| Nabarlek | |
|---|---|
 | |
| Petrogale cocinna by John Gould andH. C. Richter,Mammals of Australia (1863) | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Infraclass: | Marsupialia |
| Order: | Diprotodontia |
| Family: | Macropodidae |
| Genus: | Petrogale |
| Species: | P. concinna |
| Binomial name | |
| Petrogale concinna | |
 | |
| Distribution within Australia (green) | |
| Synonyms | |
| |
Thenabarlek (Petrogale concinna) is a small species ofmacropod found in northernAustralia. They are a shy and nocturnal animal that resides in rocky hollows and forages in the surrounding area. Their diet is grasses, sedges, and ferns found in and around their scrub covered refuges. They are distinguished by a reddish tinge to the mostly grey fur and a distinct stripe at the cheek. They move with great speed and agility when observed, with a forward leaning posture and a bushy tail that arches over the back.
The name comes from theKunwinjku language of WestArnhem Land.[3] The animal has also lent its name to the music rock group from the area,Nabarlek[citation needed] andGwendolyne Stevens'uranium mine.[4]
John Gould presented a description of this species to theZoological Society of London in 1842, which was published in itsProceedings and introduced by the presiding chairWilliam Yarrell as "two new species of Kangaroo".[2][5] The affinities of the species have been recognised in several ways, including an arrangement that sees it placed with the'brachyotis species group'. Other authors had separated this species to a new genusPeradorcas, producing a new combinationPeradorcas concinna, although the revision byD. J. Kitchener ofPetrogale did not recognise this treatment and this is maintained by other authorities. The locality of the type specimen isWyndham, Western Australia.[5] The specimen was collected and brought to England on the voyage ofHMS Beagle.[2]
Nabarlek is most closely related to the monjon and to the short-eared rock-wallabyPetrogale brachyotis.[citation needed] It was formerly considered distinct enough to be assigned its own genus,Peradorcas but it is now considered to belong, like the rest of the rock-wallabies, in the genusPetrogale.[5]
The common name designated for a similar species,monjon forP. burbidgei, is also used to refer this species in the Kimberley region; the two species are however known to be distinct by the indigenous people from whose language the name derives.[6] Common names for the species include thelittle rock-wallaby[7][8] orpygmy rock-wallaby.
Three subspecies have been recognised:[9]
The nominate subspecies, found at theTop End, follows Gould's original description.
TheArnhem Land population.The description for this subspecies was published byOldfield Thomas after examination of new specimens that confirmed morphological distinctions in different localities. The type specimen, already held at the British Museum, was collected in 1902 byJ. T. Tunney; he had killed this animal at Nellie Creek.[10]
A subspecies restricted to theKimberley region.
A species ofPetrogale, the rock wallabies, distinguished by its small size. Thepelage is a grey colour, with reddish highlights at the fore-arm, legs and hind parts. The tail is also reddish grey, with a bushy end of coarser hair that begins two thirds along its length, the total length may be from 260 to 335 millimetres. The cheek is marked with a whitish stripe from the eye to the nostrils, a lighter tone that contrasts with the blackish parts of the snout. Another darker stripe is found below the eye and down the neck, the region beneath the fore-arm is also blackish.The head and body length combined in 310 to 365 mm, the smallest of the genus but forP. burbidgei. The measurement of the hindfoot is 95 to 105 mm, the ear from base to tip is 41 to 45 mm. The weight range is from 1.2 to 1.6 kilograms.[7]
The dentition ofP. cocinna is unique amongst the marsupial species, with the supernumerary molars being continually replaced. These teeth emerge in a regular size and shape, with each row containing four to six molars and another that is yet to erupt. The early loss of the premolar appears to allow this regeneration to continue throughout their life.[8]
Nabarlek is often found with the similarP. brachyotis, whose coloration is more variable, and a young individual may be indistinguishable from this species in field observations.[11]
Nabarlek move quickly with a distinctive horizontal posture, the tail curled toward the middle of the back with raised hairs in the tufty end. The species has a timid disposition, although is somewhat gregarious in associations with others. Their feeding and other activities is usually nocturnal, and they may range beyond their refuge to forage.
The species will range several hundred metres from its secure position, foraging in the surrounding black soil terrain, this contrasts with the less venturous behaviour of the short-earedP. brachyotis.[8]
The discrete and cautious nature of narbarlek makes capture of specimens difficult, they are regarded as 'trap-shy' in attempts to survey their population.[11]
The diet includes a variety of plants, including grasses, ferns and sedges.[7] The plants consumed in Arnhem land during the wet season are the grass species ofEriachne and the sedgesCyperus cuspidatus and species ofFimbristylis, which occur in soils above the flood levels. The change in season has the species seek shelter during the day in sandstone formations and forage at localbillabongs for a fern speciesMarsilea crenata.
The high percentage of silica in its diet, 15 to 25% in some foliage, was proposed to have favoured the continual regeneration of molars.[8] Attempts to locate the high silica fern in later surveys have not recordedMarsilea crenata at any sites, and the complex relationship between diet and dentition remains to be examined.[11]
The nabarlek is found in three distinct and geographically remote populations, one inArnhem Land which includesGroote Eylandt, a larger island in theGulf of Carpentaria, and another population between theMary andVictoria Rivers at theTop End of the continent. The population in the northwestKimberley region is confined to the coastal areas and on some of the islands in theBonaparte Archipelago, these are Borda, Long, Hidden andAugustus Islands.[7]
The habitat is usually scrubby vegetation over sandstone formations, granitic outcrops, breakaways of laterite, boulder piles and rocky slopes.[7]
It is classified asEndangered by theIUCN.
