The pygmy mulga monitor (''Varanus gilleni''), also known as Gillen's monitor or just mulga monitor is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of lizard in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Varanidae The Varanidae are a family of lizards in the superfamily Varanoidea within the Anguimorpha group. The family, a group of carnivorous and frugivorous lizards, includes the living genus '' Varanus'' and a number of extinct genera more closely relat ...

Taxonomy

A description of the species was presented to the

Royal Society of Victoria The Royal Society of Victoria (RSV) is the oldest scientific society in the state of Victoria in Australia. Foundation In 1854 two organisations formed with similar aims and membership, these being ''The Philosophical Society of Victoria'' (fou ...

in 1895 by Arthur H. S. Lucas and Charles Frost. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''gilleni'', is in honor of

Australian Australian(s) may refer to: Australia * Australia, a country * Australians, citizens of the Commonwealth of Australia ** European Australians ** Anglo-Celtic Australians, Australians descended principally from British colonists ** Aboriginal Au ...

anthropologist An anthropologist is a person engaged in the practice of anthropology. Anthropology is the study of aspects of humans within past and present societies. Social anthropology, cultural anthropology and philosophical anthropology study the norms and ...

Francis James Gillen Francis James Gillen (28 October 1855 – 5 June 1912), also known as Frank Gillen and F. J. Gillen, was an early Australian anthropologist and ethnologist. He is known for his work with W. Baldwin Spencer, including their seminal work ''T ...

Distribution

The species is native to the spinifex sandplains of northwestern and

central Australia Central Australia, also sometimes referred to as the Red Centre, is an inexactly defined region associated with the geographic centre of Australia. In its narrowest sense it describes a region that is limited to the town of Alice Springs and i ...

."''Varanus gilleni'' ". www.monitor-lizards.net.
It can be found under the loose bark of desert she-oaks, and the hollows of

eucalyptus ''Eucalyptus'' () is a genus of over seven hundred species of flowering trees, shrubs or mallees in the myrtle family, Myrtaceae. Along with several other genera in the tribe Eucalypteae, including '' Corymbia'', they are commonly known as euca ...

, mulga, and

myall Myalls are any of a group of closely related and very similar species of ''Acacia'': * ''Acacia binervia ''Acacia binervia'', commonly known as the coast myall, is a wattle native to New South Wales and Victoria. It can grow as a shrub or as a t ...

trees.

Description

The pygmy mulga monitor is

arboreal Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...

, with a

prehensile tail A prehensile tail is the tail of an animal that has adapted to grasp or hold objects. Fully prehensile tails can be used to hold and manipulate objects, and in particular to aid arboreal creatures in finding and eating food in the trees. If the ta ...

. It grows to a total length of around 40 cm (16 inches). The upper surface is brown, grading to grey at the sides. The nostrils are positioned on the sides of the muzzle, about halfway between the tip of the snout and the eye. ''V. gilleni'' weighs, on average, . Males and females can be distinguished by the presence of spines on the sides of the male's vent. It is sometimes mistaken for the stripe tailed monitor, but the two species are allopatric and can be physically distinguished by the pygmy mulga monitor's slightly larger size. This species has very high endurance, owing to it having one of the highest factorial aerobic scopes of any vertebrate. A study where individuals were placed on treadmills running at a speed of 1 kilometre per hour (28 cm per second) found that they could maintain the speed for "many minutes" without tiring. It is particularly well adapted to arid conditions, losing water at half the rate of other Australian monitor species.

Diet

Although arboreal, much of their prey is found by foraging on the ground. Pygmy mulga monitors eat primarily spiders, orthopterans, beetles, and other lizards, especially geckos such as ''

Gehyra variegata ''Gehyra variegata'', the tree dtella, variegated dtella or varied dtella, is a species of gecko in the genus ''Gehyra ''Gehyra'' is a genus of geckos in the family ''Gekkonidae''. They are known as web-toed geckos or dtellas, and most spe ...

'' and ''

Heteronotia binoei ''Heteronotia binoei'', also known commonly as the Bynoe's gecko, is a species of lizard in the family Gekkonidae. The species is endemic to Australia. One of Australia's least habitat-specific geckos, it occurs naturally across much of the cou ...

''. Geckos too large to be killed may be attacked anyway to consume their autotomized tails. Bird eggs, small mammals, and even ant sized prey are also taken.

Reproduction

Ritualized fighting sometimes occurs between males. Unlike larger monitors which grapple with each other while standing on their hindlegs, they grapple each other with all 4 limbs, belly to belly, and roll around on the ground trying to force the other onto its back. Biting may also occur. Breeding likely takes place between September and October. A clutch of up to 7 eggs may be laid in a 30cm deep burrow, which may then be sealed with sand. The eggs hatch after 3 months.

Predators

This species is predated on by birds of prey, snakes, as well as larger monitors such as Gould's monitors.

References

{{Taxonbar, from=Q1422779 Varanus Monitor lizards of Australia Reptiles described in 1895