The short-tailed pygmy monitor (''Varanus brevicauda'') is the second smallest living

monitor lizard Monitor lizards are lizards in the genus ''Varanus,'' the only extant genus in the family Varanidae. They are native to Africa, Asia, and Oceania, and one species is also found in the Americas as an invasive species. About 80 species are recogn ...

in the world with a maximum length of 25 cm.

Distribution

The short-tailed monitor

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throughout central Australia from the coast of Western Australia through the interior of Northern Territory and northwestern South Australia to western Queensland. This monitor burrows in compacted sandy loam and

gravel Gravel is a loose aggregation of rock fragments. Gravel occurs naturally throughout the world as a result of sedimentary and erosive geologic processes; it is also produced in large quantities commercially as crushed stone. Gravel is classifi ...

, in areas dominated by spinifex (''Triodia'' spp.). This terrestrial species is secretiveVaranus brevicauda
mampam.com and rarely seen active above ground; it is mainly encountered by digging up its

burrow An Eastern chipmunk at the entrance of its burrow A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of sh ...

Physical Description

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. 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.

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. 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.

Diet

The short-tailed monitor is strictly carnivorous. Short-tailed pygmy monitors are highly active foragers in the wild, unlike most lizards.Short Tailed Pygmy Monitor - Varanus brevicauda
pilbarapythons.com They eat insects such as grasshoppers, beetles, roaches, caterpillars, as well as reptile eggs, isopods, spiders, scorpions, small

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

s and occasionally frogs and even small snakes. These small monitors are bold and fierce predators, despite their size.

Reproduction

The short-tailed monitor is

oviparous Oviparous animals are animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive method of most fish, amphibians, most reptiles, and all pterosaurs, dinosaurs (including birds), and ...

. 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. Mating occurs for this monitor lizard in September and October after

hibernation Hibernation is a state of minimal activity and metabolic depression undergone by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It most ...

, and by February, the eggs hatch. The

clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...

size usually is two or three, but in some coastal areas, up to five eggs are produced. "In dry years when food is scarce no reproduction occurs at all."

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.

Conservation

The main threat to short-tailed pygmy monitors is predation by larger animals.

References

* Cogger, H. (1967). ''Australian Reptiles in Colour''. Sydney: A. H. & A. W. Reed, * King, Dennis & Green, Brian. 1999. ''Goannas: The Biology of Varanid Lizards''. University of New South Wales Press. {{Taxonbar, from=Q649664 Varanus Monitor, short-tailed Reptiles described in 1898 Monitor lizards of Australia Taxa named by George Albert Boulenger