submitted by Alex Grier   Class of 2004

Introduction of Alien Species - The Cain Toad

        The introduction of alien species has had devastating effects on many habitats all over the planet.  Cane Toads have been a problem in Australia ever since they were introduced to the sugar cane plantations of North Queensland in July 1935.  Cane Toads were introduced to Australia to eat French's Cane Beetle and the Greyback Cane Beetle. The 'whitegrub' larvae of these beetles eat the roots of sugar cane and kill or stunt the plants. The Australian Bureau of Sugar Experimental Stations imported about 100 toads from Hawaii to the Meringa Experimental Station near Cairns. The toads bred quickly and more than 3000 ended up being released.  

        Cane Toads occur throughout the eastern and northern half of Queensland and have extended their range to the river catchments surrounding Kakadu National Park in the Northern Territory. In New South Wales they occur on the coast as far south as Yamba, and there is an isolated colony near Port Macquarie.  Female Cane Toads can lay up to 35,000 eggs at a time, and can do it twice a year.  The eggs hatch within 24-72 hours, and about 0.5% of them reach the age of sexual maturity.  The tadpoles can mature into toadlets in as little as three weeks, and once they become toadlets they have very few predators due to their poison.

        The spread of Cane Toads is out of control in Australia, and there are several reasons that their high numbers are such a problem.  They poison pets and injure humans with their toxins, they poison many native animals whose diet includes frogs, tadpoles, and frogs’ eggs, they eat large numbers of honey bees creating management problems for bee keepers, they prey on native fauna, they compete for food with vertebrate insectivores such as small skinks, and they carry diseases that can be transmitted to native frogs and fish.

        Cane Toads are an immediate and severe problem that must be addressed.  Scientists at the CSIRO Animal Health Laboratory in Victoria have been searching for biological controls of Cane Toads and in 2001 they began investigating gene technology as a mechanism of control. Scientists at the University of Adelaide have isolated a sex pheromone in a native Australian frog; they hope that a similar pheromone will be found in Cane Toads and that it could be used to disrupt their breeding cycle. The main controls on the spread of Cane Toads in southern Australia are quarantine checks and public awareness and response. One publicity campaign on the north coast of New South Wales resulted in 100 people collecting more than 900 Cane Toads. Toads can be excluded from garden ponds and dams by a 50 cm high barrier such as a thick hedge or a wire mesh fence.

        Cane Toads pose an extremely difficult problem to deal with, because they reproduce so well, have so few predators, and can eat almost anything.  For this reason I believe that the most effective way to combat the Cane Toad in Australia would be an extremely large scale, government supported effort by the people.  Like the one in New South Wales, except in this case the government could offer a cash reward for a certain amount of toads.  If 100 people could collect 900 toads without monetary motivation, I think that a national effort that was highly publicized would have a substantial effect.  While this is an extremely costly and time-consuming proposal, it seems to be one of the only plausible solutions to the problem at this stage.

Source

Name: Australian Museum Online

Article: Cane Toads, Giant Toads or Marine Toads

 Address: http://www.amonline.net.au/factsheets/canetoad.htm