The
Wallace Line or
Wallace's Line is a faunal boundary line drawn in 1859 by the British naturalist
Alfred Russel Wallace that separates the
ecozones of
Asia and
Wallacea, a transitional zone between Asia and
Australia. West of the line are found organisms related to Asiatic species; to the east, a mixture of species of Asian and Australian origin is present. Wallace noticed this clear division during his travels through the
East Indies in the 19th century. The line runs through
Indonesia, between
Borneo and
Sulawesi (Celebes), and through the
Lombok Strait between
Bali and
Lombok. The distance between Bali and Lombok is small, about . The distributions of many
bird species observe the line, since many birds do not cross even the smallest stretches of open ocean water. Some
bats have distributions that cross the line, but other mammals are generally limited to one side or the other; an exception is the
crab-eating macaque. Other groups of plants and animals show differing patterns, but the overall pattern is striking and reasonably consistent.