Tandem virus cocktail kills pest rabbits more effectively



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Tagged European rabbit kitten infected with myxoma virus, but that died from rabbit haemorrhagic virus disease (RHDV).
Photo by David Peacock, Biosecurity South Australia, CC BY-NC-SA

Corey Bradshaw, Flinders University; Louise Barnett, Flinders University, and Thomas Prowse, University of Adelaide

Farmers, landowners and conservationists across Australia are benefiting from an unexpected, combined effect of two biological controls that target feral populations of European rabbits (Oryctolagus cuniculus), according to our research, published in the Journal of Applied Ecology.




Read more:
Explainer: how ‘biocontrol’ fights invasive species


Pest rabbits cost the Australian economy over A$200 million each year in lost production, and millions more in pest control. They compete with livestock for food and cause enormous environmental damage.

Rabbits previously reached plague numbers in much of agricultural and outback Australia, until the introduction of two rabbit-specific viruses and insect vectors.

Myxoma virus was first introduced in 1950, followed by European rabbit fleas in the 1960s to help spread the virus, and then Spanish rabbit fleas in the 1990s to increase spread into arid areas.

Then, in 1995, rabbit haemorrhagic disease virus (RHDV) escaped from quarantine, before an official release in 1996. These biocontrols have reduced rabbit numbers by an estimated 75-80% (see references in our paper) in South Australia alone since the 1950s.

Rabbits around a waterhole at the myxomatosis trial enclosure on Wardang Island in 1938.
National Archives of Australia/Wikimedia Commons

Together, myxoma virus and RHDV saved the Australian economy an estimated A$70 billion by 2011.

But managing rabbits’ growing immunity to these virus biocontrol agents is now presenting new challenges for Australian land managers.




Read more:
Controlling rabbits: let’s not get addicted to viral solutions


This is why our new discovery of a positive interaction between the two main viruses is great news for the Australian environment and economy.

Our study represents the first solid evidence that a combination of these two rabbit diseases is more effective in reducing rabbits’ abundance, providing agencies and landowners with more bang for their buck during rabbit control programs.

Our findings were made possible by one of the longest-running monitoring programs in disease ecology: the 21-year (and ongoing) Turretfield Rabbit Research Project north of Adelaide.

Roughly every two months for more than two decades, PIRSA Biosecurity South Australia has counted, tagged, virus-tested, and released rabbits of all ages from the isolated sentinel rabbit population.

Analysing this unrivalled dataset, we discovered that the probability of dying from rabbit haemorrhagic disease was 10% higher than expected when an individual rabbit had previously been exposed to myxoma virus. These means that rabbits that are now immune to the myxoma virus (Australia’s first rabbit biocontrol) are nevertheless more susceptible to RHDV (Australia’s second rabbit biocontrol).

In other words, the two diseases (a poxvirus and a calicivirus) interacted to give a population-level effect that resulted in more rabbit deaths overall.

Such an interaction between biocontrol agents is rare; in fact, it is the first discovery of its kind in the world.

Tagged rabbit from Turretfield (photo taken September 8, 2014). This individual had no antibodies against RHDV or myxoma virus, but was found dead from haemorrhagic disease two hours later.
David Peacock/Biosecurity SA

The knowledge that the two viruses combine as a potent weapon against rabbits has major implications for land owners and farmers around the world who battle pest rabbits. Disease outbreaks could potentially be timed to ensure that the death rate of pest rabbits is as high as possible.

In Australia, rabbits are a dietary mainstay for two other damaging invasive species: feral cats and red foxes. A large rabbit population can keep the two predator species at high densities, thus promoting their high predation rates on native wildlife.




Read more:
Invasive predators are eating the world’s animals to extinction – and the worst is close to home


Keeping rabbit numbers low can therefore benefit our environment. In fact, the rate of native vegetation cover has increased since RHDV began to spread in 1995, and there have been documented increases in the numbers of small native mammal species since that time.

Ecologically informed biocontrol is therefore just another smart way to manage invasive species.

Our discovery also has implications right across the world. European rabbits cause environmental and agricultural damage in places as diverse as the United Kingdom, New Zealand, and in parts of South America.

The ConversationOur findings will also help researchers and conservationists to safeguard the rabbit in its natural range in Europe, and support Australia’s search for other biocontrols in the future.

Corey Bradshaw, Matthew Flinders Fellow in Global Ecology, Flinders University; Louise Barnett, Adjunct researcher, Flinders University, and Thomas Prowse, Postdoctoral research fellow, School of Mathematical Sciences, University of Adelaide

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

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Hold your horses – brumby fertility control isn’t that easy



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A government plan to ‘dart’ wild horses with fertility control drugs ignores science and expert advice.
Author provided

Andrea Harvey, University of Technology Sydney; Carolynne Joone, James Cook University, and Jordan Hampton, Murdoch University

A proposed Kosciuszko Wild Horse Heritage Bill that rules out shooting horses is based on a flawed understanding of fertility control. Unfortunately, by ignoring scientific evidence and expert advice horses will be condemned to slow starvation.




Read more:
NSW’s no-cull brumby bill will consign feral horses to an even crueller fate


The bill, which also proposes relocating horses within the park, or removal and domestication, intends to use fertility control for longer-term population control. But this simply isn’t feasible, and is unlikely to become so in the near future.

Vaccine darts are not a panacea

Immunocontraceptive vaccines that have been used for fertility control in wild horses in North America include the gonadotrophin releasing hormone (GnRH) vaccine, GonaCon, and porcine zona pellucida (PZP) vaccines. Administration requires injection: there is no effective oral vaccine. Injection requires either trapping horses and injecting them by hand, or darting them.

Darting brumbies requires getting very close, which is impossible in many parts of the Kosciuszko National Park.
Author provided

Immunocontraception has only been successfully used in smaller and more isolated populations (such as islands). Population modelling has estimated that over 50% of mares would need to be treated in KNP just to slow the rate of population increase within 2–5 years.

Although the precise number of horses in KNP is hotly debated, even at the lowest estimates almost 1,000 mares would need to be treated to have the desired impact on population growth – and it would still take 10–20 years before the population size was reduced substantially through natural mortality. And that is on the proviso that we could actually administer the vaccine to this number of mares.

Trapping enough horses across KNP (an area of about 700,000 hectares) would likely be impossible. Dart administration sounds intuitively appealing but is a complex process and will not be possible for large numbers of horses in difficult, mountainous terrain.

Staff must be extensively trained for licences before they can administer darts. More importantly, darting can only be safely performed within around 40 metres of a stationary horse, and with a clear line of vision. This must be done accurately and without causing ballistic injuries.

Injected animals must be marked (with dye, for example) so that they can be identified for booster shots as needed.

As demonstrated in a recent trial of fertility control darting for eastern grey kangaroos in the ACT, it is extremely challenging to manage all of these goals in the field. Helicopters can be used to dart animals, but this adds animal welfare impacts due to pursuit and lower levels of accuracy.

In other parts of the world where dart administration of immunocontraceptives has been successful, they have been applied to horses that are used to people, allowing staff to approach horses on foot. This is a very different situation to KNP.

Although it is possible to closely approach some horses in KNP, ongoing research has revealed that it is only possible to get within 200–500m of most horses in the larger populations.

Furthermore, it would be close to impossible to both identify and locate the same horses on multiple occasions, as required for booster vaccination injections. In more densely forested areas, it can be challenging to even see horses, let alone dart them.

There is no vehicle access to many parts of KNP where horses live, and long treks across challenging terrain would make attempts to locate all horses very labour-intensive. Furthermore, many areas of KNP are completely inaccessible in winter due to snow, making darting before the spring breeding season even more problematic.

What would we be vaccinating the horses with?

There’s also the question of what exactly the horses would be vaccinated with. GonaCon and PZP are not produced in commercial quantities, are not currently available in Australia and are not straightforward to import. Australian quarantine regulations may prevent the import of reagents derived from animals, such as conventional PZP which is derived from pig ovaries.

Producing PZP in Australia brings additional challenges, without guaranteeing the same efficacy. While work on a synthetic PZP formulation is ongoing, initial results in mares were disappointing.

There are two alternative GnRH vaccines available in Australia. One has shown less effectiveness than required in a pilot trial and while the other is registered for use in domestic mares, it lasts a relatively short time and is prohibitively expensive.

Most contraceptive vaccines require an initial injection followed by a second injection about one month later to achieve maximum efficacy, and then annual booster injections. GonaCon is promoted as having 3-year efficacy after a single injection, but that significantly reduces after the first 12 months. Long-acting PZP formulations have been investigated in North America; while results appeared promising initially, more recent work showed a contraceptive efficacy of under 60% beyond one year after treatment. Furthermore, the viscous nature of these longer-acting formulations make administration by dart more challenging.

Alternative fertility control options such as surgical sterilisation or intra-uterine devices have even more practical hurdles. For all of these reasons, a recent peer-reviewed study by two Australian reproductive experts concluded that current fertility control methods are not feasible for halting the population growth of wild horses in Australia.

Although some newer technologies are undergoing investigation, realistically it will be a long time before contraception for wild horses becomes an effective reality in Australia.

‘No-kill’ bill means slow starvation

Without a feasible method for sterilising horses, the newly proposed bill will mean population control is mainly through food limitation.

While “no kill” is seemingly more compassionate, it may ultimately and unintentionally be crueller.

As horse populations reach the carrying capacity of their habitats, they become malnourished and their fertility declines. Horses in very poor condition will not produce foals. When malnutrition persists, many horses will die young and many will die slowly.

This was dramatically demonstrated four years ago, when researchers discovered emaciated brumbies in the Snowy Mountains cannibalising their fellows and more emerging research is further confirming that extreme malnutrition is ongoing in parts of KNP.




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


The ConversationIn time, the number of horses suffering chronic malnutrition and dying of starvation is likely to increase. Is this truly humane population control?

Andrea Harvey, Veterinary Specialist, PhD scholar (wild horse ecology & welfare), University of Technology Sydney; Carolynne Joone, , James Cook University, and Jordan Hampton, Adjunct Lecturer, Murdoch 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.

Queensland moves to control land clearing: other states need to follow


Megan C Evans, Australian National University

Queensland’s land clearing has yet again become a national issue. After laws were relaxed under the then Liberal-National state government in 2013, land-clearing rates tripled, undermining efforts to conserve wildlife and reduce carbon emissions.

Now the Labor state government wants to re-tighten the laws. The revised legislation is expected to be debated after June 30.

Land clearing is a highly contentious and polarising issue in Queensland. Scientists and environmental groups have voiced concerns about the dramatic increase in land clearing. But some rural landholders are reportedly worried about the prospect of re-tightened regulations and their possible impact on property values and business certainty.

So, what does the big picture suggest?

Then and now

Since the 1980s, all Australian states and territories have introduced laws to protect native vegetation, in response to rising public concern about land degradation, salinity, biodiversity loss and greenhouse gas emissions.

The most significant policy reforms have been in Queensland – where the vast majority of land clearing in Australia has occurred over the past four decades – as I show in a new paper published in Pacific Conservation Biology.

Total forest loss due to human activity from 1972 – 2014. Data is sourced from the National Carbon Accounting System (NCAS), Australian Department of the Environment (2015). Image: Evans (2016) http://dx.doi.org/10.1071/PC15052

Changes to land-clearing laws in 2007 were heralded as the end of broad-scale clearing in Queensland. Clearing of remnant (old-growth) forest was restricted on freehold land, all remaining clearing permits (issued under a ballot) expired and A$150 million of compensation was provided to landholders. Further amendments in 2009 placed protections on “high value” (more than 20 years old) regrowth forest.

Fast forward to 2012, and Premier Campbell Newman was elected on a promise to keep Queensland’s land clearing laws in place. Soon afterwards though, Natural Resources Minister Andrew Cripps announced the Government would “take an axe” to tree-clearing laws.*

The 2013 amendments:

  • removed protections on “high value” regrowth forest

  • allowed landholders to self-assess clearing for activities such as fodder harvesting and vegetation thinning

  • allowed clearing of remnant forest for “high-value agriculture”

  • changed the onus of proof so that the Queensland government had to prove that land-clearing laws had been violated.

Queensland’s current Labor government intends to reverse most of the 2013 amendments to vegetation-clearing laws, as well as extending protections on regrowth forest to three additional catchments, to reduce runoff onto the Great Barrier Reef.

The laws will also be retrospective, in an effort to prevent panic clearing before the changes come in.

How does Queensland compare?

Queensland is not alone in its recent changes to vegetation protection laws.

New South Wales introduced self-assessment for “low risk” clearing in 2013. It also promised to repeal the Native Vegetation Act and replace it with a new Biodiversity Conservation Act. An independent review recommended that these changes occur, but environmental groups remain opposed.

Victoria’s vegetation laws were also changed in 2013. The then Coalition government’s changes included the removal of the “net gain” target in vegetation extent and quality that had been in place since 2003. The Victorian Labor government is now undertaking another review of the state’s regulations.

Laws have also been relaxed in Western Australia, where landholders may now clear up to 5 hectares per year on individual properties without a permit (an increase from 1 ha per year).

From state to self-regulation

Within ten years of what looked like the end of broad-scale land clearing in Australia, most state vegetation laws across the country have been relaxed.

Government regulation of native vegetation is generally unpopular with landholders and so maintaining these policies has proven to be politically unpalatable. At this stage, only Queensland is looking to re-strengthen land-clearing laws – and, even so, self-assessment for some clearing activities will remain.

What does this all mean for native vegetation in Australia? This is actually a difficult question to answer.

Many factors influence land clearing: rainfall, the price of key agricultural commodities and the amount of land available to clear. This complexity means it’s difficult to know what impact (if any) changes in policy have on the rate of land clearing.

Trends in national-scale deforestation and key macroeconomic variables. Plots are total deforestation versus: a) Year, b) Extent of primary forest remaining, c) Log-transformed total rainfall, d) Gross domestic product per capita (current USD) , e) Agriculture, value added (% total GDP) f) Farmer’s terms of trade. Image: Evans (2016) http://dx.doi.org/10.1071/PC15052

It’s quite clear that the relaxation of Queensland’s clearing laws was followed by a sharp increase in vegetation clearing, but it’s not yet apparent whether this has happened in other states.

A big issue is a lack of reliable data. There’s no consistent reporting of vegetation clearing across Australia. Some states, such as New South Wales, only publish information on the amount of clearing permitted by regulation.

As reported last week, total vegetation clearing in New South Wale is much higher than official data shows as most clearing is exempt from regulation, or illegal.

Better policy needed

If we’re serious about protecting Australia’s native vegetation for the sake of soil health, biodiversity and the climate, we need to use all the tools we have available to achieve this goal.

Using a mixture of government regulation, self-regulation and genuine economic incentives, such as carbon farming, is the best approach.

But no matter which policies we use, they all need to be monitored and evaluated to be effective. Otherwise, we have no idea whether all the time and money devoted to designing and implementing new policies has been worthwhile.

The inconsistency between the federal government’s Direct Action policy and the relaxation of state restrictions on vegetation clearing is a big problem. Landholders need a clear and consistent message from all levels of government if they are to adapt and make long-term business decisions.

Interestingly, around 75% of the recent clearing in Queensland has occurred in the Brigalow Belt and Mulga – areas where we’ve found that carbon farming could be more profitable than cattle grazing.

If only the price, and the policies, were right.

*This sentence was amended on May 10 2016 to clarify that land clearing laws were originally to be maintained.

The Conversation

Megan C Evans, PhD Candidate in Environmental Policy, Australian National University

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

Huge fires are burning northern Australia every year: it’s time to get them under control


Owen Price, University of Wollongong

On October 1, 2015 a fire lit to manage weeds at the Ranger Uranium Mine burned through 14,000 hectares of Kakadu National Park, threatening important rock-art sites and closing several tourist attractions.

The Northern Territory Government and Energy Resources of Australia (the mine operators) are conducting enquiries to work out what went wrong and how to prevent similar accidents in the future, because like all natural disasters each one is an opportunity to learn.

As it happens, this fire coincided with the publication this month of my research that helps us to understand the problem posed by unplanned fires in the savannas of northern Australia.

That research highlights a 60-day window between August 9 and October 7 each year when huge fires can occur and these contribute an inordinate amount to the total area burnt across the north.

Going up in smoke

Before August mild weather and moisture in the vegetation constrain fires. After October rain and high humidity do the same. Natural fires, caused by lightning, occur from November onwards, and although these account for more than 60% of unplanned fires started, they cause less than 10% of the total area burnt.

Rather, it is fires in the high risk window that are the real problem for fire management over a vast slab of Australia and they are neither natural nor planned.

My study used MODIS satellite mapping to examine the ignition date, duration and eventual size of 126,000 fires in Arnhem Land over a 10 year period. The largest fire ignited in late August 2004 and burned 445,000 hectares, 30 times the area burnt by the Ranger Mine or equivalent to a quarter of the size of Kakadu, our country’s largest national park.

But other regions have it worse: an accidental fire in the northern Tanami ignited on August 4 2011 burnt an area at least 5 million ha. There are 22 European countries smaller than that. So the Ranger Mine fire is in no way unique: it just happened to occur in a highly visible area.

Let’s take a step back and consider what is at stake with fires such as these. Research over many decades have shown that many species of fire-sensitive plants and animals are in decline across the north this is at least partially related to the loss of traditional burning practices which has led to an increase in fire frequency and a predominance of high-intensity late dry season fires (such as the Ranger Mine fire).

It is not certain whether high fire frequency or high fire intensity is the main problem, but it is probably a bit of both.

Stop fires starting

Managers of country such as Kakadu National Park and Arnhem Land recognise this problem and have taken steps to wrest back control of the fire regime. Their main tool is the use of planned burning in the early dry season fires (April – July), akin to traditional burning practices.

By treating the land with a patchwork of these low intensity, low impact fires, subsequent fires can be prevented or constrained to protect sensitive areas. In some areas, including Kakadu and Western Arnhem Land, between 10% and 30% of the country is burnt each year by planned burns. This year 31% of Kakadu National Park had been treated in this way and this patchwork of burnt areas was the context in which the Ranger Mine fire started.

This approach has been successful at reducing the area burnt by unplanned late dry season fires, but it is only a partial fix. The Ranger Mine fire illustrates the main problem: that fires will burn around previously burnt patches.

This fire spread through a small gap between previous patches (at point A on the map below), enlarging its size five-fold. It is fair to say that the southern and western progress of the fire was contained by the planned burning. This protected Nourlangie Rock and Jabiru township and the fire could have been much larger without it.

The large fire that threatened Aboriginal heritage burned around previous burnoffs.
Owen Price, Author provided

The consequence of this “leaky” patchwork of protection is that early dry season burning on its own does not do much to reduce the overall area burnt. Rather it replaces high intensity late dry season fires with low intensity fires (which itself is a good thing).

This replacement phenomenon has been demonstrated
using fine scale fire mapping in Western Arnhem Land. My new study points out that if reducing fire frequency across the north is a goal (and it ought to be), then we need to place more focus on stopping fires starting in the main danger period (mid August to mid October).

Achieving substantial reduction in these ignitions is a huge challenge, and I don’t have any easy answers, but it would help if burn-offs such as the one that started the Ranger Mine fire were not allowed at this risky time of year.

The Conversation

Owen Price, Senior Research Fellow, Centre for Environmental Risk Management of Bushfires, University of Wollongong

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

Guam Mice Drop


The link below is to an article that looks at efforts to control the Brown Tree Snake on Guam.

For more visit:
http://usnews.nbcnews.com/_news/2013/12/02/21724382-two-thousand-mice-dropped-on-guam-by-parachute-to-kill-snakes

Guam: Destroying the Snakes


The link below is to an article reporting on efforts to control introduced Brown Tree Snakes on Guam.

For more visit:
http://bigstory.ap.org/article/us-govt-air-drop-toxic-mice-guam-snakes