Cats, foxes and fire: quantitative review reveals that invasive predator activity is most likely to increase shortly after fire

Abstract

Background Predators and fire shape ecosystems across the globe and these two forces can interact to impact prey populations. This issue is particularly pertinent in Australia where there is considerable scientific and public interest in the post-fire impacts of two invasive predators—the feral cat and red fox. It remains unclear, though, whether increased cat and fox activity in response to fire is a general phenomenon, or whether the responses are highly context-specific and not generalisable. Results We reviewed and analysed existing literature and found that a range of positive (e.g., increased activity in burnt areas), negative (decreased activity), and neutral responses have been recorded across different studies and locations. Mixed effects modelling revealed that positive responses to fire were more likely when areas were burnt more recently (shorter time since fire). The mean likelihood of increased activity by cats decreased from 41% at 0 months post-fire to 10% at 100 months post-fire, whereas the mean probability for foxes decreased from 53 to 10%. This suggests that there may be a critical time period immediately post-fire when prey are most vulnerable to elevated impacts of predators, and within which management interventions are likely to be most impactful. Conclusions Many of our findings can be identified as potential cases of either mechanistic or apparent context dependency (variation in recorded patterns due to observational and ecological factors). This provides a pathway for the design of future studies that will enhance our understanding of predator responses to fire, both in Australia and globally. Conservation policy and management will benefit from additional research spanning a greater range of ecosystems and fire events, along with a more comprehensive and nuanced interpretation of existing evidence.

After the ‘Black Summer’ fires: Faunal responses to megafire depend on fire severity, proportional area burnt and vegetation type

“…Other research found no discernible difference in fox occurrence between burnt and unburnt sites around 1 year after the Black Summer fires (Spencer et al, 2022). This further suggests that these responses driven by hunting opportunities are time-sensitive and more likely to occur shortly after the fires, supporting existing findings on this topic (Doherty et al, 2023).…”

“…Feral cats had lower activity at sites dominated by high-extreme severity burns and moderate activity in sites burnt at a low-moderate severity, however, these patterns were weak. Although cats target severe fires in tropical northern Australia to take advantage of vulnerable prey (McGregor et al, 2016), there is little evidence of cats increasing their activity after severe fires in temperate Australia (Doherty et al, 2023). Cats have generalist diets and occupy a broad variety of habitats, and often have large home ranges (Santos et al, 2014).…”

How do invasive predators and their native prey respond to prescribed fire?

“…For instance, in the USA, swift foxes ( V. velox ), which are closely related to red foxes, only used burnt areas more frequently if their existing core home ranges were burnt (Thompson et al., 2008 ). Indeed, a recent analysis of existing evidence from Australia found that there was a high likelihood of neutral responses to fire being recorded for both cats and foxes in Australia (55% and 67%, respectively; Doherty et al., 2023 ).…”

“…The occurrence and relative abundance (i.e. activity) of these predators can increase in response to prey abundance (Scroggie et al., 2018 ), recent burning (Birtsas et al., 2012 ; Doherty et al., 2023 ; Nalliah et al., 2022 ), and anthropogenic features (such as tracks and farms) that provide efficient movement and foraging opportunities in structurally complex environments like forests (Colón & Kamil, 2020 ; May & Norton, 1996 ; Schwemmer et al., 2021 ). Ecosystem‐specific knowledge of 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 ).…”

“…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 (Ashman et al., 2021 ; Legge et al., 2023 ; Woinarski, Braby, et al., 2019 ).…”