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Home -> Kingdom Animalia -> Phylum Chordata -> Subphylum Vertebrata -> Class Reptilia -> Order Squamata -> Suborder Autarchoglossa -> Family Varanidae -> Species Varanus brevicauda

Varanus brevicauda
short-tailed monitor



2008/07/20 08:48:40.252 GMT-4

By John Herman

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Reptilia
Order: Squamata
Suborder: Autarchoglossa
Family: Varanidae
Genus: Varanus
Species: Varanus brevicauda

Geographic Range

The short-tailed monitor occupies arid regions of western Australia (Pianka 1969).

Biogeographic Regions:
australian (native ).

Habitat

The preferred habitat of the short-tailed monitor is arid regions dominated by spinifex. Spinifex are perennial grasses that form dense clumps, up to several feet in diameter, consisting of a central dense complex lattice-work and numerous outwardly directed needle-like spines (Pianka 1969).

Terrestrial Biomes:
desert or dune .

Physical Description

Mass
8 to 10 g; avg. 9 g
(0.28 to 0.35 oz; avg. 0.32 oz)


The short-tailed monitor is the smallest of the Varanid lizards, attaining a maximum adult length of only 8 inches. Newly hatched short-tailed monitors look just like the adults, but weigh about 1 to 2 grams and are only 1 to 2 inches in total length (Pianka 1969). Like all monitors the short-tailed monitor has a long neck, well developed limbs with five toes on both fore and hind limbs, strong claws, and a powerful tail that cannot undergo autotomy (Cogger and Zweifel 1998). The body color is usually a drab olive to brown color with lighter ocelli on the trunk. It is nearly impossible to determine the sex of most monitors by their outward appearance and the short-tailed monitor is no exception, as it is monomorphic (Bartlett and Bartlett 1996).

Some key physical features:
ectothermic ; bilateral symmetry .

Reproduction

The short-tailed monitor is oviparous. Short-tailed monitors exhibit internal fertilization. The male has paired intromittent organs known as hemipenes. Although the hemipenes are paired they are only used one at a time, depending on which is more convenient. The clutch size will vary from 1 to 4 eggs, with a clutch size of 2 being the most frequent (Pianka 1969). The female will dig a burrow in which to deposit her eggs. The eggs will hatch between 70 and 100 days depending upon incubation temperature. The hatchlings are precocial and grow quickly attaining maturity and adult length within the first year to year and a half (Bartlett and Bartlett 1996).

Key reproductive features:
gonochoric/gonochoristic/dioecious (sexes separate).

Behavior

Like most monitors, the short-tailed monitor is solitary in nature and avoids contact with other monitors, especially those that are bigger and could be a predator. However, due to the fact that short-tailed monitors are so small and mainly live in burrows it is not uncommon to find a very large population in a very small area (Pianka 1969). These monitors are very active diurnal foragers. The short-tailed monitor has a very keen sense of sight and hearing but attains the bulk of its sensory information through chemical signals picked up by the Jacobson's organ. These signals include mate recognition and competitor recognition. During the breeding season males will engage in combat for the right to mate with a female. The males will raise up on their hind limbs supported by their tails and wrestle until one is thrown to the ground (Cogger and Zweifel 1998).

Key behaviors:
motile .

Food Habits

The short-tailed monitor is strictly carnivorous. Unlike most lizards, monitors are active foragers with a very high metabolic rate. Monitors use their long forked tongue much like a snake to pick up chemical cues in the air. The tongue, when flicked out, draws in these chemical cues and transfers them to the Jacobson's organ where the cues are analyzed (Pough et al. 1998). The diet of the short-tailed monitor is composed primarily of insects, other arthropods, smaller lizards (especially of the family -Ctenotus-, Australian skinks), and like most other monitors, they will not turn down carrion (Bartlett and Bartlett 1996). However, any prey item that has a chance of fitting in the monitor's throat will be actively pursued and consumed. One short-tailed monitor was reportedly found with a -Ctenotus calurus- in its stomach that made up 16.5% of the monitor's total weight. The monitor is able to eat such large prey because it utilizes a technique for feeding called mesokinesis. Mesokinesis is the dislocation of the jaw to swallow prey larger than the head (Pianka 1969).

Economic Importance for Humans: Positive

While the short-tailed monitor does not have a positive economic value there is a slight scientific interest in how it deals with the arid conditions in which it lives (Pianka 1969).

Conservation Status

IUCN Red List: [link]:
Not Evaluated.

US Federal List: [link]:
No special status.

CITES: [link]:
No special status.

Although there is no special concern about the short-tailed monitor all monitors from Australia are protected under CITES. There has been no extensive pressure from the pet trade on the short-tailed monitor (Pough et al. 1998).

Contributors

John Herman (author), Michigan State University.
James Harding external link (editor), Michigan State University.

References

Bartlett, R., P. Bartlett. 1996. Monitors, Tegus, and Related Lizards. NY: Barron's Educational Series, Inc..

Cogger, H., R. Zweifel. 1998. Encyclopedia of Reptiles and Amphibians, 2nd Edition. San Diego: Academic Press.

Pianka, E. May 1969. Habitat Specificity, Speciation, and Species Density in Australian Desert Lizards. Ecology, 50: 498-502.

Pough, F., R. Andrews, J. Cadle, M. Crump, A. Savitzky. 1998. Herpetology. New Jersey: Prentice-Hall, Inc..

2008/07/20 08:48:41.105 GMT-4

To cite this page: Herman, J. 2000. "Varanus brevicauda" (On-line), Animal Diversity Web. Accessed July 25, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Varanus_brevicauda.html.

Disclaimer: The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

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