P. J. Mayes’s research while affiliated with Edith Cowan University and other places

In remote field localities, given limited access to specialized equipment, determining the sex of captured adult varanid lizards before release can be problematic. Determining the sex of the tropical semiaquatic Varanus mertensi, a species with significant tail musculature, is difficult using traditional hand-pressure-induced hemipenile eversion. As an alternative, we propose an extended technique for identifying the sex of adult V. mertensi. We recommend using a combination of the traditional field-based hemipenile eversion technique and a measurement of the ratio of androgens to estradiol in plasma samples taken from field-captured animals.

We report on the aquatic and terrestrial foraging behaviour and diet of the semi-aquatic Varanus mertensi. Foraging behaviour of V. mertensi is similar to that of other large terrestrial varanids: slow, methodical forwards movement with the head swaying from side to side with regular tongue flicks. Both olfactory and visual cues are used to detect prey. Foraging in the water is remarkably similar to that in the terrestrial environment, with this species using both visual and olfactory cues. Like other varanids, this species is able to use previous experiences to maximise its chance of locating prey. V. mertensi consume a large number of freshwater crabs (Holthuisana sp.) and a variety of small invertebrate and vertebrate prey across their distribution. Dietary differences across geographic regions are minor. Its diet is sufficiently catholic to enable it to adapt to seasonal and spatial differences in prey availability, one reason for its widespread distribution in the wet–dry tropics of Australia. Stomach contents differ from those of scats, with soft-bodied prey items being absent from scat samples.