Thinking big gives top predators the competitive edge



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Dingoes can help manage devastating red fox and feral cat numbers, but only if we let enough of them live in key areas.
Bobby Tamayo, Author provided

Thomas Newsome, Deakin University

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.

The density effect

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 looked at three regions in our study. Predator distribution is shown for: a) coyotes (hashed) and grey wolves (orange) in Saskatchewan, North America (present day); b) golden jackals (hashed) and grey wolves (orange) in Bulgaria and Serbia (present day); and c) red foxes (hashed) and dingoes (orange) in Queensland, Australia (in the 1950s).
Predator images: Doug McLaughlin; Bobby Tamayo, Harley Kingston/flickr, Larry Lamsa/flickr

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.

Predator bounties and top predator range edges in each continent. The number of bounties (representing the number of animals killed) are given for each hunting unit in North America (collated from 1982 to 2011) and Europe (collated from 2000 to 2009), whereas each square in Australia represents the number of bounties in a 100-by-100km area (collated from 1951 to 1952). Top predators are in a–c. Mesopredators are in d–f. Darker colours within each hunting unit indicate greater bounty return numbers and, by inference, a higher abundance for the respective predator. Dashed black lines indicate top predator range edges. Australia was divided into two sections for the analysis (east and west) as shown.

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.

Example of the results from Australia (western side of Queensland). The blue lines indicate the abundance of each predator (note that the values on the y-axis are scaled so do not reflect actual numbers). The black dashed line indicates where there is a sharp change in predator abundance (the breakpoint). The red dashed lines indicate 95% confidence intervals (a measure of uncertainty) either side of the breakpoint. Distance values less than zero relate to areas outside the dingoes’ range, while distance values greater than zero relate to areas within the range. In summary, abundances of the red fox decline sharply as you move further into the range of the dingo.

The ‘enemy constraint hypothesis’

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.

This is a conceptual model of the Enemy Constraint Hypothesis. On the edge of a top predator’s range, mesopredator abundance should decline as top predator numbers increase. The breakpoint for the mesopredator indicates where their population nears zero. The breakpoint for the top predator indicates where their abundance starts to decline sharply on the edge of the range.

How many top predators do we need?

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.

The ConversationChanging 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.

Thomas Newsome, Fulbright Scholar and Postdoctoral Research Fellow, Deakin University

This article was originally published on The Conversation. Read the original article.

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Why do some graziers want to retain, not kill, dingoes?



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Australia has a complex relationship with the dingo.
Angus Emmott, Author provided

Euan Ritchie, Deakin University

Vast, ancient, nutrient-poor, with wild swings between droughts, floods and fires: this describes much of the Australian continent. Livestock grazing and farming in such a land is certainly not without its challenges. The Conversation

Where we’ve failed to work with the local conditions, we see barren plains, dust storms, the extinction of native species, and the repossession of properties by banks, among many ills.

But such a dire picture is far from universal, and belies the fact that many who live on the land are also among our most innovative land managers. Many projects offer potential benefits for livestock production and the environment alike, but without support progress may be hindered.

Putting dingoes to work

One of the most contentious examples involves encouraging dingoes. Many pastoral areas require land managers to take “all reasonable and practical steps” to manage the risk of dingoes, which are classed as pest animals.

But a growing body of research argues that dingoes can be effective at controlling kangaroo and feral goat populations, especially on cattle stations.

A Western Australian couple, David Pollock and Frances Jones, were recently featured on Australian Story for their decision to regenerate their property, Wooleen, by de-stocking, encouraging local flora and fauna, and investing in ecotourism.

Their neighbours, including sheep graziers whose stock are vulnerable to dingoes, feel this is an irresponsible decision. Graziers have a mandate to control dingoes (“wild dogs”, to many) and dingo-domestic dog hybrids — which can’t be easily and reliably distinguished in the wild.

Dingoes are known to be very effective at controlling kangaroo populations.
Angus Emmott

While the impacts and merits of encouraging dingoes in sheep country are hotly debated, their role in the management of cattle stations is much better understood. But restrictive legislation and the stigma attached to dingoes are frustrating for those who see them as having a vital ecological and economic role for their properties.

Queensland grazier Angus Emmott writes that his beef cattle enterprise, Noonbah station, has benefited from leaving dingoes and kangaroos alone:

We run a beef cattle enterprise in the top end of the Queensland channel country, southwest of Longreach. As a part of our management plan, we leave the dingoes and the ’roos alone. We see a range of benefits to our operation.

When the dingoes don’t have their social structure disrupted by poison baiting, trapping and shooting, only the apex bitch breeds, once a year at most. These family groups have strictly defined ranges, and they kill or chase off other wild dogs or dingoes that intrude. They also keep kangaroos down to very low numbers, which is a huge benefit in regards to pasture growth and being able to rest our paddocks. The dingoes also keep down feral pig, cat and fox numbers.

Yes, dingoes do take some of our calves, but the benefits of pasture growth and feral animal control result in a net benefit of better land condition and a greater dollar return. Dingoes also benefit biodiversity conservation and soil condition. We acknowledge this management model does not work in sheep country, including for some of our nearby neighbours, and in these cases we need to look at different forms of management, such as fencing and/or companion and guardian animals.

Research supports the financial benefits of this approach in certain circumstances. Some studies have found that, perversely, taking lethal action against dingoes can increase the incidence of attacks on stock and boost the population of herbivores that compete with cattle for pasture.

Solutions for protecting livestock against attack, such as guardian dogs, are also at hand and may be considerably cheaper than constructing and maintaining extensive predator-proof fences. Livestock guardian dogs have been shown to be effective in numerous locations across Australia, on large and small grazing properties. But investment from state and federal government (and related agencies) aimed at encouraging such innovation has been lacking.

Kangaroos can become very abundant following rain and without control by dingoes.
Angus Emmott

Working with the land

Regardless of whether graziers take the drastic steps seen at Wooleen, now is the time to reflect on the direction of Australia’s land management.

If we’re to overcome the many challenges we face, including the impacts of climate change on food production, then we need to support the bold new thinking emerging from rural and regional Australia, and our scientific institutions.

Such ideas could include making better use of native animals – better suited to Australian conditions – as sources of meat, and reforming land use legislation to allow new industries.

Seeing some of the worst land degradation first hand it’s easy to think that it’s all too hard and that environmental repair will take decades, if not centuries. This can invite inertia and apathy, the enemies of positive change.

But the stories of Wooleen, Noonbah and other innovators show us what is possible. Science has helped demonstrate ecological repair can happen faster and to a greater extent than many might appreciate.

Big changes certainly carry risks, and these must be managed carefully, but new and sometimes brave ideas will always improve our understanding of the land. Whatever the outcome, such knowledge helps guide better decisions for more sustainable grazing, farming and bio-diverse conservation.


Euan Ritchie would like to acknowledge the contribution of Angus Emmott to this article.

Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University

This article was originally published on The Conversation. Read the original article.

A wolf in dogs’ clothing? Why dingoes may not be Australian wildlife’s saviours


Helen Morgan, University of New England; Guy Ballard, University of New England, and John Thomas Hunter, University of New England

Dingoes have often been hailed as a solution to Australia’s threatened species crisis, particularly the extreme extinction rate of the country’s small mammals.

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.

Cascading species

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.

Wolves play a key role in Yellowstone’s ecosystems.
Wolf image from http://www.shutterstock.com

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.

Comparing apples with quandongs

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.

Herds of bison in Yellowstone National Park.
Helen Morgan

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 Sturt Desert has a highly unpredictable climate.
Helen Morgan

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.

Wolves in dingo clothes?

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.

The Conversation

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

This article was originally published on The Conversation. Read the original article.

Dingoes do bark: why most dingo facts you think you know are wrong


Eloïse Déaux, Université de Neuchâtel

As I visited a wildlife park in New South Wales in 2011, the keeper at the daily “dingo talk” confidently told us that “pure dingoes don’t bark”. After five years studying dingoes’ vocal behaviours, I can tell you that this is a myth. Dingoes do bark!

While travelling around Australia to study dingoes, I have had the opportunity to meet and talk with all sorts of people. One thing I realised is that the “dingoes don’t bark” belief is widespread – and it isn’t the only unproven dingo myth out there.

Lots of people in Australia take these three myths as hard facts:

  1. “pure” dingoes don’t bark

  2. “pure” dingoes are all ginger

  3. dingoes are “just dogs”.

But none of these are actually true and here’s why.

Myth 1: dingoes don’t bark

Anyone who has been around dingoes for long enough will tell you that they do bark, but not like domestic dogs. Dingoes’ barks are generally harsher, and given in short bursts.

Domestic dogs will bark anytime, anywhere, for anything (often to their owners’ or neighbours’ chagrin). This is not the case with dingoes. They will generally bark only when alarmed – such as when researchers trap them to fit a radio tracking collar, or if you stumble across one in the bush.

Dingo barking sequence.
Eloïse Déaux, CC BY-NC-ND133 KB (download)

Dingoes can also bark if they get very excited (about food, for example) but this is quite uncommon. The rarity of these events probably explains the prevalence of the “no barking” myth – wild dingo barking just doesn’t happen often enough for most people to witness it.

Another associated misconception is that captive dingoes will learn to bark from listening to domestic dogs. Although humans are very good at learning new sounds – indeed, that’s how we acquire our language – most other species (including canines) can make only a limited range of vocal sounds, and can’t learn new ones.

So the fact that captive dingoes bark actually confirms that they have barking abilities right from the start. It is, however, possible that by listening to nearby domestic dogs, captive dingoes learn to bark more often and in more situations than they otherwise might.

It is easy to see how this myth might harm efforts to protect dingoes. Imagine a well-meaning pastoralist shooting or baiting anything that barks, in the mistaken belief that it’s not a dingo.

Myth 2: all pure dingoes are ginger

The “typical” dingo that people picture in their minds – think Fraser Island – will be ginger (or tan) with white feet and a white-tipped tail. But dingoes, like people, come in a variety of shapes and colours.

Importantly, although ginger dingoes make up about three-quarters of the population, there is genetic evidence that their coats can also be black, black and tan, black and white, or plain white.

A black and tan dingo…
Tim Pearson
…and a white one.
Tim Pearson

There is also a lot of variation in the size and shape of white patches and these may even be absent altogether. It’s often thought that dingoes that lack ginger fur or white patches are dingo-dog hybrids, but this is not necessarily true.

Like the no-barking myth, misconceptions about coat colour can potentially harm dingo conservation. If we were to protect only ginger dingoes, we would unwittingly reduce the natural genetic variation of the population, making it more vulnerable to extinction.

Myth 3: dingoes are just dogs

This is perhaps the hardest belief to address, because it can vary depending on whether we look at their behaviours, ecology or origins. But this concept is arguably even more relevant to their conservation and management.

So is a dingo a dog? Although dogs’ evolutionary origins are still unclear, we know that dingoes are descendants of animals domesticated long ago somewhere in Asia and then brought to Australia. Dingoes are thus an ancient dog breed and so, yes, dingoes are dogs.

However, we also know that dingoes arrived in mainland Australia roughly 5,000 years ago and have since been isolated from all other canines right up until European settlement. Some experts argue that this makes them distinct enough to warrant protection from hybridisation with domestic dogs.

As dingo researcher Ben Allen puts it, “pure ones need to be distinguished from hybrid ones somehow, and it is the pure ones that have conservation value as a species”.

But as fellow dingo expert Guy Ballard points out, dingoes are undeniably a type of dog, so arguably all that really matters is that their function as top predators in the ecosystem is preserved.

But there’s a catch (as Ballard has acknowledged): we do not know whether dingoes, feral dogs and hybrids behave similarly – or in other words, whether all three can perform the same ecological role.

We do know that India’s free-ranging dogs behave very differently from Australian dingoes: they are inefficient predators, do not form packs and do not breed cooperatively. This suggests that, in terms of their behaviours, dingoes may be very different from other types of dogs after all.

Until we know more, the best approach to safeguarding dingoes and their role in the ecosystems might be to view and treat them as completely separate and distinct from other free-ranging dogs in Australia.

Far from being “just dogs”, dingoes really are unique dogs.

The Conversation

Eloïse Déaux, Postdoctoral fellow in mammal vocal communication, Université de Neuchâtel

This article was originally published on The Conversation. Read the original article.