Suchergebnisse

Context The decline and extinction of native burrowing mammals across much of Australia has resulted in a loss of underground refugia constructed by native fauna in the environment. The introduced European rabbit (Oryctolagus cuniculus) is now the most widespread mammalian burrower across Australia. Rabbits are an invasive species in Australia, and the destruction of rabbit warrens for pest management is common practice. This destruction of warrens removes a potential refuge for both rabbits and other species in the environment. In landscapes where critical weight range burrowing mammals have declined, the widespread destruction of rabbit warrens removes many underground refuges for several commensal animal species. Aims To identify the use of rabbit warrens by fauna in the seasonally hot, semi-arid Ikara-Flinders Ranges National Park (IFRNP) in South Australia. Methods We used camera traps placed at burrow entrances of warrens and nearby structure to identify the vertebrate species that interact with rabbit warrens in the IFRNP. Key results We recorded 11 bird, nine mammal and eight reptile species present at the entrances of rabbit warrens. Only four of the taxa recorded on cameras in our study showed a preference for warrens over adjacent above-ground structure, three of them introduced species. The alien commensal species recorded using the burrows were rabbits, house mice (Mus musculus) and feral cats (Felis catus). Conclusions Rabbit warrens in the IFRNP are an important resource for a range of native and alien commensal species. In our study, they seem to be of special importance for introduced species. Implications Warren removal in the IFRNP may negatively impact native commensal species in treated areas but is likely to be of long-term net benefit for a wider range of native animals.

Context
Changes in abundance following fire are commonly reported for vertebrate species, but the mechanisms causing these changes are rarely tested. Currently, many species of small mammals are declining in the savannas of northern Australia. These declines have been linked to intense and frequent fires in the late dry season; however, why such fires cause declines of small mammals is unknown.

Aims
We aimed to discover the mechanisms causing decline in abundance of two species of small mammals, the pale field rat, Rattus tunneyi, and the western chestnut mouse, Pseudomys nanus, in response to fire. Candidate mechanisms were (1) direct mortality because of fire itself, (2) mortality after fire because of removal of food by fire, (3) reduced reproductive success, (4) emigration, and (5) increased mortality because of predation following fire.

Methods
We used live trapping to monitor populations of these two species under the following three experimental fire treatments: high-intensity fire that removed all ground vegetation, low-intensity fire that produced a patchy burn, and an unburnt control. We also radio-tracked 38 R. tunneyi individuals to discover the fates of individual animals.

Key results
Abundance of both species declined after fire, and especially following the high-intensity burn. There was no support for any of the first four mechanisms of population decline, but mortality owing to predation increased after fire. This was related to loss of ground cover (which was greater in the high-intensity fire treatment), which evidently left animals exposed to predators. Also, local activity of two predators, feral cats and dingoes, increased after the burns, and we found direct evidence of predation by feral cats and snakes.

Conclusions
Fire in the northern savannas has little direct effect on populations of these small mammals, but it causes declines by amplifying the impacts of predators. These effects are most severe for high-intensity burns that remove a high proportion of vegetation cover.

Implications
To prevent further declines in northern Australia, fire should be managed in ways that limit the effects of increased predation. This could be achieved by setting cool fires that produce patchy burns, avoiding hot fires, and minimising the total area burnt.