After the summer’s devastating bushfires, the New South Wales government announced a plan to airdrop one million poisoned baits in the state’s most vulnerable regions over the next year. The plan is aimed at protecting surviving native animals from foxes, feral cats and wild dogs.
This isn’t the first time aerial baiting has been used in NSW recently. As the fire season got underway in September last year, the government’s biannual aerial baiting program scattered baits over nearly 8 million hectares in the Western Division alone – dispensing 43,442 aerial baits and 115,162 ground-laid baits over the drought-stricken region.
In a study published this week, I explore Australia’s history as pioneers of this technology. The review raises serious concerns about the ethics and poor results of baiting programs, and the high uptake of baits by non-target species such as marsupials.
Aerial baiting has been Australia’s foremost weapon against pest species for the past 74 years. The initial target was the dingo, to protect unguarded livestock from being killed.
How Australia made poisoning animals normal
It started on Remembrance Day in 1946. Around 367,000 dry meat baits were airdropped across Queensland, each containing enough strychnine to kill an adult dingo. The campaign was considered a victory, despite only recovering one dingo carcass during the initial operation. Livestock predation apparently decreased; tracks in the sand vanished.
The following year, 1.5 million baits were distributed. Then in 1948 the quantity increased to 2.5 million baits across remote regions of Queensland and the Northern Territory.
The strychnine tablets took up to 12 tortuous hours for the poison to deliver its lethal kill. The baits used in research trials were still toxic after 14 weeks.
There was huge public criticism of the project at the time – much of it from graziers. They claimed ants and valuable pest-eating birds – magpies, small hawks, butcher birds, crows, ibis and curlew – were eating the baits.
In response, the Queensland government set up the first monitored trials. The 1954 report from the Chief Vermin Control Officer recorded:
In the dry season campaigns, the baits are dropped on water-holes, soaks, junctions of dried water courses, gorges in hills and all places where dogs must travel or gather in their search for water and game and in their movements with pups from the breeding areas.
The data recorded an average 14,941 baits dispensed for every dingo carcass recovered. Anecdotal evidence suggests the program was considered a success.
Then in 1968 – 21 years after aerial campaigns began – a four-year CSIRO study tested the effectiveness of aerial baiting. It found the 1954 report was far from conclusive – the dingoes may just have moved elsewhere. And it concluded: “clearly aerial baiting was not effective”.
But there was an important caveat:
It is important to emphasise that, though this aerial baiting campaign was a failure, such a conclusion does not necessarily apply to any other campaign.
On the strength of that, aerial baiting programs continued.
Despite millions of baits applied annually to the environment since the 1940s, Australia’s biodiversity has plummeted.
What’s more, developments in the technology haven’t come far. Raw meat baits eventually replaced dry baits in some areas. Strychnine was superseded by 1080, a less harmful poison to non-target native species, and less persistent in the environment.
Trials in the 1980s brought the bait-to-kill rate down to 750 to 1 (baits per dingo carcass recovered). This was considered a cost-effective and successful outcome.
Soon after, aerial baiting found a new market, becoming the frontline defence against Australia’s plummeting biodiversity from invasive predators.
In 2008, the Australian Pesticides and Veterinary Medicines Authority imposed a limit of ten baits per kilometre to reduce risk to non-target species.
Pest control agencies need four times that amount of poison to achieve a successful kill rate. Yet planes have been dispensing baits at this lower and ineffective rate since 2008.
Why? It seems a balance between wildlife safety and effective canine or predator eradication isn’t possible with this technology.
In fact, it has been impossible to accurately trace the fate of baits thrown from aeroplanes into remote terrain. Even ground baiting trials have proved difficult to monitor. A 2018 trial found non-target species consumed more than 71% of ground-laid meat baits, including ravens, crows, goannas, monitor lizards, marsupials and ants.
Four young dingoes died during this trial, representing only a 1.25% uptake by target. Despite monitoring with cameras and sand traps, 599 baits out of 961 in the trial disappeared without a trace.
These baits are not benign. Repeat doses can kill marsupials; non-lethal doses can kill pouch young. Secondary poisoning can also be lethal. Applying this outdated technology to vulnerable bushfire regions is from a historical viewpoint, potentially hazardous.
There are new technologies available to help protect and repair Australia’s fragile and broken ecosystems. Remote surveillance, drones, AI, heat sensing equipment, and more could locate populations and dispatch dangerous animals.
If aerial baiting continues, aerial surveillance could at least follow the fate of the one million baits and tell us what and who is eating them – who lives and who dies in the stripped-bare landscape.
One thing is for certain: halting the program would prevent hundreds of thousands of these poisoned meat baits ending up in the stomachs of our treasured native animals.
There is a widespread belief dingoes are as good as extinct in New South Wales and nearly all dog-like animals in the wild are simply wild dogs. This belief is bolstered by legislation and policies in NSW, which have removed the word dingo and refer only to “wild dogs”.
But our research, recently published in the journal Conservation Genetics, challenges this assumption. We performed DNA ancestry testing, much like the ancestry tests available to people, on 783 wild canines killed as part of pest control measures in NSW.
Roughly one in four of the animals we tested were pure dingoes, and most were genetically more than three-quarters dingo. Only 5 of the 783 animals we tested turned out to be feral domestic dogs with no dingo ancestry.
This policy requires all public and private landholders in NSW to display signs warning when poison baits have been laid to kill wild dogs.
But our DNA testing found three hotspots of high dingo ancestry within northeastern NSW: Washpool National Park; the coast north of Port Macquarie; and the Myall lakes region.
There were more pure dingoes in these areas. Despite these positive findings, dingo-dog hybridisation is still very prevalent in NSW. Three-quarters of wild animals carry some domestic dog ancestry.
This is not entirely surprising. Domestic pet and working dogs have lived alongside dingoes for centuries. Widespread killing of dingoes also increases the risk of hybridisation because it breaks family groups apart, giving domestic dogs the opportunity to mate with dingoes. Small populations also have a higher risk of hybridisation.
Hybridisation is generally considered detrimental to conservation because it alters the genome. In the case of dingoes, hybridisation is a problem because hybrids may be different to dingoes and “true” dingoes will eventually disappear.
While our results show dingoes still exist and their genes are predominate, their conservation will be greatly helped if we can prevent further interbreeding with domestic dogs.
Our study has important implications for both how we describe dingoes, and the future conservation of dingoes in NSW. Most of the animals labelled as wild dogs in NSW had predominantly dingo DNA, and fewer than 1% were actually feral dogs.
The term wild dog obfuscates the identity of wild animals whose genes are mostly dingo but sometimes carry dog genes. For all intents and purposes, these animals have dingo DNA, look like dingoes and behave like dingoes, and consequently should be labelled as dingoes rather than escaped pets gone wild.
Hotspots with high dingo ancestry have significant conservation value and urgently need new management plans to ensure these pure dingo populations are protected from hybridisation. These populations could be protected by restricting the killing of dingoes in these areas and restricting access to domestic dogs on public land such as state forests.
Further ancestry testing should be conducted in more areas to determine whether there are other pockets of high dingo purity in NSW.
Undeniably, dingoes can negatively impact livestock producers, especially sheep farmers. Non-lethal strategies such as electric or exclusion fencing, and livestock guarding animals such as dogs, llamas and donkeys, may balance the need to conserve dingoes and protect vulnerable livestock.
In some circumstances, dingoes can benefit farmers because they reduce numbers of native and feral herbivores like kangaroos, feral goats, rabbits and pigs, boosting pasture growth for livestock.
If lethal control is justified, then targeted strategies such as shooting and trapping may be more suitable in high dingo conservation areas rather than landscape-wide poison aerial baiting.
It is time to resurrect the dingo. The term dingo needs to come back into official language, and we need practical strategies for limiting dingo-dog hybridisation and protecting dingo hotspots.
Kylie M Cairns, Research fellow, UNSW; Brad Nesbitt, Adjunct Research Fellow, University of New England; Mathew Crowther, Associate professor, University of Sydney; Mike Letnic, Professor, Centre for Ecosystem Science, UNSW, and Shawn Laffan, Associate professor, UNSW
Humans and dogs go way back. From wolf totems to the big bad wolf of fact and fairy tale, through sheepdogs, lap dogs, and labradoodles, our relationships with these animals are complex, emotionally charged and sometimes contradictory.
The split between humanity’s lavishing of affection on domestic dogs and our contrasting animosity towards their wild relatives is well-documented. But what of domestic dogs and dingoes?
Our research, published today, found similarly contrasting relationships in Australia, where the dingo, Australia’s native dog, is frequently killed for management. We suggest that an inexpensive “dingo conservation levy” on domestic dog costs could fund more ethical management of dingoes. In this way our affection for domestic dogs could be harnessed to improve conservation outcomes for their wild relatives.
Australians collectively spend over A$10 billion each year on their domestic dogs – housing, feeding, and sometimes even giving them the status of honorary family members. Meanwhile, government and landowners jointly spend at least A$30 million on large-scale exclusion fencing and lethal control of dingoes.
Industry funded research suggests that dingoes killing livestock, especially sheep, and efforts to control dingoes, cost at least A$145 million annually. What’s more, such losses also come with psychological stress, which you can’t always put a price on.
Other research suggests dingoes, as top predators, provide considerable economic benefits. For example, dingoes prey upon kangaroos and other herbivores that may compete with livestock for food and water. In fact, some estimates suggest dingoes improve gross margins by $0.83 per hectare in this context.
Australia’s current approach to dingo management highlights the paradox of an animal viewed both as a valuable native predator that should be conserved, and as a pest to be destroyed. And this makes it a nightmare to manage.
Current dingo management relies heavily on exclusion fencing and lethal control, and around 200kg of 1080 powder (poison) is administered to baits and peppered across the continent annually.
Countless bullets are also fired, and traps set, as the lion’s share of management budgets is allocated to business as usual. To break this deadly cycle, there is a clear need to provide farmers and governments with good evidence that different approaches could work. This can only be done through substantial parallel investment in robust, independent experimental tests of alternative approaches.
Despite broad support in society for non-lethal management, accessing sufficient funds to support such a transition remains challenging.
A modest dingo conservation levy could fund this. With a levy on the A$10 billion domestic dog industry, we could harness humanity’s affinity for domestic dogs to improve conservation and welfare outcomes for their wild counterparts.
It wouldn’t need to be prohibitively expensive either.
A levy on the sale of pet dogs, dog food, or both, of only about 0.3% of the amount that pet owners spend on this annually – or A$7.36 per dog – would generate A$30 million each year.
That is similar to the lowest estimates of current national spending on dingo control, which means we would potentially see the current spending doubled.
Applying a levy to all dog owners may seem unfair, and perhaps it is. But as Australia’s “dingo problem” is, arguably, at least in part caused by domestic dogs gone feral, such a levy would seem no more unfair on conscientious dog owners than third-party insurance is on careful drivers.
An alternative approach might be to seek the voluntary involvement of pet-food manufacturers in such a scheme, giving consumers choice over whether to support it.
A dingo conservation levy – perhaps supplemented by a voluntary fund for donors without dogs – might also be more acceptable and attractive if it were clear the funds would be specifically channelled towards research and uptake of non-lethal tools.
Generally, we are broadly in favour of any techniques designed to reduce the animosity towards dingoes, reduce the costs and negative impacts of living alongside them, and boost the positive effects dingoes have on ecosystems.
As some have already argued, they are all dogs at the end of the day. Perhaps then it is time that we treated them as such.
We would like to gratefully acknowledge the contributions of Mike Letnic, Henry Brink, Brad Purcell and Hugh Webster to this article.
Bradley Smith, CQUniversity Australia; Corey J. A. Bradshaw, Flinders University; Euan Ritchie, Deakin University; Justin W. Adams, Monash University; Kylie M Cairns, UNSW, and Mathew Crowther, University of Sydney
Of all Australia’s wildlife, one stands out as having an identity crisis: the dingo. But our recent article in the journal Zootaxa argues that dingoes should be regarded as a bona fide species on multiple fronts.
This isn’t just an issue of semantics. How someone refers to dingoes may reflect their values and interests, as much as the science.
How scientists refer to dingoes in print reflects their background and place of employment, and the Western Australian government recently made a controversial attempt to classify the dingo as “non-native fauna”.
Over many years, dingoes have been called many scientific names: Canis lupus dingo (a subspecies of the wolf), Canis familiaris (a domestic dog), and Canis dingo (its own species within the genus Canis). But these names have been applied inconsistently in both academic literature and government policy.
This inconsistency partially reflects the global arguments regarding the naming of canids. For those who adhere to the traditional “biological” species concept (in which a “species” is a group of organisms that can interbreed), one might consider the dingo (and all other canids that can interbreed, like wolves, coyotes, and black-backed jackals) to be part of a single, highly variable and widely distributed species.
But the “biological” species concept used to name species came about long before modern genetic tools, or even before many hybrid species were identified by their DNA (such as the “red wolf,” an ancient hybrid of grey wolves and coyotes found in the southeastern United States).
Few people would really argue that a chihuahua, a wolf, and a coyote are the same species. In reality there are many more comprehensive and logical ways to classify a species. In our latest paper we argue that a holistic approach to defining species is essential in the case of the dingo and other canids.
Our work shows conclusively that dingoes are distinct from wild canids and domestic dogs based on many different criteria.
The first criterion is that dingoes are wild animals, and live completely independent from humans. This is fundamentally different to domestic, feral, or wild dogs, which must live near human settlements and rely on humans for food and water in some way to survive.
Yes, the dingo might have arrived in Australia with humans, and we know that Aboriginal Australians have had a close relationship with dingoes following the latter’s arrival. But neither of these observations excludes dingoes from being wild.
For example, a relationship with humans does not constitute the rigorous definitions of domestication. Consider the red fox (Vulpes vulpes), which was also introduced to Australia by people and are now free-ranging: they are also not considered to be domesticated. Neither are wild animals such as birds that we feed in our backyards domesticated simply because they are sometimes fed by us.
In fact, dingoes have been living wild and independently of humans for a very long time — they have a distinct and unique evolutionary past that diverged some 5 to 10 thousand years ago from other canids. This is more than enough time for the dingo to have evolved into a naturalised predator now integral to maintaining the health of many Australian ecosystems.
Dogs do not have the brain power or body adaptations to survive in the wild, and they cannot play the same ecological role as dingoes. From this ecological perspective alone, the two species are not interchangeable. Dingoes are Australia’s only large (between 15-20 kg), land-based predator, and as such play a vital role in Australia’s environment.
Viewed alone, the overall shape of the body and skull does not easily distinguish wild canids from dogs, mainly because of the sheer diversity among different breeds of domestic dogs.
Dingoes (and other truly wild canids) have some fundamentally unique behaviours that set them apart from dogs (although like shape, there are often exceptions among the artificial dog breeds). For example, dingoes have significantly different reproductive biology and care-giving strategies.
While dingoes and dogs obviously share an ancestral relationship, there is a lot of genetic data to support the distinction between dingoes and dogs.
While dingoes share ancestry with ancient Asian dogs from 10,000 years ago, the dingo has been geographically isolated from all other canids for many thousands of years, and genetic mixing has only been occurring recently, most probably driven by human intervention.
Since the 1990s, genetic markers have been in widespread use by land managers, conservation groups, and researchers to differentiate dingoes from domestic dogs.
Even acknowledging the dingo’s uncertain and distant past, lumping dingoes and dogs together is unjustified.
Labelling dingoes as “feral domestic dogs” or some other misnomer ignores their unique, long, and quintessentially wild history in Australia.
Inappropriate naming also has serious implications for their treatment. Any label less than “dingo” can be used to justify their legal persecution.
Bradley Smith, Senior Lecturer in Psychology, CQUniversity Australia; Corey J. A. Bradshaw, Matthew Flinders Fellow in Global Ecology, Flinders University; Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Justin W. Adams, Senior Lecturer, Department of Anatomy and Developmental Biology, Monash University; Kylie M Cairns, Adjunct associate lecturer, UNSW, and Mathew Crowther, Associate professor, University of Sydney
The dingo is Australia’s largest land-based predator, occurring across most of the mainland and on many nearshore islands.
Our new research, published in the journal Mammal Review, reveals the breadth and diversity of dingo diets across the continent.
We compiled and analysed 73 sets of data, containing details of more than 32,000 dingo droppings or stomach contents, to document the range of different species that dingoes eat, and how their diets vary between different environments.
We found that dingoes eat at least 229 vertebrate species. This includes 62 small mammals (less than 500 grams in mass), 79 medium-sized and larger mammals, 10 species of hoofed mammals, 50 birds and 26 reptiles. Dingoes also eat insects, crustaceans, centipedes, fish and frogs.
The true number of species is likely to be much higher because dingo diets have been poorly studied in many parts of Australia, such as Cape York Peninsula.
Large (at least 7kg) and medium-sized (0.5-6.9kg) mammals were the most common components of dingo diets, followed by small mammals, rabbits, arthropods, reptiles, birds and hoofed animals.
A range of introduced pest species also feature in dingo diets, including deer, goats, rabbits, hares, black rats, house mice, foxes and cats. In recent decades, the occurrence of sambar deer in dingo diets has increased as this invasive species has expanded its range.
Dingoes also eat sheep and cattle, although dietary samples are unable to distinguish between predation and scavenging, and hence tell us little about dingo impacts on livestock production. Dietary samples also do not reveal instances of dingoes killing livestock without eating them.
We found that what dingoes eat depends on where they live. For instance, in arid central Australia, birds, reptiles, rabbits, small mammals and insects form major parts of dingo diets. In contrast, these food groups are less important in temperate and subtropical eastern Australia, where medium-sized and large mammals such as kangaroos, bandicoots and possums are more important.
The higher occurrence of medium-sized mammals in dingo diets in eastern Australia may be due to the lower extinction rates of native mammals there. In contrast, central Australia is a global mammal extinction hotspot, which probably accounts for the low occurrence of medium-sized mammals in dingo diets in arid and semi-arid areas.
Nonetheless, one medium-sized mammal was a major food item for dingoes in arid areas: the European rabbit. In some areas, more than 50% of dingo droppings or stomachs contained the remains of this invasive species. It is possible that native medium-sized mammals previously constituted a major part of dingo diets in arid Australia, but have since been replaced by rabbits.
Local prey availability plays a major role in determining what dingoes eat. For instance, in the Tanami Desert, reptiles were most common in dingo diets during warmer months when they are most active. However, very few studies have collected data on prey availability, partly because of the sheer number of different animals that dingoes eat.
This tally is higher than the number of threatened species in feral cat diets (based on a previous study that used similar methods), even though cats eat almost twice as many different species overall as dingoes (400 and 229, respectively).
Today’s threatened native species co-existed with dingoes for a long time before European colonisation, which means they were able to withstand dingo predation without going extinct.
But now a combination of small population sizes of some threatened species and exacerbating factors such as habitat loss, foxes and cats means some threatened species could be vulnerable to even low levels of dingo predation. Predation by dingoes should therefore be a key consideration when attempting to conserve or restore threatened species.
Dietary studies are one way we can understand how dingoes interact with other species. Our study also highlights that we still have much to learn about our native top predator. In many parts of Australia, the favourite foods of dingoes are still a mystery.
The authors acknowledge the contribution of Naomi Davis, Dave Forsyth, Mike Letnic, Russell Palmer, Joe Benshemesh, Glenn Edwards, Jenny Lawrence, Lindy Lumsden, Charlie Pascoe, Andy Sharp, Danielle Stokeld, Cecilia Myers, Georgeanna Story, Paul Story, Barbara Triggs, Mark Venosta and Mike Wysong to this research.
Tim Doherty, Research Fellow, Deakin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Dale Nimmo, Associate professor/ARC DECRA fellow, Charles Sturt University; Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Thomas Newsome, Lecturer, University of Sydney
The case of Debbie Rundle, who was attacked by dingoes at a mine site in Telfer, in Western Australia’s Pilbara region, evokes our instinctive horror at the idea of being attacked by wild animals.
Rundle suffered severe leg injuries in the incident, and said she feared she may have been killed had her colleagues not come to her aid.
We know that there are carnivores throughout the world with the potential to kill us. And while most of us will never come face to face with a hungry wolf, lion, tiger or bear, such attacks do unfortunately still occur.
In the scale of things, such attacks are very uncommon – although that is little consolation to the victim. Australia’s dingoes are no exception; despite some infamous examples, dingo attacks on humans are mercifully rare. But people will still understandably want to know why they happen at all, and what can be done to prevent them.
Research on wolf attacks shows that, absent the influence of rabies which can increase wolves’ aggression, two common factors associated with attacks are that they often happen in human-modified environments, and by animals that are habituated to human presence.
These two variables are obviously linked: many species of mammalian carnivore are highly adaptable, and soon learn that human settlements are sources of food, water and shelter.
These human resources can have a profound effect on the behaviour of wild animals. Abundant human food often reduces animals’ aggression towards one another, and can result in the presence of much larger numbers of individuals than normal.
This is equally true of dingoes. Although they are usually observed alone, it is not uncommon to see groups of ten or more dingoes foraging at rubbish dumps associated with mine sites in the Tanami Desert of central Australia. There are thought to be around 100 dingoes that forage in and around the Telfer mine where Rundle was attacked.
Waste food may inadvertently entice animals to human settlements, and this may lead to predators becoming habituated to human presence. In Canada, a young man fell victim to a wolf attack at a mine site; the local wolves were reported to be used to humans, and would even follow rubbish trucks to the tip. They may have come to associate human smells with the provision of food.
Animals that are habituated to humans lose some of their natural wariness towards them. This is typical of many animal species that adapt to urban habitats, and while this may be an appealing trait in squirrels or garden birds, it can be quite different if the animal is a predator capable of attacking a human.
In the United States, there have been many reports of coyotes attacking humans. The coyote, like the dingo, is reasonably large (typically weighing 10–16kg) and can be found in close association with urban areas. The coyote’s natural range has expanded as wolves (their competitor) have dwindled, and their numbers have increased in and around cities where they find copious and consistent supplies of food and water.
A survey of reported attacks on humans by coyotes showed that many were “investigative”, often involving the animal trying to steal something they perceived as food from the person. Other attacks by coyotes could be identified as “predatory”, in which the victim was pursued and bitten, and often occurred when the coyotes were in a group.
The Telfer dingo attack similarly appears to have been investigative – a young dingo climbed onto a table and grabbed Rundle’s phone. But the incident turned nasty when Rundle (perhaps understandably) followed the dingo that had her phone; this seemed to trigger a defensive or predatory attack from two other dingoes.
On Queensland’s Fraser Island, more than half of the recorded aggressive incidents by dingoes towards humans happened when the person was walking or running, suggesting that a “chase” response may have been involved.
The Telfer site, like other mine sites, has strict rules about putting waste food in bins, and managers have been proactive in training workers to not feed dingoes, in an attempt to prevent just such attacks. Rundle certainly seems to have followed these rules.
Unfortunately, in her case, other variables contributed to the attack – an investigative approach by one dingo that stole an item (that may have smelled of food) seems to have turned into an aggressive group attack when she followed the animals.
What can we do to prevent such attacks? Mine site managers already do much to reduce the likelihood of such incidents by reducing dingoes’ access to food. Fencing off eating areas or storing food in cages – as is done at Fraser Island – can help in this regard.
Interestingly, many people believe that it is best not to act aggressively when they encounter a large carnivore, but in reality it depends on the species. For wolves and pumas, the best tactic seems to be to shout and throw objects to put them off.
Ultimately, the onus is on individual people to be aware of the potential danger of wild predators, and always to treat them with wariness and respect.
Dingoes could be the key to controlling red foxes and other invasive predators, but only if we encourage them in large enough numbers over a wide enough area, our research shows.
Interest in re-introducing or restoring top predators, like dingoes and wolves, has been fuelled by recent studies demonstrating their important roles in their ecosystems. They can especially be vital in suppressing the abundance of lower-order competitors or “mesopredators”, like red foxes and possibly feral cats (which can have devastating effects on native species).
But researchers have found top predators aren’t always successful in reducing mesopredator numbers. Until now, such variation has been linked to human presence, land-use changes and environmental factors such as landscape productivity.
However, our research, published yesterday in Nature Communications, found that a key factor for success is high numbers of dingoes and wolves across their natural range.
If you look at how species are typically distributed across a landscape – their range – ecological theory predicts there’ll be lower numbers at the outer edges of their range.
If you do need large numbers of top predators to effectively suppress mesopredators, the core of their range is potentially the best place to look.
We tested this idea, looking at the dingo in Australia and the grey wolf in North America and Europe. The mesopredators included the red fox in Australia, the coyote in North America and the golden jackal in Europe.
We used information from bounty hunting programs, as these provide data on predator numbers across a wide geographical area. In the case of Australia we used historic data from the 1950s, as this is the most recent reliable information about red fox and dingo distribution. The actual population numbers of red foxes and dingoes have changed substantially since then, but the nature of their interactions – which is what we were investigating – has not.
We determined that top predators exist in higher numbers at the core of their ranges in comparison to the edges. We then looked at mesopredator numbers across the range edges of their respective top predator.
The results, which were consistent across the three continents, suggest that top predators can suppress mesopredators effectively (even completely) but only in the core of their geographic range, where their numbers are highest.
In other words, abundant top predators can exert disproportionate mesopredator control once their numbers increase past a certain point.
The relationship we uncovered is now formalised as the “Enemy Constraint Hypothesis”. It could apply to other predator dyads, where two animals compete for similar resources – even relationships involving parasites and pathogens.
Our findings are important for understanding species interactions and niches, as well as the ecological role of top predators. It could explain why other studies have found top predators have little influence on mesopredators: they were looking at the edge, not the core, of the top predators’ range.
Dingoes can be vital for reducing red fox and possibly feral cat numbers. In our case studies the ranges of each top predator were limited primarily by human use of the land and intensive shooting, trapping and poisoning.
Killing pack animals like dingoes can fracture social groups, potentially altering their natural behaviour and interactions with other species. Future studies on predator interactions therefore need to consider the extent to which the animals are acting in response to human intervention.
If we want to benefit from the presence of top predators, we need to rethink our approach to management – especially where they are subjected to broad-scale control, as the dingo is in some parts of Australia.
Changing our relationship with top predators would not come without its challenges, but high extinction rates around the world (and especially in Australia) clearly indicate that we urgently need to change something. If this includes restoring top predators, then we need to think big.
But are dingoes really the heroes-in-waiting of Australian conservation? The truth is that no one knows, although our recent research casts a shadow over some foundations of this idea.
The notion of dingoes as protectors of Australian ecosystems was inspired largely by the apparently successful reintroduction of wolves into Yellowstone National Park in the United States. But Australia’s environments are very different.
To understand the recent excitement about wolves, we need to consider an ecological phenomenon known as “trophic cascades”. The term “trophic” essentially refers to food, and thus trophic interactions involve the transfer of energy between organisms when one eats another.
Within ecosystems, there are different trophic levels. Plants are typically near the base; herbivores (animals that eat plants) are nearer the middle; and predators (animals that eat other animals) are at the top.
The theory of trophic cascades describes what happens when something disrupts populations of top-order predators, such as lions in Africa, tigers in Asia, or Yellowstone’s wolves.
The wolves’ decline allowed herbivores, such as elk, to increase. In turn, the growing elk population ate too much of the shrubby vegetation alongside rivers, which, over time, changed from being mostly willow thickets to grassland. Then another herbivore – beavers – that relies on willows went locally extinct. This in turn affected the ecology of the local streams.
Without beavers to engineer dams, local waterways changed from a series of connected pools to eroded gutters, with huge flow-on effects for smaller aquatic animals and plants.
Now, the reintroduction of wolves appears to have reduced the impact of elk on vegetation, some riparian areas have regenerated, some birds have returned and there are signs of beavers coming back. That said, wolf reintroduction has not yet fully reversed the trophic cascade.
Sturt National Park, in the New South Wales outback, has been nominated as an experimental site for reintroducing dingoes. Recently, we compared the environment of Sturt with Yellowstone to consider how such a reintroduction might play out.
These regions are clearly very different. Both are arid, but that is where the similarity ends. Yellowstone has a stable climate and nutrient-rich soils, sits at high altitude and features diverse landscapes. Precipitation in Yellowstone hasn’t dropped below 200mm per year in more than a century.
Yellowstone’s precipitation falls largely as heavy winter snow. Each spring the snowmelt flows in huge volumes into rivers, streams and wetlands across the landscape. This underpins a predictable supply of resources which, in turn, triggers herbivores to migrate and reproduce every year.
These predictable conditions support a wide range of carnivores and herbivores, including some of North America’s last-remaining “megafauna”, such as bison, which can tip the scales at over a tonne. Yellowstone also has many large predators – wolves, grizzly bears, black bears, mountain lion, lynx and coyotes all coexist there – along with a range of smaller predators too.
Predators in Yellowstone can be sure that prey will be available at particular times. The environment promotes stable, strong trophic links, allowing individual animals to reach large sizes. This strong relationship between trophic levels means that when the system is perturbed – for instance, when wolves are removed – trophic cascades can occur.
Unlike Yellowstone, arid Australia is dry, flat, nutrient-poor and characterised by one of the most extreme and unpredictable climates on Earth. The yearly rainfall at Sturt reaches 200mm just 50% of the time.
Australia’s arid ecosystems have evolved largely in isolation for 45 million years. In response to drought, fire and poor soils, arid Australia has evolved highly specialised ecosystems, made up of species that can survive well-documented “boom and bust” cycles.
Unlike the regular rhythm of Yellowstone life, sporadic pulses of water and fire affect and override the trophic interactions of species, between plants and herbivores, and predators and their prey. Our native herbivores travel in response to patchy and unpredictable food sources in boom times. But however good the boom, the bust is certain to follow.
Unpredictable but inevitable drought weakens trophic links between predators, herbivores and plants. Individuals die due to lack of water, populations are reduced and can only recover when rain comes again.
Our arid wildlife is very different from Yellowstone’s too. Our megafauna are long gone. So too are our medium-sized predators, such as thylacines.
Today, arid Australia’s remaining native wildlife is characterised by birds, reptiles and small mammals, along with macropods that are generally much smaller than the herbivores in Yellowstone.
Our predators are small and mostly introduced species, including dingoes, foxes and cats. None is equivalent to wolves, mountain lions or bears, which can reach more than three times the weight of the largest dingo. Wolves are wolves, and dingoes are dogs.
What does all this mean for Australia? Yellowstone’s stable climate means that there are strong and reliable links between predators, prey and plants. By comparison, arid Australia’s climate is dramatically unstable.
This raises the question of whether we can reasonably expect to see the same sorts of relationships between species, and whether dingoes are likely to help restore Australia’s ecosystems.
We should conduct experiments to understand the roles of dingoes and the impacts of managing them. How we manage predators, including dingoes, should be informed by robust knowledge of local ecosystems, including predators’ roles within them.
What we shouldn’t do is expect that dingoes will necessarily help Australia’s wildlife, based on what wolves have done in snowy America. The underlying ecosystems are very different.
Many people are inspired by the apparently successful example of wolves returning to Yellowstone, but in Australia we should tread carefully.
Rather than trying to prove that dingoes in Australia are just as beneficial as wolves in Yellowstone, we should seek to understand the roles that dingoes really play here, and work from there.
Helen Morgan, Phd candidate, Ecology, University of New England; Guy Ballard, Adjunct Senior Lecturer, University of New England, and John Thomas Hunter, Adjunct Associate Professor in Landscape Ecology, University of New England