Conservation ecology and trophic interactions of the Northern Quoll, Dasyurus hallucatus

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NO FULL TEXT AVAILABLE. This thesis contains 3rd party copyright material. ----- Northern Australia is experiencing an unprecedented small mammal decline. The northern quoll, Dasyurus hallucatus, is one species that has suffered significant declines, and is locally extinct across much of its previous range. The decline of quolls has been largely attributed to cane toads, as quolls lack immunity to toad toxins. We modified predator behaviour by feeding quolls small, non-lethal toads laced with a nausea-inducing chemical. Quolls that consumed toads became ill and ignored live toads thereafter. We reintroduced 50 captive-reared ‘toad-smart’ quolls to Kakadu National Park, to determine whether aversion training enhanced their long-term survival. ‘Toad-smart’ female quolls survived in a toad-infested landscape, as did two generations of their descendants. Our results suggest that each generation of quolls learns to avoid toads, either via social learning, or non-lethal encounters with small toads that induce aversion. Hence, training a single cohort of quolls can yield a long-term conservation benefit. Despite this initial success, quoll numbers did not recover to pre-toad levels. Population monitoring revealed an initial increase post re-introduction followed by a crash, coincident with high level of dingo and free-ranging dog trap disturbance. Radio-tracking revealed that quolls denned only in narrow rocky dens inaccessible by larger bodied predators. Canid predation was the major source of mortality for radio-tagged quolls; a threat that has been neglected in the current mammal decline. To examine the continued existence of the population, I modelled the population viability of quolls. Without canid control, the quoll population has a 52% chance of extinction by 2034. In contrast, reducing canid-induced mortality minimised the extinction probability to 16%. Canids are potentially preventing the recovery of quoll populations. Rock rats (Zyzomys spp.) are important prey for northern quolls. I investigated how rock rats modify their behaviour in the presence of dingoes, quolls and rock wallabies. In the field, rats demonstrated a stronger avoidance to quoll odour than dingo odour. Further experiments conducted on wild rock rats in captivity revealed the influence of individual personality on behaviour, with some individuals displaying bold traits that appear counterproductive to survival. My results suggest that prey vary behaviour according to perceived predator threat, and highlight the need for consideration of personality when investigating behavioural responses in wild populations. My thesis highlights the need to identify and address all threatening processes in order to conserve threatened species. In the wake of current mammal declines, we need innovative conservation actions, such as conditioned taste aversion, to ensure the survival of our iconic wildlife.
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