Odour-Mediated Interactions Between an Apex Reptilian Predator and its Mammalian Prey

Abstract An important but understudied modality for eavesdropping between predators and prey is olfaction, especially between non-mammalian vertebrate predators and their prey. Here we test three olfactory eavesdropping predictions involving an apex reptilian predator, the sand goanna Varanus gouldii, and several species of its small mammalian prey in arid central Australia. Firstly, as expected, we found that small mammals recognised and avoided the faecal odour of sand goannas, feeding less intensively at food patches where the odour of V. gouldii was present than at patches with no odour or a pungency control odour. Secondly, V. gouldii was attracted to the odour of small mammals in artificial burrows, and dug more frequently at burrows containing the odour of species that were energetically profitable than at those of species likely to yield diminished returns. Our third prediction received mixed support. Rates of movement of three species of small mammals were no different where V. gouldii was present or absent, but burrow fidelity in two of these species increased as expected in an area where V. gouldii had been removed. We conclude that olfaction plays a key role in the dynamic interaction between V. gouldii and its mammalian prey, with the interactants using olfaction to balance their respective costs of foraging and reducing predation risk. We speculate that the risk of predation from this apex reptilian predator drives the marked and highly unusual burrow-shifting behaviour that characterises many of Australia's small desert mammals.