Order: Squamata

Family: Varanidae

 

Size:  up to 100 cm in length.

Weight: up to 7.2 kg

 

Key Features: The desert monitor is the most northerly distributed monitor species and one of the largest reptiles in its expansive range. The body is long and robust, with sturdy limbs, and a long, powerful tail which can be used liked a whip in defence. The nostrils of this species are particularly distinctive, comprising diagonal slits much closer to the eye than the tip of the snout. Colouration is highly variable, but is always far more vivid in juveniles, which are generally yellow or orange with bold black bands running across the body and tail. As the desert monitor ages its colour and markings fade, becoming light brown, yellow or dark grey, with faint or non-existent banding. In some adults the upperside may be marked with creamy spots and mottling or with small, dark spots extending to the tail and throat. This species is divided into three subspecies which occupy distinct geographical regions and can be identified by size, tail shape, and the number of bands on the body and tail. Varanus griseus griseus has a rounded tail and highest number of bands, Varanus griseus caspius reaches the largest size and has a laterally compressed tail, while Varanus griseus koniecznyi is the smallest subspecies and has the fewest bands.

 

Breeding: Egg-laying generally occurs from late June to early July, and is preceded by the female digging a burrow with two shafts, one leading to a chamber which the female inhabits, and the other to a chamber in which a clutch of between 10 and 20 eggs is laid. After depositing the clutch, the female tightly packs the shaft leading to the eggs with sand, and then remains in the vicinity of the burrow to defend it from other desert monitors. In early October, after an incubation period of around 110 days, the eggs hatch, but the young do not yet attempt to dig to the surface.

 

Diet: diet includes small mammals, birds, eggs and insects, and they will even tackle challenging prey such as hedgehogs, tortoises and venomous snakes. 

 

Habitat: Although predominantly desert-dwelling, the desert monitor occupies a variety of arid and semi-arid habitats including clay steppe, savannah and riverbeds up to elevations of 1,300 metres. A specific habitat requirement for this species is the presence of sand or soft soil in which tracks can be made for communication and orientation.

 

Habits: Active during the day, the desert monitor emerges from its burrow in the early morning, and basks in the sun at the entrance in order to raise its body temperature. When sufficiently warmed, it begins to forage, using its long forked tongue to detect chemical cues in the air that help it to track down prey. Once its quarry has been sighted, the desert monitor either rushes at it directly, or stalks it to within a few metres, before sprinting forwards. Prey is dispatched by biting the neck, which disrupts breathing, and also by violently shaking the animal in its jaws, after which it is swallowed whole. Desert monitors are opportunistic predators, and employ an impressive range of skills in the pursuit of food, including tree-climbing, swimming and digging. During a single day, desert monitors range over large distances, usually between five and six kilometres, returning to their burrow before sunset.

 

Conservation Status: Least Concern on the IUCN Red List of Threatened Species.

 

 

 

 

 

References:

Stanner, M. (2004) Varanus griseus. In: Pianka, E.R. and King, D.R. (Eds) Varanoid lizards of the world. Indiana University Press, Bloomington, Indiana.

 

Hellyer, P. and Aspinall, S. (2005) The Emirates: A Natural History. Trident Press Limited, United Arab Emirates.

 

Halliday, T. and Adler, K. (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford University Press, Oxford.

 

Photo Courtesy

Knockout mouse. Licensed under CC BY-SA 3.0 via Wikimedia Commons.