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Dendrolagus inustusgrizzled tree kangaroo

By Yan-Iuan Ho

Geographic Range

The distribution of Dendrolagus inustus includes northern and western New Guinea. It ranges from the Vogelkop and Fak Fak Peninsula to the north coast of Papua New Guinea. There are also unconfirmed reports of D. inustus in Salawati, Irian Japen, and the Waigeo Islands. (Flannery, 1995a; Flannery, 1995b; Nowak, 1997)

Habitat

Grizzled tree kangaroos inhabit a broad spectrum of habitats. Most records are from primary forests. ("Nature Conservation in Indonesia", 1998; Flannery, 1995b; Nowak, 1997)

  • Range elevation
    100 to 1400 m
    328.08 to 4593.18 ft

Physical Description

The body of D. inustus is stern-heavy with a small head and flat muzzle. Grizzled tree kangaroos bear a close resemblance to forest and plains kangaroos and are often mistaken as terrestrial mammals. They have very long hindlegs and forelegs and long hind feet in comparison to other arboreal mammals but they are relatively short compared to kangaroos. The fourth toe is usually longer than the others. They also possess powerful arms and long curved claws to help them climb and move from tree to tree. The grizzled coloration of D. inustus distinguishes them from other tree kangaroos. The coat is slate gray to chocolate brown and of medium length. The thick fur on the shoulders grows in a reverse direction and acts as a natural water shedding device. This characteristic is shared by their tree kangaroo relatives in Australia. Grizzled tree kangaroos have distinct black ears on a gray head and have toes and a tail that is usually dark. The tail is bushy and uniform in thickness, but often hairless at the base. The tail is often used as a balancing organ, bracing the animal when climbing, although it is not prehensile. It has been recorded at an average length of 75-90 cm. The inside surface of the ears are also hairless. Grizzled tree kangaroos are sexually dimorphic, the males being much larger than the females. ("Tree Kangaroos", 1990; Flannery, 1995a; Flannery, 1995b; Walker, 1964)

  • Sexual Dimorphism
  • male larger
  • Range mass
    8 to 15 kg
    17.62 to 33.04 lb
  • Range length
    80 to 90 cm
    31.50 to 35.43 in

Reproduction

There is not much known about the mating systems of D. inustus but their relative in Australia, Dendrolagus lumholtzi, is known to be polygynous. A male investigates a receptive female by standing in front of her, making soft clucking sounds, and pawing gently at her head and shoulders. When the female moves away, the male follows and paws at the base of her tail. Also in the other tree kangaroo species of Australia, Dendrolagus bennettianus, males are very territorial with other males but their territory often overlaps with several females, leading to the idea that they are polygynous. Captive specimens have shown that in the presence of a female, two males fight competitively, but without the female they live in peace. (Strahan, 1995)

It is believed that the breeding of D. inustus is non-seasonal. Also, the females give birth soon after a young leaves the pouch, and before the older young becomes independent. The number of offspring is usually one, but on extremely rare cases, twins occur. Sexual maturity is reached at 8.5 to 10.6 kg in weight for females and 12 kg for males. Males continue to grow throughout their lifetime, growing to weights of 17 kg. The females of D. bennettianus breed annually and the pouch life is around 9 months. The young is known to live with the mother up to 2 years. ("Tree Kangaroos", 1990; Flannery, 1995b)

  • Breeding season
    This species breeds year-round.
  • Range number of offspring
    1 to 2
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Average weaning age
    8-9 months
  • Range time to independence
    2 (high) years
  • Average age at sexual or reproductive maturity (female)
    2 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    510 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    2 years

Not much is known about the parental investment of D. inustus. Like all kangaroos, females protect and nurse their young while they develop in the pouch. Female D. inustus will protect their offsrping for up to two years.

  • Parental Investment
  • altricial
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

The lifespan of D. inustus is up to 10 years. ("Tree Kangaroos", 1990)

  • Typical lifespan
    Status: wild
    10 (high) years

Behavior

Grizzled tree kangaroos are very agile in trees and travel from tree to tree by leaping. They are believed to belong to a primitive group of tree-kangaroos because their hind limb morphology that is less adapted for arboreal behavior than in realted species. When leaping from tree to tree, they always flee downward, so are easily and often captured by hunters who grab their tail as they flee. They prefer sleeping on strong, horizontal branches and spend most of their lives in trees, but they do frequently come to the ground. On the ground, D. inustus is able to hop on its long hind legs, although not very gracefully. The tail is held off the ground and the body moves forward to counterbalance it. It is not known if it is a solitary or social species, but D. lumholtzi and D. bennettianus are both solitary species. ("Tree Kangaroos", 1990; Flannery, 1995b; Strahan, 1995; Walker, 1964)

Home Range

There is not much information of the home range of D. inustus

Communication and Perception

There is not much known about how D. inustus communicates with others or perceives the environment. Presumably, it relies on visual and tactile cues to aid its arboreal lifestyle.

  • Communication Channels
  • visual

Food Habits

The main food sources in the wild for D. inustus are leaves, fruit, and soft bark. Grizzled tree kangaroos in captivity do not eat animal protein such as chicken, but they do eat mealworms and boiled eggs. In zoos, they are fed carrots, bananas, etc. ("Tree Kangaroos", 1990; Flannery, 1995b)

  • Plant Foods
  • leaves
  • wood, bark, or stems
  • fruit

Predation

The predators of D. inustus are unknown. ("Tree Kangaroos", 1990)

Ecosystem Roles

There is little information of how D. inustus play a roles in the ecosystem. As herbivores, they may limit plant populations.

Economic Importance for Humans: Positive

It is known that D. inustus are important as game for hunters; possibly for food but most likely for the pet trade. Grizzled tree kangaroos are also used in science for research. There is one case studied where a female grizzled tree kangaroo died from systemic arterial calcinosis, a disease resembling arteriosclerosis of the Monckeberg type in man. There is little information describing cardiovascular disorders in marsupials, therefore this case is of special interest. (Flannery, 1995b; Schoon, et al., 1985)

Economic Importance for Humans: Negative

There is little information pertaining negative effects on humans.

Conservation Status

Grizzled tree kangaroos are commonly kept as pets. They are also hunted intensively, often killed before reaching maximum size. They are also over exploited due to growing human population. (Flannery, 1995b)

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Yan-Iuan Ho (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Australian

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

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

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

embryonic diapause

At about the time a female gives birth (e.g. in most kangaroo species), she also becomes receptive and mates. Embryos produced at this mating develop only as far as a hollow ball of cells (the blastocyst) and then become quiescent, entering a state of suspended animation or embryonic diapause. The hormonal signal (prolactin) which blocks further development of the blastocyst is produced in response to the sucking stimulus from the young in the pouch. When sucking decreases as the young begins to eat other food and to leave the pouch, or if the young is lost from the pouch, the quiescent blastocyst resumes development, the embryo is born, and the cycle begins again. (Macdonald 1984)

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.

food

A substance that provides both nutrients and energy to a living thing.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

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.

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

sexual

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

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

References

1998. "Nature Conservation in Indonesia" (On-line). Accessed March 30, 2004 at http://users.bart.nl/~edcolijn/diproto.html.

1990. Tree Kangaroos. Pp. 390-392 in S Parker, ed. Grzimek's Encyclopedia of Mammals, Vol. Volume 1, 1 Edition. New York: McGraw-Hill Publishing Company.

Flannery, T. 1995. Mammals of New Guinea. Australia: Reed Books.

Flannery, T. 1995. Mammals of the South-West Pacific and Moluccan Islands. Australia: Reed Books.

Ganslosser, U. 1977. Observationss on behavior of doria tree kangaroos and grizzled grey tree kangaroos in zoological gardens. Zoologischer Anzeiger, 198 (5-6): 393-412.

Nowak, R. 1997. "Walker's Mammals of the World 5.1" (On-line). Accessed March 30, 2004 at http://www.press.jhu.edu/books/walkers_mammals_of_the_world/marsupialia/marsupialia.macropodidae.dendrolagus.html.

Schoon, H., M. Rosenbrunch, G. Ruempler. 1985. Systemic arteria calcinosis in a grey tree kangaroo Dendrolagus inustus, resembling Monckeberg type arteriosclerosis in man. Journal of Comparative Pathology, 95 (3): 319-324.

Strahan, R. 1995. The Mammals of Australia. Australia: Reed Books.

Walker, E. 1964. Mammals of the World Volume 1. Baltimore: The Johns Hopkins Press.

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