Monitor lizard

Abstract: During the breeding season, in the western Great Victoria Desert, Western Australia, male Varanus tristis move greater daily distances (186.5 m) than females (99.7 m) and have larger activity areas (40.3 ha vs 3.7 ha). V. tristis retreat predominantly to live and dead upright Eucalyptus gongylocarpa (marble gum) trees that have hollows in their trunks and limbs. There is no observable difference between males and females in their preferred habitat, but females are found more frequently in a lesser number of preferred retreats during the breeding season.

Abstract: Since Vmanus varius (the lace monitor or lace were no other sheep in the two study areas (Bendethera 2 goanna) is the second largest terrestrial carnivore inand Mallacoota). However, carrion may be otherwise digenous to mainland south-eastern Australia (Weavers under-represented in scats because, unless the animal 1988), its diet is of some ecological interest To date, howhas ingested fur, little identifiable material is present after ever, there have been no auantitative descri~tions of the diaestion of carrion. diet of V. varius. ~ustrali& varanids are generally considered carnivores which ingest plant material near prey only by accident, although Johnson (1972) has reported that V. gouldii in captivity ate a mixture of "pet meat and vegetables". Food items recorded from stomach contents of museum specimens of Australian Varanus spp. other than V. varius ranged from arthropods and reptile eggs for the smallest species, V. giueni; to arthropods, mammals, birds, lizards, and reptile eggs for larger species such as V. panoptes, V. tn'strs, V gouldii, or V. rosenbergi (varanid diets reviewed by Losos and Green 1988). According to anecdotal accounts, the diet of V. varius includes arthropods, reptiles, amphibians, eggs, birds, small mammals and carrion including dead conspecifics (e.g. Broadbent 1910; Gogerley 1922; Hindwood 1926; Worrell 1963; Bustard 1970; Vestjens 1973; Houston 1978; Tidemam 1980; Manserah and Hdey 1985; Cogger 1986; Losos and Green: 1988; Ward and Carter 1988). Several of these accounts emphasize the importance of nesting birds in the diet. Gogerley (1922) even speculated that some species of "low-nesting birds" including the superb lyrebird (Menura superba), nest during winter to avoid predation by the ". . . Gohanna (Varanus varius)". Vestjens (1977) examined the stomach contents of 18 V. varius from north-western New South Wales, but did not quantify hi results. He identified prey including one species of bird, egg shell of one unidentified species of bird, three species of introduced mammals, tortoise eggs, and seven groups of arthropods. Vestjens (1977) further observed 10 acts of predation by V. varius on eggs or chicks of five species of birds.

Abstract: In this study, we used analyses of stable isotopes of nitrogen (delta(15)N) and carbon (delta(13)C) to determine the trophic ecology of the monitor lizard Varanus mabitang. Stable isotopes from claws, gut contents, and soft tissues were measured from the type specimen. Samples from Varanus olivaceus, Varanus prasinus, Varanus salvator, the herbivorous agamid lizard Hydrosaurus pustulatus, and some plant matter were included for comparison. Our data show a rapid decrease in delta(13)C (about 10 per thousand) from food plants towards gut contents and soft tissues of herbivorous species. For the varanids, we found a significant linear correlation of decreasing delta(13)C and increasing delta(15)N from herbivorous towards carnivorous species. In terms of trophic isotope ecology, the type specimen of V. mabitang is a strict herbivore. Thus it differs significantly in its isotopic composition from the morphologically next closest related species V. olivaceus. The most highly carnivorous species is V. salvator, while delta(15)N values for V. prasinus and V. olivaceus are intermediate. Claws provide very valuable samples for such measurements, because they can be sampled from living animals without harm. Additionally, their range of variability is relatively small in comparison with measurements from soft tissues.