Rhinos may look tough, but their skin is actually quite sensitive. They can sunburn, and biting insects "bug" them. That's why they like to wallow in mud—it puts a layer between their skin and the sun, and insects. Greater one-horned rhinos look as if they are wearing armor, but they are actually covered with a layer of skin that has many folds. Formerly called Indian rhinos, they are native to humid, swampy areas of Northeast India and Nepal. Greater one-horned rhinos are listed as Vulnerable on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species and white rhinos are listed as Near Threatened. Black, Javan, and Sumatran rhinos are all listed as Critically Endangered.