Biology Reference
In-Depth Information
Would new species of apes or monkeys be spotted in the Fojas? Would the researchers
need to be vigilant for prowling leopards or tigers? If this were Sumatra, such concerns would
be accurate. Tigers, leopards, apes, and monkeys, however, are part of the Indo-Malayan but
not the Australian faunal realm. New Guinea sits east of what is known as Wallace's Line;
most of the islands west of that demarcation were physically connected to Asia (via a land-
mass known as the Sunda Shelf) during recent glacial periods when sea levels were much
lower than they are today. Asia's large vertebrates had no need to swim across even shallow
waters to reach Sumatra, Java, Borneo, and Bali. They simply walked.
Technically, Wallace's Line falls between the islands of Bali and Lombok and divides the
Indonesian archipelago in two. Alfred Russel Wallace was the first to identify this natural
longitude, so the name celebrates his insight. On the western side of Wallace's Line live an-
imals of largely Asian origin; on the eastern side are those common to Australia, to which
New Guinea was at times connected (to the Sahul Shelf) by a land bridge over the Torres
Strait prior to about 20,000 years ago. The lack of land bridges spanning Wallace's Line and
the presence of deep ocean trenches precluded the mixing of faunas. The simple fact is that
most mammals are poor long-distance swimmers, and they can't drink seawater. So even
those that managed to hitch rides on floating mats of vegetation—natural rafts—would have
died of dehydration before they reached land. In New Guinea, then, birds of paradise and tree
kangaroos would be evident, but no orangutans, gibbons, macaques, or leaf monkeys ever ar-
rived there. The range of large terrestrial carnivores also stopped farther west, in Bali (tigers)
and Borneo (clouded leopards), because they too could not cross deep water. Absent as well
would be the giant herbivores, such as tapirs and wild cattle, that the big cats prey upon.
