The northern marsupial mole or kakarratul (Notoryctes caurinus) is a marsupial in the family Notoryctidae, an endemic animal of arid regions of Central Australia. It lives in the loose sand of dunes and river plains in the desert, spending nearly its entire life beneath ground. The facial features are reduced or absent; their small and strong bodies, weighing little more than 30 grams (1 ounce), are extremely specialised in moving through sand in search of prey. The species is elusive and it is one of the most poorly understood mammals of Australia.
Taxonomy A description of the species was published by Oldfield Thomas in 1920. One of two extant species of the genus Notoryctes, following recognition of its separation from Notoryctes typhlops in 1988. The specimen described by Thomas was collected in 1910 by a postal official at Wollal, at Ninety Mile Beach in north-western Australia, and this was conveyed to the Western Australian Museum. Thomas distinguished the new species from the southern N. typhlops, described in 1891 by E. C. Stirling, as smaller, particularly its claws and muzzle/nose, but with larger auditory bulla. He also described them as differing in dentition to the southern species, especially in their lower jaw. The northern marsupial mole is also called the northwestern marsupial mole. Described as 'unimaginative', these common names were replaced with that derived from indigenous languages of the region in 1996, which has been widely accepted since.
Description The kakarratul and the itjaritjari, species Notoryctes typhlops, are superficially indistinguishable and unmistakable for any other animal. The dense pelage is short, smooth and finely haired, and is a uniform and pale yellow-pink colour. The length of the head and body combined is 120–160 mm (4.7–6.3 in), and the length of the stubby, leathery tail is 20–25 mm (0.79–0.98 in). The weight range is 40–70 g (1.4–2.5 oz). The vestigial eyes are a non-functioning subcutaneous lens, and a leathery covering at the pointed snout protects the nostrils. No external ear is present, and the opening for the reduced structure is covered in a dense layer of hairs. A fossorial animal, the highly specialised form of the body is tubular, its head narrowing in view to a conical shape and the limbs are short and well suited to digging. The two claws of the third and fourth front toe are enlarged and able to shovel the sand ahead of themselves. A pouch used in rearing young, a feature common to marsupials and as is usual for subterranean species, faces away from the direction of travel to avoid sand entering it. The anatomy of N. caurinus has been examined with CT scans, showing the skeletal tomography, and MRI that give some details of soft tissue structures, the 2003 study being the first since the details given by Thomas in 1920. The vertebrae at the hind part of kakarratul are completely fused, a unique characteristic amongst the marsupials, and the spinal column is greatly strengthened; the side view of the spine shows a flattened profile that is also advantageous to its fossorial habits. Results of soft tissue examination showed large amounts of subcutaneous fat at the shoulders and pelvic regions. In an example of convergent evolution, the unusual metabolism of the species was compared to the physiology of a placental mammal of a golden mole found in Africa, similar in form and ecological factors, the subspecies Eremitalpa granti namibensis.
Distribution and habitat The species is distributed over an area of northwest Australia, at aeolian dunes and other soft sand terrain of the Australian interior. The records include the Little Sandy and Great Sandy Deserts, and at northern areas of the Gibson Desert (Western Australia), and possibly the Tanami Desert (Western Australia/western Northern Territory. The kakarratul is not able to easily traverse hardened sands or other terrain. It is thought both of these notoryctid species, the kakarratul and itjaritjari, may be sympatric where their distribution range overlaps in the south and east. The population structure within the range is poorly examined. There are around three hundred specimens available in collections of museums and elsewhere, although information on the range is limited to the two thirds with details of the collection site. The habitat is at the series of sand dunes arising from the adjacent sandy plains, the populations seem to be restricted to these formations; they are noted as absent when dunes are poorly connected or become isolated. The vegetation is typical of the central regions, acacia and other hardy shrubs or small trees, and this species is also often associated with habitat around Triodia (spinifex) hummocks.
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