The separation between the North and South Pacific land masses is known as the Wallace Line, after the naturalist who first noticed the essential differentiation between marsupial and non-marsupial mammals in the region.
The birds and reptiles of Papua New Guinea are also mostly from this side of the Wallace line. The flora, conversely, is predominantly South East Asian. However, both flora and fauna have evolved long enough in this part of the world to become distinct species with unique features. There are more than 700 species of birds and over 150 species of mammals.
Many Papua New Guinea birds are restricted to the lowland forest areas, where a typical square kilometre may support no less than 150 species. An unusually large proportion of them are fruit- or nectar -eaters, nearly twice as many as in comparable lowland forest areas of the South American continent. Perhaps the best known of all Papua New Guinea’s birds is its national emblem, the splendid Raggiana Bird of Paradise Raggiana Paradisaea. All in all, there are thirty eight species of birds of paradise here, their plumage ranging from pure black to red, orange and irridescent green. Hardly less striking in appearance are the over three hundred species of parrot, lory and cockatoo. New Guinea parrots range in size from the pygmy-parrots to the huge Palm Cockatoo, nearly ten times larger.
PNG also boasts eleven species of the renowned bowerbird, nine of which can be found in the wooded highland areas and the other two on lowland grassland and savanna.In most of these species, it is the male who builds a sophisticated nest or ‘bower’ and decorates it with flowers and berries. The large flightless cassowary, standing at anywhere from 1.3 – 1.7 metres tall and weighing up to 60 kg, is particularly valued in PNG, both for its meat and its feathers. Various species of kookaburra and kingfisher abound, though most of the latter rarely go near water or feed on fish like their counterparts elsewhere in the world. Although many of the birds in PNG are sedentary, a number migrate from nearby Australia and some from much further afield. The largest group of migrants are the waders and seabirds, but the variety is enormous. PNG is truly a birdwatchers paradise.
In addition to its large number of birds, PNG has nearly two hundred indigenous species of mammals, only about one third less than the whole of the Australian continent. Most of these are marsupial, the largest being a type of tree kangaroo known as the tenkile, a full-grown male weighing up 20 kg. One of the best-known species of mammal, the cuscus, can be found in the remote lowland forest areas. There are over fifty species of bat, several species of wallaby and Raffray bandicoot, one of the largest in the world. There two species of crocodile, freshwater and saltwater.
Among the ninety species of snake, forty three of which are poisonous but only seven that are regarded as deadly, are the death adder, a variety of Papuan Taipans (with one of the most potent toxins of any snake in the world) and a host of smaller species. The non-poisonous snakes include the pythons and boas, the largest measuring eight metres. Nearly two hundred types of lizard inhabit the mainland and the islands and fall mainly into four groups: monitors, dragons, geckos and skinks. The Salvadori Dragon, at nearly four metres, is the longer even than the Komodo Dragon of Indonesia which makes it the longest lizard in the world and one of the Bougainville skinks has a prehensile tail and grows to a length of nearly one metre. Among the several hundred species of spider, only two are dangerous to humans, the huge Bird-Eating Spider, and the smaller Redback Spider. similar in appearance to the South American Tarantula, but quite harmless to human beings. There are hundreds of indigenous species of moths and butterflies. The reddish-brown male Hercules Moth with its long, distinctive tail-like hind wings is the largest known moth and the famous Queen Alexandra are even larger with a wingspan of up to twenty seven centimetres. Exquisitely coloured, they are a marvel to the eye.