Publications Research

Responses of invasive predators and native prey to a prescribed forest fire

Authors: Bronwyn A Hradsky, Craig Mildwaters, Euan G Ritchie, Fiona Christie, and Julian Di Stefano

Published in: Journal of Mammalogy (early view)


Fire shapes biome distribution and community composition worldwide, and is extensively used as a management tool in flammable landscapes. There is growing concern, however, that fire could increase the vulnerability of native fauna to invasive predators.

We developed a conceptual model of the ways in which fire could influence predator–prey dynamics.

Using a before–after, control–impact experiment, we then investigated the short-term effects of a prescribed fire on 2 globally significant invasive mesopredators (red fox, Vulpes vulpes, and feral cat, Felis catus) and their native mammalian prey in a fire-prone forest of southeastern Australia. We deployed motion-sensing cameras to assess species occurrence, collected predator scats to quantify diet and prey choice, and measured vegetation cover before and after fire. We examined the effects of the fire at the scale of the burn block (1,190 ha), and compared burned forest to unburned refuges.

Pre-fire, invasive predators and large native herbivores were more likely to occur at sites with an open understory, whereas the occurrence of most small- and medium-sized native mammals was positively associated with understory cover. Fire reduced understory cover by more than 80%, and resulted in a 5-fold increase in the occurrence of invasive predators. Concurrently, relative consumption of medium-sized native mammals by foxes doubled, and selection of long-nosed bandicoots (Perameles nasuta) and short-beaked echidnas (Tachyglossus aculeatus) by foxes increased. Occurrence of bush rats (Rattus fuscipes) declined. It was unclear if fire also affected the occurrence of bandicoots or echidnas, as changes coincided with normal seasonal variations.

Overall, prescribed fire promoted invasive predators, while disadvantaging their medium-sized native mammalian prey. Further replication and longer-term experiments are needed before these findings can be generalized. Nonetheless, such interactions could pose a serious threat to vulnerable species such as critical weight range mammals. Integrated invasive predator and fire management are recommended to improve biodiversity conservation in flammable ecosystems.

Hradsky BA, Mildwaters C, Ritchie EG, Christie F, Di Stefano J (2017) Responses of invasive predators and native prey to a prescribed forest fire, Journal of Mammalogy PDF DOI


Resolving the value of the dingo in ecological restoration

Authors: Thomas M Newsome, Guy-Anthony Ballard, Mathew S Crowther, Justin A Dellinger, Peter J S Fleming, Alistair S Glen, Aaron C Greenville, Chris N Johnson, Mike Letnic, Katherine E Moseby, Dale G Nimmo, Michael Paul Nelson, John L Read, William J Ripple, Euan G Ritchie, Carolyn R Shores, Arian D Wallach, Aaron J Wirsing and Christopher R Dickman.


There is global interest in restoring populations of apex predators, both to conserve them and to harness their ecological services.

In Australia, reintroduction of dingoes (Canis dingo) has been proposed to help restore degraded rangelands. This proposal is based on theories and the results of studies suggesting that dingoes can suppress populations of prey (especially medium- and large-sized herbivores) and invasive predators such as red foxes (Vulpes vulpes) and feral cats (Felis catus) that prey on threatened native species. However, the idea of dingo reintroduction has met opposition, especially from scientists who query the dingo’s positive effects for some species or in some environments.

Here, we ask ‘what is a feasible experimental design for assessing the role of dingoes in ecological restoration?’ We outline and propose a dingo reintroduction experiment — one that draws upon the existing dingo-proof fence—and identify an area suitable for this (Sturt National Park, western New South Wales).

Although challenging, this initiative would test whether dingoes can help restore Australia’s rangeland biodiversity, and potentially provide proof-of-concept for apex predator reintroductions globally.

Newsome TM, Ballard G, Crowther MS, Glen AS, Dellinger JA, Fleming PJS, Greenville AC, Johnson CN, Letnic M, Moseby KE, Nimmo DG, Nelson MP, Read JL, Ripple WJ, Ritchie EG, Shores CR, Wallach AD, Wirsing AJ, Dickman CR (2015) Resolving the value of the dingo in ecological restoration, Restoration Ecology PDF DOI

Publications Research

Does fire influence the landscape-scale distribution of an invasive mesopredator?

Authors: Catherine J Payne, Euan G Ritchie, Luke T Kelly and Dale G Nimmo.


Predation and fire shape the structure and function of ecosystems globally. However, studies exploring interactions between these two processes are rare, especially at large spatial scales. This knowledge gap is significant not only for ecological theory, but also in an applied context, because it limits the ability of landscape managers to predict the outcomes of manipulating fire and predators.

We examined the influence of fire on the occurrence of an introduced and widespread mesopredator, the red fox (Vulpes vulpes), in semi-arid Australia. We used two extensive and complimentary datasets collected at two spatial scales.

We examined the influence of fire on the distribution of introduced red foxes in semi-arid Australia. Image credit Area51Bel [CC-BY-SA 3.0] via Wikimedia Commons.
We examined the influence of fire on the distribution of introduced red foxes in semi-arid Australia. Image credit Area51Bel [CC-BY-SA 3.0] via Wikimedia Commons.
At the landscape-scale, we surveyed red foxes using sand-plots within 28 study landscapes — which incorporated variation in the diversity and proportional extent of fire-age classes — located across a 104 000 km² study area. At the site-scale, we surveyed red foxes using camera traps at 108 sites stratified along a century-long post-fire chronosequence (0–105 years) within a 6630 km² study area.

Red foxes were widespread both at the landscape and site-scale. Fire did not influence fox distribution at either spatial scale, nor did other environmental variables that we measured.
Our results show that red foxes exploit a broad range of environmental conditions within semi-arid Australia.

The presence of red foxes throughout much of the landscape is likely to have significant implications for native fauna, particularly in recently burnt habitats where reduced cover may increase prey species’ predation risk.

Payne CJ, Ritchie EG, Kelly LT, Nimmo DG (2014) Does Fire Influence the Landscape-Scale Distribution of an Invasive Mesopredator? PLoS ONE 9(10): e107862 PDF DOI 


Billy Geary: Big Desert Adventures

This post is written by Honours student, Billy Geary.

Since settlement times, Victoria’s Mallee region has captured the public imagination. Upon digging up old newspaper articles documenting early expeditions to the region, tales of ‘tiger cats’ hell bent on attacking people, and medium-sized marsupials (e.g. bettongs and bandicoots) in apparent plague proportions, are common. Over time, these bush yarns have only enhanced the region’s mystique and reputation as somewhat of a wild frontier.

Could this be?
Could this be the fabled fearsome tiger cat? Actually, no, it’s just a tiger quoll. Image credit:  JJ Harrison [CC-BY-SA-3.0] via Wikimedia Commons (modified)
In the years since, the area has experienced considerable environmental change. Surrounding large but fragmented patches of remnant Mallee now contained within national parks and state forest, wheat cropping and sheep farming abound. Importantly, fire is now a very common and heavily managed process that strongly influences the local native flora and fauna. Coupled with this, the influx of feral species such as foxes, cats, rabbits and goats has seen many native species decline or disappear all together. Significantly though, the region’s large parks still preserve some of Victoria’s most remote, majestic and largely untouched country.

These parks, including the Big Desert Wilderness Park, still hold that sense of wonder that is reported so frequently in the literature of the 1800s and early 1900s. There’s nothing quite like driving over the crest of a sand dune and being blown away by the sheer vastness of the landscape around you. Or, the sense of wonder instilled by a night sky completely unaffected by light pollution. These two experiences do a fantastic job of instilling a sense of just how remote and wild this region of Victoria remains.

Once upon a time quolls and dingoes appeared to rule the Big Desert / Wyperfeld region from the top of the food web. It’s now a slightly different storey, but no less intriguing.

The majestic Big Desert night sky makes for fantastic pondering. Image credit: Robert Geary.
The majestic Big Desert night sky makes for fantastic pondering. Image credit: Robert Geary.

This is where my research comes in, just how do invasive mesopredators (feral cats, red foxes) interact with an existing apex predator (dingoes or perhaps wild dogs)? And how well do these mesopredators deal with the challenges this semi-arid environment throws at them, in particular fire? The overarching school of thought in Australia is that our feral mesopredators respond positively to fire events, as it greatly reduces the effort required to seek out and kill prey. However, can the presence of a top predator mediate this response to fire through a reduction in cover available to the mesopredators themselves? Do predators themselves become prey, the hunters the hunted?

Given the ongoing trend of increasing fire frequency and intensity across our continent, the one-two punch of changing fire regimes and feral predators (particularly feral cats) is quite a frightful proposition for our native critters. As such, teasing out the interactions between the Mallee’s predators, their prey and the ecosystems in which they live is quite an important proposition. Indeed, it makes for something good to ponder whilst gazing at a beautiful Big Desert sky after setting up camp.

So, what do we know so far?

Having just brought in the first third of my camera traps, amongst some amazing images of other critters, it appears that foxes, cats and dogs are all well distributed across the Big Desert. For dogs and cats, there’s also considerable variation in their appearance. We’ve got feral cats that look like the legendary Victorian black panther and others with stripes like tigers. There also appears to be canids in the region at both ends of the wild dog–dingo spectrum. To what extent these animals are similar ecologically remains to be determined. These images, as well as a bunch of great shots of the local native critters have been collated into a little video below.

In addition to this the small mammal community appears to be doing okay, with Mitchells hopping mice and silky mice fairly well distributed across the park. Same too for the larger residents, western grey kangaroos and emus, which seem to materialise out of thin air over each dune crest as we drove through the park.

With only a third of our 105 sites surveyed so far, there’s still plenty more the Big Desert and its array of species can tell us. In particular, I’ll be looking to work out what habitat preferences, if any, our three predators have across the landscape. Secondly, how our predators are interacting with each other across time and space. It will be particularly interesting to investigate any interactions between the local mesopredators and top dogs. We’re only just beginning to scratch the surface of the Big Desert’s secrets, and that’s perhaps the most exciting part.

Work in the Big Desert is never a dull affair. Image credit: Robert Geary.
Work in the Big Desert is never a dull affair. Image credit: Robert Geary.

While it is a long, long drive to the Big Desert from Melbourne, it’s hard not to be arrested by the notion of just how much is yet to be explored there. Because who knows: just maybe there’s still a giant tiger cat lurking out there, somewhere.

Publications Research

Experiments in no-impact control of dingoes: comment on Allen et al. 2013

Authors: Christopher N Johnson, Mathew S Crowther, Chris R Dickman, Michael I Letnic, Thomas M Newsome, Dale G Nimmo, Euan G Ritchie and Arian D Wallach.


There has been much recent debate in Australia over whether lethal control of dingoes incurs environmental costs, particularly by allowing increase of populations of mesopredators such as red foxes and feral cats.

Allen et al. (2013) claim to show in their recent study that suppression of dingo activity by poison baiting does not lead to mesopredator release, because mesopredators are also suppressed by poisoning.

We show that this claim is not supported by the data and analysis reported in Allen et al.’s paper.

The management of dingoes is a highly conflicted and frequently emotional issue in rural Australia. Image by Peripitus [CC-BY-SA-3.0] via Wikimedia Commons. Skull and Crossbones icon by Jens Tärning [CC-BY-SA-2.0] via the Noun Project.
Johnson CN, Crowther MS, Dickman CR, Letnic MI, Newsome TM, Nimmo DG, Ritchie EG, Wallach AD (2014) Experiments in no-impact control of dingoes: comment on Allen et al. 2013. Frontiers in Zoology 11:17 PDF DOI