When the world burns, how do predators respond?

This blog post is provided by William Geary, Tim Doherty, Dale Nimmo, Ayesha Tulloch and Euan Ritchie and tells the  #StoryBehindThePaper for their article Predator responses to fire: A global systematic review and meta‐analysis, which has been shortlisted for the 2020 Sidnie Manton Award.

Over the past year, many regions of the world have experienced extensive and severe fires. More than ten million hectares across eastern and southern Australia were incinerated over the 2019/2020 bushfire season alone, an area larger than South Korea. Fires in the Amazon, the Arctic, and California have also captured global media headlines. In Australia, we now know that the fires have impacted the ranges and habitats of hundreds of plant and animal species, many of which were already threatened with extinction.

As climate change continues, large, intense, and severe fires are predicted to occur more frequently. So what does this mean for the animals living in fire-prone environments?

Our research, published recently in the Journal of Animal Ecology, looked at studies from around the world to identify how predators, which themselves have a strong influence on ecosystems and their dynamics, respond to fire.

We found that some predators seem to benefit from fires, others appear to be adversely affected, and the remainder seem largely indifferent. In a changing climate, we need to understand how fires affect predators—and potentially their prey in turn—in order to keep ecosystems healthy and manage species appropriately, including exotic and invasive species.

Predators: the good and the bad

Large predators, like wolves and lions, often play important roles in ecosystems, regulating food webs by reducing the abundance or changing the behaviour of herbivores and smaller, subordinate predators. Many large predators are at risk of extinction within their native ranges due to loss of habitat, lethal control associated with livestock protection, and human exploitation. In contrast, introduced predators, such as feral cats, red foxes, and mustelid species, have spread to new regions, where they have devastated native wildlife.

Fires can offer new opportunities as well as pose problems for predators. Some predators take advantage of charred, more open landscapes to hunt exposed prey. Others need thick vegetation to ambush their prey, and their hunting success is diminished in burnt landscapes where there are fewer places to hide and launch attacks from.

But until now, we have not had a good global perspective on which predators are typically drawn to fire, which are repelled by it, and which don’t care either way. Synthesising information on how different kinds of predators (for example, large or small, pursuit or ambush) respond to fire is vital for both the conservation of native top predators and to help protect native prey from introduced predators .

Some like it hot

We reviewed studies from around the world to identify how different vertebrate predators (birds, mammals, and reptiles) respond to fire in different ecosystems.

We found 160 studies on the response of 188 predator species to fire, including wolves, coyotes, foxes, cats, hawks, owls, monitor lizards, and snakes, amongst others. The studies came from 20 different countries, although most were from North America or Australia, and focused on canid and felid species.

There were 36 studies for which we could conduct a meta-analysis. This revealed that some predators seem to like fire: they were more abundant, or spent more time in, recently burnt areas than unburnt areas. We found that red foxes (Vulpes vulpes) mostly respond positively to fire and become more active in burned areas. Some species benefit from fire to such an extent they have even been observed helping to spread it. In northern Australia, raptors have been observed carrying burning sticks and dropping them in unburnt areas beyond the fire front, helping to spread fire and targeting prey as they flee the fire.

For other predators, fire appears to be bad news. Following wildfires in California, numbers of eastern racer snakes decreased in burnt areas. Likewise, lions in Serengeti National Park, Tanzania, avoided recently burned areas, because the dense vegetation from which they ambush prey is destroyed by fire.

WG Fig 1

Figure 1: A global summary of studies examining predators and fire.

The papers we reviewed highlighted food availability, vegetation cover, and competition with other predators as the most likely factors mediating how different species responded to fire. On the other hand, some species, including bobcats and the striped skunk, appeared largely unaffected by fire. Of the affected species, some (such as spotted owls and garter snakes) responded differently to fire in different places. This could be put down to differences in the fires being studied (e.g. high-severity fire vs. low-severity fire) or it could be due to the species behaving differently in different locations. Overall, we found it is difficult to reliably predict how a predator species will respond to fire.

We still have a lot to learn

Our results show that while many predators appear to adapt to the changes that fires bring about, some are impacted by fire, both negatively and positively. The problem is that, with a few exceptions, we will struggle to know how a given fire will affect a predator species without local knowledge, especially given that individual species, such as spotted owls, appear to respond differently across their geographic range. This means environmental managers need to monitor the local outcomes of fire management, such as prescribed burns.

There may be situations in which predator management needs to be coupled with fire management to help prevent native wildlife becoming fox food after fire. There have even been trials to see if artificial shelters can help protect native wildlife from introduced predators after fire.

Getting our knowledge base right

Critically, inference and our ability to apply knowledge, have been hampered by inconsistency in reporting or a total lack of contextual information in many studies. No two fires are the same—they differ in size, intensity, severity, and season—but these details are often not recorded or reported. The literature is also strongly biased towards felid and canid species (24% and 25%, respectively), and there are relatively few studies from Africa, Asia, and South America on predator responses to fire.

It is important to note that the effects of fire on predators may sometimes be overlooked due to the way experiments are carried out, or because monitoring happens too long after fires, potentially missing the critical window to detect predator and prey responses.

Standardising how fire, predator numbers, and environmental features are recorded would help future studies predict how predators might react to different types of fires in various situations. To assist future synthesis, we developed a list of key variables that ecologists and practitioners studying predator responses to fire should aim to record and report (Figure 2).

WG fig 2

Figure 2: Summary of the key variables that should be recorded and reported in predator fire studies

As wildfires become more frequent and severe under climate change, understanding how fire intensity and frequency shapes predator and populations will be critical for effective and informed ecosystem management and conservation.

Read the paper

Geary, WL, Doherty, TS, Nimmo, DG, Tulloch, AIT, Ritchie, EG. (2020) Predator responses to fire: A global systematic review and meta‐analysis. Journal of Animal Ecology, 89, 995-971, https://doi.org/10.1111/1365-2656.13153

191019_NORTHERNTERRITORY_0406_RobertGeary

Credit: Robert Geary

20200224_125542_TimDoherty

Credit: Tim Doherty

 

 

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