Food habits, habitats and reproductive biology of four sympatric species of varanid lizards in tropical Australia

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The morphological similarity among all living varanids, and reports of catholic diets in many species, give an impression of varanids as relatively unspecialized carnivores. However, detailed studies of four sympatric taxa reveal major interspecific differences in habitat use, diets and reproductive biology. Of two large terrestrial species studied, one (V. panoptes) is found mainly in riparian habitats and eats many aquatic prey. Its sibling species, V. gouldii, is restricted to woodland habitats and eats terrestrial prey. Of two semi-aquatic taxa studied, one (V. mitchelli) is often arboreal and changes its diet (arthropods and fishes) and habitat seasonally with the advent of wet-season flooding; V. mertensi is more highly modified for aquatic life and feeds primarily on freshwater crabs. Overall, habitat similarity between species is highly correlated with dietary similarity. Males grow up to 3× the mass of females in the two terrestrial taxa, but there is no sexual difference in body size in the semi-aquatic species. The terrestrial goannas are active year-round (and breed in the wet-season) whereas the semi-aquatic species are most active in the wet-season (but breed in the dry-season). Interspecific similarities include diurnal activity (with a peak in mid-morning) and broad taxonomic composition of the diet (with many invertebrates, few vertebrates). Diets of these varanids in the Alligator Rivers region differ from those of conspecifics in other areas, based on examination of museum specimens. The morphological similarity among varanids may mask major ecological differences among species, among populations within a species, and among individuals within a population. Opportunistic exploitation of local conditions may be a key feature of varanid ecology and may result in significant temporal and microgeographic variation in diets.

Original languageEnglish
Pages (from-to)346-360
Number of pages15
Issue number3
Publication statusPublished - Sept 1986
Externally publishedYes


  • Varanidae
  • Lizards
  • Goanna
  • Monitor
  • Opportunism
  • Foraging
  • Fecundity
  • Varanus panopte
  • Varanus gouldii
  • Varanus mitchelli
  • Varanus mertensi


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