Short-tailed pygmy monitor (Varanus brevicauda)
|Also known as:||pygmy goanna, short-tailed monitor|
|Size||Snout-vent length: 5.2 cm (1)|
Total length: 25 cm (1)
|Weight||1.4 g (1)|
- The short-tailed pygmy monitor is the world’s smallest monitor lizard.
- Due to its elusive behaviour, relatively little is known about the short-tailed pygmy monitor’s ecology.
- Male short-tailed pygmy monitors can be larger than females, or vice versa, depending on geographical location.
- Despite its size, the short-tailed pygmy monitor shows a threat posture and behaviour that is distinctive of other monitor lizards.
The short-tailed pygmy monitor has not yet been classified by the IUCN, but is listed on Appendix II of CITES (2).
The thick skin of the minute short-tailed pygmy monitor (Varanus brevicauda) is reddish-brown to yellowish-tan with dark flecks, and its scales are ridged down the centre, making them rough to the touch. The rounded or slightly triangular tail of this species is almost the same length as the head and body combined (3), and being muscular it is well adapted to grasp or hold on to objects such as Spinifex grass (4).
As in all monitors, the short-tailed pygmy monitor’s head is fairly elongate and it has a long, forked tongue that can be retracted into a sheath at the base. Monitor lizards also have well-developed limbs and strong claws (5).
Interestingly, in central Australia males of this species are larger and heavier than the females, compared to the Great Victoria Desert where they are smaller (6).
The short-tailed pygmy monitor occurs in the deserts of Australia (7). Geographically it is found in the Northern Territory, Queensland, and South and Western Australia (1).
The preferred habitat of the short-tailed pygmy monitor is thought to be desert Spinifex grassland. This species is most often found on flat sand plains with long, unburned clumps of Spinifex, or on the crests of sand dunes (6).
Short-tailed pygmy monitor habitat preference is known to vary between central and Western Australia. In the Great Victoria Desert in Western Australia, this species is most often found on flat desert sand plains. However, in central Australia the short-tailed pygmy monitor most often frequents sand ridge crests (6).
As the short-tailed pygmy monitor is rarely seen, relatively little is known about its ecology (6). However, despite its secrecy this species can be common in places. Travelling only short distances, the short-tailed pygmy monitor hunts by ambush, feeding primarily on grasshoppers, spiders and beetles. Less frequent prey items include centipedes, scorpions, cockroaches, isopods, caterpillars, and insect larvae and pupae. The short-tailed pygmy monitor may also sometimes feed on other lizards such as Ctenotus species (6).
In central Australia, male short-tailed pygmy monitors reach sexual maturity at snout-vent lengths of around seven centimetres, usually when they are about ten months old. Females mature later at approximately 22 months old, at a snout-vent length of 8.5 to 9.3 centimetres (6). This species breeds in the spring between July and November, when females are developing their eggs and males have enlarged testes. Usually the female short-tailed pygmy monitor lays two to three eggs, but clutch sizes of four to five eggs have also been recorded. The eggs hatch from late January to February. Newborn short-tailed pygmy monitors have a snout-vent length of approximately 4.2 centimetres (7).
As in all monitors, the short-tailed pygmy monitor displays characteristic threat postures and behaviours such as hissing and lunging with the throat inflated (4).
There are no threats currently known to be affecting the short-tailed pygmy monitor.
No specific conservation measures for the short-tailed pygmy monitor are in place at present.
Find out more about the short-tailed pygmy monitor:
Reptile database - Short-tailed pygmy monitor:
Find out more about conservation in Australia:
Australian Wildlife Conservancy:
Australian Conservation Foundation:
- Isopods: a diverse group of crustaceans, with flattened, segmented bodies, that includes pill bugs and woodlice.
- Larva: immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
- Pupa: in some insects, a stage in the life cycle during which the larval form is reorganised into the adult form. The pupa is usually inactive, and may be encased in a chrysalis, cocoon or other protective coating.
- Snout-vent length: a standard measurement of body length for reptiles and amphibians. The measurement is taken from the tip of the snout to the vent (cloacal opening), and excludes the tail.
The Reptile Database (December, 2012)
CITES (November, 2012)
- Wilson, S. (2005) A Field Guide to Reptiles of Queensland. Reed New Holland, Sydney.
- Pianka, E. and Vitt, L. (2003) Lizards: Windows to the Evolution of Diversity. University of California Press, Berkeley.
- McCoy, M. (2006) Reptiles of the Solomon Islands. Pensoft Publishers, Sofia, Bulgaria.
- King, D. and Pianka, E. (2007) Ecology of the pygmy monitor Varanus brevicauda in Western Australia. Mertensiella, 16: 304-311.
- James, C. (1996) Ecology of the pygmy goanna (Varanus brevicauda) in spinifex grasslands of central Australia. Australian Journal of Zoology, 44(2): 177-192.