Feral cats, foxes and fire
Foxes, cats and fire in the Otways
The devastating impact of foxes and cats on Australia’s native wildlife is well documented and the situation is no different in the Otways where our most vulnerable small mammals are at risk from these feral predators.
In 2017, Parks Victoria rolled out their Otway Ark program with the aim of reducing fox numbers across the Otways to protect our small native mammals, and in 2019 the Conservation Ecology Centre undertook to expand this program onto Otway Forest Park, private forestry and a large block of private properties to improve biodiversity outcomes.
Unfortunately, as a result of work being undertaken by University of Melbourne PhD student Matt Rees in partnership with the CEC, we now know that the densities of feral cats in the Otways are unexpectedly high.
In addition to the direct threat to small mammals posed by these introduced predators, a growing body of evidence from around Australia suggests fire may increase the vulnerability of native mammals to predation by foxes and feral cats after fire, by removing the dense understory vegetation that provides cover for small mammals and making it easier for predators to move around.
The Wild Otways Initiative
As a part of the Wild Otways Initiative, the Conservation Ecology Centre is investigating the relationship between fire and these feral pests in the Carlisle Health region of the Otways.
This project is testing whether localised control of predators after planned burns can mitigate the impacts of predation on threatened mammal populations, such as the Long-nosed Potoroo, which we’ve been tracking since 2021 with The University of Melbourne, funded by the Hermon Slade Foundation. The results of this work to date were presented at the Otways Ecological Research Forum in 2021 and you can watch the presentation online here.
We’re also working with Forest Fire Management Victoria and Eastern Maar Aboriginal Corporation to modify planned burn practice, including by increasing the size of unburnt patched within burn blocks, and measure whether this improves post-fire survival of threatened mammals.
Understanding the ecosystem
Baseline data on predator activity pre-fire has been collected by the Conservation Ecology Centre by attaching GPS tracking collars to 7 foxes and 5 cats in the Carlisle Heath.
We’ve also deployed a large predator camera grid and conducted fox scat surveys along a 16km road transect within the same study area. Fox scats have been sent for genetic analysis to determine prey species / composition.
Adding fire to the landscape
Over the 2022 burn season, Forest Fire Management Victoria will be undertaking a series of planned burns across the Carlisle Heath. Each of these burns will be a different intensity and subject to different predator control regimes (see diagram) to test the response of both predators and small mammals to these different treatments.
Once the burns have gone through our camera monitoring grids will be reinstated to monitor the post-fires landscape, and the collared predators will keep their collars on for up to 9 months.
Having collars on both the predators and the prey species allows us to continually track these animals during and immediately post-fire, where motion-sensing cameras can only be deployed once a burn block is deemed safe by land managers, which may be more than 3 weeks post-fire.
By simultaneously tracking predators and their prey species with GPS collars, as well as via cameras and scat analysis we hope to determine whether the interaction between fire and ferals presents an increased risk to threatened native species.
We’ll be addressing three main questions:
- Do fox and cat movements change in response to fire?
- Does the patchiness of the burn influence predator or prey behaviour?
- Does lethal control of foxes and cats help small mammals survive in the post-fire landscape?
Knowing how invasive predators move in these heathy woodlands, and how their movements change after fire, can help us determine when and where we need to step in with additional targeted management actions to improve native mammal survival post-fire.
One potential solution may be to integrate the control of these invasive predators with planned burning operations – removing those predators most likely to exploit the burn areas before they get a chance to do damage.
Alternatively, if there are factors like fire pattern or severity that influence how invasive predators move after fire, it may be possible to apply fire in a way that prevents or mitigates the response of predators in the first place, for example by altering fire lighting patterns to produce ‘patchy’ burn scars.