Friday essay: the cultural meanings of wild horses



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Wild horses, known as brumbies, in Australia.
Shutterstock.com

Michael Adams, University of Wollongong

I am walking quietly through the forest. As I reach the edge of the trees there is a snort and a staccato of hoofbeats, and four horses materialise only metres in front of me: a foal, two mares and a dark stallion. The stallion, ears pricked, tosses his head and prances forward. As I crouch to pick up a branch, the stallion wheels and gallops off with the group. They hurdle an old stock fence, and almost as soon as their hoofs touch down, another big grey stallion comes towards them over the hill.

The next minutes are completely mesmerising. The two stallions fight, 50 metres from me. Dust hangs in the air around them, their screams echo off the hills, the impact of their hoof strikes reverberates in my belly. They rear, scream; snake heads out to bite, whirl and kick. Eventually, bleeding and bruised, the dark stallion breaks and runs. The grey makes a show of chasing, then canters back to the mares, arching his neck, prancing with lifted tail.

This is one of many times I have seen horses, called brumbies in Australia, in the mountains. While cross-country skiing in the south I have watched them in the snow – ragged manes flying, galloping through a mist of ice crystals – and many times while driving and bushwalking in both the north and south of Kosciuszko National Park. I have also watched them cantering in clouds of dust in central Australia, and grazing in the swamps of Kakadu. Each of these wild horse encounters has been deeply visceral and emotional, elemental expressions of life in dramatic and beautiful landscapes.

Horses are large, powerful and charismatic animals, and humans have ancient connections to them. Wild horses are dominant among the 13 species painted on the caves of Chauvet in France 30,000 years ago, and while there continues to be debate, archaeologists suggest evidence for horse domestication is at least 5,500 years old. And like the oldest human-animal relationship outside hunting – with dogs – the horse relationship is unique because we now mostly do not eat this animal.

Like dogs, horses now occur on every continent except Antarctica, and humans have been the primary agent for their dispersal. In North America, where the first true horses evolved and then died out, they were reintroduced by Columbus in 1493. Horses are the most recent of the main species humans domesticated, and the least different (with cats) from their wild counterparts.

Horses and other animals on the walls of the Chauvet Cave in southern France, from 30,000 years ago.
Claude Valette/Wikimedia, CC BY-SA

Australia has the largest wild horse herd in the world, maybe 400,000 or more horses, spread across nearly every bioregion from the tropical north to the arid centre to the alpine areas. That sounds like a dramatically large number, but Australia also has around one million domestic horses, about 100 million cattle and sheep, maybe 20 million feral pigs and 25 million kangaroos. But the presence of wild horses here is deeply controversial.

Six thousand of these horses are in Kosciuszko National Park. Ongoing controversy around these wild horses encompasses debate about their impact and their cultural meaning. There is very little systematic research and a large amount of emotive and anecdotal argument, from both sides. There is circularity and self-referencing in government wild horse management plans, very little reference to studies from Australia and almost no peer-reviewed research on horse impacts in the Snowy Mountains, despite decades of argument that they cause environmental degradation.

And Kosciuszko is right next to Canberra and the Australian Capital Territory, which has the highest per capita horse-ownership of anywhere in Australia. Several enterprises run horse-trekking trips into the Snowy Mountains, often interacting with brumbies. The Dalgety and Corryong annual shows on the boundaries of the park highlight horse skills, including catching and gentling brumbies. In many places mountain cattle properties are increasingly using horses instead of motorbikes to handle stock.

The Kosciuszko wild horses are also tangled within the embedded idiosyncrasies and contradictions of the largest national park in New South Wales. Here there are protected populations of two species of invasive fish (brown and rainbow trout) that are demonstrably responsible for local extinctions of native fish and frog species; a gigantic hydro-electric scheme with dominant infrastructure across large areas of the park; and expanding ski resorts where it is possible to buy lodges. Much of the landscape that is now part of the park has a long history of summer grazing by sheep and cattle, with stockworkers’ huts scattered across the high country. This “wilderness” has been home to Aboriginal people for millennia, as well as well-known grazing grounds for more than a century.

These complexities and contradictions reflect our often unconscious modern propensity for hubris: we insist we are in charge of what happens on the planet, including in its “wild” places and “wild” species. Terms like “land management”, “natural resource management”, and “conservation management”, all reflect this assumption of superiority and control.

Roping wild horses, Gippsland, Arthur John Waugh, circa 1910-1920.
State Library of Victoria

Indigenous interactions

The United States has similar controversies over the management of mustangs across large areas of the west. New Zealand has the Kaimanawa horses, a special and isolated herd on army land. In both of those countries, as in Australia, there is a unique history of horse interactions with Indigenous communities. The great Native American horse cultures are well known and extraordinary, as Indians had no introduction to equestrian skills from the Spanish invaders, they learnt extremely quickly from scratch.

The first horses in New Zealand were a gift to Maori communities from missionary Samuel Marsden in 1814, and a Waitangi Tribunal Claim has been brought to protect the Kaimanawa horses as Maori taonga (treasures). Aboriginal stockmen and stockwomen were the mainstay of the pastoral industry all over Australia until the equal wage ruling of 1968 resulted in the wholesale expulsion of Aboriginal stockworkers in north and central Australia.

Peter Mitchell’s recent book Horse Nations uses that term to describe the people-animal relationship in certain Indigenous communities. Both Native American and Aboriginal cosmologies often place animals including horses, as their own “nations”, with whom they have a responsibility to respectfully interact.


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The wild horses of the Australian Alps are arguably the strongest cultural icons. The enduring legacy of The Man from Snowy River, both the iconic Banjo Paterson poem and the 1980s film, but also the Silver Brumby series of novels by Elyne Mitchell, still in print after nearly 70 years, idealise the strength, beauty and spirit of wild mountain horses. At least one source suggests that “the man” from Paterson’s poem was in fact a young Aboriginal rider.

This is not at all implausible – there is much documentation, as well as strong oral histories, of Aboriginal men and women working stock on horseback across the Snowy Mountains. The Aboriginal mountain missions at Brungle and Delegate both have many stories of earlier generations working as stock riders and also mustering wild mountain horses. David Dixon, Ngarigo elder, says

Our old people were animal lovers. They would have had great respect for these powerful horse spirits. Our people have always been accepting of visitors to our lands and quite capable of adapting to change so that our visitors can also belong, and have their place.

While the iconic figure of the cowboy and stockman is masculine, amongst Aboriginal stockworkers women and girls were likely as common as men and boys. In contemporary times, women far outnumber men in equestrian participation, and brumby defenders are equally represented by men and women. Four Australian horsewomen generously shared their knowledge and skills in the research that backgrounds this essay.

Animal intelligence

In the mid 1970s, I worked as a ranger in Kosciuszko National Park. In those days rangering was a seat-of-the-pants enterprise: we used to buy at least part of our uniforms out of our own money because the issued items were so inadequate, we taught ourselves to cross-country ski, we drank socially with the brumby-runners and other people from the surrounding rural communities.

Shooting wild horses, Samuel Calvert, 1889.
State Library of Victoria

In many places rangers were and are intimately part of the community, not seen as “public servants”. There is a complex and interesting relationship between university-educated national parks staff and local rural workers with deeply embodied knowledge and skills, with rangers acknowledging that they need the skills of these locals to carry out much animal-related work in the parks, including trapping and mustering wild horses. Recent proposals to helicopter shoot large numbers of wild horses in Kosciuszko would potentially sever this link. Helicopter shooting requires specific marksmanship skills not common in rural communities.

While we debate how to reduce our wild horse numbers, other countries are working to re-establish wild horse herds in Europe and Asia. It is often argued that domestication saved horses (and many other species) from extinction, aiding their establishment all over the planet while their wild ancestors diminished or disappeared. Creating populations of newly wild species is termed both “rewilding’ and ”de-domestication“, and there are numerous and increasing examples around the world. Some of these proposals include the reestablishment of species long extinct, or their ecological equivalents.

In the period increasingly accepted as the Anthropocene, species are both declining and flourishing. Domesticated species have been moved all over the world; other introduced species flourish in new landscapes, and many of these are escaped or released domesticates. In the oceans, as large predators have declined all the cephalopods (octopus, squid and cuttlefish) are increasing. Highly specialised species that evolved on isolated islands have declined precipitously, while generalist species are flourishing.

Global conservation management attempts to work against both of these trends: we attempt to suppress populations of flourishing species, while supporting or increasing populations of declining ones, including through translocations and captive breeding programs. These activities call into question the nature of nature in the 21st century: what is the “wild” in all this management and manipulation?

While Australia debates removing wild horses, other countries are seeking to increase their wild herds.
Shutterstock.com

In these questions, the lives and cosmologies of Indigenous peoples, and the lives of other species, offer us serious teachings. The agency and intelligence of animals, the increasing discoveries of distinct cultures amongst animal populations, the agency of planetary systems in continually reorganising around changing inputs, all stand against the modern human insistence on control, stability and stasis.

While hiking mountain grasslands looking for wild horse bands, I have several times come across horse skeletons whitening in the sunlight, their energy and power transmuted back into the source from which new lives will spring. In a world where human societies are increasingly narcissistic, where our dominant concern is ourselves, recognising the agency and intelligence of other species can be deeply humbling.

Perhaps our task is to harmonise ourselves with these old and new environments, not continually attempt to “manage” them into some other state that we in our hubris think is more desirable, whether ecologically, economically or culturally.

The ConversationThanks to Adrienne Corradini, Jen Owens, Blaire Carlon and Tonia Gray for improving my understanding of horse and brumby issues.

Michael Adams, Associate Professor of Human Geography, University of Wollongong

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

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From feral camels to ‘cocaine hippos’, large animals are rewilding the world



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Most of the world’s wild horses, such as the Australian brumby, are outside their historic native range.
Andrea Harvey

Erick Lundgren, University of Technology Sydney; Arian Wallach, University of Technology Sydney; Daniel Ramp, University of Technology Sydney, and William Ripple, Oregon State University

Throughout history, humans have taken plants and animals with them as they travelled the world. Those that survived the journey to establish populations in the diaspora have found new opportunities as they integrate into new ecosystems.

These immigrant populations have come to be regarded as “invaders” and “aliens” that threaten pristine nature. But for many species, migration may just be a way to survive the global extinction crisis.

In our recently published study, we found that one of the Earth’s most imperilled group of species is hanging on in part thanks to introduced populations.

Megafauna – plant-eating terrestrial mammals weighing more than 100kg – have established in new and unexpected places. These “feral” populations are rewilding the world with unique and fascinating ecological functions that had been lost for thousands of years.

Today’s world of giants is only a shadow of its former glory. Around 50,000 years ago, giant kangaroos, rhino-like diprotodons, and other unimaginable animals were lost from Australia.


Read more: Giant marsupials once migrated across an Australian Ice Age landscape


Later, around 12,000 years ago, the last of the mammoths, glyptodonts, several species of horses and camels, house-sized ground sloths and other great beasts vanished from North America.

In New Zealand, a mere 800 years ago, a riot of giant flightless birds still grazed and browsed the landscape.

The loss of Earth’s largest terrestrial animals at the end of the Pleistocene was most likely caused by humans.

Sadly, even those large beasts that survived that collapse are now being lost, with 60% of today’s megafauna threatened with extinction. This threat is leading to international calls for urgent intervention to save the last of Earth’s giants.

A wilder world than we think

Formal conservation distribution maps show that much of Earth is empty of megafauna. But this is only a part of the picture.

Many megafauna are now found outside their historic native ranges. In fact, thanks to introduced populations, regional megafauna species richness is substantially higher today than at any other time during the past 10,000 years.

Megafauna have expanded beyond their historic native range to rewild the world. Number of megafauna per region, in their ‘native’ range only (a) and in their full range (b)
Modified and reproduced from Lundgren et al. 2017

Worldwide introductions have increased the number of megafauna by 11% in Africa and Asia, by 33% in Europe, by 57% in North America, by 62% in South America, and by 100% in Australia.

Australia lost all of its native megafauna tens of thousands of years ago, but today has eight introduced megafauna species, including the world’s only wild population of dromedary camels.

Australia lost all of its native megafauna tens of thousands of years ago, but is now home to eight introduced species, including the world’s only population of wild dromedary camels. Remote camera trap footage from our research program shows wild brumbies, wild donkeys and wild camels sharing water sources with Australian dingoes, emus and bustards in the deserts of South Australia.

These immigrant megafauna have found critical sanctuary. Overall, 64% of introduced megafauna species are either threatened, extinct, or declining in their native ranges.

Some megafauna have survived thanks to domestication and subsequent “feralisation”, forming a bridge between the wild pre-agricultural landscapes of the early Holocene almost 10,000 years ago, to the wild post-industrial ecosystems of the Anthropocene today.

Wild cattle, for example, are descendants of the extinct aurochs. Meanwhile, the wild camels of Australia have brought back a species extinct in the wild for thousands of years. Likewise, the vast majority of the world’s wild horses and wild donkeys are feral.

There have been global calls to rewild the world, but rewilding has already been happening, often with little intention and in unexpected ways.

A small population of wild hippopotamuses has recently established in South America. The nicknamed “cocaine hippos” are the offspring of animals who escaped the abandoned hacienda of Colombian drug lord Pablo Escobar.

Colombia’s growing ‘cocaine hippo’ population is descended from animals kept at Pablo Escobar’s hacienda.

By insisting that only idealised pre-human ecosystems are worth conserving, we overlook the fact that these emerging new forms of wilderness are not only common but critical to the survival of many existing ecosystems.

Vital functions

Megafauna are Earth’s tree-breakers, wood-eaters, hole-diggers, trailblazers, wallowers, nutrient-movers, and seed-carriers. By consuming coarse, fibrous plant matter they drive nutrient cycles that enrich soils, restructure plant communities, and help other species to survive.

The wide wanderings of megafauna move nutrients uphill that would otherwise wash downstream and into the oceans. These animals can be thought of as “nutrient pumps” that help maintain soil fertility. Megafauna also sustain communities of scavengers and predators.

In North America, we have found that introduced wild donkeys, locally known as “burros”, dig wells more than a metre deep to reach groundwater. At least 31 species use these wells, and in certain conditions they become nurseries for germinating trees.

Introduced wild donkeys (burros) are engineering the Sonoran Desert, United States.

The removal of donkeys and other introduced megafauna to protect desert springs in North America and Australia seems to have led to an exuberant growth of wetland vegetation that constricted open water habitat, dried some springs, and ultimately resulted in the extinction of native fish. Ironically, land managers now simulate megafauna by manually removing vegetation.

It is likely that introduced megafauna are doing much more that remains unknown because we have yet to accept these organisms as having ecological value.

Living in a feral world

Like any other species, the presence of megafauna benefits some species while challenging others. Introduced megafauna can put huge pressure on plant communities, but this is also true of native megafauna.

Whether we consider the ecological roles of introduced species like burros and brumbies as desirable or not depends primarily on our own values. But one thing is certain: no species operates in isolation.

Although megafauna are very large, predators can have significant influence on them. In Australia, dingo packs act cooperatively to hunt wild donkeys, wild horses, wild water buffalo and wild boar. In North America, mountain lions have been shown to limit populations of wild horses in some areas of Nevada.

Visions of protected dingoes hunting introduced donkeys and Sambar deer in Australia, or protected wolves hunting introduced Oryx and horses in the American West, can give us a new perspective on conserving both native and introduced species.

Nature doesn’t stand still. Dispensing with visions of historic wilderness, and the associated brutal measures usually applied to enforce those ideals, and focusing on the wilderness that exists is both pragmatic and optimistic.

After all, in this age of mass extinction, are not all species worth conserving?


The ConversationThis research will be presented at the 2017 International Compassionate Conservation Conference in Sydney.

Erick Lundgren, PhD Student, Centre for Compassionate Conservation, University of Technology Sydney; Arian Wallach, Chancellor’s Postdoctoral Research Fellow, Centre for Compassionate Conservation, University of Technology Sydney; Daniel Ramp, Associate Professor and Director, Centre for Compassionate Conservation, University of Technology Sydney, and William Ripple, Distinguished Professor and Director, Trophic Cascades Program, Oregon State University

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

‘Gene drives’ could wipe out whole populations of pests in one fell swoop



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Gene drives aim to deliberately spread bad genes when invasive species such as mice reproduce.
Colin Robert Varndell/shutterstock.com

Thomas Prowse, University of Adelaide; Joshua Ross, University of Adelaide; Paul Thomas, University of Adelaide, and Phill Cassey, University of Adelaide

What if there was a humane, targeted way to wipe out alien pest species such as mice, rats and rabbits, by turning their own genes on themselves so they can no longer reproduce and their population collapses?

Gene drives – a technique that involves deliberately spreading a faulty gene throughout a population – promises to do exactly that.

Conservationists are understandably excited about the possibility of using gene drives to clear islands of invasive species and allow native species to flourish.


Read more: Gene drives may cause a revolution, but safeguards and public engagement are needed.


Hype surrounding the technique continues to build, despite serious biosecurity, regulatory and ethical questions surrounding this emerging technology.

Our study, published today in the journal Proceedings of the Royal Society B, suggests that under certain circumstances, genome editing could work.

The penguins on Antipodes Island currently live alongside a 200,000-strong invasive mouse population.
Wikimedia Commons, CC BY

Good and bad genes

The simplest way to construct a gene drive aimed at suppressing a pest population is to identify a gene that is essential for the pest species’ reproduction or embryonic development. A new DNA sequence – the gene-drive “cassette” – is then inserted into that gene to disrupt its function, creating a faulty version (or “allele”) of that gene.

Typically, faulty alleles would not spread through populations, because the evolutionary fitness of individuals carrying them is reduced, meaning they will be less likely than non-faulty alleles to be passed on to the next generation. But the newly developed CRISPR gene-editing technology can cheat natural selection by creating gene-drive sequences that are much more likely to be passed on to the next generation.


Read more: Now we can edit life itself, we need to ask how we should use such technology.


Here’s how the trick works. The gene-drive cassette contains the genetic information to make two new products: an enzyme that cuts DNA, and a molecule called a guide RNA. These products act together as a tiny pair of molecular scissors that cuts the second (normal) copy of the target gene.

To fix the cut, the cell uses the gene drive sequence as a repair template. This results in a copy of the gene drive (and therefore the faulty gene) on both chromosomes.

This process is called “homing” and, when switched on in the egg- or sperm-producing cells of an animal, it should guarantee that almost all of their offspring inherit the gene-drive sequence.

As the gene-drive sequence spreads, mating between carriers becomes more likely, producing offspring that possess two faulty alleles and are therefore sterile or fail to develop past the embryonic stage.

Will it work?

Initial attempts to develop suppression drives will likely focus on invasive species with rapid life cycles that allow gene drives to spread rapidly. House mice are an obvious candidate because they have lots of offspring, they have been studied in great detail by biologists, and have colonised vast areas of the world, including islands.

In our study we developed a mathematical model to predict whether gene drives can realistically be used to eradicate invasive mice from islands.

Our results show that this strategy can work. We predict that a single introduction of just 100 mice carrying a gene drive could eradicate a population of 50,000 mice within four to five years.

But it will only work if the process of genetic homing – which acts to overcome natural selection – functions as planned.

Evolution fights back

Just as European rabbits in Australia have developed resistance to the viruses introduced to control them, evolution could thwart attempts to use gene drives for biocontrol.

Experiments with non-vertebrate species show that homing can fail in some circumstances. For example, the DNA break can be repaired by an alternative mechanism that stitches the broken DNA sequence back together without copying the gene-drive template. This also destroys the DNA sequence targeted by the guide RNA, producing a “resistance allele” that can never receive the gene drive.

A recent study in mosquitos estimated that resistance alleles were formed in at least 2% of homing attempts. Our simulation experiments for mice confirm this presents a serious problem.

After accounting for low failure rates during homing, the creation and spread of resistance alleles allowed the modelled populations to rebound after an initial decline in abundance. Imperfect homing therefore threatens the ability of gene drives to eradicate or even suppress pest populations.

One potential solution to this problem is to encode multiple guide RNAs within the gene-drive cassette, each targeting a different DNA sequence. This should reduce homing failure rates by allowing “multiple shots on goal”, and avoiding the creation of resistance alleles in more cases.

To wipe out a population of 200,000 mice living on an island, we calculate that the gene-drive sequences would need to contain at least three different guide RNA sequences, to avoid the mice ultimately getting the better of our attempts to eradicate them.

From hype to reality

Are gene drives a hyperdrive to pest control, or just hype? Part of the answer will come from experiments with gene drives on laboratory mice (with appropriate containment). That will help to provide crucial data to inform the debate about their possible deployment.

The ConversationWe also need more sophisticated computer modelling to predict the impacts on non-target populations if introduced gene drives were to spread beyond the populations targeted for management. Using simulation, it will be possible to test the performance and safety of different gene-drive strategies, including strategies that involve multiple drives operating on multiple genes.

Thomas Prowse, Postdoctoral research fellow, School of Mathematical Sciences, University of Adelaide; Joshua Ross, Associate Professor in Applied Mathematics, University of Adelaide; Paul Thomas, , University of Adelaide, and Phill Cassey, Assoc Prof in Invasion Biogeography and Biosecurity, University of Adelaide

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

Are Australia’s native pigeons sitting ducks?



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These migratory pied imperial-pigeons in Far North Queensland, like many of Australia’s 22 species of native pigeons and doves, play an important role in our ecosystems but may be at risk from emerging viruses in domestic pigeons.
Dejan Stojanovic, CC BY-SA

Andrew Peters, Charles Sturt University

The word “pigeon” evokes thoughts of gentle cooing, fluttering in rafters, and poo-encrusted statues. The species responsible for the encrustation is deeply familiar to us, having ridden waves of European expansionism to inhabit every continent, including Australia. First domesticated thousands of years ago, urban pigeons have turned feral again.

Less familiar are the native species that are not your stereotypical pigeons: a posse of pointy-headed crested pigeons in a suburban park, or a flock of topknot pigeons feeding in a camphor laurel.

Crested pigeons (left), brush bronzewings (centre) and pied imperial-pigeons (right) are amongst the 22 species of native pigeons and doves in Australia. Their charm and beauty belies the important functions they play in ecosystems.
Author provided

Australia and its neighbouring islands are the global epicentre of pigeon and dove (or “columbid”) diversity with the highest density of different columbids – an impressive 134 species – found in the region. Twenty-two of these native species are found in Australia alone, in just about every habitat.

These native species play an important role in ecosystem functioning: they forage for and disperse seeds, concentrate nutrients in the environment, and are a source of food for predators. Fruit doves for example, are zealous fruitarians, and the region’s tropical rainforests depend on them for tree diversity. Where fruit-doves have disappeared in the South Pacific, numerous plant species have lost an effective dispersal mechanism.

The rose-crowned fruit-dove is not only beautiful but also plays an important role in dispersing seeds in Australian rainforests.
Author provided

The future of Australia’s native pigeons however, may depend on our domestic pigeons. Australia’s domestic pigeon population — both feral and captive – is large and interconnected by frequent local and interstate movements. Pigeon racing, for example, involves releasing captive birds hundreds of kilometres from their homes only so they may find their way back. While most birds do navigate home, up to 20% will not return, of which some will join feral pigeon populations. Birds are also traded across the country and illegally from overseas. These movements, together with poor biosecurity practices, mean that captive pigeons can and do mingle with feral domestic pigeons.

And here’s a paradox. Could Australia’s feral domestic pigeons become the vector for a dramatic decline of columbids – native species on which Australian ecosystems rely?

Emerging viral epidemics

In recent years, two notable infectious diseases have been found to affect our captive domestic pigeons: the pigeon paramyxovirus type 1 (PPMV1) and a new strain of the pigeon rotavirus (G18P). These diseases are notable because in captive domestic flocks they are both spectacularly lethal and difficult to control.

PPMV1, although likely to have originated overseas, is now endemic in Australia. This virus has jumped from captive to feral domestic pigeon populations on several occasions, but fortunately has yet to establish in feral populations.

Domestic pigeons suffer high mortality rates after being infected with either pigeon paramyxovirus ‘PPMV1’ or pigeon rotavirus ‘G18P’.
Dr Colin Walker

G18P is thought to have spread to Victoria and South Australia from a bird auction in Perth in 2016. PPMV1 also spread rapidly to multiple states following its first appearance in Melbourne in 2011.

The movements of captive pigeons, and their contact with their feral counterparts, can be the route through which virulent and lethal diseases – such as the PPMV1 and the G18P – may spread to Australia’s native columbids.

Pigeon paramyxovirus and pigeon rotavirus are known to have escaped from captive domestic pigeons into feral domestic pigeons (black arrow). The risk is that these viruses will establish in feral pigeon populations and cause epidemics in our diverse and ecologically important wild native columbids (red arrow).
Author provided

What have we got to lose?

Fortunately, neither PPMV1 nor G18P has crossed over to Australia’s native columbids. We can’t say how likely this is, or how serious the consequences would be, because we have not previously observed such viral infections among our native pigeons.

If the viruses prove equally lethal to native columbids as they are to domestic pigeons, we could see catastrophic population declines across numerous columbid species in Australia over a short period of time.

Should these viruses spread (via feral domestic pigeons), the control and containment of losses among our native pigeon species would be near impossible. Such a nightmare scenario can only be avoided by predicting if and how these viruses might “spill over” into wild columbids so that we can prevent this in the first place.

Maps of Australia showing the overlapping distribution of our 22 native pigeon and dove species (left) and the distribution (in orange) and verified individual records (red dots) of introduced feral domestic pigeons (right).
Atlas of Living Australia, Birdlife International

Protecting our pigeons

Agricultural poultry is routinely screened to check their vulnerability to threats like the PPMV1 and G18P. Such screening is an appropriate response to protect our agricultural industry.

For our native pigeons and doves however, no such similar testing is planned. Based on progress in veterinary vaccine development and advancements in understanding of feral pigeon control, the knowledge and technology required to mitigate this threat should be relatively inexpensive. The threat for these species can be actively managed, now, by improving our biosecurity and vaccination programs for captive domestic pigeons, and eradicating feral domestic pigeons.

The ConversationThe protection of our native columbids however, ultimately relies on valuing their ecosystem functions in the first place.

Andrew Peters, Senior Lecturer in Veterinary Pathology, Charles Sturt University

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

Widespread invasive species control is a risky business



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Partula snails were driven to extinction in the wild by introduced predators.
Wikimedia Commons

R. Keller Kopf, Charles Sturt University; Dale Nimmo, Charles Sturt University, and Paul Humphries, Charles Sturt University

In 1977, on the islands of French Polynesia, government authorities released a predatory snail. They hoped this introduction would effectively control another species of invasive snail, previously introduced to supply escargot.

Instead, by the early 1980s, scientists reported alarming declines of native snail populations. Within ten years, 48 native snail species (genus Partula) had been driven to extinction in the wild.

The extinction of the Partula is notorious partially because these snails were, before going extinct, the study subjects of the first test in nature of Darwin’s theory of evolution by natural selection.

In the decades since, attempts to control and eradicate invasive species have become common, generally with far better results.

However, our paper, published today in Nature Ecology and Evolution, highlights the importance of scientific evidence and independent assessments when deciding whether to control or eradicate invasive species.

From islands to continents

Increasingly, large-scale invasive species control initiatives are being proposed worldwide. As early as 2018, a herpes virus will be released in Australia’s largest river system, targeting invasive common carp. As part of its Threatened Species Strategy, Australia is also planning to kill two million feral cats.

Across the Tasman Sea, New Zealand has made a bold commitment to remove three groups of invasive predators entirely by 2050.

New Zealand looks to eradicate three groups of invasive predators: rodents, mustelids, and the common brushtail possum.
Geoff Whalan/Flickr, CC BY-NC-SA

It’s not just Australians and Kiwis making ambitious invasive species control proposals: bounties are being paid to catch invasive fish in the United States. The European Union has blacklisted 37 species of plants and animals within 4 million square kilometres, many of which are well-established and will be targeted by control (not preventative) measures.

Meanwhile, new gene editing technology has made the continental-scale eradication of invasive species a real possibility, for example by implementing gene drives that reduce breeding success. If you haven’t heard of it, CRISPR is a startling new biotechnology that makes genetic modification of plants and animals much easier. It offers new potential solutions to some of the world’s worst environmental, agricultural and human health problems.

These schemes will be implemented across large and complex social-ecological systems, and some options – like releasing a virus or genetically engineered species – may be irreversible.

Managing risk

While these projects may yield great benefits, we must be aware of the potential risk of unexpected and undesirable outcomes.

A prime example is the project to remove invasive carp from a million square kilometres of Australia’s rivers. Some scientists have expressed concern about the potential for the virus to jump species, and the effects of having hundreds of tonnes of dead fish fouling waterways and sapping oxygen from the water. The CSIRO and those planning the release of the virus suggest it is safe and effective.

Despite extensive media reporting giving the impression that the plan is approved to go ahead, the National Carp Control Plan has yet to publish a risk assessment, and is planning to deliver a report in 2018.

Removing well-established invasive species can create unforeseen consequences. These species can play significant roles in food webs, provide shelter for native animals, support ecosystem services, and their sudden death can disrupt ecological processes that are important to native species.

For example, a large amount of time and effort was spent in removing the non-native tamarix (or “salt cedar”) in the southwestern United States, because of the belief it was harming the water table.

Yet, subsequent research has indicated that the negative effects of tamarix have been exaggerated. In some areas, the plant is actually used by large numbers of endangered flycatchers to nest and fledge their young.

A corn bunting perches on a blooming tamarix.
Georgios Alexandris/shutterstock

A science-based solution

In our paper, we highlight a series of considerations that should be addressed before plunging into large-scale invasive species control.

Fundamentally, there must be a demonstrable ecological and social benefit from control or eradication, above and beyond the purely ideological. At first this might seem facile, but invasive species control initiatives are often highly politicised, with science taking a back seat. Given scarce funding for conservation, it is crucial that resources are not squandered on programmes that may not deliver – or could cause environmental damage.

We must avoid assuming that attempting to control invasive species will, by default, solve our environmental problems. This means addressing the full range of human pressures which negatively affect biodiversity. We must also consider how removing an influential invasive species could benefit other invasive species, harm native species through increased predation and competition, or alter ecological processes or habitat.

Comprehensive risk-benefit assessment of invasive species control programs allow decision-makers to proactively avoid, manage or accept these risks.

For example, tonnes of decomposing carp post-virus may cause short-term water quality issues, or the death of native species. Ultimately, however, these risks could be acceptable if the virus is effective, and allows native species a window of opportunity to recover.

The ConversationLarge-scale invasive species control demands careful investigation of the risks and rewards. We hope our paper can provide policy-makers with better guidelines for science-based decision-making.

R. Keller Kopf, Research fellow, Charles Sturt University; Dale Nimmo, ARC DECRA Fellow, Charles Sturt University, and Paul Humphries, Senior lecturer in Ecology, Charles Sturt University

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

The bark side: domestic dogs threaten endangered species worldwide



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A feral dog chasing a wild boar, Banni grasslands, India.
Chetan Misher/Facebook

Tim Doherty, Deakin University; Aaron J. Wirsing, University of Washington; Chris Dickman, University of Sydney; Dale Nimmo, Charles Sturt University; Euan Ritchie, Deakin University, and Thomas Newsome, Deakin University

Humans and their canine companions share many close bonds. Wolves (Canis lupus) were the first animal domesticated by people, some time between 15,000 and 50,000 years ago. The Conversation

There are now an estimated 1 billion domestic dogs across their near-global distribution.

Domestic dogs include feral and free-ranging animals (such as village and camp dogs), as well as those that are owned by and completely dependent on humans (pet dogs).

Our latest research reveals that the ecological “pawprint” of domestic dogs is much greater than previously realised.

Using the IUCN Red List of Threatened Species, we counted how many species are negatively affected by dogs, assessed the prevalence of different types of impacts, and identified regions with the greatest number of affected species.

A dog with a black-naped hare, Maharashtra, India.
Hari Somashekhar/Facebook

Dogs are third-most-damaging mammal

We found that dogs are implicated in the extinction of at least 11 species, including the Hawaiian Rail and the Tonga Ground Skink. Dogs are also a known or potential threat to 188 threatened species worldwide: 96 mammal, 78 bird, 22 reptile and three amphibian species. This includes 30 critically endangered species, two of which are classed as “possibly extinct”.

These numbers place dogs in the number three spot after cats and rodents as the world’s most damaging invasive mammalian predators.

Even though dogs have an almost global distribution, the threatened species they are known to affect are concentrated in certain parts of the globe. South-East Asia, South America, Central America and the Caribbean each contain 28 to 30 threatened species impacted by dogs. Other hotspots include Australia, Micro/Mela/Polynesia and the remainder of Asia.

Lethal and non-lethal impacts

Predation was the most commonly reported impact of dogs on wildlife. The typically omnivorous diet of dogs means they have strong potential to affect a diversity of species. For instance, dogs killed at least 19 endangered Kagu (a ground-dwelling bird) in New Caledonia in 14 weeks. Threatened species with small population sizes are particularly vulnerable to such intense bouts of predation.

The frequency of different types of dog impact on threatened species.
https://authors.elsevier.com/a/1Uxs~1R~e71Xl

Aside from simply killing animals, dogs can harm wildlife in other ways, such as by spreading disease, interbreeding with other canids, competing for resources such as food or shelter, and causing disturbances by chasing or harassment. For example, contact with domestic dogs increases disease risk for endangered African Wild Dogs in Kenya.

Part of the problem is that when wild animals perceive dogs as a threat, they may change their behaviour to avoid them. One study near Sydney found that dog walking in parklands and national parks reduced the abundance and species richness of birds, even when dogs were restrained on leads.

None of the Red List assessments mentioned such indirect risk effects, which suggests that their frequency is likely to be much higher than reported.

Feral dogs chasing Indian wild ass at Little Rann of Kutch, India.
Kalyan Varma/Facebook

Friend and foe

Despite their widespread and sometimes severe impacts on biodiversity, dogs can also benefit some species and ecosystems.

For example, in Australia, the closely related dingo (Canis dingo) can suppress populations of introduced predators such as red foxes (Vulpes vulpes), and in doing so can benefit smaller native prey. It is possible that domestic dogs could perform similar ecological roles in some situations.

In some regions, dogs and their keen noses have been trained to help scientists find threatened species such as Tiger Quolls. Elsewhere they are helping to flush out and control feral cats.

An emerging and exciting conservation role for dogs is their growing use as “guardian animals” for wildlife, with the remarkable story of Oddball being the most well known.

Managing the problem

Dogs not only interact with wildlife, but can also attack and spread disease to humans, livestock and other domestic animals. As such, managing the problem requires looking at ecological, cultural and social perspectives.

Some of the regions with high numbers of species threatened by dogs are also hotspots for urbanisation and road building, which make it easier for dogs to access the habitats of threatened species. Urban development increases food waste, which feeds higher numbers of dogs. As dogs expand into new areas, the number of species they impact is likely to grow.

Street dogs scavenging food waste in India.
Achat1234/wikimedia

We can protect wildlife by integrating human health and animal welfare objectives into dog management. Vaccination and desexing campaigns can reduce disease risk and overpopulation problems. We should also focus on responsible dog ownership, removing dogs without owners, and reducing access to food waste.

Given the close relationship between humans and dogs, community engagement should form the basis of any management program. More research is needed to get a better picture of the scale of the problem, and of how dogs interact with other threats such as habitat loss. Such actions are critically important for ensuring the conservation of wildlife threatened by dogs around the world.


This article was co-authored by Dr Al Glen from Landcare Research, New Zealand and Dr Abi Vanak from the Ashoka Trust for Research in Ecology and the Environment, India. These institutions had no role in the design or funding of this research.

Tim Doherty, Research Fellow, Deakin University; Aaron J. Wirsing, Assistant Professor, School of Environmental and Forest Sciences, University of Washington; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Dale Nimmo, ARC DECRA Fellow, Charles Sturt University; Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Thomas Newsome, Fulbright Scholar and Postdoctoral Research Fellow, Deakin University

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

Tipping the scales on Christmas Island: wasps and bugs use other species, so why can’t we?


Susan Lawler, La Trobe University

A couple of days ago I published an article with Peter Green about the imminent release of a tiny wasp that will be used for biological control of a bug that feeds the crazy ants that kill red crabs on Christmas Island.

It is understandable that people are nervous about the introduction of exotic species to manage wildlife in a natural setting. It turns out that ecologists are even more nervous than the public about this, so if they have decided to do it anyway, then there is a remarkably good reason.

Parasitoid wasps use scale insects

The release of the wasp has concerned some readers because they imagine swarms of biting insects setting up their nests in the back garden. The truth is that the wasps that will be released are tiny and unlikely to be noticed at all.

First of all, Tachardiaephagus somervillei are only 2 mm long and cannot sting humans or other animals. They do not form colonies, they do not swarm, and they do not build nests. In fact, they won’t be at all interested in hanging around human habitations unless there is a tree nearby containing a colony of the yellow lac scale insect (Tachardina aurantiaca).

This is because these wasps are parasitoids – a type of parasitic organism that kills its host species. They don’t need a nest or a colony because the scale insects they target are both their food source and their home.

The specificity of the wasp for this particular type of scale insect can be seen in the first part of their Latin names: Tachardiaephagus literally means “eater of Tachardina”.

Scale insects use ants

Scale insects are a type of true bug (in the Order Hemiptera) that line up along tree branches like barnacles, sucking sap from the tree and in their mature form, releasing a sweet liquid known as honeydew from their backsides for the benefit of ants. They don’t do this for nothing. Their strategy is to use the ants as body guards.

In a situation where scale insects are relatively rare this increases the number of the ants who will in turn protect the scale insects. On Christmas Island, where the introduced yellow lac scale insects have become common because they do not have any natural predators, the invasive crazy ants have access to large quantities of honeydew. In this case, the crazy ants are using the yellow lac scale insects as a super abundant food source.

The super colonies that have formed as a result have instigated an environmental disaster. The crazy ants kill red crabs and other species mostly due to their extremely high densities driven by the abundance of honeydew.

Any detractors concerned about the dangers of yet another invasive species have not fully grasped the consequences of doing nothing. Chemical baiting of the ants is ongoing but has consequences for other animals and is not environmentally desirable or sustainable.

People using wasps

If the scale insects can use the ants as bodyguards and the ants can use the scale insects as a free food source, why can’t we use a tiny wasp as a biological control?

Unlike birds, lizards or other predators that may be deterred by ants crawling all over the scale insects, the tiny parasitoid wasps can slip through and lay their eggs in a scale insect without being noticed by the ants. Their eggs hatch and develop inside the scale insect, emerging as adult wasps that are ready to lay their eggs in another scale insect nearby.

In essence, the wasp uses the scale insect as a one-stop nursery, food source and conveniently located launching pad for the next generation. Inside a scale insect colony, they are likely to find another scale insect less than a centimetre from where they were born.

Consider how this will allow the wasp population to quickly grow and, perhaps, reduce the scale insect colony density so that the wasps will eventually have to fly further and further to find another scale insect. At some point the effort to find more scale insects will balance the benefit of finding an insect, and the two populations (wasp and scale insect) will reach a new equilibrium at a lower density.

How will the crazy ants respond?

The wasp will not run out of food, nor will the scale insects become extinct, but the ants will find themselves deprived of excess honeydew and will have to adjust their populations accordingly.

How do you empirically test the response of the ants to the removal of excess honeydew from their environment? Well, you can’t remove the scale insects but you can prevent the ants from getting into the trees where the scale insects live, even though it wasn’t easy. Apparently, doing this involves Glad wrap, Mr Sheen furniture polish, and daily vigilance by a research student.

The result was a 95% decrease in crazy ant activity in a few weeks, an outcome that suggests this approach has every chance of reducing the impacts of crazy ants on Christmas Island.

What happens next?

I understand that the team is gathering in Malaysia today to pack up some wasps and fly them to Christmas Island. The release will not happen right away, as the wasps will be acclimatised and grown up in large numbers in a dedicated facility. Monitoring programs are planned to observe the impacts, both short and long term, on the scale insects, the ants, the crabs and the forest structure.

The research to understand the ecology of Christmas Island sufficiently to identify a biological control agent started decades ago, and many scientists were involved along the way. It is not possible to provide links to all the research articles produced thus far, but here is a link to the final risk report.

I am not involved with the research but am familiar with it and in my view there are two things that could happen next. Either the wasp will fail to reduce the scale insect populations and nothing changes, or they will reduce the scale insect populations which could kick start a cascade of beneficial environmental outcomes for Christmas Island.

We are all really hoping that it is the latter.

The Conversation

Susan Lawler, Senior Lecturer, Department of Ecology, Environment and Evolution, La Trobe University

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