Australia’s reptiles may be spreading rat poison through the food chain



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Gould’s goanna is commonly eaten in Indigenous communities, but can contain high levels of rat poison.
Robert A. Davis, Author provided

Michael Lohr, Edith Cowan University and Robert Davis, Edith Cowan University

Introduced rats and mice have probably troubled most of us at some time in our lives. These pesky invasive rodents are found around the world. We usually target them with toxic baits to stop them spreading disease and causing environmental or commercial damage.

In some instances rat baits are useful. They can protect crops, reduce the spread of disease, keep the contents of your pantry from disappearing, or even protect endangered wildlife on islands where rats have invaded.

These baits are freely available to homeowners and are used liberally by pest controllers. However, they have potentially deadly consequences for native predatory animals that eat poisoned rats and mice.

Our new research shows that this secondary poisoning may be worsened in Australia by reptiles, which are extremely effective at spreading these poisons up the food chain – a process that may even have consequences for human health.




Read more:
Hidden housemates: rats in the ranks


While little is known about how well reptiles tolerate rodent baits, several studies have suggested that at least some reptiles are extremely resistant. In a toxicity study using one lizard species, all of the test subjects survived an incredibly high dose of the strongest poison on the market – over 4,000 times the poison per body weight needed to kill most rats.

This is probably good news for the lizards, but eating poison-supercharged reptiles may be a serious concern for their predators – and for us.

Humans eat lizards too

During a rat eradication program in the Montebello Islands, one goanna species was seen eating poisoned rats – without apparent ill effect – to the point that the green dye used in the bait was visible in their droppings. Unfortunately, this species of goanna is an important traditional food in Indigenous communities throughout Australia. To make matters worse, these poisons usually build up in commonly eaten parts of the goannas, like fat and liver tissue.

The risks associated with sublethal human exposure to rodent baits are not well known. However, recent studies in some wildlife species show that even mild chronic exposure to the longer-lasting poisons can lead to dangerous changes in the immune system.

With so many unknowns in a potentially dangerous situation, more research is urgently needed. We need to know how often and how severely the reptiles that humans eat are exposed to poison. Otherwise, some Indigenous people may have to choose between losing traditional hunting practices and risking exposure to rat poison.

Poison in the food web

In our research, we reviewed all published examples of wildlife deaths from exposure to rat bait. We found that rat poison has killed members of at least 32 native wildlife species in Australia. There are probably many more; only a few studies have looked at this problem in Australia, compared with other parts of the world.

We found that a small species of owl called the Southern Boobook is exposed to rat poison frequently, and sometimes lethally, in developed areas of Western Australia. Scavengers and prolific predators of rodents are likely to be even worse off – and these predators include a variety of threatened or endangered species such as Masked Owls, Tasmanian Devils and various species of quolls.

Most deaths will occur far from the original bait, as the poison travels through other species in the food web to reach its final destination. Without a better understanding of how baits affect Australian predators, we are unlikely to appreciate the scale of this invisible threat.




Read more:
Killing cats, rats and foxes is no silver bullet for saving wildlife


At present, powerful rat poisons are available at most supermarkets and hardware stores. The Australian Pesticides and Veterinary Medicines Authority is now reviewing how these are regulated because of concerns about human health and impacts on wildlife populations.

Other countries like the United States and Canada have already restricted the stronger poisons to licensed pest controllers. They have banned outdoor use and require lockable bait boxes to keep children and pets away from baits.

The ConversationThese steps might not be enough to overcome Australia’s unique risks, but allowing the current situation to continue is guaranteed to result in more poisonings of wildlife – and possibly unseen and unstudied effects on humans too.

Michael Lohr, PhD Student – Wildlife Ecology, Edith Cowan University and Robert Davis, Senior Lecturer in Vertebrate Biology, Edith Cowan University

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

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Cat plague is back after nearly 40 years in hiding – here’s what you need to know


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No cases of feline parvovirus were reported from the 1980s until 2015.
Simone Dalmeri

Mark Westman, University of Sydney and Richard Malik, University of Sydney

A deadly feline disease is now spreading between cats after hiding in nature for nearly 40 years. Multiple cases of feline parvovirus, also known as cat plague, or panleukopenia, have been reported in stay kittens in the greater Melbourne area this week.

Feline parvovirus was a common disease in the 1960s and 1970s. Australia was one of the first countries to develop an effective vaccine. Once widespread vaccination became routine, the disease was pushed back into nature.

Most cases of parvovirus are in kittens and young cats.
Raphael Schaller

In the 1970s, cases were typically seen in unvaccinated kittens purchased from markets or pet stores, and in shelters where vaccination protocols were lax.

Between the early 1980s and 2015, cases were unreported, but no doubt feral and semi-owned cats were still sporadically infected.

The re-emergence first occurred in animal shelters in Mildura and Melbourne in 2016 and south-western Sydney in 2016. Many cats died. Even survivors suffered greatly. In all these outbreaks, affected cats had one thing in common – they had not been vaccinated.

What is feline parvovirus and how does it kill?

Feline parvovirus has a predilection for infecting rapidly dividing tissues. Cells lining the small intestine of infected cats are killed, resulting in vomiting, diarrhoea (often bloody), fever, lethargy, anorexia and sometimes sudden death.

The bone marrow is transiently wiped out by the virus, resulting in a depletion of white blood cells. As a result, infected cats are unable to fight the invasion by secondary bacteria that attack the leaky gut wall.




Read more:
How desexing cats saves lives


Most cases of feline parvovirus are in unvaccinated kittens or young cats. The welfare of cats is hugely impacted by this terrible disease – it makes cats miserable for many days, if they survive.

Treatment involves intensive therapy in hospital: intravenous fluids by infusion pump, medication to reduce vomiting, expensive anti-viral treatment (omega-interferon), opioids for pain relief, antibiotics to treat secondary bacterial infections, and occasionally blood or plasma transfusions and nutritional support (feeding tubes).

This eight-week-old kitten, Cola, wasn’t vaccinated and contracted feline parvovirus. She needed a transfusion and recovered from the infection.
David Hughes

Treatment can costs thousands of dollars, and many owners just can’t afford it. But even with treatment, the fatality rate remains high.

Feline parvovirus is spread by faeco-oral contamination: from infected cats shedding virus in their faeces. Litter trays and natural latrines (such as sandboxes) are prime sources of infection.

This may occur where infected cats are kept close to uninfected cats (in shelters and pounds), and in homes where cats have outdoor access. But you can track feline parvovirus into your house on your shoes or clothing, so even 100% indoor cats are not safe.

Feline parvovirus can usually be quickly diagnosed by veterinarians using rapid point-of-care test kits and then confirmed in a lab.

There is no risk of this virus spreading to human patients.

How did it re-emerge?

Feline parvovirus was never completely eliminated from the Australian cat population and instead has been maintained at low levels in the unowned and feral cat population for the past 40 years. Remember, there are perhaps six times as many unowned cats than owned cats in Australia!

This adaptable virus also has the potential to infect foxes and wild dogs, only later to be passed back to cats, providing a variety of potential environmental reservoirs.




Read more:
Our dogs and cats are spreading fleas around the world (and to us)


Perhaps with an increased effort to rehabilitate and rehome “fringe dwelling cats”, it was inevitable that the virus would spill back from these unvaccinated cats into the general pet cat population, given waning herd immunity.

Consistent with this hypothesis is the first outbreak occurring in rural Mildura, a somewhat underprivileged socioeconomic area (government figures show the median household income is A$878 per week), and subject to incursions by feral cats, foxes and wild dogs – including dogs used for hunting.

Unvaccinated pet cats permitted the re-emergence of the virus.
David Vázquez

It is our suspicion that the cost of vaccinating the family cat (currently more than A$200 for a kitten requiring a course of two to three vaccines) exceeds the budget for many pet owners.

The best protection for any cat (and every cat) is widespread vaccination of as many cats as possible in the community at large. This “herd immunity” is the best protection against this highly contagious, persistent, resistant virus. When vaccination rates fall below 70%, cat populations are in trouble.

How do we protect pet cats?

Vaccination against feline parvovirus is highly effective (more than 99%) and is given by veterinarians as part of an F3 or F4 vaccine at the same time as a routine health check.

The Australian Veterinary Association recently recommended all cats be vaccinated annually. But with the modern range of vaccines, there is good evidence that in kittens older than 16 weeks, a single vaccination produces immunity which last several years

If a kitten has received two or three kitten vaccinations (the last one at 16-18 weeks of age), and a booster one year later, it likely has excellent protection against the virus, probably for several years, and possibly for life.

Is it time to vaccinate?
Krista Mangulsone

If your adult cat has received an annual vaccination in the past three years, it likely has excellent protection.

If your cat is more than three years overdue for its vaccination, it is sensible to visit your local veterinarian soon. Your cat will develop or maintain excellent protection within a few days of vaccination.

But what about unowned and feral cats?

We need to support efforts to vaccinate cats that have never been vaccinated against feline parvovirus – cats owned by people who are unable to afford vaccinations, and cats that have been dumped and are now unowned and free-roaming.

New South Wales is making some progress in this area. The NSW Cat Protection Society responded to a 2017 outbreak by subsidising free vaccinations for cat owners in Sydney. RSPCA NSW has ongoing targeted low-cost vaccination programs for cat owners, particularly in regional and remote areas of NSW.

Trap-neuter and return programs, while controversial, usually involve administering a F3/F4 vaccination to unowned and feral cats, thereby boosting herd immunity against feline parvovirus and also possibly reducing cat numbers.




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Cat lovers rejoice: watching online videos lowers stress and makes you happy


Finally, for people who cannot afford veterinary care because of their life circumstances, Pets in the Park and similar charities can provide another option for vaccination.

The ConversationRemember, the larger the proportion of the cat population that is vaccinated, the less chance any cat and every cat has of becoming infected. Stated another way, it’s far more effective to maximise the proportion of the cat population that is vaccinated, rather than over-vaccinating only a limited proportion of cats.

Mark Westman, Postdoctoral Researcher, University of Sydney and Richard Malik, Veterinary Internist (Specialist), University of Sydney

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

South Africa should sort out the bad from the really bad on its invasive species list



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Managing trout is a contentious issue with conflicting views about whether they pose a risk, or are beneficial.
Shutterstock

Tsungai Zengeya, South African National Biodiversity Institute

This article is the third in a series The Conversation Africa is running on invasive species.

Alien species have been introduced to Africa for a variety of reasons. They provide food, raw materials for industry, ornamental plants, recreation in the form of sport fishing, hunting and pets. Some that are highly valued have been moved around widely. And in some areas they now form prominent components of societies and ecosystems like the domestic cat for example.

Many alien species bring considerable benefits. But some have become invasive, causing a loss of biodiversity, changes to ecosystems, economic losses and, in some cases, even affecting people’s health.

The shrub Prosopis or mesquite is an example. It was introduced to South Africa to provide fodder, firewood and shade in arid parts of the country. But it’s also a major water user. And two trout species (S. trutta and O. mykiss) are used for recreational angling and commercial aquaculture. But they’ve also been implicated in having a negative effect on the environment.

Managing invasive species is therefore critical. In South Africa the movement and use of 552 listed invasive species are managed under the Biodiversity Act and regulations attached to it. But not all the species on the list are equally harmful. Several may in fact be relatively harmless.

All the listed species under these regulations require management. Given that the capacity is limited, regulations should arguably focus on priority species because not all are necessarily harmful to the extent that would justify spending large amounts of time and effort on keeping them under control.

The question then is: are there some species that could be removed from the list? In our recent study we set out to answer this question by classifying species as inconsequential, beneficial, destructive or conflict generating species. This was done by assessing the relative degree of benefit they brought and their negative effects.

Beneficial and harmful species

The classification was done by using a simple scoring system. It had two categories for the negatives (ecological and socio-economic) and two for the benefits (economic and intrinsic).

  1. Inconsequential species: these make up 55% of the species listed under the act and in the regulations. They were associated with relatively low costs and low benefits to society. Species in this group had limited distribution or no known impact and were largely introduced as ornamentals or pets. Some examples include the eastern grey squirrel (Sciurus carolinensis), European perch (Perca fluviatilis), and the Père David’s Deer (Elaphurus davidianus).

  2. Destructive species: these make up 29% of the list. They don’t bring substantial benefits to society or the environment, but they have a highly negative impact. Many were introduced accidentally and are regarded largely as pests and weeds. Examples include invasive rodents like the black rat (Rattus rattus) which causes damage to infrastructure and transmission of zoonotic diseases and pitch canker (Fusarium circinatum) a growing threat to pine plantations and forests worldwide.

The jacaranda is an iconic tree species in the city of Pretoria where it’s regarded as part of the identity.
Shutterstock
  1. Beneficial species: they make up 10% of the list and have clear social or environmental benefits. For example the jacaranda (Jacaranda mimosifolia) is an iconic tree species in the city of Pretoria where the species is regarded as part of the identity and “sense of place” of the city. Active management is not necessary or should only be done in particular cases.

  2. Conflict-generating organisms: these can be either beneficial or destructive, depending on one’s perspective or what value is placed on them. They make up only 6% of the list. There’s huge disagreement about whether these species should be controlled, or how they should be controlled. Examples include woody plants introduced for forestry, erosion control, sand dune stabilisation, agriculture and as ornamentals. Acacias and pines are examples. Animal examples include species like the Himalayan tahr which was introduced to the Table Mountain National Park. The goat has been the focus of eradication attempts, despite strong opposition. It also includes species introduced for aquaculture like maroon and brown trout. Managing trout has been highly contentious with conflicting views about whether they pose a risk, or deliver a benefit. This has led to them being listed and delisted. The trout fraternity refuse to acknowledge that trout are invasive species and highlight the lack of scientific evidence of the risks they pose.

Finding common ground

We need to keep sight of the fact that there is general agreement on 94% of listed species. By identifying the small number that are generating the greatest tension, it’s more likely discussions can be held to reach common ground on regulation.

Most countries in Africa don’t have invasive species regulations. But there’s growing recognition that they’re needed. South Africa offers useful lessons on how this could be done.

The control of species listed under the country’s biodiversity act is compulsory. This means that plans to manage them have to be drawn up and implemented. But this doesn’t seem sensible given that not all are equally harmful and resources are limited. Our study suggests that some of the species currently regulated could be removed from the list.

Countries wanting to set up a system of managing invasive species could start by classifying a prospective list of candidates. Policymakers could then quickly bring out legislation against the most damaging and destructive ones. At the same time, discussions could be had on the ones that generate conflict with the aim of reaching consensus.

The ConversationThis would allow managers and regulators to focus on the most destructive species – as well as those that are at the centre of fierce disagreement.

Tsungai Zengeya, Researcher at the South African National Biodiversity Institute, South African National Biodiversity Institute

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

Alien animals and plants are on the rise in Africa, exacting a growing toll



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The larger grain borer beetle attacks crops like maize and cassava, threatening food security.
Shutterstock

Katelyn Faulkner, University of Pretoria; Brett Hurley, University of Pretoria, and Mark Robertson, University of Pretoria

This article is the first in a series The Conversation Africa is running on invasive species.

Let’s say you’re travelling from Uganda to South Africa for business. You finally arrive at your hotel after a long day and decide to change before dinner. You unlock and unzip your luggage, but there’s something in your bag that you didn’t pack. As you reach for a clean shirt, a moth flies out. Did that come with you all the way from Uganda? It’ll be fine, right? Surely, something so small won’t cause any harm.

Species are intentionally or accidentally transported by humans between continents to regions where they are not native. With the help of humans or by natural means like flight, these alien species can also spread within continents.

Their spread within continents can be rapid, affecting both the ecology as well as societies and the economy. Unfortunately, it’s really challenging to prevent species from spreading. Given the vast amount of people and goods that are transported between and around continents they can easily be moved across oceans as well as between countries.

The spread of alien species within Africa is increasing. Since 2000 more alien insect pests of eucalyptus trees have spread to other African countries from South Africa, than have been introduced to these African countries from other continents. To manage the spread of these alien species countries need to co-operate, communicate and share information and skills..

The spread of alien species

Many alien plants and animals have been introduced to Africa from other regions and then have spread from country to country, often having devastating effects.

Take the larger grain borer beetle, (Prostephanus truncatus) which is thought to have arrived on the continent in imported grain from Mexico and central America. The beetle was introduced to Tanzania before 1984, Togo before 1981 and Guinea before 1987. It then spread across the continent and within 20 years could be found further south in South Africa.

The beetle attacks crops such as maize and cassava, threatening food security and the livelihoods of the poor. Infestations often destroy maize that’s been stored by farmers, forcing them to buy maize as well as lose income they could have earned from selling any excess.

But alien species don’t just arrive from abroad. Many that are native to parts of Africa have also spread to countries on the continent where they are not native.

An example is the fish commonly known as the Mozambique tilapia (Oreochromis mossambicus) which is native to rivers on the east coast of southern Africa. Fishermen have transported the Mozambique tilapia to other areas and it is now found in river systems in southern and western South Africa and Namibia.

The Mozambique tilapia is a popular species for fishing but it can pose a threat to native fish and has been responsible for the disappearance of native species in some regions.

The spread of alien species within Africa is by no means a new thing. For instance, the bur clover (Medicago polymorpha), a plant from northern Africa, might have been accidentally transported by humans to South Africa as early as 760 AD.

A high and increasing threat

Recently a number of alien species have spread extremely rapidly across the continent, posing a particularly high threat to food security and livelihoods.

The fall armyworm, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.
Shutterstock

One is a caterpillar known as the fall armyworm (Spodoptera frugiperda). The species, native to the Americas, was first recorded in west and central Africa in early 2016 and then in South Africa in January 2017.

The moths of the armyworm are strong fliers and the species may have spread through flight to South Africa from other African countries. Although the species attacks a wide range of crops, it poses a particularly serious threat to grain farmers. It is extremely difficult to manage.

Another example is a wasp known as the bluegum chalcid (Leptocybe invasa), which is native to Australia. In 2000 it was detected in Israel and shortly afterwards it was reported in Uganda and Kenya. From there it spread rapidly to many African countries including Zimbabwe, Mozambique, and Tanzania and was finally detected in South Africa in 2007. The insect probably reached Israel on live plant material and spread into Africa the same way, or was carried by people travelling between countries.

The wasp causes swelling or growths on eucalyptus trees, which can lead to decreased growth and tree death. As eucalyptus trees are an important source of income and fuel, this species could have an impact on the livelihoods of locals in these countries.

Preventing the introduction and spread

Once a species is introduced to one African country it’s highly likely it will spread to others on the continent because borders checks are weak.

The introduction and spread of species could be reduced if countries introduced biosecurity systems. These are used extensively in countries like Australia and New Zealand and involve using technology to check for alien species when people and goods enter a country. In Australia this involves inspecting goods, vehicles and luggage before they enter the country.

But even these systems aren’t a guarantee that species won’t spread. African countries would need to work together and share information and skills. This would also allow countries to prepare for the arrival of species, and to draw up plans to reduce their impact.

The ConversationThis is a tall order. But as a country’s defence against alien species introductions is only as strong as that of its neighbours, such action would benefit all of the countries involved.

Katelyn Faulkner, Postdoctoral research fellow, University of Pretoria; Brett Hurley, Senior Lecturer Zoology and Entomology, University of Pretoria, and Mark Robertson, Associate Professor Zoology & Entomology, University of Pretoria

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

Without culling, Victoria’s feral horse plan looks set to fail


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Feral horses in the eastern Alps.
Griff en/Wikimedia Commons, CC BY-SA

Don Driscoll, Deakin University

Victoria’s new draft feral horse management plan, released on the last working day before Christmas, will be open for comment until February 2. But will it protect the Alpine National Park? The answers are yes on the Bogong High Plains, and no in the eastern Alps.

The government deserves congratulations for planning to remove all horses from the most sensitive alpine areas around Falls Creek by 2020. These areas of the Bogong High Plains have fewer than 100 horses, but also rare snow-patch and bog communities that are extremely vulnerable.

But elsewhere, the goal of removing 400 horses a year from the eastern Alps doesn’t seem to go far enough. And by refusing to countenance the idea of culling, the state government is passing up the only realistic chance of getting feral horse numbers under control.


Read more: The grim story of the Snowy Mountains’ cannibal horses


The bulk of the plan provides grounds for cautious optimism. It acknowledges that feral horses threaten a range of native mammals, frogs and lizards, as well as displacing kangaroos and wallabies. Horses have enormous impacts on vegetation in alpine bogs and streams, and in many other ecosystems too.

The plan also makes clear that reducing horse numbers is a legal requirement. Victoria’s Flora and Fauna Guarantee Act 1988 lists “degradation and loss of habitats caused by feral horses” as a threatening process. The Victorian National Parks Act 1975 calls for “exotic species” such as horses to be exterminated or controlled within national parks.

The plan also sets a realistic time frame for review (annual reviews and major review after three years), and suggests that management plans will be altered if adequate environmental protection is not achieved. All of this is extremely promising, suggesting the state government is genuinely interested in delivering tangible environmental benefits.

Numbers game

But while the aspirations are good, the details present some problems. The draft plan promises to “explore all possible control options” to deliver a low horse population in the eastern Alps.

But the proposed reliance on trapping and removal, rather than culling, suggests the government is reluctant to enter what would be a tough debate against the often vocal pro-brumby lobby groups. This reluctance is to the detriment of our native species and apparently at odds with legislation.

The problem is that the New South Wales government has already tried trapping and removing horses in Kosciuszko National Park, and it hasn’t worked. Horses have continued to spread northward onto the main range, where environmentally sensitive alpine tarn and snow-patch communities occur.

It is unclear whether Victoria’s “aspirational goal” of removing 400 horses each year over three years will actually be enough to reduce horse numbers, or even to stabilise them. The report mentions modelling showing that the population can be stabilised by taking 200 horses per year, and that it would start to decline if 400 were taken per year.

But none of this modelling is published, so it can’t be evaluated in detail. And simple calculations suggest that these figures are incredibly optimistic.

The report says there were 2,350 horses in the eastern Victorian Alps in 2014. Horse populations can increase at up to 20% per year, so by now there could be more than 4,000 feral horses.

This means that even if the government does manage to remove the full quota of 400 horses each year, it would only take a 10% population growth rate for the numbers to keep rising. At a rate of 20%, there could be well over 5,000 horses by 2020, even with trapping and removal.

Culling option

Based on this rough calculation, the plan needs to eradicate many more horses. The draft plan claims that feral horses in the eastern Alps are “well established and are considered beyond eradication using currently available control tools”. Yet this claim ignores aerial culling, which is the cheapest, most effective, and most ethical way to reduce feral horse numbers.

Highly trained sharp-shooters and helicopter pilot teams can destroy more than 50 horses per day (based on previous culls in NSW, in which three teams of three people destroyed 606 horses over three days). Three teams could solve the feral horse problem in the Victorian alpine country in a month, and at lower cost.

It cost taxpayers more than A$1,000 for each horse trapped and removed from Kosciuszko National Park. Using the NSW cull as a guide to the resources required, and assuming A$300 per day per person, and A$10,000 per day per helicopter, it might have cost around A$150 per horse using aerial culling. That’s roughly 15% of the cost of trapping and removal.

Despite the risks to wildlife canvassed in the draft plan, and similar reports from NSW, there is no peer-reviewed research that defines the threats to native animals. A revised plan must include research to understand both the impacts of feral horses on native animal populations and their welfare.

The debate over culling horses typically ignores the unseen suffering that horses cause to native animals. Quantifying that suffering will be crucial for making informed decisions around feral horse management.


Read more: The ethical and cultural case for culling Australia’s mountain horses


It is great that we have a plan for managing horses in the Victorian Alpine National Park – albeit one that seems unlikely to work in the eastern Alps. But the Victorian government needs to show courage and leadership on the issue of culling feral horses. Our alpine natural heritage will continue to decline until horses are taken out of our national parks, and that will only happen when managers can include culling among their suite of management tools.

The ConversationIn NSW, the feral horses in Kosciuszko National Park are growing in number, and doing real damage to Australia’s highest mountains. Hopefully both states can take back the reins of feral horse management from single-issue lobby groups and exercise some real control over their feral horses.

Don Driscoll, Professor in Terrestrial Ecology, Deakin University

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

How invasive weeds can make wildfires hotter and more frequent



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Mixed grill: burning combinations of invasive and native plants helps us understand how invasive plants make fires hotter and more likely.
Sarah Wyse, CC BY-ND

Tim Curran, Lincoln University, New Zealand; George Perry, and Sarah Wyse

Over the past year the global media has been full of reports of catastrophic fires in California, the Mediterranean, Chile and elsewhere. One suggested reason for increases in catastrophic wildfires has been human-induced climate change. Higher temperatures, drier weather and windier conditions all increase the impact of fires.

While climate change indeed raises the risk of wildfires, our research shows that another way humans can change patterns of fire activity is by introducing flammable plants to new environments.


Read more: How will Canada manage its wildfires in the future?


Plantations of highly flammable exotic species, such as pines and eucalypts, probably helped to fuel the recent catastrophic fires in Portugal and in Chile. In arid regions, such as parts of the US southwest, the introduction of exotic grasses has transformed shrublands, as fires increase in severity.

Invasive plants and fire

How do invasive plants change fire patterns? We burned species mixtures (aka “mixed grills”) on our plant barbecue to help find out.

Invasive plants are responsible for changing the patterns of fire activity in many ecosystems around the world. In particular, invasive species can lead to hotter and more frequent fires.

Invasive plants can also reduce fire frequency and fire intensity, but there are fewer examples of this occurring worldwide.

One of the main ways flammable invasive plants can have long-lasting impacts on an ecosystem comes from positive fire-vegetation feedbacks. Such feedbacks can occur when a flammable weed invades a less fire-prone ecosystem. By changing the available fuel the invader makes fires more likely and often hotter.

If the invading species has characteristics that allow it to outcompete native species after a fire, then it will further dominate the ecosystem. Such traits include thick bark, the ability to resprout following fire, or seeds that survive burning. This invasion will likely lead to more fires, changing the species composition and function of the ecosystem in a “fire begets fire” cycle. Extreme examples of this dynamic are where flammable grasses or shrubs invade forests, leading to loss of the forest ecosystems.

Mixed grills

We wanted to understand how invasive plants interact with other species when burned in combination. To explore the mechanisms underpinning such feedbacks, we examined how invasive plants might change the nature of a fire when burned together with native species.

We collected 70cm shoots of four globally invasive species (of both high and low flammability) and burned them in pairwise combinations with New Zealand native trees and shrubs to determine which characteristics of a fire could be attributed to the invasive plants.

Samples of Hakea sericea (foreground) and Kunzea robusta (rear) arranged on the grill of our plant barbecue.
Sarah Wyse, CC BY-ND

We found that overall flammability was largely driven by the most flammable species in the mixture, showing how highly flammable weeds could set in motion fire-vegetation feedbacks.

We established that a greater difference in flammability between the two species led to a larger influence of the more flammable species on overall flammability. This outcome suggests weeds that are much more flammable than the invaded community can have larger impacts on fire patterns.

Importantly, we also showed the influence of the highly flammable species was independent of its biomass, meaning highly flammable weeds may impact community flammability even at low abundances.

When we looked closer at the different components of flammability (combustibility, ignitability, consumability and sustainability) we found some important nuances in our results.

While the maximum temperature reached in our burns (combustibility) and the ignition speed (ignitability) were both most influenced by the more flammable species, consumability (the amount of biomass burned) and sustainability (how long the fire burns) were equally influenced by both the more flammable and less flammable species.

In short, more flammable weeds will cause a fire to ignite more quickly and burn hotter.

However, less flammable species can reduce the duration of a fire compared to when a more flammable species is burnt alone. These results could have important ecological implications, as the longer a fire burns the more likely it is to kill plants: low-flammability plants could reduce this impact.

Measuring how long a fire burns on our plant barbecue.
Tom Etherington, CC BY-ND

Managing weeds to reduce fire impacts

Even low abundances of highly flammable invasive weeds could set in motion positive fire-vegetation feedbacks that lead to drastic changes to ecosystems. If this result holds when our shoot-scale experiments are repeated using field trials, then land managers should work quickly to remove even small infestations of highly flammable species, such as gorse (Ulex europaeus) and prickly hakea (Hakea sericea).

Conversely, the role of low flammability plants in extinguishing fires further supports the suggestion that the strategic planting of such species across the landscape as “green firebreaks” could be a useful fire management tool.

The ConversationIn any case, our “mixed grill” study further highlights the role of exotic plants in fuelling hotter wildfires.

Tim Curran, Senior Lecturer in Ecology, Lincoln University, New Zealand; George Perry, Professor, School of Environment, and Sarah Wyse, Early Career Research Fellow, The Royal Botanic Gardens, Kew and Research Fellow, School of Environment

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

Friday essay: the cultural meanings of wild horses



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