One cat, one year, 110 native animals: lock up your pet, it’s a killing machine


Anton Darius/Unsplash, CC BY

Jaana Dielenberg, The University of Queensland; Brett Murphy, Charles Darwin University; Chris Dickman, University of Sydney; John Woinarski, Charles Darwin University; Leigh-Ann Woolley, Charles Darwin University; Mike Calver, Murdoch University, and Sarah Legge, Australian National University

We know feral cats are an enormous problem for wildlife – across Australia, feral cats collectively kill more than three billion animals per year.

Cats have played a leading role in most of Australia’s 34 mammal extinctions since 1788, and are a big reason populations of at least 123 other threatened native species are dropping.




Read more:
Feral cat cull: why the 2 million target is on scientifically shaky ground


But pet cats are wreaking havoc too. Our new analysis compiles the results of 66 different studies on pet cats to gauge the impact of Australia’s pet cat population on the country’s wildlife.

The results are staggering. On average, each roaming pet cat kills 186 reptiles, birds and mammals per year, most of them native to Australia. Collectively, that’s 4,440 to 8,100 animals per square kilometre per year for the area inhabited by pet cats.

More than one-quarter of Aussie households have pet cats.
Jaana Dielenberg, Author provided

If you own a cat and want to protect wildlife, you should keep it inside. In Australia, 1.1 million pet cats are contained 24 hours a day by responsible pet owners. The remaining 2.7 million pet cats – 71% of all pet cats – are able to roam and hunt.

What’s more, your pet cat could be getting out without you knowing. A radio tracking study in Adelaide found that of the 177 cats whom owners believed were inside at night, 69 cats (39%) were sneaking out for nocturnal adventures.

Surely not my cat

Just over one-quarter of Australian households (27%) have pet cats, and about half of cat-owning households have two or more cats.

Many owners believe their animals don’t hunt because they never come across evidence of killed animals.

But studies that used cat video tracking collars or scat analysis (checking what’s in the cat’s poo) have established many pet cats kill animals without bringing them home. On average, pet cats bring home only 15% of their prey.


Wes Mountain/The Conversation, CC BY-ND

Collectively, roaming pet cats kill 390 million animals per year in Australia.

This huge number may lead some pet owners to think the contribution of their own cat wouldn’t make much difference. However, we found even single pet cats have driven declines and complete losses of populations of some native animal species in their area.

Documented cases have included: a feather-tailed glider population in south eastern NSW; a skink population in a Perth suburb; and an olive legless lizard population in Canberra.

Urban cats

On average, an individual feral cat in the bush kills 748 reptiles, birds and mammals a year – four times the toll of a hunting pet cat. But feral cats and pet cats roam over very different areas.

Pet cats are confined to cities and towns, where you’ll find 40 to 70 roaming cats per square kilometre. In the bush there’s only one feral cat for every three to four square kilometres.

So while each pet cat kills fewer animals than a feral cat, their high urban density means the toll is still very high. Per square kilometre per year, pet cats kill 30-50 times more animals than feral cats in the bush.

The impact of roaming pet cats on Australian wildlife.

Most of us want to see native wildlife around towns and cities. But such a vision is being compromised by this extraordinary level of predation, especially as the human population grows and our cities expand.

Many native animals don’t have high reproductive rates so they cannot survive this level of predation. The stakes are especially high for threatened wildlife in urban areas.

Pet cats living near areas with nature also hunt more, reducing the value of places that should be safe havens for wildlife.




Read more:
A hidden toll: Australia’s cats kill almost 650 million reptiles a year


The 186 animals each pet cat kills per year on average is made up of 110 native animals (40 reptiles, 38 birds and 32 mammals).

For example, the critically endangered western ringtail possum is found in suburban areas of Mandurah, Bunbury, Busselton and Albany. The possum did not move into these areas – rather, we moved into their habitat.

What can pet owners do?

Keeping your cat securely contained 24 hours a day is the only way to prevent it from killing wildlife.

It’s a myth that a good diet or feeding a cat more meat will prevent hunting: even cats that aren’t hungry will hunt.

A bell on a cat’s collar doesn’t stop hunting, it only makes hunting a little harder.
Wes Mountain/The Conversation, CC BY-ND

Various devices, such as bells on collars, are commercially marketed with the promise of preventing hunting. While some of these items may reduce the rate of successful kills, they don’t prevent hunting altogether.

And they don’t prevent cats from disturbing wildlife. When cats prowl and hunt in an area, wildlife have to spend more time hiding or escaping. This reduces the time spent feeding themselves or their young, or resting.

In Mandurah, WA, the disturbance and hunting of just one pet cat and one stray cat caused the total breeding failure of a colony of more than 100 pairs of fairy terns.

Benefits of a life indoors

Keeping cats indoors protects pet cats from injury, avoids nuisance behaviour and prevents unwanted breeding.

Cats allowed outside often get into fights with other cats, even when they’re not the fighting type (they can be attacked by other cats when running away).

Two cats in Western Australia stopped fairy terns from breeding.
Shutterstock

Roaming cats are also very prone to getting hit by a vehicle. According to the Humane Society of the United States, indoor cats live up to four times longer than those allowed to roam freely.

Indoor cats have lower rates of cat-borne diseases, some of which can infect humans. For example, in humans the cat-borne disease toxoplasmosis can cause illness, miscarriages and birth defects.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


But Australia is in a very good position to make change. Compared to many other countries, the Australian public are more aware of how cats threaten native wildlife and more supportive of actions to reduce those impacts.

It won’t be easy. But since more than one million pet cats are already being contained, reducing the impacts from pet cats is clearly possible if we take responsibility for them.The Conversation

Jaana Dielenberg, Science Communication Manager, The University of Queensland; Brett Murphy, Associate Professor / ARC Future Fellow, Charles Darwin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; John Woinarski, Professor (conservation biology), Charles Darwin University; Leigh-Ann Woolley, Adjunct Research Associate, Charles Darwin University; Mike Calver, Associate Professor in Biological Sciences, Murdoch University, and Sarah Legge, Professor, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Last summer’s fish carnage sparked public outrage. Here’s what has happened since



Graeme McCrabb/AAP

Lee Baumgartner, Charles Sturt University and Max Finlayson, Charles Sturt University

As this summer draws to a close, it marks just over a year since successive fish death events at Menindee in Lower Darling River made global headlines.

Two independent investigations found high levels of blue-green algae and low oxygen levels in the water caused the deaths. Basically, the fish suffocated.




Read more:
We wrote the report for the minister on fish deaths in the lower Darling – here’s why it could happen again


The conditions were caused by a combination of water extraction and extremely dry conditions which effectively stopped the river from flowing. Both investigations concluded that until more water flowed in the Darling, in western New South Wales, further fish kills were very likely.

So what’s happened since, and does the recent rain mean the crisis won’t be repeated?

Federal and state government action

In April last year the federal government committed A$70 million to improve the river’s health and prevent more fish deaths. Let’s examine what’s been done so far:

– Native fish management and recovery strategy: Parts of a draft native fish management and recovery strategy have been released for public consultation. The plan has included governments, academics, the community and indigenous groups.

– Native fish hatchery: Government hatchery facilities at Narrandera in NSW will be upgraded to hold and breed more fish. But reintroducing fish into affected areas is challenging and could be a decades-long program.

– Research: The government committed to new research into hydrology and climate change. A panel has been formed and the oversight committee is scoping the most effective research outcomes to better manage water under a changed climate.

– Fish passage infrastructure: Fish ladders – structures that allow fish to travel around obstacles on a river – are needed at sites on the lower and upper Darling. Fish ladder concept designs have progressed and are also part of the NSW government’s Western Weirs project.

-In-stream cameras: Live-stream feeds of the Darling River are not yet available.

-Meter upgrades and water buybacks: Discussions have begun as part of a commitment to buy back A-class water licenses from farmers and return water to the rivers. Rollout of improved metering is due over the next five years.

Progress on these actions is welcome. But the investigation panels also recommended other actions to help fish populations recover over the long term, including ensuring fish habitat and good water quality.

Further fish deaths

In 2003, basin native fish communities were estimated to be at 10% of pre-European levels and the spates of fish deaths will have reduced this further.

Over spring and summer in 2019, conditions in the Darling River deteriorated. A series of smaller, but significant, fish deaths prompted government agencies and communities to conduct emergency “fish translocations”.. Aerators were deployed in a bid to improve the de-oxygenation. Fish were moved to more suitable water bodies, or to hatcheries to create insurance populations.

By spring, once-mighty rivers such as the Darling and Macquarie had dried to shallow pools. As summer progressed, more than 30 fish die-offs occurred in the Macquarie, Namoi, Severn, Mehi and Cudgegong rivers and Tenterfield Creek.

What about the rain?

Strong recent rainfall means upper parts of the Darling catchment are now flowing for the first time in more than two years. Flows are passing over the Brewarrina Weir and associated fishway.

A flowing Darling is great, but it raises questions over future water management. Farmers have been waiting for years for the Darling to flow and will be eager to extract water for agricultural productivity. Likewise, the environment has been awaiting a “flush” to reset the system and restore ecological productivity.




Read more:
Aboriginal voices are missing from the Murray-Darling Basin crisis


After the rains, the NSW government allowed irrigators to harvest floodwaters to reduce the threat of damage to private infrastructure. Now that threat has subsided, governments are working together to “actively manage” the event – meaning water rules will be decided as the flow progresses, in consultation with water users and environmental managers.

But there is still significant debate on how best to manage water over the longer term.

Water use on the Darling River remains highly contested.
Dean Lewins/AAP

Is a flowing Darling a return to normal?

The current flows in the Darling are far from a return to normal conditions. NSW is still in drought, and the river flows are yet to reach the Lower Darling. Many children in the Menindee township have not seen a flowing Darling in their lifetime.

Indigenous elders and recreational fishers – those who remember when the river flowed freely and was full of fish – are lamenting the recent declines. In parts of the system, dry riverbeds and isolated pools are still begging to be connected so fish can move about, spawn, and naturally recover.




Read more:
Friday essay: death on the Darling, colonialism’s final encounter with the Barkandji


River flows could take up to six weeks to reach the lower Darling, and follow-up rain is urgently needed to avoid another summer of fish carnage. Future water sharing strategies must protect both upstream and downstream communities. Some people are lobbying for the Menindee lakes to be listed as internationally important under the Ramsar Convention on Wetlands to ensure biodiversity and water management work together.

Undoing over 200 years of fish declines will require a sustained effort, with a significant investment in recovery actions over a long period. We must recognise Australia is a country of long droughts and flooding rains, and develop a proactive native fish strategy that reduces the probability of a similar disaster in future.

But unfortunately, as history has shown that when we transition from drought to flood, our memories can be short.The Conversation

Lee Baumgartner, Professor of Fisheries and River Management, Institute for Land, Water, and Society, Charles Sturt University and Max Finlayson, Adjunct Professor, Charles Sturt University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Buildings kill millions of birds. Here’s how to reduce the toll



These birds were killed by flying into a set of surveyed buildings in Washington DC in 2013.
USGS Bee Inventory and Monitoring Lab/Flickr

Norman Day, Swinburne University of Technology

As high-rise cities grow upwards and outwards, increasing numbers of birds die by crashing into glass buildings each year. And of course many others break beaks, wings and legs or suffer other physical harm. But we can help eradicate the danger by good design.

Most research into building-related bird deaths has been done in the United States and Canada, where cities such as Toronto and New York City are located on bird migration paths. In New York City alone, the death toll from flying into buildings is about 200,000 birds a year.

Across the US and Canada, bird populations have shrunk by about 3 billion since 1970. The causes include loss of habitat and urbanisation, pesticides and the effects of global warming, which reduces food sources.

An estimated 365 million to 1 billion birds die each year from “unnatural” causes like building collisions in the US. The greatest bird killer in the US remains the estimated 60-100 million free-range cats that kill up to 4 billion birds a year. Australia is thought to have up to 6 million feral cats.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


But rampant global urbanisation is putting the reliance on glass buildings front-of-stage as an “unnatural” cause of bird deaths, and the problem is growing exponentially.

In the line of flight

Most birds fly at around 30-50km/h, with falcons capable of up to 200km/h. When migrating, birds generally spend five to six hours flying at a height of 150 metres, sometimes much higher.

And that’s where the problems start with high-rise buildings. Most of them are much taller than the height at which birds fly. In Melbourne, for example, Australia 108 is 316 metres, Eureka 300 metres, Aurora 270 metres and Rialto 251 metres. The list is growing as the city expands vertically.

The paradigm of high-rise gothams, New York City, has hundreds of skyscrapers, most with fully glass, reflective walls. One World Trade is 541 metres high, the 1931 Empire State is 381 metres (although not all glass) and even the city’s 100th-highest building, 712 Fifth Avenue, is 198 metres.

To add to the problems of this forest of glass the city requires buildings to provide rooftop green places. These attract roosting birds, which then launch off inside the canyons of reflective glass walls – often mistaking these for open sky or trees reflected from behind.

Reflections of trees and sky lure birds into flying straight into buildings.
Frank L Junior/Shutterstock

A problem of lighting and reflections

Most cities today contain predominantly glass buildings – about 60% of the external wall surface. These buildings do not rely on visible frames, as in the past, and have very limited or no openable windows (for human safety reasons). They are fully air-conditioned, of course.




Read more:
Glass skyscrapers: a great environmental folly that could have been avoided


Birds cannot recognise daylight reflections and glass does not appear to them to be solid. If it is clear they see it as the image beyond the glass. They can also be caught in building cul-de-sac courtyards – open spaces with closed ends are traps.

At night, the problem is light from buildings, which may disorientate birds. Birds are drawn to lights at night. Glass walls then simply act as targets.

Some species send out flight calls that may lure other birds to their death.

White-throated Sparrows collected in a University of Michigan-led study of birds killed by flying into buildings lit up at night in Chicago and Cleveland.
Roger Hart, University of Michigan/Futurity, CC BY



Read more:
Want to save millions of migratory birds? Turn off your outdoor lights in spring and fall


We can make buildings safer for birds

Architectural elements like awnings, screens, grilles, shutters and verandas deter birds from hitting buildings. Opaque glass also provides a warning.

Birds see ultraviolet light, which humans cannot. Some manufacturers are now developing glass with patterns using a mixed UV wavelength range that alerts birds but has no effect on human sight.

New York City recently passed a bird-friendly law requiring all new buildings and building alterations (at least under 23 metres tall, where most fly) be designed so birds can recognise glass. Windows must be “fritted” using applied labels, dots, stripes and so on.

The search is on for various other ways of warning birds of the dangers of glass walls and windows.

Combinations of methods are being used to scare or warn away birds from flying into glass walls. These range from dummy hawks (a natural enemy) and actual falcons and hawks, which scare birds, to balloons (like those used during the London Blitz in the second world war), scary noises and gas cannons … even other dead birds.

Researchers are using lasers to produce light ray disturbance in cities especially at night and on dark days.

Noise can be effective, although birds do acclimatise if the noises are produced full-time. However, noise used as a “sonic net” can effectively drown out bird chatter and that interference forces them to move on looking for quietness. The technology has been used at airports, for example.

A zen curtain developed in Brisbane has worked at the University of Queensland. This approach uses an open curtain of ropes strung on the side of buildings. These flutter in the breeze, making patterns and shadows on glass, which birds don’t like.

These zen curtains can also be used to make windows on a house safer for birds. However, such a device would take some doing for the huge structures of a metropolis.

More common, and best adopted at the design phase of a building, is to mark window glass so birds can see it. Just as we etch images on glass doors to alert people, we can apply a label or decal to a window as a warning to birds. Even using interior blinds semi-open will deter birds.

Birds make cities friendlier as part of the shared environment. We have a responsibility to provide safe flying and security from the effects of human habitation and construction, and we know how to achieve that.


This article has been updated to correct the figure for the estimated number of birds killed by the cats in the US to “up to 4 billion”, not 4 million.The Conversation

Norman Day, Lecturer in Architecture, Practice and Design, Swinburne University of Technology

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why Australia needs to kill cats


John Read, University of Adelaide and Katherine Moseby, UNSW

Introduced cats are a key threat to 123 of Australia’s threatened species.

The management of cats is challenging and divisive; many options such as rehoming, trap-neuter-release and euthanasia have been used around the world with varying success.

Australia’s recent commitment to killing 2 million feral cats to protect its native wildlife has attracted international attention and some have considered the project harsh.

While the actual target of 2 million has been rightly criticised as arbitrary and more based on public relations than rigorous science, it’s true non-lethal methods are not enough to stem the environmental havoc cats cause. Particularly in light of a UN report highlighting the world’s extinction crisis, Australia urgently needs well-targeted cat culls.




Read more:
Feral cat cull: why the 2 million target is on scientifically shaky ground


Non-lethal methods

A range of effective non-lethal methods are already protecting wildlife from cats. Cat-exclusion fences have collectively improved the conservation status of many threatened species. In addition, an increasing number of Australian councils have created progressive cat management bylaws designed to protect pet cats, wildlife and humans from the effects of free-ranging cats.

The centrepiece of many of these bylaws, supported by the vast majority of animal welfare groups, is the containment of pet cats on their owner’s property. Indoor cats live longer, safer lives than cats that are allowed to roam.

Stray cats are harder to manage. These are the cats that do not have a home, but may be directly or indirectly fed by people.




Read more:
A hidden toll: Australia’s cats kill almost 650 million reptiles a year


Because they are unowned, no-one is officially accountable for their health or welfare. Groups of like-minded individuals feed and even provide veterinary assistance to some of these cats, further blurring the distinction between pet and feral cats.

A trend promoted by “no kill” shelters and advocacy groups in some US states and Europe is for clowders (groups) of stray cats to be desexed, vaccinated and released back onto the streets. This process is called trap-neuter-release (TNR).

A recent RSPCA best-practice cat management discussion paper proposed a trial of TNR in Australia too – but there are very good reasons why this would be counterproductive for cat welfare.

The risks of releasing unowned cats

Informed animal welfare advocate groups, including PETA, strongly condemn the release of unowned cats, neutered or otherwise, due to the welfare risks to these cats. Human health professionals and wildlife advocates also oppose maintaining groups of cats.

Dense outdoor cat clowders are hotbeds of toxoplasmosis infections. This cat-borne disease is increasingly being linked to a range of chronic mental health conditions including schizophrenia and Alzheimer’s disease.

“No kill” groups that promote TNR erroneously claim that neutered cats significantly reduce the breeding potential of erroneously named cat “colonies”, in the same way that release of neutered mosquitoes is a proven technique for controlling disease-bearing mosquitoes.

One of us (John) has recently written a book on protecting wildlife and cats that suggests five fatal biological flaws in this logic:

  1. Neutering mosquitoes works because impotent individuals “swamp” short-lived wild insect populations that mate only once. By contrast, female cats typically mate repeatedly when on heat, so an encounter with a neutered tom is of little consequence.

  2. Unlike lions, domestic cats evolved as solitary hunters. While domestic cats can tolerate living in high-density clowders, they do not form hierarchical colonies, packs or prides where alpha individuals restrict the feeding, breeding or survival of subordinate animals.

  3. Although loud cat fights might make you assume males fight over the right to exclusively mate with a female, most litters of outdoor cats are sired by multiple males. Even supposedly “dominant” males seldom intervene when another male courts a female. Neutered male cats will not protect females in their clowder from non-desexed interlopers. This means that more than 90% of cats need to be neutered to restrict population increases, an incredibly challenging proposition.

  4. Despite the misleading label “colony”, cat clowders are not closed populations. Rather, cats typically move around to take advantage of abundant food resources. And unwanted pets are often dumped at clowder sites. The failures of several well-studied TNR programs are attributed to cats migrating or being dumped at these sites.

  5. Despite needing repeated vaccinations to protect them from debilitating diseases, few stray cats can be captured a second time. And many can never be captured at all. This leaves them and their clowder effectively unmanageable.

TNR is biologically flawed, cruel to cats – because it returns them to a hazardous environment – and ineffective when not accompanied by high levels of adoption.

Harming marine ecosystems

Not only do predatory cats harm native wildlife, but stray or feral clowders can also directly influence marine ecosystems and fisheries.

Many commercial cat foods contain increasingly threatened predatory fish that are high in the food chain and hence use more nutrients and biological energy than plants or herbivores. US dogs and cats consume one-third of the animal-derived protein eaten by humans, with accompanying greenhouse gas emissions.

The cat food provided to stray clowders adds to this biological expense. In 2009 alone, the US-based Best Friends Animal Society, one of the major promoters of TNR, distributed over 80,000 tonnes of cat food to unowned cats. There are no similar studies in Australia, and we appear to have far lower rates of stray-cat-feeding, but it is still part of the ecological impact of stray cats.

Even more insidiously, seals, otters and dolphins in oceans around the world die from cat-borne diseases spread mainly from clowders.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


Humane euthanasia

Fortunately, both science and animal welfare standards are consistent about management of cats. All healthy domestic cats for which safe homes can be found should be adopted or rehomed, then kept indoors following neutering and vaccination. All other cats, including ferals and strays that cannot be rehomed quickly, should be humanely euthanased.

Feeding or releasing cats (neutered or otherwise) threatens our wildlife and perpetuates the cycle of suffering, disease, predation and social annoyance. Non-lethal options such as feral cat-proof fencing can still be part of the solution, but euthanasia remains an important part of controlling feral and stray cats to protect our native wildlife.


Among the Pigeons: Why our cats belong indoors (2019) by John Read is published by Wakefield Press.The Conversation

John Read, Associate Lecturer, Ecology and Environmental Sciences, University of Adelaide and Katherine Moseby, Research fellow, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How much plastic does it take to kill a turtle? Typically just 14 pieces



File 20180913 133877 1l7r55a.jpeg?ixlib=rb 1.1
Plastic bags, balloons, and rope fragments were among more than 100 pieces of plastic in the gut of a single turtle.
Qamar Schuyler, Author provided

Britta Denise Hardesty, CSIRO; Chris Wilcox, CSIRO; Kathy Ann Townsend, University of the Sunshine Coast, and Qamar Schuyler, CSIRO

We know there is a lot of plastic in the ocean, and that turtles (and other endangered species) are eating it. It is not uncommon to find stranded dead turtles with guts full of plastic.

But we weren’t really sure whether plastic eaten by turtles actually kills them, or if they just happen to have plastic inside them when they die. Another way to look at it would be to ask: how much is too much plastic for turtles?

This is a really important question. Just because there’s a lot of plastic in the ocean, we can’t necessarily presume that animals are dying from eating it. Even if a few animals do, that doesn’t mean that every animal that eats plastic is going to die. If we can estimate how much plastic it takes to kill a turtle, we can start to answer the question of exactly how turtle populations are affected by eating plastic debris.




Read more:
Eight million tonnes of plastic are going into the ocean each year


In our research, published today in Nature Scientific Reports, we looked at nearly 1,000 turtles that had died and washed up on beaches around Australia or were found in nets. About 260 of them we examined ourselves; the others were reported to the Queensland Turtle Stranding Database. We carefully investigated why the turtles died, and for the ones we examined, we counted how many pieces of plastic they had eaten.

Some turtles died of causes that were nothing to do with plastic. They may have been killed by a boat strike, or become entangled in fishing lines or derelict nets. Turtles have even been known to die after accidentally eating a blue-ringed octopus. Others definitely died from eating plastic, with the plastic either puncturing or blocking their gut.

One of the first meals eaten by this sea turtle post-hatchling turned out to be deadly. It died from consuming more than 20 tiny pieces of plastic, many of which were about the same size as a grain of rice.
Kathy Townsend, Author provided

Some turtles that were killed by things like boat strikes or fishing nets nevertheless had large amounts of plastic in their guts, despite not having been killed by eating plastic. These turtles allow us to see how much plastic an animal can eat and still be alive and functioning.

The chart below sets out this idea. If an animal drowned in a fishing net, its chance of being killed by plastic is zero – and it falls in the lower left of the graph. If a turtle’s gut was blocked by a plastic bag, its chance of being killed by plastic is 100%, and it’s in the upper right.

The animals that were dead with plastic in their gut, but had other possible causes of death have a chance of death due to plastic somewhere between 0 and 100% – we just don’t know, and they can fall anywhere in the graph. Once we have all the animals in the plot, then we can ask whether we see an increase in the chance of death due to plastic as the amount of plastic in an animal goes up.

Conceptual framework for estimating the probability of death due to plastic debris ingestion. Figure provided by the authors.

We tested this idea using our turtle samples. We looked at the relationship between the likelihood of death due to plastic as determined by a turtle autopsy, and the number of pieces of plastic found inside the animals.

Unsurprisingly, we found that the more plastic pieces a turtle had inside it, the more likely it was to have been killed by plastic. We calculated that for an average-sized turtle (about 45cm long), eating 14 plastic items equates to a 50% chance of being fatal.




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That’s not to say that a turtle can eat 13 pieces of plastic without harm. Even a single piece can potentially kill a turtle. Two of the turtles we studied had eaten just one piece of plastic, which was enough to kill them. In one case, the gut was punctured, and in the other, the soft plastic had clogged the turtle’s gut. Our analyses suggest that a turtle has a 22% chance of dying if it eats just one piece of plastic.

A green sea turtle that died after consuming 13 pieces of soft plastic and balloons, which blocked its gastrointestinal system.
Kathy Townsend

A few other factors also affected the animals’ chance of being killed by plastic. Juveniles eat more debris than adults, and the rate also varies between different turtle species.

Now that we know how much is too much plastic, the next step is to apply this to global estimates of debris ingestion rates by turtles, and figure out just how much of a threat plastic is to endangered sea turtle populations.The Conversation

Britta Denise Hardesty, Principal Research Scientist, Oceans and Atmosphere Flagship, CSIRO; Chris Wilcox, Senior Research Scientist, CSIRO; Kathy Ann Townsend, Lecturer in Animal Ecology, University of the Sunshine Coast, and Qamar Schuyler, Research Scientist, Oceans and Atmospheres, CSIRO

This article is republished from The Conversation under a Creative Commons license. Read the original article.

A hidden toll: Australia’s cats kill almost 650 million reptiles a year



File 20180625 152146 10y0h61.jpg?ixlib=rb 1.1
A feral cat snapped by a remote camera in the wild.
NT government, Author provided

John Woinarski, Charles Darwin University; Brett Murphy, Charles Darwin University; Chris Dickman, University of Sydney; Sarah Legge, Australian National University, and Tim Doherty, Deakin University

Cats take a hefty toll on Australia’s reptiles – killing an estimated 649 million of them every year, including threatened species – according to our new research published in the journal Wildlife Research.

This follows the earlier discovery that cats take a similarly huge chunk out of Australian bird populations. As we reported last year, more than a million Australian birds are killed by cats every day. Since their introduction to Australia, cats have also driven many native mammal species extinct.




Read more:
For whom the bell tolls: cats kill more than a million Australian birds every day


We collated information from about 100 previous local studies of cats’ diets across Australia. These studies involved teasing apart the contents of more than 10,000 samples of faeces or stomachs from cats collected as part of management programs.

We tallied the number of reptiles found in these samples, and then scaled it up to Australia’s estimated cat population of between 2.1 million and 6.3 million. We also collated information from museums and wildlife shelters on the various animals that had been brought in after being killed or injured by cats.

We calculate that an average feral cat kills 225 reptiles per year, so the total feral cat population kills 596 million reptiles per year. This tally will vary significantly from year to year, because the cat population in inland Australia fluctuates widely between drought and rainy years.

On the hunt.
NT government, Author provided

We also estimated that the average pet cat kills 14 reptiles per year. That means that Australia’s 3.9 million pet cats kill 53 million reptiles in total each year. However, there is much less firm evidence to quantify the impact of pet cats, mainly because it is much more straightforward to catch and autopsy feral cats to see what they have been eating, compared with pet cats.

Binge eaters

According to our study, cats have been known to kill 258 different Australian reptiles (snakes, lizards and turtles – but not crocodiles!), including 11 threatened species.

The cat autopsies revealed that some cats binge on reptiles, with many cases of individual cats having killed and consumed more than 20 individual lizards within the previous 24 hours. One cat’s stomach was found to contain no less than 40 lizards.

Cat stomach contents, including several reptile parts.
Arid Recovery, Author provided

Such intensive predation probably puts severe pressure on local populations of some reptile species. There is now substantial evidence that cats are a primary cause of the ongoing decline of some threatened Australian reptile species, such as the Great Desert Skink.

By our estimate, the average Australian feral cat kills four times more lizards than the average free-roaming cat in the United States (which kills 59 individuals per year). But there are many more such cats in the US (between 30 million and 80 million), so the total toll on reptiles is likely similar.




Read more:
The war on feral cats will need many different weapons


The conservation of the Australian reptile fauna has been accorded lower public profile than that of many other groups. However, a recent international program has nearly completed an assessment of the conservation status of every one of Australia’s roughly 1,000 lizard and snake species.

Our research provides yet more evidence of the harm that cats are wreaking on Australia’s native wildlife. It underlines the need for more effective and strategic control of Australia’s feral cats, and for more responsible ownership of pet cats.

Pet cats that are allowed to roam will kill reptiles, birds and other small animals. Preventing pet cats from roaming will help the cats live longer and healthier lives – not to mention saving the lives of wildlife.


The ConversationThe authors acknowledge the contribution of Russell Palmer, Glenn Edwards, Alex Nankivell, John Read and Dani Stokeld to this research.

John Woinarski, Professor (conservation biology), Charles Darwin University; Brett Murphy, Senior Research Fellow, Charles Darwin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Sarah Legge, Associate Professor, Australian National University, and Tim Doherty, Research Fellow, Deakin University

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

For whom the bell tolls: cats kill more than a million Australian birds every day



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On the prowl in the outback.
Hugh McGregor/Arid Recovery, Author provided

John Woinarski, Charles Darwin University; Brett Murphy, Charles Darwin University; Leigh-Ann Woolley, Charles Darwin University; Sarah Legge, Australian National University; Stephen Garnett, Charles Darwin University, and Tim Doherty, Deakin University

Cats kill more than a million birds every day across Australia, according to our new estimate – the first robust attempt to quantify the problem on a nationwide scale.

By combining data on the cat population, hunting rates and spatial distribution, we calculate that they kill 377 million birds a year. Rates are highest in Australia’s dry interior, suggesting that feral cats pose a serious and largely unseen threat to native bird species.


Read more: Ferals, strays, pets: how to control the cats that are eating our wildlife


This has been a contentious issue for more than 100 years, since the spread of feral cats encompassed the entire Australian mainland. In 1906 the ornithologist A.J. Campbell noted that the arrival of feral cats in a location often immediately preceded the decline of many native bird species, and he campaigned vigorously for action:

Undoubtedly, if many of our highly interesting and beautiful birds, especially ground-loving species, are to be preserved from total extinction, we must as a bird-lovers’ union, at no distant date face squarely a wildcat destruction scheme.

His call produced little response, and there has been no successful and enduring reduction in cat numbers since. Nor, until now, has there been a concerted effort to find out exactly how many birds are being killed by cats.

Counting the cost

To provide a first national assessment of the toll taken by cats on Australian birds, we have compiled almost 100 studies detailing the diets of Australia’s feral cats. The results show that the average feral cat eats about two birds every five days.

We then combined these statistics with information about the population density of feral cats, to create a map of the estimated rates of birds killed by cats throughout Australia.

Number of birds eaten per square kilometre.
Brett Murphy, Author provided

We conclude that, on average, feral cats in Australia’s largely natural landscapes kill 272 million birds per year. Bird-kill rates are highest in arid Australia (up to 330 birds per square km per year) and on islands, where rates can vary greatly depending on size.

We also estimate (albeit with fewer data) that feral cats in human-modified landscapes, such as the areas surrounding cities, kill a further 44 million birds each year. Pet cats, meanwhile, kill about 61 million birds per year.

Overall, this amounts to more than 377 million birds killed by cats per year in Australia – more than a million every day.

Which species are suffering?

In a related study, we also compiled records of the bird species being killed by cats in Australia. We found records of cats killing more than 330 native bird species – about half of all Australia’s resident bird species. In natural and remote landscapes, 99% of the cat-killed birds are native species. Our results also show that cats are known to kill 71 of Australia’s 117 threatened bird species.

Birds that feed or nest on the ground, live on islands, and are medium-sized (60-300g) are most likely to be killed by cats.

Galahs are among the many native species being killed by feral cats.
Mark Marathon, Author provided

It is difficult to put a million-plus daily bird deaths in context without a reliable estimate of the total number of birds in Australia. But our coarse assessment from many published estimates of local bird density suggests that there are about 11 billion land birds in Australia,
suggesting that cats kill about 3-4% of Australia’s birds each year.

However, particular species are hit much harder than others, and the population viability of some species (such as quail-thrushes, button-quails and ground-feeding pigeons and doves) is likely to be especially threatened.

Our tally of bird deaths is comparable to similar estimates for other countries. Our figure is lower than a recent estimate for the United States, and slightly higher than in Canada. Overall, bird killings by cats seem to greatly outnumber those caused by humans.

In Australia, cats are likely to significantly increase the extinction risk faced by some bird species. In many locations, birds face a range of interacting threats, with cat abundance and hunting success shown to increase in fragmented bushland, in areas with high stocking rates, and in places with poorly managed fire regimes, so cat impacts compound these other threats.

Belling the cat

What can be done to reduce the impact? The federal government’s Threatened Species Strategy recognises the threat posed by feral cats, albeit mainly on the basis of their role in mammal extinctions.

The threatened species strategy also prioritised efforts to control feral cats more intensively, eradicate them from islands with important biodiversity values, and to expand a national network of fenced areas that excludes feral cats and foxes.

But while fences can create important havens for many threatened mammals, they are much less effective for protecting birds. To save birds, cats will need to be controlled on a much broader scale.


Read more: The war on feral cats will need many different weapons


We should also remember that this is not just a remote bush problem. Roughly half of Australia’s cats are pets, and they also take a considerable toll on wildlife.

While recognising the many benefits of pet ownership, we should also work to reduce the detrimental impacts. Fortunately, there is increasing public awareness of the benefits of not letting pet cats roam freely. With such measures, cat owners can help to look after the birds in their own backyards, and hence contribute to conserving Australia’s unique wildlife.


The ConversationWe acknowledge the contribution of Russell Palmer (WA Department of Biodiversity Conservation and Attractions), Chris Dickman (University of Sydney), David Paton (University of Adelaide), Alex Nankivell (Nature Foundation SA Inc.), Mike Lawes (University of KwaZulu-Natal), and Glenn Edwards (Department of Environment and Natural Resources) to this article.

John Woinarski, Professor (conservation biology), Charles Darwin University; Brett Murphy, Senior Research Fellow, Charles Darwin University; Leigh-Ann Woolley, Research Associate, Charles Darwin University; Sarah Legge, Associate Professor, Australian National University; Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University, and Tim Doherty, Research Fellow, Deakin University

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

Little shop of horrors: the Australian plants that can kill you


Ben Moore, Western Sydney University

Australia is so famous for its dangerous creatures that visitors often arrive fearful that everything that moves is out to get them. In a land where snakes, spiders, shells and even one of the iconic mammals – the platypus – can bite or sting, should we all be worried about plants as well?

Plants around the world produce a staggering diversity of chemicals and many of these are potentially toxic to animals including humans, sometimes even upon contact. Many of these toxins have evolved to protect plant roots, leaves and unripe fruits from being eaten by herbivores, particularly insects and browsing mammals.

Australia’s toxic plants are not terribly appealing or nutritious for humans. If someone is poisoned, it’s usually accidental, and many victims are curious children.

There are many historical records of plant poisoning in Australia involving early explorers and settlers who were short of supplies or looking for new sources of food. Today, though, plant poisoning accounts for less than 1% of calls to poisons information lines in Australia.

Animals beware

The threat of poisoning to livestock is much more substantial and causes significant economic and animal welfare impacts.

It’s in the interests of cattle and sheep to become expert botanists, but even experts can get things wrong when confronted with something they’ve never seen before. Most livestock poisonings occur when animals are moving through new country or are put into new paddocks with unfamiliar plants.

Native plants that kill significant numbers of livestock include Cooktown ironwood in northern Australia (as little as 50 grams of leaf can contain a quantity of alkaloids that can kill a bull) and the poison peas and heart-leafed poison bush of Western Australia and Queensland respectively (Gastrolobium), which contain a deadly metabolic poison, sodium fluoroacetate.

Elsewhere, introduced pasture weeds such as fireweed, Senecio madagasciarensis, and Paterson’s curse, Echium plantagenium, pose significant threats to cattle, sheep and horses.

It’s in the dose

The adage that “the poison is in the dose” is correct in that small amounts of most poisonous plants are unlikely to cause permanent damage or death, although there are exceptions. Indeed, most herbivores have to tolerate some exposure to plant poisons because they’re so widespread among the plants they eat.


CC BY-NC-ND

Small amounts of some toxic compounds can even be beneficial and sometimes have traditional or medical uses. Aboriginal people, for instance, used Duboisia hopwoodii and other native tobacco species (Nicotiana) to produce a powerful and widely traded stimulant, pituri, the active ingredient of which is the potent alkaloid, nicotine.

Similarly, atropine, an alkaloid found in Angels’ trumpets and thorn-apple (Brugmansia and Datura species) is a powerful hallucinogen and toxin. But it’s also a valuable drug used to treat some heart and nervous conditions, as well as poisoning by some other plant alkaloids and cardiac glycosides.

Knowing what dose of poison a plant contains is not always easy. How much toxin an individual plant contains can vary with season, the age of the plant, soil type, drought and the plant’s genes. Just as you may be tall and your next-door neighbour short, two plants of the same species growing alongside can vary in how much toxin they produce.

On top of that, different animal species and individual people and animals can also vary in their ability to tolerate poisons. This makes ingesting toxic plants a little like Russian roulette: there’s a strong element of chance.

Deadly relatives

A significant number of Australia’s more than 20,000 plants are potentially toxic. In many cases, Australia has species or subspecies of plants that are closely related to well-known toxic plants from elsewhere. But their relative toxicity is not well established.

The Indian suicide tree, Cerbera odollum, has been described as the “perfect murder weapon”, for instance, but the toxicity of our native Cerbera manghas is less well understood, despite the fact it possesses the same cardiac poisons.

Similarly, how our native strychnine bushes Strychnos lucida and S. psilosperma compare to the better-known strychnine tree S. nux-vomica from India is not well known, but they do also produce strychnine.

Unless you’re a hungry ruminant, you’re probably unlikely to suffer death by plant poisoning in Australia, but the risk is nonetheless real. It pays to realise that garden plants and even common indoor plants are sometimes just as dangerous as what lurks in the bush. Parents and outdoorsy types should be aware of the risks posed by contact with or ingestion of plants.

This article is part of our series Deadly Australia. Stay tuned for more pieces on the topic in the coming days.

The Conversation

Ben Moore, Senior Lecturer in Ecology, Hawkesbury Institute for the Environment, Western Sydney University

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

South Africa: Rhino Poaching Continuing to Kill Many Rhinos


The article below reports on the large number of Rhinos lost to poaching this year in South Africa.

For more, visit:
http://www.cbsnews.com/8301-501710_162-57399946/135-endangered-rhino-killed-in-south-africa/