Research and management to reverse the decline of native mammal fauna

This project sought to characterise the conservation status of the mammal fauna in northern Australia, investigate factors that may be implicated in the decline of this fauna, and identify effective management responses.

The current rate and severity of decline of the mammal fauna in at least parts of northern Australia is exceptional, with analysis indicating that it exceeds that elsewhere in Australia. This is of considerable conservation concern because northern Australia has previously experienced relatively little loss of biodiversity (since European settlement) and has acted as a refuge for many species and species-groups that have exhibited substantial declines elsewhere in Australia. The current declines in the mammal fauna in northern Australia are also exceptional in a global context, because most declines and extinctions elsewhere in the world have occurred in areas affected by substantial land clearing, habitat modification or hunting, issues that are not (yet) major concerns in northern Australia. A notable feature of the decline of mammals in northern Australia is that declines have been reported from some large and relatively well-resourced conservation reserves, indicating that reservation alone has been insufficient to maintain biodiversity and that the intensity, scope or approach of management in reserves may need substantial refinement.

This project comprised multiple components, including:

• trialling two 64 cat exclosures in Kakadu National Park to monitor the response of native mammal populations in the absence of cats;
• monitoring the impact of cat predation on the survival of introduced mammals in small-scale cat exclosures;
• ongoing monitoring of mammals at Kakadu, Litchfield, Nitmiluk and Garig Gunak Barlu National Parks, plus AWC’s Mornington, Marion Downs, Tableland, and Wongalara Wildlife Sanctuaries. Mammal trends were correlated with other environmental pressures at the sites such as fire patterns and the amount of grazing stock;
• an investigation into the types and levels of disease amongst mammals at a number of sites.
• a broad scale assessment of the abundance of feral cats through extensive remote camera surveys, and of diet through stomach content analysis;
• a study of the behaviour (including response to fire and grazing intensity) and abundance of feral cats though radio-tracking;
• a study of the survival (and causes of mortality) of selected mammal species, at sites with varying fire regimes;
• a study into the effectiveness of using taste aversion training to aid the conservation of quolls by training them not to eat cane toads;
• an assessment of the effectiveness of taste-aversion training for floodplain monitors in response to cane toad invasion of the Kimberley;
• comprehensive overview of the conservation status of all Australian mammal species; and
• collaborative development of a conservation strategy for threatened species in Kakadu with Parks Australia.

Study components demonstrated that predation by feral cats caused local extinction of an experimentally reintroduced population of a native mammal species, and that feral cat impacts were much more severe in areas that had been extensively burnt; but a cat exclosure fencing study in Kakadu failed to demonstrate beneficial response by native mammals, possibly because the study period was too brief and mammal populations in the area were too depleted.

Mammal surveys across combinations of fire and grazing treatments in the Kimberley showed that the benefits of improving fire patterns to mammal richness and abundance were significantly muted if introduced herbivores were present.

The first substantial assessment of the incidence of disease in mammal assemblages of northern Australia indicates the presence of some pathogens that may have lethal or sub-lethal impacts on native mammals, but there is uncertainty around their role in the current decline.

The research took place in Kakadu, Garig Gunak Barlu and Litchfield National Parks, on the Tiwi Islands in the Northern Territory, at Australian Wildlife Conservancy properties in the Kimberley, Northern Territory and Cape York and in the Balangarra Indigenous Protected Area.