Introduction
Native terrestrial mammal species are experiencing rapid and significant
declines across the globe (Di Marco et al. 2014; Woinarskiet al. 2015; Brodie et al. 2021). In many cases, protected
areas are providing the last population strongholds (Geldmann et
al. 2013; Pacifici et al. 2020). However, altered fire regimes
and invasive species, amongst other disturbances, continue to result in
mammal decline even within protected areas (Lawes et al. 2015;
McCain 2019; Rija et al. 2020; Tedeschi et al. 2022).
Therefore, understanding which habitat attributes are important for
mammal persistence and how disturbances, like invasive species and fire,
affect mammal activity and habitat use is critical for developing
effective management strategies to facilitate their persistence within
protected areas (Driscoll et al. 2010; Maxwell et al.2020).
Topography and vegetation productivity are important attributes
influencing terrestrial mammal occurrence and diversity (Dorph et
al. 2021). Topographic variation can create heterogeneous habitats
varying in microclimate and resource availability, providing habitat for
mammals with diverse niches (Dormann et al. 2010). Similarly,
areas with high vegetation complexity and productivity offer more food
and shelter than less productive areas and support larger and more
diverse mammal communities (Sukma et al. 2019). Small mammals, in
particular, favour these productive habitats due to food
availability—such as invertebrates, seeds, and fungi—as well as
shelter from terrestrial and aerial predators (Hanser et al.2011; McCain et al. 2018; Swan et al. 2020).
Invasive mammalian predators, such as the feral cat (Felis
catus ), stoat (Mustela erminea ), small Indian mongoose
(Urva auropunctata ), and European red fox (Vulpes vulpes )
are major threats to native mammals globally (Doherty et al.2016; GISD 2023). These species are highly adaptable and opportunistic,
and can thrive across a range of landscapes, including within large
remnant forests, along edges of fragmented forests, in agricultural and
urban environments, and many other ecosystems (Nichols et al.2019; Alexandre et al. 2020; Louppe et al. 2020). Activity
of these predators can increase in response to prey abundance (Scroggieet al. 2018), anthropogenic features—like tracks and
farms—that provide efficient movement and foraging opportunities in
structurally complex environments like forests (May and Norton 1996;
Colón 2020; Schwemmer et al. 2021), and time since fire (Nalliahet al. 2022; Doherty et al. 2023). Understanding how
invasive predators respond to these factors can assist land managers in
developing more targeted strategies to effectively mitigate their
impacts (e.g., McGregor et al. 2020).
The response of mammals to fire is commonly driven by how fire alters
their food and shelter resources (Morris et al. 2011; Griffiths
and Brook 2014; Lees et al. 2022), rather than direct mortality
(Hale et al. 2021; Shaw et al. 2021). Some small mammals,
like the Trowbridge’s shrew (Sorex trowbridgii ) in North America,
decline after fire in response to a loss of food or an increased
predation risk (Greenberg et al. 2007; Culhane et al.2022), while other more generalist species, like the cliff chipmunk
(Tamias dorsalis ), can be largely unaffected by fire (Morandiniet al. 2023). The abundance of large herbivores, such as the
red-flanked duiker (Cephalophus rufilatus ) in Cameroon, can
increase in recently burnt areas, as the regenerating vegetation is
typically more palatable (Klop et al. 2007; Reid et al.2023). Fire can also create preferable hunting habitat for meso- and
apex predators, such as the coyote (Canis latrans ) and Florida
panther (Puma concolor coryi ) in the U.S.A, which benefit from
the increased exposure of their prey (Dees et al. 2001; Cherryet al. 2017).
Fire-driven changes in predator-prey interactions are especially likely
to be detrimental to native fauna when they benefit invasive mammalian
predators (Geary et al. 2020; Doherty et al. 2022). Fire
can increase the activity invasive predators, such as feral cats
(hereafter ‘cat’) and European red foxes (hereafter ‘fox’), by removing
vegetation which normally provides prey with refuge (McGregor et
al. 2015; Leahy et al. 2016; Hradsky 2020; Miritis et al.2023). Climate change is increasing the occurrence of fire in many parts
of the world (Canadell et al., 2021; van Oldenborgh et al., 2020; Jones
et al. 2022) and may facilitate range expansions for both cats and foxes
(Aguilar et al. 2015; Elmhagen et al. 2017), thus
increasing the likelihood of negative impacts on native fauna. This
highlights the need for well-informed management strategies that account
for the effects of fire, vegetation, and anthropogenic features on the
activity of cats, foxes, and native mammals, so the effectiveness of
protected areas for conservation can be optimised.
Australia serves as one of the most prominent global examples where the
potential for the interaction between fire and invasive predators
carries a great risk for native mammals (Doherty et al. 2023).
Since European colonisation, many overlapping threats have contributed
towards the decline of Australia’s mammal community (Woinarski et
al. 2019a; Ashman et al. 2021; Legge et al. 2023). The
cat and fox have played a particularly damaging role, contributing to
the extinction of >25 mammal species and killing an
estimated 556 million native mammals each year (Kearney et al.2019; Woinarski et al. 2019b; Stobo-Wilson et al. 2022).
Not all studies have found that cat and fox activity increases after
fire (e.g., Hradsky et al. 2017b; Bliege Bird et al. 2018;
Lothian et al. 2022), and a quantitative review found
that—should this phenomenon be observed—it was most likely to occur
shortly after fire (e.g., weeks to months; Doherty et al . 2023).
This indicates that there may be a critical period immediately post-fire
when prey is most vulnerable to an elevated risk of predation, although
Doherty et al. (2023) emphasised that further studies that begin
sampling shortly after fire (i.e., <1 month) are necessary to
better understand the generality of this response.
In this study, we tested whether the activity of cats, foxes, and the
native mammal community could be predicted by fire, vegetation,
topography, and proximity to anthropogenic features within a high-value
conservation reserve. We used camera traps to quantify mammal activity
across 30 sites, both before and immediately after a prescribed burn at
burnt and unburnt sites. We fitted generalised linear mixed models to
test the following predictions:
- Cats and foxes will be more active at sites burnt by the prescribed
fire (McGregor et al. 2016b; Hradsky et al. 2017a), near
anthropogenic features (Hradsky et al. 2017c; Schwemmeret al. 2021), and where mammalian prey activity is higher
(Geary et al. 2022).
- The macropod community (large herbivorous marsupials) will show
increased activity in areas burnt by the prescribed fire, due to the
availability of regenerating vegetation preferred for grazing (Klopet al. 2007; Reid et al. 2023).
- The activity of the small mammal (<2 kg) community will be
negatively influenced by the prescribed fire due to fewer resources
and an increased predation risk and be positively influenced in
riparian and highly productive areas (Lawes et al. 2015; Swanet al. 2015; Mariani et al. 2022).