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Monjon
The Monjon. (Image: © Jiri Lochman/ Lochman Transparencies)
Prince Regent River
Prince Regent River showing rugged and fractured King Leopold sandstone providing habitat to the Monjon and other Rock-wallabies.
Geographic distribution of the Monjon
Geographic distribution of the Monjon represented by coverage of 1:250,000 map sheets of Australia (see www.ga.gov.au for Australian maps).
 
 
 
 
 
 
 
 
 
 

General information

Kangaroos are marsupials and belong to the Family Macropodidae (i.e. big feet) that is grouped with the Potoroidae (potoroos, bettongs, rat-kangaroos) and Hypsiprymnodontidae (musky rat-kangaroo) in the Super-Family, Macropodoidea. This comprises around 50 species in Australia and a dozen or more in New Guinea.  Some of the smaller species, such as Yellow-footed Rock-Wallabies, Burrowing Bettongs, accompanied Pig-footed and Golden Bandicoots, Bilbies and possibly Hairy-nosed Wombats into extinction with the advent of pastoralism. However, the largest species remain in much of their original range with the grey kangaroos expanding inland as grazing habitat increased and coastal habitat was lost in clearance for agriculture. The defining feature of the kangaroo family is that they are the largest vertebrates to hop (both currently and from what we know from palaeontology).

 

The Rock-wallabies (Petrogale spp.) is the most diverse genus amongst the living macropods with 16 species ranging from 1 to 12 kg in size. They are found across mainland Australia and on some recently separated offshore islands but not on the Bass Strait Islands, Tasmania or New Guinea. The species diversified from a common ancestor about 4 million years ago and their closest affinity to other macropods is with the Tree-kangaroos. Diversification of species occurred in two waves. The first gave rise to the Short-eared Rock-wallaby, the Monjon, the Narbelek, the Yellow-footed Rock-Wallaby and the Proserpine Rock-wallaby. The second was about a million years ago and lead to species that are not all morphologically distinctive like those along the Queensland seaboard. All Rock-wallabies favour habitat with rocky outcrops and slopes, cliffs and gorges or are found on boulder piles and escarpments especially in the wet-dry tropics. Their ability to scale precipitous rock faces in leaps that appear to defy gravity comes from adaptations to the feet and tail. The feet are short relative to the majority of macropods that inhabit flat ground. The pads are thick, spongy and highly granulated so that they compress on the rock surface and maximise grip. The tail is long and cylindrical with little taper and great flexibility. The tail acts as a counterbalance and rudder in rapid hopping across uneven surfaces and allows changes of direction in mid-air.

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Species

Monjon

Petrogale burbidgei ('Burbidge's rock-weasel')

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Best place to see

Prince Regent Nature Reserve, Western Australia

The Prince Regent Nature Reserve covers more than 600 000 hectares of wilderness in the Ngauwudu Management area of the Kimberley in Western Australia. It is contiguous with the Mitchell Plateau National Park to the north which has some rangers and guidance for visitors including walks and bush camping areas. All visitors to this area must be self-sufficient and access is limited to a very few 4WD tracks. Access to the Nature Reserve is by air or boat. There are no roads and a permit is required from Conservation and Land Management if you wish to enter the area. Some of its spectacular sites include King's Cascade, Mount Trafalgar, Python Cliffs, Pitta Gorge, and the Prince Regent River which runs  between near vertical cliffs. The Reserve harbours more than half the mammal and bird species found in the Kimberley and more than 500 species of plants. This part of the Kimberley is the only part of mainland Western Australia where no extinctions are known since European settlement. The area is about 16 h from Kununurra with the nearest towns being Derby to the south-west and Wyndham to the north-east.

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Identification

The Monjon is the smallest of the Rock-wallabies (and the Macropodidae) with a weight range of  1 - 1.4 kg and average weight of 1.3 kg.

The fur is soft and the general colour of the back is brown-grey with tawny and black marbling that darkens towards the rump.  The base of the fur is a charcoal black.  The face and sides of the neck are  a pale brown to buff colour, which extends part way down the centre of the back.  There is an indistinct grey head-stripe down to the nape.  The tip of the nose is covered with very short hair on the upper part whereas the lower part is naked and black.  There is very sparse pale fur on the short dark ears and the insides of the ears are almost naked.  The shoulders are marked by a small dark patch or stripe.  The sides of the legs are pale-brown or grey, and  the fore arms and feet are grey with a pale brown tinge.  The undersides are pale grey with white-tipped hairs.  The tail is a light grey-brown. There is a pronounced dark brown to black brush on the tail tip with long hairs on the distal third to half of the tail.

The Monjon is difficult to distinguish in the field from the Narbalek but does not seem to inhabit the same locations. The main characters that differentiate the species apart from their teeth (unique molars in the Narbalek) are the shorter ears and feet of the Monjon.

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Habitat

The Monjon lives in one of the most remote parts of Australia and was only discovered by taxonomists in 1976. It is found in the highly dissected sandstone plateaus and gorge of the King Leopold region of the Kimberley. It is also found on some offshore islands in the Bonaparte Archipelago including Bigge, Katers and Boongaree Islands. Interestingly they are not sympatric with Narbalek amongst the Bonaparte Islands but do co-occur in the Mitchell Plateau on the mainland.

 

Monjon shelter is shallow caves and crevices during the day and forage in adjacent vegetation. This may be a low open woodland of Eucalypts like tropical woolybutts and stringybarks, interspersed by Acacias, Figs and deciduous tropical trees. Or they may forage in vines thickets growing amongst boulders. In most locations there is an understorey of spinifex (Plectrachne spp.).

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Foraging behaviour

The diet of the Monjon has not been studied but includes dry leaves and presumably higher quality items like fruits and flowers.

 

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Reproductive behaviour

The Rock-wallabies have a common pattern of post-partum oestrus and probably all are capable of embryonic diapause. Breeding is usually continuous but may be seasonal in the wet-dry tropics. For the Monjon, similar sized small pouch young have been recorded in August-October suggesting some synchrony in births and pouch exit at the onset of the Wet.

 

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Social organisation

The behaviour of the Monjon has been little studied because of their remote habitat, nocturnal activity and small and cryptic size. However, they may be curious and approach people in some localities and so may be the subject of future behavioural study.

 

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Further readings

Campeau-Peloquin A, Kirsch JAW, Eldridge MDB, Lapointe FJ (2001) Phylogeny of the rock-wallabies, Petrogale (Marsupialia: Macropodidae) based on DNA/DNA hybridisation. Australian Journal Of Zoology 49, 463-486.

Freeland WJ, Winter JW, Raskin S (1988) Australian Rock-Mammals: A Phenomenon of the Seasonally Dry Tropics. Biotropica 20, 70-79.

Kitchener DJ, Sanson GD (1978) Petrogale burbidgei (Marsupialia: Macropodidae), a new rock wallaby from the Kimberley, Western Australia. Records Of The Western Australian Museum 6, 269-285.

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