Varanus acanthurus

Odatria

Varanus acanthurus BOULENGER 1885
Ridged Tailed Monitor

subspecies:

V. a. acanthurus BOULENGER 1885
V. a. brachyurus STERNFELD 1919
V. a. insulanicus MERTENS 1958

V. acanthurus
Cape Crawford, NT

Varanus acanthurus is a medium-sized monitor of the subgenera Odatria, which can reach a total length of 60-70 cm. The back pattern consists of a dark brown reticulation with numerous small to medium-sized light brown to yellow spots, lines or ocelli. The ocelli mostly have 1-2 dark central scales. The head is brown, broken off by yellow or cream colored spots, which often go into lengthways stripes over the nape of the neck. A deep brown stripe stetches alongside of the head through the eye and continues to the neck region. It is framed by pale yellow spots or rows of yellow scales. A wider yellow stripe goes along the lower jaw up to the neck. The color of the underside is white or cream. The head sclales are small and smooth. The nostril is situated at the side and stands in the middle between eye and tip of the snout. 70-150 smooth scale rows are ordered around midbody. The tail is easily squeezed together more or less round in the cross section, without a keel on the top side. It is 1.3-2.3 times as long as snout-vent-length, and it has strongly spiny scales. Males normally have lateral anal scales, which are spiny.
In the subspecies V. a. brachyurus the tail is shorter in proportion to the SVL and reaches only around 1.5 times the length of SVL.


V. acanthurus Pt. Hedland, WA	V. acanthurus Wave Hill, WA	V. acanthurus Tanami Desert, NT

V. acanthurus Dajarra, Qld.	V. acanthurus Barkly Tableland, NT	V. acanthurus Pt. Hedland, WA

V. acanthurus Warmun, WA	V. acanthurus Freweena, NT	V. acanthurus Barkly Tableland, NT

The pattern of V. a. insulanicus is more dominant, and the ocelli on the back are intensive melanistic.
In the wild the food of V. acanthurus and its subspecieses consists of insects, spiders, small geckos and skinks (LOSOS & GREENE 1988). They also will overpower specimen of their own species.

Distribution, habitat and behavior

acanthurus

The distribution of V. acanthurus and its subspecies extends on the west, the north and the center of Australia as well as on some offshore islands off the northern coast (V. insulanicus on Groote Eylandt and Wessel Island). It occures from Carnarvon in the west to Mt Isa in the east. The distribution of the nominate species is limited to the northern part of the range, from Broome on the west coast, through the Kimberleys and the Top End to the Gulf of Carpentaria, while V. a. brachyurus occurs the center, the western and the eastern part of the range (MERTENS 1942d, 1958, KEAST 1959, WORELL 1966, BUSTARD, 1968, SWANSON 1976, STORR 1980, STORR et al. 1983b, WILSON & KOWLES 1988, HOSER 1989, COGGER 1992, EHMANN 1992). Ridged Tailed Monitors live preferentially within scattered smaller rocky outcrops, where they can search for shelter between those rocks and in the crevices. With the tail they can wedge themselves and could not be reached by predators.

Keeping and breeding

The clutch size of V. acanthurus is between 5 and 12 eggs. The eggs are approx. 25 mm long and have a diameter of 13 mm. The mass is approximately 3 - 4 g. The eggs were incubated in vermiculite or perlite. The temperature should be between 27 and 30°C. After approximately 120 days the young animals will hatch, the total length is about 12 cm and the body mass is 3.5 g (ERDFELDER 1984, JAUCH 1984, THISSEN 1991, 1992, 1993, WICKER 1993, EIDENMÜLLER 1994, WICK 1996).
The rearing of the offspring should not cause any problems. They may be kept together at the beginning in one enclosure. This enclosure are similar to the one of the parents. We offer small crickets, house crickets, grass hoppers, and cockroaches to the animals, which are always dusted with a vitamin mineral powder.

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