Dendrolagus bennettianusBennett's tree kangaroo

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Geographic Range

Bennett's tree-kangaroo, Dendrolagus bennettianus, is endemic to tropical rainforests in northeastern Queensland, Australia. Its range is very limited, extending from the Daintree River in the south to Mt. Amos in the north and Mt. Windsor in the west (Newell, 1999), an area covering less than 4000 square-kilometers (Martin, 1995).

Habitat

Within their range, Dendrolagus bennettianus inhabit highland rainforest down to lowland riparian forests (Newell, 1999). They are usually found in the canopy, but will locomote terrestrially to travel within their territory or consume leaves and fruit that have fallen to the ground (Martin and Johnson, 1995).

Physical Description

Though similar in overall form to kangaroos, wallabies, and other macropods, when compared with these terrestrial kangaroos, Dendrolagus has longer forelimbs and shorter hindlimbs (Martin and Johnson, 1995) so that the limbs are of similar proportions (Grzimek, 1990).

The largest of Australia's arboreal mammals (Martin, 1995), Dendrolagus bennettianus exhibits sexual dimorphism in size, with males weighing 11.5-13.7 kg, and females weighing 8-10.6 kg. The non-prehensile tail (730-800 mm females, 820-840 mm males) is longer than head and body length (690-705 mm females, 720-750 mm males), of uniform width (Martin and Johnson, 1995), and used as a counterbalance (Grzimek, 1990).

With mostly dark brown pelage, the chin, throat, and belly are lighter in D. bennettianus. It also has black feet, a greyish forehead, and rusty tint to its snout, shoulders, neck, and back of the head. The tail is marked at the base with a black patch, and dorsally with a light patch. (Martin and Johnson, 1995).

  • Range mass
    8 to 14 kg
    17.62 to 30.84 lb
  • Average mass
    10.5 kg
    23.13 lb

Reproduction

Whereas certain species of tree-kangaroo, such as Dendrolagus matschiei, have been successfully bred and studied in captivity, most are little studied so that reproductive behavior and processes are poorly understood.

Females breed annually (Martin and Johnson, 1995), producing one young per litter (Grzimek, 1990). Young accompany their mothers for up to two years (Martin and Johnson, 1995), of which the first nine months is spent in the pouch. Females may exhibit embryonic diapause or quiescence (Martin and Johnson, 1995), in which case quiescence is most likely lactational, as with other macropods. Living in tropical rainforest with little differentiation between seasons, Dendrolagus are not likely to be seasonal breeders, and, instead, are probably opportunistic breeders (Tyndale-Biscoe and Renfree, 1987).

Joeys typically remain with their mothers until developing into sub-adults, usually weighing over 5 kg. Adult males usually only contact juveniles when consorting with adult females, although males accompanying juveniles have been observed after the loss of the mother (Martin, 1995). Mating appears to be polygynous, with the territories of several females encompassed by that of a single male (Martin and Johnson, 1995).

Captive tree-kangaroos (e.g. D. matschiei and D. goodfellowi) have lived and remained reproductively capable for over 20 years, though this is probably more than exhibited in the wild. It is estimated that Dendrolagus may ideally produce 6 offspring in a lifetime. (Newell, 1999)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    1
    AnAge

Behavior

Very wary and predominantly nocturnal, Dendrolagus bennettianus forage and navigate their territories largely at night (Martin and Johnson, 1995). Though secondarily adapted to an arboreal lifestyle, tree-kangaroos are quite agile and mobile in the canopy, able to leap 9 meters downward to the branch of an adjoining tree, and make use of their tail as a counterbalance when locomoting along branches. Dendrolagus can even drop up to 18 meters to the ground without injury. Descending down tree trunks, Dendrolagus will usually back down. Once on the ground, they are still able to move about capably, hopping with the body leaning forward and the tail arched upward (Grzimek, 1990).

One of the few distinctly territorial macropods, adult males will maintain territories up to 25 hectares, overlapping the territories of several females, which also maintain discrete territories. Abundances of up to 0.3 D. bennettianus per hectare can be supported by preferable habitats. Virtually all adult males carry scars from numerous intense, territorial conflicts, some even missing ears. Though solitary, adult males will often come within the vicinity of a female while navigating their territories, especially near food trees (Martin and Johnson, 1995). The territories of adult females do not overlap. Individual females are solitary escept when accompanied by one or two young or interacting with an adult male (Martin, 1995).

Territories are usually centered around large trees used to roost diurnally. These roosts are left at night for foraging amongst preferred feed trees, which are often found toward the edge of closed forest areas. During the day, D. bennettianus is very cryptic, sitting high within the canopy, often hidden by vines (Martin, 1995). They will also sun themselves atop the canopy, sitting upon vines, also hiding them from view from below (Martin and Johnson, 1995).

Communication and Perception

Food Habits

Dendrolagus bennettianus exhibits mostly folivory, particularly favoring trees such as Ganophyllum, Aidia, and Schefflera, the vine Pisonia, and the fern Platycerium (Martin and Johnson, 1995). Fruit is also taken, when available (Martin and Johnson, 1995), both arboreally and terrestrially (Grzimek, 1990). Food trees are defended within territories, where preferred ones are visited regularly (Martin, 1995).

Economic Importance for Humans: Positive

Though mostly inhabiting protected areas delineated by the Wet Tropics World Heritage Area, Dendrolagus bennettianus is susceptible to hunting from aboriginal tribes in the area. Hunting, including that of tree-kangaroos, is important to some local tribes both for sustenance and for cultural reasons (Newell, 1999).

Economic Importance for Humans: Negative

Bennett's tree-kangaroos, being rare and extremely elusive, seldom come in contact with humans, the main factor that makes them difficult to study (Martin and Johnson, 1995). Their range is largely encompassed by the limits set by the Wet Tropics World Heritage Area (WTWHA), and so their foraging does not extend into human-inhabited areas to cause agricultural or other problems for humans (Newell, 1999).

Conservation Status

(Wilson and Reeder, 1993)

Though quite rare and probably with relatively small total population numbers, virtually all Dendrolagus bennettianus inhabit protected areas. Their most dangerous potential threat, hunting by humans, is quite limited, and poses no immediate risk of hampering survival of this species. Dendrolagus bennettianus actually appears to be expanding its utilized habitats within its range, with the modern decline in aboriginal hunting, dispersing from montane highlands to lower elevation forest habitats (Newell, 1999). Previously, hunting drove them to the mountains, where taboos apparantly prevented further pursuit by humans (Martin, 1995) (Martin and Johnson, 1995).

Areas of deforestation and habitat interruption by roads, however, undoubtedly have a negative impact on Dendrolagus populations, however. Though deforestation does not seem to have direct, immediate impact on populations, the resulting fragmentation of habitats leaves Dendrolagus more susceptible to terrestrial predation. Intended "safe" passageways to allow animals to avoid roads do not seem to work well for tree-kangaroos, due to preferred routes within territories and their large body size relative to other local arboreal mammals. (Newell, 1999)

Other Comments

Dendrolagus bennettianus appears to enjoy relatively little threat of predation, being the largest of Australian arboreal mammals. Its main predators, other than humans, are dingos (/Canis lupus dingo/) and the Amethystine Python (/Morelia amethistina/) (Martin and Johnson, 1995). These two species pose significant threats in their own right, but do not appear to have necessitated a greater rate of reproductive output in Bennett's tree-kangaroo (Martin, 1995).

Contributors

Hien Nguyen (author), University of California, Berkeley, James Patton (editor), University of California, Berkeley.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Grzimek, B. 1990. Grzimek's Encyclopedia of Mammals. New York: McGraw Hill Publishing Company.

Martin, R., P. Johnson. 1995. Bennett's Tree-kangaroo. Pp. 307-308 in R Straham, ed. Mammals of Australia. Washington, DC: Smithsonian Institute Press.

Martin, R. 1995. Field observation of predation on Bennett's Tree-kangaroo (Dendrolagus bennettianus) by an Amethystine Python (Morelia amethistina). Herpetological Review, 26(2): 74-76.

Newell, G. 1999. Australia's tree-kangaroos: current issues in their conservation. Biological Conservation, 87: 1-12.

Tyndale-Biscoe, H., M. Renfree. 1987. Reproductive physiology of marsupials. Cambridge: Cambridge University Press.

Wilson, D., D. Reeder. 1993. Mammal Species of the World: a taxonomic and geographic reference. Washington, DC: Smithsonian Institution Press.