Fire as a driver and mediator of predator-prey interactions

Abstract

Both fire and predators have strong influences on the population dynamics and behaviour of animals, and the effects of predators may either be strengthened or weakened by fire. However, knowledge of how fire drives or mediates predator-prey interactions is fragmented and has not been synthesised. Here, we review and synthesise knowledge of how fire influences predator and prey behaviour and interactions. We develop a conceptual model based on predator-prey theory and empirical examples to address four key questions: (i) how and why do predators respond to fire; (ii) how and why does prey vulnerability change post-fire; (iii) what mechanisms do prey use to reduce predation risk post-fire; and (iv) what are the outcomes of predator-fire interactions for prey populations? We then discuss these findings in the context of wildlife conservation and ecosystem management before outlining priorities for future research. Fire-induced changes in vegetation structure, resource availability, and animal behaviour influence predator-prey encounter rates, the amount of time prey are vulnerable during an encounter, and the conditional probability of prey death given an encounter. How a predator responds to fire depends on fire characteristics (e.g. season, severity), their hunting behaviour (ambush or pursuit predator), movement behaviour, territoriality, and intra-guild dynamics. Prey species that rely on habitat structure for avoiding predation often experience increased predation rates and lower survival in recently burnt areas. By contrast, some prey species benefit from the opening up of habitat after fire because it makes it easier to detect predators and to modify their behaviour appropriately. Reduced prey body condition after fire can increase predation risk either through impaired ability to escape predators, or increased need to forage in risky areas due to being energetically stressed. To reduce risk of predation in the post-fire environment, prey may change their habitat use, increase sheltering behaviour, change their movement behaviour, or use camouflage through cryptic colouring and background matching. Field experiments and population viability modelling show instances where fire either amplifies or does not amplify the impacts of predators on prey populations, and vice versa. In some instances, intense and sustained post-fire predation may lead to local extinctions of prey populations. Human disruption of fire regimes is impacting faunal communities, with consequences for predator and prey behaviour and population dynamics. Key areas for future research include: capturing data continuously before, during and after fires; teasing out the relative importance of changes in visibility and shelter availability in different contexts; documenting changes in acoustic and olfactory cues for both predators and prey; addressing taxonomic and geographic biases in the literature; and predicting and testing how changes in fire-regime characteristics reshape predator-prey interactions. Understanding and managing the consequences for predator-prey communities will be critical for effective ecosystem management and species conservation in this era of global change.

Keywords: carnivore; foraging behaviour; hunting behaviour; interaction; landscape of fear; mega-fire; multiple threats; predation rates; prescribed burning; wildfire.

Fig. 1

Conceptual framework illustrating how fire can drive changes in vegetation structure, shelter availability, visibility, and visual, olfactory and acoustic cues. These changes influence different components of predation risk (Lima & Dill, 1990), which in turn lead to behavioural responses by predators and prey, and consequences for population dynamics. Behavioural responses can feed back into the predation risk equation as predators and prey adjust to changes in one another's behaviour. The manifestation of these top‐level components can also be affected by moderating factors, including fire characteristics, rainfall, vegetation type, food availability, composition of predator and prey assemblages, management activities, and the spatial and temporal scales over which these factors operate. Images are courtesy of the Integration and Application Network (ian.umces.edu/media‐library) and the NESP Northern Australia Hub (nespnorthern.edu.au). ¹Food availability for predators refers to alternative foods beyond the prey species in question.

Fig. 2

Unburnt and burnt grassland (top), woodland (middle), and forest (bottom). The grassland and woodland were burnt in planned burns, while the forest was burnt in a wildfire. Photograph credits: T. Doherty (top), D. Watchorn (middle) and V. Miritis (bottom).

Fig. 3

Representation of how fire in tropical northern Australia influences predator and prey behaviour and interactions (McGregor et al., , , ,; Leahy et al., 2015). The strength of the effects is highly time dependent because studies found that feral cats used fire scars that were 0–2 (McGregor et al., 2016a) or 0–3 months old (McGregor et al., 2014) more intensively than older fire scars. Images are courtesy of the Integration and Application Network (ian.umces.edu/media‐library) and the NESP Northern Australia Hub (nespnorthern.edu.au).

Fig. 4

Generalised changes in predation risk in response to fire and vegetation structure. The blue dashed line represents a prey species that experiences lower predation risk when habitat is opened up by fire, the solid orange line represents the opposite response (increased predation risk post‐fire), and the green dotted line represents a prey species for which predation risk is independent of vegetation structure and burning.

Fig. 5

Contrasting responses of white‐tailed deer Odocoileus virginianus to fire‐induced changes in predation risk in two ecosystems. (A) In longleaf pine woodlands in Georgia, USA, deer avoided recently burnt areas, despite forage availability being higher there, most likely to reduce risk of predation by coyotes Canis latrans (Cherry et al., 2017). (B) In the Greater Everglades, Florida, USA, deer increased their use of a burnt area to capitalise on increased food availability and lower risk of predation by Florida panthers Puma concolor coryi, which use cover for ambushing prey (Cherry et al., ; Abernathy et al., 2022). Images are courtesy of the Integration and Application Network (ian.umces.edu/media‐library).