Tree-kangaroos are macropods adapted for life in trees. They are found in the rainforests of New Guinea, far northeastern Queensland, and nearby islands, usually in mountainous areas. Although most are found in mountainous areas, several species also occur in lowlands, such as the aptly named Lowlands Tree-kangaroo.
It is understood that tree-kangaroos evolved from creatures similar to modern kangaroos
, as they retain many standard macropod
adaptations to life in the plains—notably the massive hind legs and long, narrow feet which allow orthodox macropods to travel fast and economically on the ground. Tree-kangaroos have developed exceptionally long tails for balance, and stronger forelimbs for climbing. The feet are shorter and wider, they have longer claws on all feet, and rubbery soles for better grip. Unlike orthodox macropods, who can only move by moving both feet at the same time, tree-kangaroos can move their legs independently.
The ancestors of all kangaroos are believed to have been small arboreal marsupials that looked like some of Australia's present-day possums. The earliest macropods diverged from this line when they descended to the ground and evolved bodies adapted for rapid motion over the earth and rocks. Why the ancestors of the tree-kangaroos returned to the trees is not known.
Tree-kangaroos are slow and clumsy on the ground. They move at about walking pace and hop awkwardly, leaning their body far forward to balance the heavy tail. But in trees they are bold and agile. They climb by wrapping the forelimbs around the trunk of a tree and hopping with the powerful hind legs, allowing the forelimbs to slide. They are expert leapers; 9-metre (29.5 feet) downward jumps from one tree to another have been recorded, and they have the extraordinary ability to jump to the ground from 18 metres (59.0 feet) or more without being hurt.
Tree-kangaroos feed mostly on leaves and fruit, taken both in trees and on the ground, but other foods are eaten when available, including grain
, flowers, sap
and young birds. Their teeth are adapted for tearing leaves rather than cutting grass. They have large stomachs that function as fermentation vats in a manner similar to those of eutherian ruminant herbivores
, in which bacteria break down fibrous leaves and grasses. Although the arrangement of the stomach compartments in kangaroos is quite different than eutherian ruminants, the end result is similar.
The following species are assigned to the genus Dendrolagus
- Grizzled Tree-kangaroo, Dendrolagus inustus; northern and western New Guinea, plus the island of Yapen, and possibly Salawati and Waigeo.
- Lumholtz's Tree-kangaroo, Dendrolagus lumholtzi; Queensland, Australia.
- Bennett's Tree-kangaroo, Dendrolagus bennettianus; Queensland, Australia.
- Ursine Tree-kangaroo, Dendrolagus ursinus; Vogelkop, New Guinea.
- Matschie's Tree-kangaroo, Dendrolagus matschiei; Huon Peninsula, New Guinea.
- Doria's Tree-kangaroo, Dendrolagus dorianus; western, central, and southeastern New Guinea.
- Seri's Tree-kangaroo, Dendrolagus stellarum; highlands of west-central New Guinea.
- Goodfellow's Tree-kangaroo, Dendrolagus goodfellowi; central and southeastern New Guinea.
- Golden-mantled Tree-kangaroo, Dendrolagus pulcherrimus; Foja and Torricelli Mountains, New Guinea.
- Lowlands Tree-kangaroo, Dendrolagus spadix; south-western lowlands of Papua New Guinea.
- Dingiso, Dendrolagus mbaiso; highlands of west-central New Guinea
- Tenkile, Dendrolagus scottae; Sandaun Province, New Guinea.
The taxonomy, especially of the Dendrolagus dorianus and Dendrolagus goodfellowi superspecies, is complex. The taxon stellarum was described as a subspecies of the D. dorianus, but some recent authorities have treated it as a species based on its absolute diagnostability. It has further been suggested that the taxon mayri, known only from a single old specimen, may represent a valid species, but as it is virtually unknown, most authorities have retained it as a subspecies of D. dorianus. The case for pulcherrimus is comparable to that of stellarum. It was initially described as a subspecies of Dendrolagus goodfellowi, but recent authorities have elevated it to species status based on its absolute diagnostability. A population of the Tenkile recently discovered from the Bewani Mountains may represent an undescribed subspecies.
- Flannery, Timothy Fridtjof, et al. 1996. Tree Kangaroos: A Curious Natural History. Reed Books, Melbourne. ISBN 0-7301-0492-3