Physical Characteristics:
The cane toad, or
bufo marinus, is a rather heavily built and ugly
amphibian. The skin on its
dorsal region is a shade of brown, which, depending on each toad, can range from olive-brown to reddish-brown. The skin on the
ventral area can be a shade from white through to yellow and is often speckled with brown spots. The skin is leathery and covered in brown warts, with male toads usually being more coated in the warts than females.
Two of the most distinctive features of the cane toad are its paratoid glands and the dinstinct bony ridges that extend over each eye. The prominent paratoid glands are positioned behind the ears and extend to around halfway down the back. The glands will release a milky bufotoxin (which is basically a poisonous venom) when the animal feels threatened. The toxin can cause vomitting, twitching, shallow breathing, short-term paralysis and may be lethal to its predators. This toxin is also quite capable of killing humans.
The hands and feet of the cane toad are small. Between the toes there are leathery webbing however this webbing is missing between the fingers. Because of its small hands and feet and relatively large body, the cane toad takes short, speedy hops. Their structure makes it unable for them to make high leaps, thus these amphibians only live on the ground.
Cane toads can grow up to 20 centimetres and can live up to 20 years.
Habitat:
Cane toads are usually found in wet and seasonally dry tropics or in warm temperate to semi-arid climates. They can, however, easily adapt to other environments, able to survive in a temperature range of 0 degrees Celsius to 41 degrees Celsius. Providing that an area has a decent supply of water for breeding, suitable temperatures, shelter and a sufficient food supply, cane toads will survive.
Distribution:
Cane toads are the most commonly introduced species of amphibian in the world. Although they have been introduced to Hawaii, Puerto Rico, Florida, American Samoa, the Virgin Islands and Guam, its notoriety is more commonly thought of in Australia. Cane toad infestation in Queensland is so bad, population density is some ten times more than it is in its native home of Venezuela.
Cane toads were first introduced in Gordonvale, a town near Cairns. Over the past 67 years the cane toad has spread across a significant portion of Australia. Their range stretches from the north eastern half of Queensland, northern New South Wales and the Northern Territory. Cane toads are also capable of inhabiting Western Australia, but this hopefully won't happen (if it does) for years.
Introduction:
The toads were initially introduced into the country by the Australian Bureau of Sugar Experiments Station in Gordonvale 1935. More were later released around Cairns and Innisfail. Initially, 3400 toads were released in hope they would control the infestation of greyback and frenchie beetles, whose larvae was causing serious damage to Queensland's sugar cane industry. The beetles couldn't be controlled with the aide of insecticides because there weren't any. The only method that could be used back then was by collecting and removing each beetle by hand. Obviously, farmers weren't keen on the idea of wasting valuable time picking up the beetles.
Farmers all over Queensland supported the move to import cane toads. Scientists did not. They tried to warn people of the risks, but many people felt the benefits outweighed the risks. They also couldn't see any other suitable alternatives.
Impact:
Sadly, the plan of introducing cane toads to eliminate the greyback and frenchie beetles backfired. Instead of eradicating the pests, the cane toad quickly became a pest itself and bred rapidly, spreading throughout the state in a westerly and southerly direction at an alarming rate.
The cane toads weren't very effective because the beetles they were supposed to eat rarely ventured onto the ground. Seeing as cane toads cannot jump high, the beetles weren't readily available for the cane toads to eat. Instead, the cane toads ate other insects and small animals. By 1940, an insecticidal spray was developed to combat the beetles and farmers lost interest in the cane toads.
Because the cane toad found it so easy to adapt to the Australian climate, it thrived. There are no natural predators of the toad in Australia and it seems that most animals who do prey on it are quickly repelled or even killed by the bufotoxin. Aswell as this, they breed extremely fast, with each pair of cane toad able to lay somewhere between 20,000 and 60,000 eggs in the one breeding season. It is also worth noting that a lot of unseasonal breeding has taken place since introduction into Queensland.
There are a large amount of negative impacts brought on by the introduction of this amphibian. There are little, if any, positive impacts. The widespread infestation of the toads is a man-made disaster. Even worse, the toads often compete for food with native Australian frog species and almost always win, and may sometimes eat the frogs they are competing with. A drop in the numbers of native Australian frogs has been blamed on the cane toad.
Control:
While the cane toad is not a declared pest and no one is legally required to destroy a cane toad upon sight, it is encouraged that people help control the toad in a humane manner. In 1989 the Brisbane City council formed a Cane Toad Eradication Committee in hope it would convince residents to help bring the problem under control.
Probably the best method of destroying a cane toad is by freezing it. When this is done, a toad becomes dormant because of the cold and soon dies while asleep.
Another humane method is disposing the toad's eggs. This is quite simple, one only needs to put the eggs into their compost bin or garden, or perhaps even leaving them on the lawn to dry in the sun. However people should be absolutely certain that the eggs they are disposing of are infact the eggs of cane toads, and not of a native frog species.
No one should ever beat a cane toad to death. Apart from being cruel to the toad, bufotoxin may splatter you if you rupture one of the paratoid glands. Spraying the animal with chemicals (eg. bleach, hydrogen peroxide) is not humane behaviour. It may kill a toad quite fast, but the sensation can be similar to electrocution. A cane toad does not deserve to suffer simply because its species has become too widespread.
Today, the search is on for an effective method of biological control. The CSIRO has received plenty of funding in hope that they may be able to develop a way of killing cane toads that native frogs are immune to. Such a task is considered to be difficult and it could be decades before a solution is found.
References cited:
http://www.fbe.unsw.edu.au/exhibits/scientia/wwwjul96/jenkins/mjaustra.htm
http://www2.open.ac.uk/biology/froglog/FROGLOG-15-4.htm
http://rubens.anu.edu.au/student.projects/rabbits/wildanim.html
http://www.biotechnology.gov.au/biotechnologyOnline/environment/PestSpecies/e_TheCaneToad.htm
http://www.ozramp.net.au/~senani/aniausti.htm
http://animaldiversity.ummz.umich.edu/accounts/bufo/b._marinus.html
http://www.csiro.au/index.asp?type=faq&id=CaneToadControl
http://www.env.qld.gov.au/cgi-bin/w3-msql/environment/plant/animals/resultframe.html?id=13
http://www.nrm.qld.gov.au/factsheets/pdf/pest/PA21.pdf
http://www.smuggled.com/CanToa2.htm
http://www.fdrproject.org/pages/toads.htm
http://www.werc.usgs.gov/hq/invasive/toad-frog.html
http://www.agric.wa.gov.au/agency/Pubns/infonote/infonotes/toad.htm
http://members.tripod.com/%7Eiambic_ian/introspecies4.html
http://hometown.aol.com/kphairdeal/introspecies.html