Abstract

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.