Steve
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The Cane Toad

The Cane Toad, Bufo Marinus, was introduced to Australia to control the Greyback Cane Beetle,

Dermolepida albohirtum, and Frenchi’s Cane Beetle, Lepidiota frenchi.  Both these beetles are native Australian animals.  There was no effective method of control for these pests in the 1930’s. 

Biological Control

In 1926, after extensive testing the moth Cactoblastis cactorum was introduced to control Prickly Pear.  It was an amazing success.

It seemed natural to some government scientists to repeat this success with a predator that would eat the beetles damaging the Sugar Cane crops.

The Cane Toad is native to the central part of the two American continents from the southern United States to tropical South America.  They had been introduced to Hawaii and had helped to control Sugar Cane pests there.  It seemed logical to introduce it to Australia.

Protests

There were quite a few protests about introducing this animal.  Some of the protesters were extremely well respected scientists.  They failed to prevent the initial release.  They did succeed in slowing the continued introduction although it was renewed later.  This moratorium was pointless in retrospect because once it was released it would have been very difficult to stop the Cane Toad.

Effectiveness

It is often stated that Cane Toads failed to control the pests it was introduced to control, but the statements like this that I have seen have not cited any research into the effectiveness of the control.

Diet

Cane Toads are mostly carnivorous.  Their main prey is insects but they will eat a wider range of foods than many frogs.  They also eat small vertebrates, carrion, pet food, household scraps, etc.

Their diet includes native frogs.

Poison

Cane Toads are poisonous at all stages of their life cycle. But percentage of poison in their body varies enormously.  The eggs are very poisonous and frogs and fish which eat them will normally die quickly.

After they metamorphosise into little toads, they have much less poison.  The adult Cane Toads are very poisonous.

Deaths

No Humans in Australia have been recorded as being killed by Cane Toads.  World wide there have been two Human deaths from Cane Toad poisoning.

Our native mammals, amphibians, fish and reptiles have not done so well, and millions of them have been killed.  However, although the numbers of some of these predators have been greatly decreased, in areas where Cane Toads have been established for many years, the numbers of the native predators seem to be increasing again.

Birds seem to be much less affected by the poison.  Invertebrate predators like the Meat Ant appear to be immune.  I have not seen much research concerning invertebrate aquatic predators of Cane Toad tadpoles and eggs.

Extinction

When it was realised how dangerous Cane Toads were to the Australian environment, it was predicted that several species of the already threatened native predators would become extinct.  So far there is no evidence of any extinctions being caused by the Cane Toad.

This is in contrast to the extinctions caused or contributed to by the Fox.

Breeding

Cane Toads have separate sexes.  The fertilization is external.  A reasonably big female Cane Toad can produce 30,000 eggs at a spawning.  Probably most only spawn once a year although it is likely that some will spawn twice.

This is a high rate of reproduction.

Many people who are studying this Toad think that extermination is impractical, but control both of the numbers of Toads and of the damage they do is possible.

Native Predators

Personally I am not in favour of introducing any new foreign predators to control this animal, but there are some native ones.  One that seems particularly promising is the Meat Ant.

Meat Ants

Meat Ants kill a large number of baby Toads near the water’s edge.  Native frogs will hop away when they see a Meat Ant, but the Cane Toads have no built in defence.  Once they are seized by a Meat Ant they are liable to react with immobility.  Even the ones that do escape their insect attacker usually die within 24 hours.

By the simple method of putting some tinned pet food in the area the baby toads will come out, more Meat Ants are attracted.  They can eat most of the babies.
 
Crayfish
 
Some native crayfish including those of the genera Cherax and Euastacusa eat the cane toad tadpoles.

Birds

Birds are more mobile than mammals.  Many of our birds have come from Asia.  In Asia there are native toads.  Not identical to the Cane Toad, but their poison is sufficiently similar that birds with resistance to the Asian toad poison also have resistance to the Cane Toad poison.

Several Australian bird species have learned way of safely eating even large toads.

Sources

http://australianmuseum.net.au/Cane-Toad

http://www.jcu.edu.au/school/phtm/PHTM/staff/rsbufo.htm

http://www.canetoadsinoz.com/

http://news.bbc.co.uk/2/hi/asia-pacific/6498137.stm

http://www.canetoadsinoz.com/canetoadsex.html

http://www.canetoadsinoz.com/babytoads.html

http://www.canetoadsinoz.com/invasion.html

http://www.canetoadsinoz.com/stowaways.html

http://www.canetoadsinoz.com/biodiversity-impact.html

http://www.canetoadsinoz.com/toadevolution.html

http://www.canetoadsinoz.com/evolutioncausedbycanetoads.html

http://www.canetoadsinoz.com/debunkingcanetoadimpactmyths.html

http://www.canetoadsinoz.com/debunkingcanetoadcontrolmyths.html

http://www.canetoadsinoz.com/killingtoads.html

http://www.canetoadsinoz.com/currentcontrols.html

http://www.canetoadsinoz.com/newideasoncanetoadcontrol.html

http://www.canetoadsinoz.com/othercontrolideas.html

http://www.canetoadsinoz.com/otheraustralianresearchers.html

http://www.canetoadsinoz.com/reducingimpact.html

http://www.canetoadsinoz.com/teachertoads.html

http://www.canetoadsinoz.com/controlfeasibility.html

http://www.canetoadsinoz.com/foggdam.html

http://www.canetoadsinoz.com/teambufo-at-foggdam.html

http://www.canetoadsinoz.com/toad-eating-frogs.html

http://www.canetoadsinoz.com/canetoadsintimor.html

http://www.canetoadsinoz.com/meatants.html

http://www.nt.gov.au/nreta/wildlife/animals/canetoads/index.html


 
Cane Toads in Cairns
Photo by Tom Challis AB
 
 
Distribution of the Cane Toad in 2006


 
The Cane Toad is speading west at about 50 Kilometres a year, and south at about 10 Kilometres a year.
Map by Froggydarb at the English language Wikipedia [GFDL (www.gnu.org/copyleft/fdl.html)], from Wikimedia Commons.
This file is licensed under the Creative Commons Attribution ShareAlike 3.0 License.
 
 
Northern Quoll
By Wildlife Explorer (Picasa Web Albums) [CC-BY-3.0 (www.creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
This file is licensed under the Creative Commons Attribution 3.0 Unported license.
 
 
Meat Ant
Photo by  Vicki Nunn