The desert rat-kangaroo (Caloprymnus campestris), also called the buff-nosed rat-kangaroo or the plains rat-kangaroo, is an extinct small hopping marsupial endemic to desert regions of Central Australia. It was discovered in the early 1840's and described by John Gould in London in 1843, on the basis of three specimens sent to him by George Grey, the governor of South Australia at the time.^[2][3]

Description

It was built like a kangaroo, but had the bulk of a small rabbit, however it was described as being of a delicate and slender form.^[4] Its average body size was estimated to be about 254-282mm in addition to a long 307-377mm long tail. Its head was short, blunt and wide, different from that of any kangaroo or wallaby^[3] with a naked nose, short and rounded ears.^[5]

The color of its dense, straight, soft fur was appropriate for its desert surroundings. It was very pale yellowish brown, the hairs tipped with sooty brown; interspersed with the under fur were many long brownish white hairs. Its underbelly was described as white with very pale yellowish brown feet and tail.^[6]

A distinguishing feature of this speciesis the difference in size between fore and hindlimbs. Forelimbs are quite delicate with bones weighing 1 gram, while hindlimbs are large with bones weighing 12 grams. This difference is related to saltation.^[7] Other characteristics related to hopping locomotion include a long, bur rather thin tail.

Distribution and Habitat

Caloprymnus campestris is thought to occupy a relatively small area in South Australia, extending just over the borders of southwestern Queensland and Northern Territory.^[8] It was it was last seen in 1935 in the eastern Lake Eyre basin of northern Southern Australia

Caloprymnus campestris lived in an desert regions of Australia, including clay pans, loamy flats, sandridges and gibber plain habitats. Its native habitat is very arid, cover is sparse and consists of saltbrush, cherropods and Emu bush.

Ecology and Behaviour

Caloprymnus campestris was solitary except for young offspring with mothers. It lived in nests built over shallow depressions in the ground. These nests ware excavated or found and are crucial in the desert, where temperatures can be high, while there is relatively little brush or foliage to find cover under. The "pits" ware lined with grass, which females carried to the nest with their tails. The nest would then be covered with twigs to provide cover from the scorching sun. Oftentimes, the desert rat kangaroo was found peeking out of the top of the nest to observe its surroundings. This species would spend most of the day taking cover in the nest, and emerge at dusk to feed.^[9] Thus it was at least partially nocturnal.

Diet

Caloprymnus campestris was mainly herbivorous feeding on foliage and stems of desert vegetation, but has also been found to eat insects such as beetles and weevils. It was so independent of water that it even shunned the succulent plants of the sand hills. It was able to survive without any surface water while feeding on green plants.

Locomotion

Caloprymnus campestris has a distinct method of hopping. Its posture wass forward and the long tail is extended when it moved at high speeds. Unlike other marsupials, Caloprymnus would land with the right foot in front of the left foot. It showed great endurance while being chased on horseback at high speeds (Finlayson reported chasing an individual over 12 miles), and "paused only to die".^[10]

Reproduction

Caloprymnus campestris females reached sexual maturity at approximately 11 months, while males reached maturity some 2 months later. There was marked sexual dimorphism with females being larger. Females went through estrous at 3 week intervals and coukd mate throughout the year. Although able to mate all year, Caloprynmus had an irregular breeding season when most mating took place. Females with pouched joeys have been found between June and December. Young were born very undeveloped, as is typical of marsupials. Gestation was probably around 1-2 months, with a pouch period of 2-3 months. All females were found with only 1 young at a time. Young remained dependent for over 1 month after leaving the pouch and soon after would leave permanently.^[11]

Rediscovery and Extinction

The desert rat-kangaroo was discovered in the early 1840's. However, after these early sightings, it was no longer recorded for 90 years (aside from an unconfirmed report in 1878), and was widely believed to be extinct.^[3] This species, even before european colonisation, was apparently never abundant ^[12] Following the relief of drought conditions which improved the local habitat, the animal was rediscovered in 1931 when Hedley Finlayson found a thriving colony of them.^[2][3] He made multiple returns, but after a few years the population disappeared. The last confirmed record of the species came in 1935 from near Ooroowilanie, east of Lake Eyre.^[8]

Caloprymnus campestris was well adapted to the extremely barren and arid regions it inhabited, these traits of its which saved it from competition by introduced species like the rabbit or sheep. However, as early as the 1930s the red fox has spread to the areas inhabited by the desert rat kangaroo. Thus the rapid decline of the desert rat-kangaroo shortly after its recovery in 1931 correlates with the invasion of its habitat by the red fox.^[13] Predation by the red fox and cats^[14] as well as variable seasonal patterns and overhunting by indigenous australians^[15] were blamed for the extinction of this species.

There have been no reliable records of the species since 1935, but there were unconfirmed sightings in Queensland following periods of rain in 1956-1957 and 1974-1975.^[16] Also, recent remains of this species have been found in the mid 1980s inside caves.^[17]

The desert rat-kangaroo was declared extinct in 1994,^[1] making it the only mammal species to be recovered and then lost again.^[13]

Possible survival

In view of its amazing recovery following a ninety year period when it wasn't seen, the extinction of the desert rat-kangaroo is not certain; thus, sightings of this animal would not fall into the cryptozoology category. In similar cases, the broad-faced potoroo was last seen in the late 19th century and is considered extinct, Gilbert's potoroo was considered extinct for 120 years prior to its rediscovery in 1994, while the long-footed potoroo was only discovered in 1967.

The finding of recent remains in the 1980s casts some doubt on the extinction of this species. Professor Ronald Nowak stated in his 2005 book that "perhaps a small population still survives, awaiting the time when it again may increase in response to proper conditions."^[18]

References