Featured Image Caption: Many of us have lived or seen how forest fires affect human settlements, but have we ever stopped and wondered how they affect animals and how they interact with each other? (Image Source: “Sweden: fighting forest fires” by EU Civil Protection and Humanitarian Aid, licensed under CC BY-NC-ND 2.0).
Reference: Doherty, T.S., Geary, W.L., Jolly, C.J., Macdonald, K.J., Miritis, V., Watchorn, D.J., Cherry, M.J., Conner, L.M., González, T.M., Legge, S.M., Ritchie, E.G., Stawski, C., & Dickman, C.R. (2022). Fire as a driver and mediator of predator-prey interactions. Biological Reviews, 97, 1539–1558. https://doi.org/10.1111/brv.12853
Forest fires, sometimes called wildfires, can be caused by natural occurrences, like lightning and extreme droughts, or by human intervention, like brush fires caused by camping fires. However, one thing is certain: these fires are unpredictable once started and hard to control and suffocate. Environmental factors–like wind and topography–can affect how fast fires spread, but they tend to burn for days, causing great loss of human and animal lives and surmounting massive economic damage. Yet not all fires are bad. Sometimes, there are prescribed fires, also called controlled burns, which are essentially fires that are purposely started under planned and controlled conditions for a number of reasons, such as to help endangered species recover or to prevent a destructive fire by reducing the wooden fuel available.
How Do Fires Affect Animal Behavior?
When fires course through forests that many animals consider home, these animals may shift their behaviors to survive the habitat modification. Beginning to explain how fires affect animal behavior is an extremely complex task. As can be seen below, in the first figure postulated in the paper published by Doherty et al. (2022), there are many factors to take into consideration. Variables like the source and size of the fire, the preexisting vegetation type and structure, food and shelter availability, and ultimately the predator-prey assemblages will tell how much a fire can affect the behavior of either the predator or prey or both.
With so many factors potentially affecting animal behavior, a group of scientists, led by Dr. Tim Doherty, set out to determine how fires affect interactions between predators and their prey through 4 questions:
• How and why do predators respond to fire?
• How and why does prey vulnerability change post-fire?
• What mechanisms do prey use to reduce predation risk post-fire?
• What are the outcomes of predator-fire interactions for prey populations?
In the end, these scientists consider that understanding how fire affects animal hunting and foraging behavior, predation rates, physiology, and population dynamics will help us understand how and why some species persist in burnt landscapes while others don’t.
Stop, Drop, and Rolling Out Answers
How and why do predators respond to fire?
Predators can respond to fire numerically or behaviorally. A numerical change would be if predator density or activity changes after a fire, while a behavioral change would be a change in prey selection by the predator or in hunting activity. In both cases, encounter rates with the prey may change, potentially affecting predator-prey interactions. They hypothesize that predators respond to fire this way because of the changes taking place in the physical habitat. For instance, recently burnt habitats tend to make it easier for predators to spot prey while also supplying prey with less shelter.
How and why does prey vulnerability change post-fire?
Prey vulnerability may change post-fire because their habitat changes to a more open one, but this doesn’t always affect prey the way one may think. For instance, some prey may have higher survivability due to their predators being easier to spot, while others may have lower survivability because they find it harder to escape due to lower shelter availability. In both cases, prey vulnerability changes, for better or for worse.
What mechanisms do prey use to reduce predation risk post-fire?
Prey use many mechanisms to reduce predation risk post-fire, but some of the most studied mechanisms are how prey change their foraging, resting, and predator avoidance practices in order to survive in these adverse circumstances. But one of the most surprising findings was how these mechanisms change, even within the same species when put in different ecosystems. Doherty and research colleagues gave the example of how white-tailed deer behave differently after a fire when they’re facing different predators. These deer, when facing coyotes in longleaf pine woodlands, avoid burnt areas, even if foraging availability is higher in those areas, while the opposite is true when they’re facing pumas in the Greater Everglades; in this ecosystem they prefer burnt areas, as pumas use unburnt areas with cover to ambush prey.
What are the outcomes of predator-fire interactions for prey populations?
The outcomes of predator-fire interactions for prey populations are better understood if we look at studies where both fire and predators are controlled, and these are precisely the studies Doherty et al. (2022) report on. The team describes how it seems like predator-prey interactions almost always lead to a decrease in prey populations. Some long-term population studies, where the fires were not controlled, also show the same outcome: prey populations decrease, sometimes even close to the near extinction of said population.
Another One Bites the Dust
The authors suggest that all fires, even prescribed fires, affect predator-prey interactions in similar ways. Scientists are therefore suggesting that more research be conducted on the benefits and risks of controlled fires, and on how behavior is modified under those strenuous circumstances. Overall, it seems like fires tend to affect prey more negatively than they affect predators, but there are always exceptions to the rule. Sadly, it seems that although fires symbolize new beginnings in the botanical world, with the rebirth of pine trees and the diversification of plants after a fire; they seem to lead to conflicting results in the zoological world, with the decrease of prey populations and the unpredictable changes in predator-prey interactions.