also known as the Gangetic dolphin or the South Asian river dolphin, is a freshwater dolphin species found in the rivers of India, Bangladesh, and Nepal. They are primarily found in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems.
b) Ganges river dolphins are essentially blind and hunt by emitting ultrasonic sounds: This statement is correct. Ganges river dolphins have small, non-functional eyes and rely heavily on echolocation to navigate and hunt in their aquatic environment. They emit ultrasonic sounds that bounce off objects in the water, allowing them to locate prey and navigate their surroundings.
c) Female Ganges dolphins are larger than males: This statement is incorrect. In the case of Ganges river dolphins, males are larger than females. Adult males typically range from 2 to 2.6 meters in length, while adult females are generally smaller, ranging from 1.8 to 2.2 meters. Males also tend to have larger and more curved dorsal fins compared to females.
d) It is the only species of river dolphin found in India: This statement is incorrect. While the Ganges river dolphin is indeed found in India, it is not the only species of river dolphin found in the country. The Indus river dolphin, also known as the Indus blind dolphin, is another species of river dolphin found in India. It is primarily found in the Indus river system in Pakistan and India.
In conclusion, the correct answer is option 'D' because the Ganges river dolphin is not the only species of river dolphin found in India.
To make sure you are not studying endlessly, EduRev has designed UPSC study material, with Structured Courses, Videos, & Test Series. Plus get personalized analysis, doubt solving and improvement plans to achieve a great score in UPSC.