There are two primary zoogeographical zones in Indonesia: Sundaland in the west and Wallacea in the east. These are divided by the Wallace Line, an imaginary line that runs between Borneo and Sulawesi. West of the line are found mostly Asian-related species, to the east, Australian species. In all, about half of Indonesia is uninhabited, mostly occupied by rainforest.
In Sundaland, there are 381 native mammal species, with 173 being endemic. During past Ice Ages, the sea level in the area was low enough that animals could travel from the Asian mainland to the islands. Thus, tiger, rhino, elephant, and leopard can be found here. The most famous species endemic to Indonesia, the orangutan, can be found on Borneo and Sumatra, where they make up two separate species. These orange great apes are highly intelligent tool users, but they are endangered by human activity and habitat destruction. The beautiful Sumatran Tiger, the smallest tiger species, can be found ion spots over the island, where it numbers only 500 individuals.
Two other species endemic to Indonesia are the Sumatran and Javan rhinoceros, two of the rarest and most endangered large mammal species in the world. They have long been hunted for their horns, which have value in Chinese medicine. There are only about 300 Sumatran rhinos and just 60 Javan rhinos. Substantial conservation effort will be needed to ensure that these species recover their populations. The process could take centuries.
Bekantan (Nasalis Larvatus)
Other species endemic to Indonesia are found in Wallacea, the region east of the Wallace Line. Wallacea has 126 endemic species, including seven species of macaque monkey, five species of tarsier, the anoa, a rare subgenus of buffalo, and the babirusa, a pig-like animal with two sets of curving horns. On the island of New Guinea are species endemic to Indonesia, such as the bizzare Goodfellow's Tree-kangaroo, numerous species of rodents, some a foot long, the beautiful Papuan Hornbill, and the famous Komodo Dragon, the largest living lizard. As the only native placental mammals are bats and mice, other species, such as the Komodo Dragon, have adopted the niches which would have otherwise been adopted by large placentals.