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 West African Nile monitor, one species is also found in south America as an invasive species. A ...

in the world with a maximum length of 25 cm.

Distribution

The short-tailed pygmy monitor

ranges In the Hebrew Bible and in the Old Testament, the word ranges has two very different meanings. Leviticus In Leviticus 11:35, ranges (כירים) probably means a cooking furnace for two or more pots, as the Hebrew word here is in the dual numbe ...

throughout central Australia, from the coast of

Western Australia Western Australia (WA) is the westernmost state of Australia. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to the south, the Northern Territory to the north-east, and South Australia to the south-east. Western Aust ...

through the interior of the

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

, and from northwestern

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

to western

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

. The short-tailed pygmy monitor burrows in compacted, sandy loam and

gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...

, in areas dominated by spinifex (''Triodia'' spp.). This

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

species is secretiveVaranus brevicauda
mampam.com and rarely seen active above ground; it is mainly encountered by digging up its

burrow file:Chipmunk-burrow (exits).jpg, 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 Animal lo ...

Physical description

The short-tailed monitor is the smallest of the

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

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

forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing livestock. Historically, the term ''forage'' has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used m ...

rs in the wild, unlike most lizards.Short Tailed Pygmy Monitor - Varanus brevicauda
pilbarapythons.com They eat

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s such as grasshoppers, beetles, roaches, caterpillars, as well as reptile eggs, isopods,

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

scorpion Scorpions are predatory arachnids of the Order (biology), order Scorpiones. They have eight legs and are easily recognized by a pair of Chela (organ), grasping pincers and a narrow, segmented tail, often carried in a characteristic forward cur ...

centipede Centipedes (from Neo-Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...

s, small

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

s and occasionally

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

s and even small

snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

s. These small monitors are bold and fierce predators, despite their size.

Reproduction

The short-tailed monitor is

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

. Short-tailed monitors exhibit

internal fertilization Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. For inte ...

. The male has paired intromittent organs known as

hemipenes A hemipenis (: hemipenes) is one of a pair of intromittent organs of male squamates (snakes and lizards). Hemipenes are usually held inverted within the body, and are everted for reproduction via erectile tissue, much like that in the human peni ...

. 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 reduction entered by some animal species. Hibernation is a seasonal heterothermy characterized by low body-temperature, slow breathing and heart-rate, and low metabolic rate. It is mos ...

, and by February, the

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

hatch. The

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

size usually is two or three, but in some

coastal A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...

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.

Predation and conservation

As the species’ numbers are currently listed as ‘least concern’ by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

, the main threat to short-tailed pygmy monitors is

predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

by larger animals; predators include (but are not limited to)

birds of prey Birds of prey or predatory birds, also known as (although not the same as) raptors, are hypercarnivorous bird species that actively predation, hunt and feed on other vertebrates (mainly mammals, reptiles and smaller birds). In addition to speed ...

dingoes The dingo (either included in the species ''Canis familiaris'', or considered one of the following independent taxa: ''Canis familiaris dingo'', ''Canis dingo'', or '' Canis lupus dingo'') is an ancient ( basal) lineage of dog found in Austr ...

feral cats A feral cat or a stray cat is an unowned domestic cat (''Felis catus'') that lives outdoors and avoids human contact; it does not allow itself to be handled or touched, and usually remains hidden from humans. Feral cats may breed over dozens ...

and

dogs The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers ...

owls Owls are birds from the Order (biology), order Strigiformes (), which includes over 200 species of mostly Solitary animal, solitary and Nocturnal animal, nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vis ...

, certain

snakes Snakes are elongated Limbless vertebrate, limbless reptiles of the suborder Serpentes (). Cladistically Squamata, squamates, snakes are ectothermic, amniote vertebrates covered in overlapping Scale (zoology), scales much like other members of ...

and introduced

red fox The red fox (''Vulpes vulpes'') is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia, plus ...

es. Other, larger species of

monitor Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, Wes ...

may pose a threat.

Gallery

Varanus brevicauda.jpg Varanus brevicauda 2.jpg

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