Rottnest Island (known as Wadjemup to the local Noongat people, and otherwise colloquially known as Rotto) is an island off the coast of Western Australia, located 18 kilometres (11 mi) west of Fremantle. A sandy, low-lying island formed on a base of limestone, Rottnest is an A-class reserve, the highest level of protection afforded to public land. Rottnest is a popular holiday destination, and there are daily ferry services to Perth, the state’s capital and largest city. It has a permanent population of around 100 people, with around 500,000 annual visitors (and up to 15,000 visitors during periods). Rottnest is perhaps best known for its population of quokkas, a small native marsupial found in very few other locations. The island also includes colonies of Australian sea lions and southern fur seals. A number of native and introduced bird species nest near the shallow salt lakes in the island’s interior, and Rottnest has consequently been designated an Important bird area.