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Australian Environmental Issues

Blue-tongue
A true-blue battler

Box jellyfish
How to avoid the stings and what to do if stung

Crocodile
So you wrestle crocs...

Dingo
Unfairly judged in killing off the thylacine?

Echidna
The wise little gnomes of Australia

Emu
Victors of the great Emu war

Flies
Shaping everything from how Australians speak to how they salute

Funnel Web spider
Yyou'll never leave your ugg boots outside

Kangaroo
Most herbivores don't grow a spine until they are the size of an elephant. Not so the roo.

Snakes
Kill less people than cows

Shark attack Australia
How to ensure you don't go by the name of Bob

Tasmanian Devil
The solution to mainland extinctions?

Tasmanian Tiger
A sad tale

Wombat
Keg of muscle

Quoll
The mainland's largest marsupial carnevore

Mythical creatures
Yowies and dropbears; some say they are myths but those who are not afraid to talk have shared their stories

 

 

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Cane Toad Predators 

Cane Toad

When the ecocystem adapts by itself

Australians are encouraged to kill cane toads. The Australian Government publication, Standard Operating Procedure for the Humane Field Euthanasia of Cane Toads (SOP) recommends this be done by hitting them on the head with a hammer. Some members of the public find this a bit clumsy so instead spray them with dettol, drive over them in cars or hit them with golf clubs. Thus far, the methods have done with little to reduce the estimated two billion cane toads in Australia.

Rather than question the futility of the trying to eliminate two billion toads by killing a few of them, some researchers have instead decided that the important question is whether the hammer is indeed the most humane method. In 2015, Professor Rick Shine led a team from the University of Sydney to find which methods of destruction caused the cane toad the least pain. In justifying the importance of the research, Shine said:

"We need to offer a humane death to the toads - it's not their fault they were brought to Australia 80 years ago - but until now nobody has been sure how to do it," (1)

Shine's team eventually decided that the best solution was,

"Popping toads into the fridge for a few hours to cool down then moving them to the freezer beside the ice cream" 

It is not clear why research funding bodies felt the important scientific question of our age was how to kill toads humanely. Perhaps it is because there is a widely populated myth that toads have no natural predators. Therefore, if humans are not hitting them with golf clubs or putting them in the freezer, then the 2 billion toads that live today will be 5 billion tomorrow. Native fauna will then be decimated and there will be nothing but toads! As Shine inferred, because they have no natural predators, "We need to offer a humane death to the toads."

In truth, the toad has so many natural predators that only 3 in every 10,000 tadpoles grow into adults. (6 )These predators include dragonfly nymphs, water beetles, saw-shelled turtles, keelback snakes, wolf spiders, and freshwater crayfish. In addition, water rats and birds have learnt to eat only parts of the toad, such as tongue, internal organs or legs which contain little poison. Chickens can usually eat cane toads without ill effect as can many water birds that migrate back and forth with Asia where toads have always existed. Putting a toad in the freezer is therefore potentially denying these animals a meal.

As for the myth that the cane toad is pushing native fauna to extinction, in truth, when toads enter a new ecosystem, populations of some predators like goannas, snakes and quolls rapidly collapse before they either learn how to avoid toads or develop some kind of immunity to the toad's toxins. As predator populations collapse, populations of things eaten by predators, such as frogs, actually increase. As yet, not a single species has gone extinct as a result of the toad.

The danger of the myths is that they are being used to justify the CSIRO developing a virus to decimate toad populations much like the CSIRO's myxomatosis virus decimated rabbit populations. If a virus is developed and released, then Australia will really suffer an environmental catastrophe. If the virus causes a rapid crash in toad numbers, all the predators that had been eating the toads will have to hunt native fauna instead, before suffering a decline in populations as well. Toads will eventually develop immunity to the virus and recover. They will then re-enter ecosystems where predator numbers are lower than before, and where they will be even less competitors than before. Although the virus will be a short-term decline in toad numbers, in the long-term, there will be a decline in biodiversity and an increase in toad numbers.

Similar problems were seen with the CSIRO's myxomatosis virus. Rabbit numbers crashed and predators started hunting native fauna before declining in numbers as well.  Rabbits eventually developed immunity to the virus, recovered, and repopulated ecosystems with less predators, less competitors and less biodiversity than there had been before.

Despite being a disaster for natural fauna and flora, the release of the myxomatosis virus could at least be justified on short-term economic grounds. By reducing rabbit numbers on farmland, the virus saved farmers billions in lost agricultural output. The release of a cane toad virus can not be justified on economic grounds because the toad is not harming agricultural output.

Alternative Solutions

The cane toad poses almost no threat to agriculture and may even help farmers by eating large volumes of insects. (Just as it has never been researched whether the toad ate the beetle it was imported to eat, it has never been researched whether toads eat other insect pests.) The main problem is the threat the toads pose to quolls, goannas, freshwater crocodiles, blue-tongue lizards and species of snakes when they first colonise areas.  Hammers, golf clubs or freezers are not going to save these native animals no matter how enthusiastically they are used on toads.

The simplest solution is to do nothing and let nature adapt on its own. This is a bit problematic as it is in human nature to want to do something (which is why golf clubs and hammers have been so popular despite not being effective at removing toads from the ecosystem.) In addition, there needs to be a method that some university researchers can make money. This is essential as the funded researchers will subsequently put out press releases advocating the good work they are doing and in turn urging others to follow their lead. If the money making solution were a virus, then the solution would be worse than no solution. If the solution were the humane use of freezer, then no harm would be done but money would basically be wasted. Ideally, the money making solutions would do more good than bad. The following seem to fit the category as they basically aim to monitor evolution or hasten its rate.

Quolls
Some quoll populations have demonstrated an aversion to eating cane toads and the aversion is inherited (2). Researchers from Melbourne University are breeding  the quoll populations with the intention of re-wilding them and presumably gaining more funding to monitor the outcome.

Freshwater crocodile
Some species of freshwater crocodiles have started eating the legs of the toad where there is no poison.(3) Researchers from Charles Darwin University are monitoring the behaviour of the crocodiles. Potentially, monitoring could be escalated to include breeding and re-wilding.

Red belly black snake
Red belly black snakes have showed some adaption to the toads. Evolutionary biologist Ben Phillips was presumably funded to study toads for his Phd where he found that they have evolved to have smaller heads and longer bodies to hunt toads in a size ratio that allow their bodies to better cope with toad poison (4). Red belly black snakes live in areas where toads will never colonise so there is little need to breed them to ensure the survival of the species. Nevertheless, ongoing monitoring could be a source for funding.

Blue-tongues
Blue tongues exist in higher numbers so it is likely that they too would make a relatively quick adaptation like the snakes and freshwater crocodiles. This appears to have occured with a population of blue tongues who had previously eaten the invasive plant  mother-of-millions (Bryophyllum spp) which has a poison similar to the cane toad's poison. Over 20 to 40 generations, natural selection resulted in the lizards tolerating the plant's poison which also gives it tolerance to the toad's poison. (5)

Funding could be made available to breed and relocate the lizards with immunity. Ongoing monitoring of adaptive behaviour could be a source for funding.

Goannas
Goannas in Queensland have largely learnt to avoid toads. The Queensland goannas could be bred and relocated to other parts of Australia. In areas where toads have yet to colonise, researchers form the University of Sydney have tried to make goannas sick from eating baby toads in order to teach them not eat full grown toads that could kill them. (6) It is unlikely this would help the goanna’s off spring as education is not believed to be genetically inherited in the animal world. After hatching, the goannas would just eat a toad and die. Pragmatically speaking, funding to teach goannas not to eat toads is probably as pointless as funding professors to research the most humane method to kill a toad.

If the goannas mostly die out in an area as expected, more could be bred from areas where behaviour to avoid toads is inherited. These goannas could be subsequently re-wilded. Money could then be allocated for monitoring.

  Potentially there could be scope to introduce the Asian water monitor lizard into Australia to eat cane toads. The species in Australia and Asia are seperated by around 15 million years of evolution. In Asia, the monitor eats an Asian toad that produces the same poison as the cane toad. Therefore, it is immune to the cane toad’s poison and is probably the reason why toads have not invaded the Asian mainland.

Distribution of cane toads. Despite making it throughout the Pacific, the toad has not been able to invade the habitat of the water monitor.

Admittedly, because the cane toad itself failed as a method of biological control, there are many concerned citizens that oppose any form of biological control for fear history would repeat. While the toad was indeed an obvious failure of biological control, Australia does have success. In the 1920s, the Cactoblastis Moth was imported to control the invasive prickly pear and virtually destroyed all populations without any apparent side effects. Sometimes the best response to a mistake is to learn how to do better rather than vow to never try again.

 

Asian monitor lizard (left) and Australian lace monitor (right)

References

1)What is the best way to kill a cane toad? By University of Sydney https://phys.org/news/2015-05-cane-toad.html

2) McKie, Robie “Can science save Australia’s quoll from a deadly diet?” The Guardian Sunday 29th August 2018 https://www.theguardian.com/environment/2018/jul/28/australia-northern-quoll-endangered-cane-toad

3)Terzon, Emma Northern Territory's dwarf crocodiles fighting back against 'toxic prey' by nibbling cane toad's back legs ABC Radio Darwin 17 Nov 2014 https://www.abc.net.au/news/2014-11-17/dwarf-crocodiles-learning-to-fight-back-to-cane-toad/5896738"

4) Salleh, Anna “Cane toads make snakes adapt to survive” ABC Science Tuesday, 30 November 2004 https://www.abc.net.au/science/articles/2004/11/30/1250708.htm

5) Samantha J. Price-Rees, Gregory P. Brown and Richard Shine (Vol. 179, No. 3 (March 2012), pp. 413-422)
Interacting Impacts of Invasive Plants and Invasive Toads on Native Lizards
The American Naturalist

6)Stewart, Anthony “Goannas trained to eat baby cane toads to prevent poisoning by adults before invasion” ABC news 6 Jan 2016, https://www.abc.net.au/news/2016-01-06/monitors-goannas-urvive-baby-toad-exposure-western-australia/7070524

6) Cane Toads in Oz

https://www.pestsmart.org.au/wp-content/uploads/2010/03/CaneToadReport2.pdf

 

Invasive ferals

Carp

Carp and Trout
A tale of two ferals

New hope for Cane Toads
The many unknown predators of the toad

Rabbits
A fence almost 2,000 km long to keep rabbits out of WA? Sounds like a great idea! If it doesn't work, we'll build another one!

The Willow
How a change in its status from asset to weed led to fish kills with blackwater and blue-green algae outbreaks

To bait dingos?
Should the health of the ecosystem be considered or just the kennel club registration?

Koala control
What to do about the "koala plague" on Kangaroo Island

Cat
Apex predator in Australia. Confined to urban areas in America.

Environmental values

Environmental problems
How money and ideology shapes environmental "science."

Bushfire
Australia's Stockholm Syndrome with gum trees.

The Kangaroo industry
Should we eat skippy?

Climate change in Australia
Australia was once covered in rainforest. Could it be again?

Sustainability
The dark side of sustainable environmental policies

Native pets
Why no pet wombats?

 

 

       

Australian environmental science is defined by an ideology that is not unlike a prison warden. There, the scientists are not seeing themselves as part of the ecosystem, but as masters over it; protecting the rights of the species that they say have rights and killing those that they say do not…but inevitably killing both.

"It was always seen as desirable to remove or cull the introduced species. We also need to ask whether it was possible to do so, how it should be done, whether it could have unintended consequences and what it would cost? I don't think anyone really asked those questions." Physicist John Reid - 2012