COS 109-6 - CANCELLED - Does invasive predator control improve threatened native mammal responses to fire?

Abstract: Fire is a natural disturbance known to shape ecosystems around the world. One major concern is that fire often interacts with other processes, including anthropogenic drivers such as climate change, land use and biotic invasions. In Australia, many native mammals are under threat from changes in fire regimes and predation by invasive species like red foxes (Vulpes vulpes) and feral cats (Felis catus). Concerningly, these threats can interact. For example, fire can reduce understory cover, making ground-dwelling native mammals more vulnerable to predation. While long-term poison baiting programs for invasive predators in Australia have been successful in suppressing populations, it is unclear if long-term fox baiting can improve native mammal responses to fire. Further, invasive predator management programs are rarely coordinated with fire.

We address this knowledge gap by using a replicated before-after control-impact design to assess whether landscape-scale fox control improved responses to planned fire for five medium-sized mammals. We surveyed 402 sites using camera traps to monitor changes in invasive predator and native mammal occurrence before and after fire across fox-baited and unbaited landscapes. We also assessed how changes in vegetation structure, proximity to unburnt patches and fire severity influenced species responses to fire. We tested our predictions using dynamic occupancy models and accounted for changes in colonization and extinction rates following a fire.

Prior to fire, fox-baiting had no effect on invasive predator or on native mammal occupancy rates. Fox occupancy increased across all sites post-fire but the increase was larger in unbaited areas. Feral cat occupancy only increased post-fire in areas where fox baiting occurred, potentially due to mesopredator release. The occupancy rates for most native mammals declined following fire; there was evidence that fox baiting improved their responses to fire. Preliminary results showed a positive relationship between invasive predator occupancy post-fire and increasing burn severity. Understory cover was the strongest predictor of native mammal occupancy before and after fire. Ground-dwelling native mammals are increasingly under threat from fire and predation by invasive species, and immediate attention is necessary to further limit these disturbances. This study shows that invasive predators increase their use of burnt areas in fox-baited landscapes as well, highlighting the need to consider the importance of unburnt habitat as refugia and managing fire severities for improving native mammal responses to fire. This study helps inform integrated fire management and invasive predator control approaches and so design efficient strategies for conserving native mammals.