Animal Info - Central Rock Rat

(Other Names: Central Thick-tailed Rock Rat, MacDonnell Range Rock Rat, MacDonnell Rat, Rat à Grosse Queue, Rata Coligorda)

Zyzomys pedunculatus (Laomys pedunculatus)

Status: Critically Endangered

1. Profile (Picture)
2. Tidbits
3. Status and Trends (IUCN Status, Countries Where Currently Found, History of Distribution, Threats and Reasons for Decline)
4. Data on Biology and Ecology (Size and Weight, Habitat, Birth Season, Birth Rate, Diet, Behavior)
5. References

Profile

Pictures: Central Rock Rat #1 (52 Kb JPEG) (Aust. Fauna.com); Central Rock Rat #2 (71 Kb JPEG) (Arkive)

The central rock rat is a medium-sized rodent that weighs 70 - 120 g (2.5 - 4.3 oz). Adults are stocky with thick fur that is yellowish-brown on the upper body and cream or white below. Rock rats can be distinguished from rodents of other genera by their characteristically thickened tails. The central rock rat utilizes a range of habitats from tussock and hummock grasslands to low open woodland on ridge tops, cliffs, scree slopes, hills and valley floors. Its diet consists primarily of the seeds of shrubs, forbs and grasses, with leaves, fern sporangia and insects being consumed in smaller quantities. The central rock rat is believed to be nocturnal.

The central rock rat is endemic to the arid southern portion of Australia’s Northern Territory. It was first scientifically described in 1896. No records had been obtained between 1970 and 1995, but it was rediscovered in 1996 and is now known from 14 sites scattered over a 77 km (48 mi) length of the MacDonnell Ranges west of Alice Springs. The full range of its current distribution is unknown. There is concern over the status of the central rock rat because its populations are fragmented and its density is low. No specific threats have been identified to date.

Tidbits

*** Despite the central rock rat having been first described over 100 years ago, almost nothing is known about its life history or ecology (Cole 2000).

*** Rock rats are known to lose their tails, fur and skin very easily and are, therefore, difficult to handle (Cole 2000).

*** Characterizing the conservation status of the central rock rat is difficult because it is similar to other arid zone rodents in undergoing dramatic population fluctuations in response to climatic conditions. For example, the species is now the most frequently trapped small mammal at some sites around Ormiston Gorge although it was not recorded there during 1991 - 1993 despite over 20,000 trap-nights of effort. (Pavey 2002)

*** Although there are 3 other species of rock rats in Australia, central rock rats are the only arid zone species. The others mainly occur in tropical northern Australia. Therefore it is questionable as to whether what is known about the other species can be applied to the central rock rat. (Threat. Spec. Network 1999)

Status and Trends

IUCN Status:

1982 - 1988: Indeterminate
1994: Endangered
1996 - 2004: Critically Endangered (Criteria: A1ce+2ce) (IUCN 2004)

Countries Where the Central Rock Rat Is Currently Found:

2004: Occurs in Australia (IUCN 2004).

History of Distribution:

The central rock rat is endemic to the southern portion of Australia’s Northern Territory. It was first scientifically described in 1896. Between 1896 and 1960, specimens were recorded at a handful of locations. No records were obtained between 1970 and 1995, and the species was presumed to be extinct. However, it was rediscovered in 1996 and is now known from 14 sites scattered over a 77 km (mi) length of the MacDonnell Ranges west of Alice Springs. The full range of the current distribution of the species is unknown. (Cole 2000, Pavey 2002)

Locations where the central rock rat has been recorded include Uluru - Kata Tjuta (Ayers Rock - the Olgas) National Park, West MacDonnell Ranges, The Granites (Tanami Desert), James Range, Alice Springs, Napperby Hills, and Davenport Range. (Cole 2000, Pavey 2002)

Threats and Reasons for Decline:

There is concern over the status of the central rock rat because its populations are fragmented and its density is low (Cole 2000). No specific threats have been identified, and at present these are difficult to identify because the species is currently colonizing areas that it may formerly have occupied. However, among the potential threats are predation by dingos, inappropriate fire regimes, and habitat degradation as a result of grazing by feral herbivores, particularly horses. (Pavey 2002)

Data on Biology and Ecology

Size and Weight:

The central rock rat is a medium-sized rodent weighing 70 - 120 g (2.5 - 4.3 oz) (Pavey 2002). Its head and body length ranges from 108 - 140 mm (4.3 - 5.5") (Strahan 1995).

Habitat:

The central rock rat lives in the arid zone of central Australia. It has been found at only 17 sites in a variety of vegetation communities from tussock and hummock grassland through low open shrubland over hummock grassland to low open woodland. All sites have had a high proportion of rock outcrop and a very stony soil surface, with physical features including ridge tops, cliffs, scree slopes, hills and valley floors. Vegetation elements common to most sites are Native Pine, Hill Mulga, various tussock grasses and close proximity to dense spinifex grass. (Cole 2000)

Several sites where the central rock rat has been found share the following characteristics: south or east facing, a high proportion of rock outcrop, very steep slope, very stony soil surface, presence of Native Pine ( Callitris glaucophylla) and Hill Mulga ( Acacia macdonnellensis) and close proximity to dense spinifex (Triodia brizoides and T. spicata); however, some sites contain only a few of these elements. (Cole 2000)

Birth Season:

Juveniles have been captured in the wild in June (Cole 2000).

Birth Rate:

Captive animals have bred and have had litters of 3, 2, 2, 2, 1, 1 and 4 young (Cole 2000).

Diet:

The central rock rat is primarily granivorous. Seeds (1 - 10 mm (0.04 - 0.4") in size) of shrubs, forbs and grasses are the main component of the diet, with leaf material of secondary importance. The majority of the plant species identified in the diet are regarded as fire-encouraged rather than fire-sensitive species. The most commonly consumed seeds are from the species Glyceine canescens as well as species of the genera Sida and Solanum. (Pavey 2002) The central rock rat also eats fern sporangia and insects in small quantities (Cole 2000).

Behavior:

The central rock rat is believed to be nocturnal.

References

Arkive, Aust. Fauna.com, Burton & Pearson 1987, Cole 2000, IUCN 1994, IUCN 1996, IUCN 2000, IUCN 2003a, IUCN 2004, Lidicker 1989, Nowak 1999, Nowak & Paradiso 1983, Oryx 1997g, Pavey 2002, Strahan 1995

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Last modified: June 2, 2005;