Unravelling the multiple levels of prey naiveté to alien predators in Australian critical weight range mammals

A project undertaken at the University of New South Wales, and supervised by A/Prof Peter Banks


Alien predators such as dogs, foxes and cats can have devastating impacts on native wildlife. In Australia, alien predators have extirpated many native prey populations whilst in other cases there is prolonged coexistence.  Naiveté towards new enemies is the traditional explanation for alien impacts - the notion that native prey lack the ability to recognise a novel threat and are easily captured. This simple idea may explain the rapid devastation wrought by alien predators on small island fauna but it fails to explain why native prey aren't always driven to extinction and whether past experience with other predators influences responses to new threats.


Banks and Dickman (2007) proposed a new model of naiveté, identifying the existence of three levels of naiveté determined by the evolutionary history of prey and the traits of predators; (1) where there is no recognition of risk, (2) where the risk is identified but the response is wrong and (3) where the alien predator is recognized and a response made but the new predator is simply superior. In this project, we will make the first tests of this theory in order to explain the role of naiveté in the vulnerability of Australian mammals to alien predators.


We aim to demonstrate that naiveté goes beyond the current simple notions and can take many forms to determine the current vulnerability of native prey to alien predators.  In experiment (1) we test for the presence of level 1 naiveté (no recognition) in free ranging bandicoots, a classic critical weight range species, towards predation risk from dogs and cats. In experiment (2) we use chemical analysis of the social and body odours of a suite of native and alien predators in order to determine whether common constituents exist amongst evolutionary divergent predators: to humans, each predator has a unique odour.  In experiment (3) we test between level 1 and level 2 naiveté (recognition but showing the wrong response) for free living mammals. In experiment (4) we experimentally test for naiveté and learning in the recognition of novel predators assessing both predator experienced and inexperienced prey.


Our results will reveal the many complex forms of naiveté, which ultimately determine the likely extent of predator impacts.  The world already looks to Australia for insights to manage invasive species because of our long and notorious history with alien impacts - this project tackles the root cause driving the differences between impacts of alien and native predators.

 
Figure 1. Foraging holes left by bandicoots in a suburban lawn, the telltale signs of bandicoot activity surveyed in experiment 1.

Figure 2. The field set up for experiment 3 at one station.  Food (peanut pieces) is mixed through the tray of sawdust.  The infrared motion-sensor camera points at the tray to film foraging behaviour.  The perspex cover provides protection from rainfall.

Figure 3. from footage obtained in a trial for experiment 3; a bush rat, Rattus fuscipes.

 

Figure 4. Still from footage obtained in a trial for experiment 3; a northern brown bandicoot, Isoodon macrourus.