Tag Archives: ecology

David Attenborough says the Great Barrier Reef is in ‘grave danger’ – it’s time to step up

The Conversation

Ove Hoegh-Guldberg, The University of Queensland and Tyrone Ridgway, The University of Queensland

Over three weeks, Australians have been taken on an incredible journey through the biology, beauty and wonder of the Great Barrier Reef, guided by Sir David Attenborough.

As individuals who have had the privilege of working on the Reef for much of our lives, the wonderful storytelling, exquisite photography and stunning production of the Great Barrier Reef with David Attenborough has been inspiring. It’s a great reminder of how lucky we are to have this wonder of nature right on our doorstep.

Particularly special has been the wonderful black-and-white footage of Sir David’s first visit to the Reef in 1957, a trip down memory lane. His attachment and fascination with the Reef are hard to dismiss.

However, as the curtain closes on this wonderful series, Sir David concludes that the Reef that he visited nearly 60 years ago is very different from today.

Research backs up this personal experience. The Australian Institute of Marine Science has shown that the Great Barrier Reef has lost around 50% of its coral cover between 1985 and 2012.

A reef in peril

The Great Barrier Reef is in grave danger. The twin perils brought by climate change – an increase in the temperature of the ocean and in its acidity – threaten its very existence. – Sir David Attenborough

As this television series has aired in Australia, an underwater heatwave has caused coral bleaching on 93% of the reefs that make up the Great Barrier Reef. Up to 50% of corals in the worst-affected regions may die as a result of this bleaching.

We should not be too surprised. Reef scientists have been warning about this for decades. In 1998, the warmest year on record at the time, the world lost around 16% of its coral reefs in the first global-scale mass coral bleaching event.

Before the current bleaching, the reef bleached severely in 1998 and 2002, with a substantial bleaching event in 2006 around the Keppel Islands. Outside these events, there has been moderate mass bleaching on the reef since the early 1980s (particularly 1983 and 1987), although never to the extent and intensity that we are witnessing today.

Rising sea temperatures

The current bleaching event has drawn widespread media coverage. One of the arguments we have seen raised is that coral bleaching is natural – and that the reef will bounce back as it always has, or even adapt to warming seas.

It is true that certain coral species, and even certain individual colonies within the same species, do perform better than others when stressed by warmer-than-normal sea temperatures. However, the extent of these differences is only 1-2℃. Given that even moderate climate change projections involve temperatures 2-3℃ higher than today, these differences offer little comfort for reefs like the Great Barrier Reef in a warmer world.

The observation that corals grow in warm areas of the globe is a demonstration that corals can and do adapt to local temperatures. However, the time frames involved are hundreds of years, not a single decade. Current rates of warming are much faster than anything for tens of millions of years, which makes the prospect of evolution keeping pace with a changing ocean even more improbable.

Mass bleaching is a new phenomenon that was first reported in the early 1980s. Before this, there are no reports of corals bleaching en masse across any coral reef or ocean region.

Experts are in agreement that mass coral bleaching and death on the Great Barrier Reef is driven by climate change resulting from human activities (mainly burning fossil fuels). This is the conclusion at the heart of the latest consensus of the United Nations scientific report.

Rising sea temperatures coupled with strong El Niños are unfortunately pushing corals to their thermal tolerance limits and beyond. It only takes a temperature increase of 1-2℃ to disrupt the special relationship between corals and tiny marine algae that live inside their tissue, resulting in bleached corals.

In fact, as CO₂ concentrations rise, sea temperatures will continue to climb – increasing the likelihood that mass coral bleaching events will become more frequent and more destructive. Recent research has shown that near-future increases in local temperature of as little as 0.5℃ may lead to significant degradation of the Great Barrier Reef.

Rising temperatures are not the only climate threat. Cyclones are predicted to become stronger (if less frequent) in a warmer world. Since 2005 there have been eight cyclones on the reef of category 3 or above – more than previous decades. We would argue this is evidence that these predictions are already coming true and form part of our current reality.

Heat stress is not just affecting corals on the Great Barrier Reef either. We are seeing reports of bleaching across all of Australia’s coral real estate (Coral Sea, Torres Strait, Kimberley, North West Shelf), the South Pacific and the central and western Indian Ocean.

It is likely only a matter of time before we start to see reports of bleaching from other coral reefs around the world. We are indeed dealing with changing times and a global issue.

It’s not too late to act

It’s not too late to act – but we will need very deep and significant action to occur within three to five years or face a collapse of ecosystems like the Great Barrier Reef.

Climate change is just one of the threats facing the Great Barrier Reef. Fortunately, it is not too late to give the reef a fighting chance.

Ove Hoegh-Guldberg on the future of the reef

However, it does require strong, immediate and decisive action from our political leaders.

In the lead-up to the federal election, we believe that four major steps are required by our leaders to ensure a future for the Reef:

  1. Mitigate: we need to – as per the Paris Agreement – keep average global surface temperature increases to below 2.0°C, and hopefully 1.5°C in the long term. This means we must adopt a pathway that will bring our greenhouse gas emissions to zero over the next few decades. Our leaders must live up to the global agreement that they committed to in Paris at COP21.
  2. Invest: we need to ultimately close our coal mines and stop searching for more fossil fuels. The experts tell us that we must leave 80% of known fossil fuels in the ground. Let’s invest in coral, renewables and the planet, and not in coal, emissions and ecosystem collapse.
  3. Strengthen: we need an urgent and concerted effort to reduce other non-climate change threats to build the resilience of the reef so it can better withstand the impacts of climate change over the coming years.
  4. Integrate: Australian and Queensland governments have begun a process to address declining reef health through the Reef 2050 Long-term Sustainability Plan. This plan has a strong focus on coastal water quality. The 2050 Reef Plan and its resourcing will need to consider climate change – especially given that it is likely to make achieving the objectives of the plan even more challenging and impossible (if no action). Otherwise we run the risk of ending up with a great plan for improving water quality by 2050 but no Great Barrier Reef.

We hope that Sir David Attenborough will help inspire Australians to demand action from their political leaders to ensure that this natural wonder of the world continues to inspire, employ, educate and generate income for generations to come.

It seems fitting to end with Sir David’s closing words with a call to our political leaders and fellow Australians:

Do we really care so little about the earth upon which we live that we don’t wish to protect one of its greatest wonders from the consequences of our behaviours?

After all, it is our Great Barrier Reef – let’s keep it great.

Or at least let’s fight to keep it.

The ConversationOve Hoegh-Guldberg, Director, Global Change Institute, The University of Queensland and Tyrone Ridgway, Healthy Oceans Program Manager, Global Change Institute, The University of Queensland

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

 

Leave a comment

Filed under Reblogs

How curiosity can save species from extinction

The Conversation

Merlin Crossley, UNSW Australia

If I had been given one wish as a child I, it would have been that the Tasmanian tiger wasn’t extinct. To me extinction was a tragedy. I expect that many people feel the same way.

But it is not easy to save dwindling populations and prevent extinctions. Sure it takes money, but it also takes knowledge. One simple story about butterflies illustrates the complexity of ecosystems and shows how important research and understanding are to preserving biodiversity.

It is the story of the European butterfly, the large blue or Phengaris arion (Maculinea arion in older literature).

In Australia we have lots of butterflies and literally countless moths; the total number is not known. In the United Kingdom, on the other hand, virtually all species have been described.

I visited England several times as a child, and at one stage I sought to see as many of the 60 different species of butterfly as possible. But I was particularly keen to see the large blue because it was rare. It was the first butterfly recorded in the British Isles in 1795 and was much prized by collectors for the very simple reason that it was so scarce.

But over the years the known populations gradually died out and it was given protected status. Britons made efforts to fence off reserves where it remained but, oddly, its numbers continued to decline. By 1979 it was declared extinct in Britain.

But why had all the steps to save this iconic species failed?

One researcher from Oxford University, Jeremy Thomas, led a team of large blue experts to investigate the ecosystem in which it existed. The first step was to try to understand the butterfly. And there was a lot to understand.

A pretty butterfly that hides a remarkable life cycle.
PJC&Co, CC BY-SA

Interdependence

It is a remarkable species. The female lays eggs on wild thyme flower buds. Each caterpillar bores into the bud and eats the growing seeds. It needs all the energy in the seeds to survive, and if more than one caterpillar is sharing the bud they will fight things out in a cannibalistic bout until only one remains. This is a taste of things to come.

After about a week eating the seeds and flower it drops to the ground and waits until it is found by a special species of ant. It excretes a substance that feeds the ant, but also influences the ant’s behaviour. The ant goes and fetches fellow ants that carry the caterpillar down into the nest.

Once inside the nest the caterpillar does a remarkable thing: it feeds on ant larvae until it finally pupates. When it is ready to emerge as a vulnerable new butterfly it begins making sounds that appear to appease the ants. It then emerges, protected by a guard of ants, and climbs up out of the nest to stretch out its wings.

The critical point is that the large blue doesn’t just depend on any old species of ant, but on very particular species. It has evolved to exude chemicals that influence red ants of the species Myrmica sabuleti or M. scabrinodis.

These ants also have very specific requirements, this time in terms of temperature and moisture. If the ground is too hot or too cold they don’t thrive and other species take over.

Ground temperature and moisture depend on the height of the grass. The grass needs to be short, so grazing is important. It turns out that fencing off reserves actually interfered with the life cycle of the butterfly because the grass grew too long, and the ground wasn’t right for the ants.

Similarly, the spread of myxomatosis and reductions in the rabbit populations also meant the grass grew too tall, again altering ground temperature and helping drive the decline in large blue populations.

Due to the careful work by Jeremy Thomas and colleagues, all this is now known. Fortunately, unlike the Tasmanian tiger, the large blue was extinct only in the British Isles, and not in mainland Europe, thus it has been possible to re-introduce it into Britain.

It has also been possible to manage the habitat to allow grazing so that the ant colonies thrive and the butterfly also seems to be doing well.

Parts of the odd life cycle of this butterfly were known as far back as 1915, but there was no understanding of the connection to the ecosystem and landscape, so the vital step of controlling the grazing was not considered.

The large blue has been successfully returned to Collard Hill
in the Polden Hills in Somerset.

Curiosity

The story shows how things can be complex and inter-connected, and that only by understanding all the facets can one intercede to put things right. It also illustrates how the careful application of science can make a difference.

One can never tell when and how, or even if, new knowledge will ever be useful. Scientists collect knowledge partly because they want to improve the world, but often just out of curiosity.

Sometimes curiosity driven research is criticised as self-indulgent, and unlikely to make a real difference to our circumstances. Sometimes it is said that researchers should just go straight for the biggest problems and tackle them straight on, or that research should be aimed purely at applications. This is increasingly heard these days given the new emphasis on innovation and the commercialisation of research.

But in reality we need science most when we have tried tackling the problem and got stuck. Everything people had tried to preserve the large blue had failed. Only knowledge provided a way forward.

Curiosity driven science often provides solutions when we are stuck and without it we will sometimes remain stuck forever. In the case of the Tasmanian tiger I believe we are stuck forever, but there are many other things to preserve and careful in depth science can make a difference.

The ConversationMerlin Crossley, Dean of Science and Professor of Molecular Biology, UNSW Australia

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

Leave a comment

Filed under Reblogs

Viruses don’t deserve their bad rap: they’re the unsung heroes you never see

The Conversation

Peter Pollard, Griffith University

The word “virus” strikes terror into the hearts of most people. It conjures up images of influenza, HIV, Yellow Fever, or Ebola. Of course we worry about these viruses—they bring us disease and sometimes an excruciatingly painful death.

But the 21 viral types that wreak havoc with the human body represent an insignificant fraction of the 100 million viral types on earth. Most viruses are actually vital to our very existence. No-one seems to stick up for the good guys that keep ecosystems diverse and balanced (although I did recently in a TEDx talk in Noosa).

The sheer number of these good viruses is astonishing. Their concentration in a productive lake or river is often 100 million per millilitre – that’s more than four times the population of Australia squeezed into a ¼ of a teaspoon of water.

Globally the oceans contain 1030 viruses. If you lined them all up they would extend for 10 million light years, or 100 times the distance across our galaxy. Collectively they would weigh as much as 75 million blue whales.

In short, there are a lot.

What are viruses?

Viruses are not living organisms. They are simply bits of genetic material (DNA or RNA) covered in protein, that behave like parasites. They attach to their target cell (the host), inject their genetic material, and replicate themselves using the host cells’ metabolic pathways, as you can see in the figure below. Then the new viruses break out of the cell — the cell explodes (lyses), releasing hundreds of viruses.

The viral cycle. Peter Pollard

Viruses are very picky about who they will infect. Each viral type has evolved to infect only one host species. Viruses that infect bacteria dominate our world. A virus that infects one species of bacteria won’t infect another bacterial species, and definitely can’t infect you. We have our own suite of a couple of dozen viral types that cause us disease and death.

A deadly dance

Algae and plants are primary producers, the foundation of the world’s ecosystems. Using sunlight they turn raw elements like carbon dioxide, nitrogen and phosphorus into organic matter. In turn, they are eaten by herbivores, which are in turn eaten by other animals, and so on. Energy and nutrients are passed on up the food chain until animals die. But what ensures that the primary producers get the raw elements they need to get started?

The answer hinges on the viruses’ relationship with bacteria.

A virus doesn’t go hunting for its prey. It relies on randomly encountering a host — it’s a numbers game. When the host, such as a bacterial cell, grows rapidly, that number increases. The more of a bacterial species there is, the more likely it will come into contact with its viral nemesis — “killing the winner”. This means that no single bacterial species dominates an ecosystem for very long.

In freshwater, for example, you see very high rates of bacterial growth. You would think this high bacterial production would become part of the food chain and end up as fish food. But that is rarely the case.

We now realise that the bacteria actually disappear from these ecosystems. So where do the bacteria go?

The answer lies in the interaction of the bacteria and viruses. When a virus bursts open a bacterial cell its “guts” are spewed back into the water along with all the new viruses. The cell contents then become food for the neighbouring bacteria, thereby stimulating their growth. These bacteria increase in numbers and upon coming into contact with their viral nemesis they, too, become infected and lyse.

Viruses make the world go ‘round

This process of viral infection, lysis, and nutrient release occurs over and over again. Bacteria are, in effect, cannibalising each other with the help of their associated viruses. Very quickly, the elements that support the food web are put back into circulation with the help of viruses, as you can see in the graphic below.

How nutrients are recycled. Peter Pollard

This interaction ensures inorganic nutrients are readily available to algae and plants on which ecosystems depend. It’s the combination of high bacterial growth and viral infection that keeps ecosystems functioning. This explains why we don’t see bacteria in food webs. Viruses short circuit bacterial production passing higher up the food chain so it doesn’t become fish food in freshwater ecosystems.

Most of the food (dissolved organic carbon) that drives the very high bacterial growth in freshwater comes from the terrestrial environment. Indeed, freshwater viral/bacterial interactions appear to be a critical link in carbon cycle between the land and atmosphere.

Soil viral ecology studies lag way behind water research. Viral dynamics in terrestrial ecosystems are complicated as soils can bind and inactivate viruses to limit their ability to infect other organisms. We may well be relying on freshwater processes to complete the global carbon cycle, as shown in the graphic above.

In freshwater, viruses are enhancing the rate of bacterial decomposition whereby complex organic matter is quickly and efficiently mineralised into their simple inorganic components such as carbon dioxide, nitrogen, and phosphorus.

Thus viruses are a critical part of inorganic nutrient recycling. So while they are tiny and seem insignificant, viruses actually play an essential global role in the recycling of nutrients through food webs. We are only just now beginning to appreciate the extent of their positive impact on our survival.

One thing is for sure, viruses are our smallest unsung heroes.

The ConversationPeter Pollard, Associate Professor, Griffith University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.
 

Leave a comment

Filed under Reblogs

Mike Baird is right, culling sharks doesn’t work – here’s what we can do instead

The Conversation

Jane Williamson

New South Wales is the latest Australian state to hear calls for sharks to be culled, in response to a spate of fatal and non-fatal incidents.

NSW Premier Mike Baird has implemented a new surveillance program, while resisting calls for a cull on the basis that it doesn’t work.

Put simply, there is no scientific support for the concept that culling sharks in a particular area will lead to a decrease in shark attacks and increase ocean safety.

Western Australia tried culling sharks with baited drum lines last year. The tactic did not improve the safety of swimmers, surfers or divers – one of the reasons why scientists actively opposed the cull. A similar long-standing policy in Queensland has shown little evidence of effectiveness.

Born survivors

Sharks have inhabited this planet for more than 400 million years, and have survived five mass extinctions. Earth is now entering its sixth – this time caused by humans – and sharks are at the pointy end, with 90% of the species already considered threatened.

It is not just an issue on NSW’s surf breaks. Humanity’s growing demand for protein has put substantial pressure on oceanic systems, and industrial fishing techniques have have reduced predatory fish populations to less than 10% of their historic numbers. Sharks are especially vulnerable because of their low reproductive rates, slow growth and delayed rates of maturity.

The Indo-Australasian region is recognised as a hot-spot for global shark biodiversity, and in in this region Australia trumps all, with more than 36% of all known shark species living in Australian waters.

What’s more, sharks play a pivotal role within the ecosystems they inhabit. As apex predators, they maintain community structure and biodiversity by regulating predator and prey abundance. Even light fishing pressure such as species-target line fisheries can cause dramatic declines in populations of large coastal sharks. Meanwhile, indirect fishing via shark meshing programs can catch a range of targeted and non-targeted species of sharks.

Blanket measures don’t tend to work well as a rule. AAP Image/Dave Hunt

What would a cull do to sharks and ecosystems?

Shark culling is best thought of as an indiscriminate method of removing sharks from our coastal ecosystems. The WA and Queensland culls have led to the capture and death of many non-targeted sharks. We also know that many shark species do not cope with capture well – a recent Australian study found that 100% of hammerheads caught by line fishing will die of stress within an hour of capture.

Similarly, spinner and dusky sharks have very low survival rates within the first few hours of being hooked, and sharks that are hooked and subsequently released do not necessarily survive.

Hooking in the gut is very common. New South Wales’ flagship threatened aquatic species, the greynurse shark, will most probably die over time if hooked in the gut and then released. Stainless steel hooks do not rust out but become encapsulated in the tissue over time, causing starvation, wasting of the body (known as cachexia), and eventual death.

If we remove sharks as top predators from the ecosystem, the effects will filter down to animals lower down the food chain and cause unexpected changes to ecosystems. We are already seeing such changes in areas where sharks are overfished.

Declines in the number of blacktip sharks in North Carolina in the late 1970s and 1980s caused an increase in the relative abundance of cownose rays and a corresponding decrease in scallops over the ensuing decades. Healthy aquatic ecosystems are typified by a complexity of players in the food chain, and removing such macropredators will result in decreasing ecosystem resilience.

What can we do instead of culling?

Indiscriminately culling sharks is dangerous to marine ecosystems, not to mention expensive and futile. We would be far better off allocating resources to achieving a greater understanding of the ecology and behaviour of these large predators. We can increase knowledge of why and where sharks are likely to attack humans by tagging sharks and following their movements over time, or through genetic studies that can assess effective population sizes.

Current aerial surveys are unlikely to be a successful strategy, however. Scientific analysis has already discredited aerial programs in NSW. Aerial surveys have only a 12.5% success rate in spotting a coastal shark from a fixed-wing aircraft, and a 17.1% success rate in helicopters. As surveys are only done for a few hours per week, and pass over a particular beach in minutes, these patrols can give the public a false sense of security.

Other non-invasive methods of mitigation are currently being developed, including the use of erratic walls of bubbles to deter sharks, and the development of wetsuits and surfboards that sharks are less likely to mistake as prey.

But ultimately, we also need to take personal responsibility, and reduce the likelihood of an attack by not swimming at dawn and dusk, not entering the water at the mouth of estuaries with poor visibility, or in areas of baitfish. After all, even sharks can make mistakes.

The ConversationJane Williamson is Associate Professor in Marine Ecology

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

 

Leave a comment

Filed under Reblogs

The war on feral cats will need many different weapons

The Conversation

Katherine Moseby and John Read

At the Threatened Species Summit last week in Melbourne, Environment Minister Greg Hunt and Threatened Species Commissioner Gregory Andrews declared war on feral cats.

Cats are thought to be a significant contributor to the decline of many threatened species.

Targets in the released threatened species strategy include culling two million cats by 2020, creating new safe havens for threatened species (cat-free islands and sanctuaries), restoring habitat and emergency intervention for our most critically endangered species.

Excluding cats using fencing is an increasingly important tool used to protect threatened species. New exclusion fencing projects received significant funding under the latest strategy.

One of us (Katherine) was lucky enough to be asked to give a presentation at the summit on alternative methods of controlling feral cats. The following article summarises this presentation and highlights the importance of investing in a broad range of cat control methods.

Cats are highly adaptable and highly variable, hence we must continue to search for their Achilles Heel and invest in a wide range of control methods.

Poison baiting

Widespread poison baiting for cats has come a long way in the last few decades with baits such as Eradicat, Curiosity and a new hybrid Eradicat bait being produced.

These baits were developed after years of research conducted initially by the WA Department of Parks and Wildlife and are a soft meat sausage injected with 1080 poison or containing an encapsulated PAPP (Para-aminopropiophenone) pill. These baits have had most success in island eradications and areas where alternative prey are scarce.

In order to kill a cat using poison baits, cats must first find and then ingest the bait.

Unfortunately, cats hunt mainly using sight and sound so finding an inert sausage is a challenge for a cat.

Large numbers of baits must be laid, the usual density is 50 per square km, 10 times higher than the recommended fox baiting density of 5 per square km.

Despite this, many cats fail to find a poison bait before they break down and are no longer toxic. Even when cats do find baits, up to 80% of encounters do not lead to bait ingestion, with cats often ignoring, sniffing or avoiding baits when detected. This is because cats prefer to catch their own prey and will only ingest a bait when hungry.

Non-target uptake can also be high – species such as crows, goannas and quolls can take more than half of laid baits in some instances.

Successful baiting relies on using large densities of baits in areas with low food availability at the right time of year when cats are hungriest. Practitioners are continuing to develop ways of improving bait uptake and several important baiting programs received funding under the Threatened Species Strategy.

Grooming traps

A recent invention removes the need for cats to be hungry to ingest poison. An automated grooming trap squirts a poisonous paste onto the fur of the cat as it walks past a trap station, which it then ingests through compulsive grooming.

Cats are fastidious groomers and pen trials have found 9 out of 10 cats will ingest the paste when it is squirted on their fur. The trap uses an array of sensors to restrict triggering to target species and is currently being developed for field trials around Australia. The grooming traps have a silent activation, can store up to 20 doses and can sit unattended for months at a time.

Although unlikely to be used in broadscale applications, the grooming trap may be critical for protecting small threatened species populations and reducing the impacts of cats in areas where food availability is high.

The grooming trap received much needed funding for further development at the Threatened Species Summit.

Get rid of rabbits, get rid of cats

Widespread indirect methods of reducing cat impacts are also important. Recent work has found that the Rabbit Haemorrhagic Virus Disease (RHVD) (otherwise known as Rabbit Calicivirus) released in 1995 has had a significant positive impact on many desert threatened mammal species.

The range of species such as the Plains Mouse, Dusky Hopping Mouse and Crest-tailed Mulgara has increased by as much as 70 fold in the last 20 years due largely to reduced predation.

RHDV reduced rabbit abundance by up to 95% in the arid zone of Australia which resulted in a natural steep decline in feral cats and foxes, the main predator of rabbits in that region.

The increase in vegetation cover coupled with a massive decline in predation pressure has allowed these native rodents and marsupials to recover.

This would undoubtedly be one of the most significant recoveries of threatened species in Australia. RHVD was relatively cheap, for an initial investment of only $12 million. The agricultural benefit alone totalled more than A$6 billion and the benefits to threatened species have been dramatic but remain unquantified.

Other researchers have also found that by manipulating fire and stock grazing pressure, broadscale indirect benefits can be achieved for threatened species through a reduction in susceptibility to cat predation.

These indirect benefits include making it more difficult for cats to hunt by increasing ground cover, and increasing the productivity of the landscape thereby allowing native species to increase their reproductive output and tolerate higher predation pressure.

Serial cats

All cats are not created equal and recent work in the Flinders Ranges National Park has highlighted the impact of catastrophic cats on reintroduction programs. The reintroduction of the western quoll resulted in nearly a third of the quolls being killed by feral cats.

A quoll killed by a feral cat in the Flinders Ranges, South Australia. Melissa Jensen, Author provided

DNA analysis indicated that quolls were killed by large male cats with most cats responsible for multiple kills (Moseby, Peacock and Read,in press,Biological Conservation). These specialist hunters could be targeted by making their prey toxic, in other words employing toxic Trojans (poison capsules implanted under the skin of prey species where they remain stable) to control specialist cats.

Poison capsules can be implanted under the skin of prey species where they remain stable. If a cat kills and ingests a toxic Trojan, the capsule will break down in the acidic environment of the cat’s stomach releasing the poison and preventing it from killing more individuals. Research is continuing into this poison delivery device which may result in improved targeted cat control.

Get smart

Finally, an ARC linkage grant between the University of New South Wales and Arid Recovery is researching ways to improve the anti-predator behaviour of threatened species.

Our native species did not evolve with introduced cats and foxes and hence may exhibit inappropriate or ineffective anti-predator responses. This prey naivety can lead to high susceptibility even to low levels of exotic predators.

Containing our threatened species on off-shore islands or behind fences is potentially exacerbating the issue as they are not exposed to mammalian predators and can develop “island syndrome” where they fail to recognise predators as dangerous.

The project involves trialling “in situ” predator training where low levels of predators are added to populations of threatened species for extended periods to improve their anti-predator behaviour.

The theory is that natural selection and learning will lead to improved survival and behaviour of successive generations of threatened species.

Whilst this may be a long term endeavour, ways of facilitating co-existence and increasing the resilience of our native species to exotic predators are urgently needed as it is likely that the wily feral cat is here to stay.

The authors would like to acknowledge the following for contributions. Poison Baits – Dave Algar, Michael Johnston, Keith Morris; Grooming traps- Invasive Animals CRC; Broadscale indirect methods – Reece Pedler, Peter Bird, Rob Brandle Rick Southgate, Rachel Paltridge, Sarah Legge; Specialist Hunters – Dave Peacock; Improving Prey Responses – Mike Letnic, Dan Blumstein, Bec West. Ecological Horizons has received funding from Sporting Shooters, FAME, Bush Heritage and SA and Australian Govt for development of Feral Cat Grooming Traps.

The ConversationKatherine Moseby is Associate Lecturer, Ecological and Environmental Sciences at University of AdelaideJohn Read is Associate Lecturer, Ecology and Environmental Sciences at University of Adelaide.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.


Leave a comment

Filed under Reblogs

Feral feast: cats kill hundreds of Australian animals

The Conversation

By Tim Doherty

Feral cats are estimated to eat tens of millions of native animals each night in Australia. But what kinds of wildlife are they eating? In research published today in the Journal of Biogeography, my colleagues and I show that cats kill hundreds of different kinds of animals, including at least 16 species considered globally threatened.

Feral cats are a serious threat to wildlife globally, contributing to the extinction of numerous birds, mammals and reptiles worldwide. In Australia, cats have been implicated in the extinction of at least 20 mammal species and sub-species, including the lesser bilby and desert bandicoot.

Cats are widespread across the country, so it’s likely that their diet varies according to the local environment and fauna community – which might be affected by many factors, such as the amount of rainfall that an area receives or the native plant life.

Knowing what cats eat can help us decide how best to manage them.

Feline feast

What we found supports earlier research – the feral cat is an opportunistic predator – a generalist carnivore that eats a wide range of wildlife across Australia.

A feral cat degustation.
Tim Doherty, Author provided

Feral cats help themselves to a phenomenal number of species in Australia – 400 different vertebrates. This includes 123 bird species, 157 reptiles, 58 marsupials, 27 rodents, 21 frogs and nine exotic medium- and large-sized mammals. This is more than double the 179 species of animals that cats have been recorded eating on other islands worldwide.

However, this list only includes those species that have been recorded in diet studies, so it’s likely that there are many other species of native animals that cats kill and eat, that we just don’t know about yet.

Feral cats also eat many threatened species in Australia, and have been implicated in the decline of many species including the bilby, numbat, and western ground parrot.

We found that cats kill at least 16 globally threatened species and 12 others classed as near-threatened. This include mammals like the critically endangered mountain pygmy-possum and the brush-tailed bettong (woylie); the endangered northern quoll; as well as the critically endangered Christmas Island whiptail-skink and the vulnerable malleefowl.

Feral cats prey on the endangered northern quoll.
University of Technology Sydney/AAP

Desert desserts

What feral cats eat varies depending on where they are.

In our study, cats ate rodents most often in Australia’s tropical north. They ate medium-sized mammals, such as possums and bandicoots, most frequently in the south-east of the country. Still, cats ate rodents three times more often than other small, carnivorous mammals known as dasyurids (like dunnarts for example).

Cats also ate many mammals from a group that has suffered severe declines and extinctions over the past 200 years. These are known as “critical weight range” mammals, and weigh between 0.35 and 5.5 kilograms. Unfortunately, these mammals make suitable sized prey for many predatory species such as the feral cat and the introduced red fox.

What cats eat also depends on the amount of rainfall an area receives. Cats fed on reptiles most frequently in the central deserts, where rainfall is lowest. These deserts are also the most reptile-rich part of Australia (and the world).

Cats commonly feed on another widespread pest species: rabbits. Where cats ate fewer rabbits, the frequency of small mammals (rodents and dasyurids) in their diet increased. In Australia’s tropical north where rabbits are mostly absent, cats ate the highest frequency of rodents and dasyurids of anywhere in the country.

Rabbits are a major food source for feral cats.
Eddy Van 3000, CC BY-SA

This has important implications for how we manage pest animals. If rabbits are culled from an area, but cats aren’t controlled at the same time, then cats might switch prey and eat more small native mammals.

Past experience tells us how these programs can go awry. For example, when feral cats were eradicated from Macquarie Island in 2000, rabbit numbers exploded because the cats had kept the rabbits in check. Rabbits caused severe damage to the island’s native vegetation before being eradicated themselves in 2014. This suggests that a multi-species approach should be adopted for pest animal control.

Cat control

Large-scale control of feral cats is very difficult, particularly on the mainland, although some programs have been successful on islands. The use of poison baits can reduce cat density, but even low levels of cat predation can exterminate threatened mammal populations, such as when cats killed at least seven bilbies reintroduced outside the Arid Recovery reserve in South Australia.

Predator-free islands and fenced reserves on the mainland are the most effective short-term protection for our threatened mammals. However, fences that exclude predators are very expensive to build, and they require constant monitoring, maintenance and funding.

Non-lethal methods have traditionally been overlooked in the fight against invasive predators, such as the feral cat. However, new research suggests that smart fire and grazing management can help preserve the natural shelters that provide native animals with refuge from predators.

Reducing the impact of feral cats on our native animals is a challenging endeavour, but it is essential in the fight to conserve our unique fauna.

The ConversationThis article was originally published on The Conversation. (Reblogged by permission). Read the original article.

Leave a comment

Filed under Reblogs

New research shows alpine grazing does not reduce blazing

The Conversation

By Grant Williamson, University of Tasmania; Brett Murphy, University of Melbourne, and David Bowman, University of Tasmania

The scale and impact, both economic and ecological, of recent bushfire disasters demands a rethink of fire management strategies. A controversial approach receiving more attention internationally is the use of large grazing animals to reduce fuel loads.

But research we published this week shows cattle grazing does little to reduce Australia’s most destructive bushfires.

There are few specific examples of this management intervention being used in Australia. The exception is cattle grazing in the Victorian High Country, part of the Australian Alps. This has been controversial, pitting pastoralists against environmentalists, and scientists against scientists.

It raises questions about acceptable and unacceptable land uses in national parks. And it raises the issue of Australian cultural heritage, including the perpetuation of an iconic “Man from Snowy River” cultural tradition of summer pasturing of cattle in the Australian Alps.

Proponents of grazing within the Alpine National Park claim “grazing reduces blazing”. The clear public message is that the severe fires seen in Australia’s alpine forests in recent years can be reduced in extent, intensity, and ultimately damaging effects by the continuation of cattle grazing.

But environmentalists point to the degradation cattle cause to alpine ecosystems by spreading weeds, triggering erosion, trampling bogs and fouling streams.

Some scientific studies have shown that there is no link between grazing and reduced fire severity but the generality of these findings has been disputed.

This debate involves an unusual intersection of scientific, environmental, legal and political dimensions. The Victorian Labor Government banned grazing in the Alpine National Park in 2005 because of environmental concerns. When the Coalition came to power in Victoria in 2010, they proposed resolving this issue with a grazing trial of 400 head of cattle per year to investigate hypothesised fire mitigation.

This trial was then blocked by the then Labor Federal Environment Minister on the grounds it would have an unacceptable impact on endangered species under the Environment Protection and Biodiversity Conservation Act.

A Federal Court case brought by the Victorian government subsequently found the Federal Environment Minister acted appropriately. Grazing is still banned within the Park.

In this context, we tried a “natural experiment” to discover whether cattle grazing can reduce blazing. We surveyed over 11,400 km2 of the Victorian Alps by analysing satellite images of the area. We looked at vegetation maps, looked back in time using historical satellite pictures, and took advantage of the cessation of grazing this decade and the extensive area burnt by fires over this period.

To implement our study as a classical experiment – for example by manipulating grazing pressure and imposing experimental fires – would be completely impractical, and prohibitively expensive given the same geographical scale and the risks of application of extensive high-severity fires. It would also be unethical given the potential threats to biodiversity, and under current legislation, unlawful.

We overlaid maps of crown scorch derived from satellite imagery following large bushfires in 2002/03 and 2006/07 with the location of pastoral leases. Crown scorch is a measure of fire intensity, based on the degree to which flames have reached a height which enables them to burn the forest canopy. This crown scorch can be detected in satellite images.

Using geospatial statistics we found that cattle grazing had no effect on the likelihood of crown scorch in eucalypt forests and woodlands.

This result is biologically plausible given that cattle are grazing animals, not browsing animals – they do not extensively feed on woody vegetation focusing on grasses instead. Our study is also consistent with previous ground-based studies that have demonstrated the cattle prefer to graze in grassy areas.

Fires in eucalypt forests are important to study, because to their extreme intensity. Fires in these forests are driven by high fuel loads on the forest floor and dense forest structure. Eucalypt forests have the added capacity for fast-moving fires to occur in the upper canopy, carried by the highly flammable leaves. Such fires are nearly impossible for fire fighters to control.

In comparison, fire intensity in grasslands is much lower, fires are easier to control, and grasslands recover rapidly after fires.

Our study does not rule out the use of cattle to manage grassy fuels – this approach may be crucial in tropical savannas, especially where invasive grasses fuel fires that compromise the ecological integrity of native vegetation.

This article was originally published on The Conversation. (Reblogged with permission). Read the original article.

Leave a comment

Filed under Reblogs