Correct Option
The correct option isOne-horned Rhinoceros
Explanation
The biogeographical distribution of Indian wildlife species based on their specific habitat requirements. The swampy, marshy lands and tall grasslands of the Terai and Brahmaputra basins constitute a distinct ecosystem known as the Terai-Duar savanna and grasslands.
Option Analysis
- Wild Ass Wild Ass: Incorrect. The Indian Wild Ass (Equus hemionus khur) is endemic to the Little Rann of Kutch in Gujarat. Its natural habitat consists of saline deserts, arid grasslands, and shrublands, which are ecologically distinct from the humid swamps of eastern India.
- One-horned Rhinoceros One-horned Rhinoceros: Correct. The Great One-horned Rhinoceros (Rhinoceros unicornis) is specifically adapted to the alluvial plain grasslands and swampy forests. The majority of its population is currently found in Assam (e.g., Kaziranga National Park, Manas National Park) and West Bengal (e.g., Jaldapara National Park, Gorumara National Park).
- Camel: Incorrect. Camels are xerocoles, animals adapted to arid and semi-arid desert environments. They are primarily found in Rajasthan and Gujarat and are physiologically unsuited for marshy, high-humidity terrains.
- Nilgai: Incorrect. The Nilgai (Boselaphus tragocamelus) is the largest Asian antelope and prefers dry areas with short bushes, scattered trees, and grassy plains. While widely distributed across Northern and Central India, it is not the characteristic species of the wet marshlands of Assam and West Bengal.
Key Takeaway: The Great One-horned Rhinoceros is the flagship species of the tall wet grasslands and swamps found in the Brahmaputra valley and the Terai region of India and Nepal.