Australia has one of the most unique and isolated natural environments in the world. The continent is teeming with odd-looking animals, interesting plants, and specialized ecosystems. Unfortunately, Australia's isolation makes it that much more susceptible to damage by invasive species.
Australia's war on invasive species began with the arrival of its first colonists from Europe in the 1700s. Many of the animals on this list were brought to Australia to make the country look more like Europe, like foxes and rabbits for hunting. However, in their attempt to make their new country look like home, the colonists put a massive strain on native flora and fauna.
Non-native Australian animals are responsible for extensive damage to the native ecosystems, as well as huge financial loses for agricultural operations. Some, like deer and horses, seem to have become an almost loved part of the landscape, but even they take part in the destruction.
Most invasive species in Australia were introduced with good intentions, but truthfully the introduction of these animals has had many tragically negative implications for the country.
Wild or feral horses in Australia are known as "brumbies." Of all the invasive species on the continent, Australians have the strongest emotional attachment to these equines. Many people have a romantic notion of the wild horses, but in reality they are destroying a very fragile ecosystem.
Thousands of brumbies live in the region known as the Australian Alps, in Victoria. They cause physical damage to the landscape (the only other animals of the same size in Australia are camels and water buffalo, which are also invasive species), and the native plants that they graze on have such a short growth season in the summer that they struggle to grow back.
The Australian government is attempting to implement control programs before the population grows even more, but they have met considerable resistance from animal activists and residents who love the horses.
Although they are native to North and South America, cane toads were released in Australia in 1935. Sugar cane is a large cash crop in Australia, and there were several types of beetles whose larva were destroying the sugar cane as it grew. The toads were released with the expectation that they would eat the beetle larva and save the crops, but things quickly got out of hand.
The toads are prolific breeders, laying between 8,000 and 35,000 eggs at a time, twice a year. They rapidly spread throughout the state of Queensland and into New South Wales, and they had few natural predators. The biggest problem with the cane toad is that it is poisonous, meaning that the native populations of birds, snakes, and lizards that try to eat it are usually killed by its toxins. As a result, native populations of several snake species have been in decline.
To fight back against the toads, the Australian government has come up with a variety of creative plans. One of those is using pheromones to disrupt their breeding cycle, and another is using public participation and awareness to help control the population - during one event in New South Wales, 100 people caught 900 toads.
In 1778, 24 European rabbits were released for hunting purposes in the southern state of Victoria. English colonists were attempting to make Australia as similar to their homeland as possible; they also released other hunting animals like red foxes. They quickly turned into pests, and 150 years later the rabbits are still a major nuisance.
Rabbits spread rapidly across the continent, and in 1907 Western Australia attempted to block the charge by erecting a rabbit-proof fence; it was too late, since rabbits had already spread beyond where they built the fence. The rabbit population had grown to 10 billion by the 1920s (yes, billion), and the little animals were becoming a major problem.
They compete with native animals for food and space; they also eat the sprouts of young native plants, preventing them from regrowing. The Australian government introduced several rabbit-specific viruses starting in the 1950s, which only somewhat stemmed the growth of the population. Today, prevention measures are in place (bringing rabbits across the New South Wales border into mostly rabbit-free Queensland is illegal) and the government is continuing to look into biological options for getting rid of them.
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Red foxes were introduced by British settlers for sporting purposes. They were set loose near Melbourne, Victoria, back in the 1850s, but have since spread to almost every part of Australia. Even the island state of Tasmania is experiencing fox problems, after a more recent illegal release.
Foxes may have thrived after the release of European rabbits, a fellow invasive species. They are seen as a species that has been key in the reduction of Australian biodiversity; they are a threat to "14 species of birds, 48 mammals, 12 reptiles and two amphibians." They also can carry diseases that can be passed to domestic dogs such as mange and distemper, and can have a negative impact on livestock.
In order to manage the red fox population, the Victorian government currently recommends baiting, fumigation, shooting, and exclusion fencing.