Environmental

Trends of population that has invaded the territory. The effect of the of the population on the territory. Look for an invasive species. Introduced accidentally. Effect of this species on the territory. Predict long-term effects using past data. Australia – cane toad Before 1935, Australia did not have any toad species of its own. What the country did have however, was a major beetle problem. Two species of beetles in particular, French's Cane Beetle and the Greyback Cane Beetle, were in the process of decimating the northeastern state of Queensland's sugar cane crops. The beetle's larvae were eating the roots of the sugar cane and stunting, if not killing, the plants. The anticipated solution to this quickly escalating problem came in the form of the cane toad. After first hearing about the amphibians in 1933 at a conference in the Caribbean, growers successfully lobbied to have the cane toads imported to battle and hopefully destroy the beetles and save the crops. The plan backfired completely and absolutely. As it turns out, cane toads cannot jump very high, only about two feet actually , so they did not eat the beetles that for the most part lived in the upper stalks of cane plants. Instead of going after the beetles, as growers had planned, the cane toads began going after everything else in sight--insects, bird's eggs and even native frogs. And because the toads are poisonous, they began to kill would-be predators. The toll on native species has been immense. the Green and Yellow bell frog, (litoria aurea). If the predicted effects of global climate change hold true for Australia, scientists suggest that the cane toad's range will expand into pockets of Western Australia and as far south as Sydney as a whole within the next 20 years. Researchers hypothesize that when the cane toads are introduced or spread into a new area, they gorge themselves on the sudden new unlimited or uncontested food supply and grow quite large. After some time in the same place, the environment is never fully able to restore itself to its former bounty, the future generations of cane toads do not have as much to eat and so none grow as large as their predecessors -- australia’s carrying capacity. This may be due especially to its impressive breeding capacity. Females lay between 8000 and 35000 eggs at a time and do this usually twice a year, with wild toads living up to five years. Approximately 0.5 percent of cane toads hatched from eggs survive to reach sexual maturity and reproduce. There are also certain developmental factors that give cane toads a specific advantage over other species. The tadpoles of cane toads develop faster than many endemic frog species, so these young can out compete the native juveniles for food. Also, in all stages of development, the cane toads seem to be more resistant to ] herbicides and eutrophic water that would generally kill frogs and their young. Further, cane toads can tolerate salinity levels up to 15 percent. The most profound advantage cane toads have over native species however, both prey and predator alike, is their toxicity. Fish that eat the tadpoles die; animals that eat the adult toads die. Cane toads can even poison small amounts of water such as pet water dishes, causing animals to get sick without even having direct contact. Some native bird and rodent species are learning how to eat the toads without fully exposing themselves to the toxins by killing the toads and then turning them over onto their backs. By pulling away the soft skin of the belly and eating only the mildly but not fatally poisonous internal organs, the animals avoid the skin and the toxin-producing parotoid glands, keeping death at bay. The predators, not the prey, are at the highest risk. Currently, the Australian government is preparing to spend between five and seven million dollars over the next 15 years to combat the cane toads. In 2004, a National Cane Toad Task Force was established and the government has also sponsored a design contest that aims to develop a more selective trap, to avoid catching more welcome creatures in addition to the toads. Methods of extermination One approach that is being explored involves infecting cane toad tadpoles with an engineered virus that would immunize them against a protein their bodies make when they become adults. As the toads mature and begin producing the protein, their immune system will theoretically recognize and begin attacking the protein, killing the toads. Another intriguing possibility that those opposed to genetic experiments hope scientists pursue is the study of the Lavender Beetle. Common in the Northern Territory, the Lavender Beetle is apparently poisonous to amphibians. Endemic frogs know to avoid the beetle, but cane toads do not, and when they eat the insects, they die. http://news.mongabay.com/2005/0417-tina_butler.html