The correct option is (b) Indian wild ass.
Explanation
The question describes a unique biogeographic zone characterized by saline mudflats and sandy terrain, specifically pointing to the Rann of Kutch in Gujarat. This region serves as the last natural refuge for a specific endemic subspecies.
Analysis of the Description:
- Habitat (Sandy and Saline): The Little Rann of Kutch is a saline desert (salt marsh). This is the exclusive natural habitat of the Indian Wild Ass (Equus hemionus khur).
- Predation Pressure: In this specific open and arid terrain, adult Indian Wild Asses have no significant natural predators. While wolves and hyenas exist in the periphery, they pose little threat to healthy adults due to the animal's speed and stamina.
- Threats: The species is listed as 'Near Threatened' (formerly Endangered). The primary threat to its existence is habitat destruction due to salt panning activities, the expansion of the invasive shrub Prosopis juliflora, and competition with livestock for grazing.
Analysis of Other Options:
- Indian Wild Buffalo: This species inhabits wet grasslands, swamps, and river valleys (e.g., Kaziranga in Assam, Indravati in Chhattisgarh). It requires water-rich environments, not saline deserts.
- Indian Wild Boar: This is a generalist species found in diverse habitats across India, including forests and agricultural fields. It has several natural predators, including tigers and leopards.
- Indian Gazelle (Chinkara): While found in arid and semi-arid regions (such as the Thar Desert), it is not restricted solely to saline flats. It also faces significant predation pressure from wolves, leopards, and jackals.
Key Takeaway: The Indian Wild Ass is endemic to the Little Rann of Kutch (Gujarat). It is adapted to saline deserts and faces threats primarily from habitat loss rather than predation.