Invasive Species Australia - How Much Damage Do They Cause?

Australia has a huge problem with introduced species. The world has become a much smaller place over the last few hundred years and human beings have been travelling around and migrating to other countries in unprecedented numbers. Wherever humans go they tend to take their animals with them; their pets, their farm animals and animals needed for transportation. Some animals even arrive uninvited, having hitched a lift on ships or in cargoes.

These animals either escaped or were released into the wild, and it is only in fairly recent times that the damage they have done to native species and the local environment has been acknowledged and attempts to protect the native species have been attempted. One of the best examples here in the United Kingdom is the Grey Squirrel. They were introduced here from America around the turn of the twentieth century, and as they are bigger and much more aggressive than the native Red Squirrels, they have driven them out of much of their territory. Now only pockets of Red Squirrels remain in the remoter regions of the country.

When European settlers first started arriving in Australia in the late eighteenth century, they found a pristine environment teeming with unique animals and plants. Australia has many diverse habitats and climatic conditions, and encompasses everything from tropical, wetland species to cooler alpine species. The settlers brought with them their domestic animals, such as cattle, horses, sheep, pigs and goats, their pets such as dogs and cats, and creatures such as rats and mice that had come along on the ships they arrived in. As times went by, even species like foxes were introduced so that the landed gentry could be reminded of their home land and carry on hunting as they had always had.

So let us have a look at some of the introduced species and see when they arrived and what impact they have had on the environment and habitats of Australia.

A lot of people think that dingoes are native Australian animals, when in fact they only arrived four to five thousand years ago. It is believed that they came from South East Asia and are assumed to be descended from domestic dogs. However, in Australia they established themselves in the wild and swiftly became the apex predator. Before European settlement they were the only placental mammals in Australia apart from humans.

Dingoes are highly sociable animals that live and hunt in packs, and are highly territorial. The number of individuals in a pack varies, but is usually between 3 and 14. The pack will usually consist of an alpha male and female, and their offspring. Dingo females produce one litter a year, and the alpha female will kill the offspring of other females in the pack if they breed. It is believed that the most genetically pure dingoes are those living on Fraser Island, as on the mainland interbreeding occurs with domestic and other feral dogs.

Dingoes have some interesting physical characteristics. They have wrists that are unique in the canine world as they can rotate, their ears are permanently erect, and they can turn their heads almost 180 degrees in each direction and howl rather than bark. Probably the most famous dingo vocalisation in the world comes from Dinky who regularly ‘sings’ when someone plays the piano at Jim’s Place in the Northern Territory.

It is suspected that the arrival of the dingo had an impact on the ecology of Australia. Its arrival has been connected to the demise of the thylacines also known as Tasmanian Tigers, Tasmanian Devils and the Tasmanian Native-Hen from the mainland.

Camels were first introduced into Australia in the nineteenth century with the first – called Harry – arriving in 1840.  They were introduced as a means of transport, especially suited to the desolate, desert regions.  Indeed the famous train that runs between Adelaide and Darwin, via Alice Springs is known as the Ghan, short for Afghan Camel Train and refers to a camel route that used to run from the railhead at Oodnadatta in South Australia to Alice Springs before the rail line was extended.  Camel racing also became popular and still goes on today.

Populations of camels were soon established in the wild from escaped or released animals and it is now estimated that there are now over 1,000,000 feral camels distributed over the Northern Territory, Western Australia, South Australia and the north eastern part of Queensland.  Camels do not cause as much damage to the terrain as the hoofed animals that have been introduced, as their feet are adapted for desert and scrub conditions and have soft pads.  However, they do eat most plant species and can deplete the local supplies if there are too many camels in one area.  They also destroy taps, pumps and cattle watering facilities in their search for water and can damage salt lake ecosystems and sand dunes, destroy fences and degrade water holes.

Pigs were introduced into Australia by the early European settlers and inevitably some escaped or were deliberately released. It is estimated that there are now over twenty three million feral pigs living in the wild in Australia, mainly distributed in New South Wales, Queensland and the top of the Northern Territory. Feral pigs are highly destructive to the environment as they root for their food and rip out plants by their roots. This destroys the native ecosystems as it is very difficult for the native plant life to re-establish itself, which leads to soil erosion and weeds taking over. Feral pigs are also opportunistic predators and scavengers and can decimate local populations of reptiles, birds, bird’s eggs, insects and small mammals.

As pigs are susceptible to the heat, they are drawn to water holes, rivers and wetlands, and again, their wallowing and digging behaviours are highly damaging to sensitive ecosystems and native species. They also have the potential to carry and spread a lot of diseases such as Foot and Mouth, leptospirosis, encephalitis and brucellosis.

Feral pigs also cause a great deal of damage to Australia’s agricultural industry, as they damage fences, pasture, water supplies, and prey heavily on lambs and goats.

Cattle were also introduced into Australia by the early European settlers and vast tracts of the country are now used as cattle stations containing huge numbers of cattle. As we have seen before, some of these cattle escape or were released and have formed wild populations. As cattle are a hoofed animal they cause a great deal of damage to the fragile soil and ecosystems of Australia, causing soil erosion They are also big animals so do damage to trees and shrubs as they move around the bush and can destroy riverbanks and the edges of water holes by churning them up with their hooves. As herbivores, they also consume a large quantity of native plant life, thus depriving the native species and depleting the environment.

Water buffaloes were introduced into the northern parts of Australia in the nineteenth century to supply meat to remote areas. The buffaloes were abandoned and they then bred in the wild and spread rapidly. Their numbers soared and they destroyed precious wetland environments and spread diseases. Mass culling, in the form of The Brucellosis and Tuberculosis Eradication Campaign, was introduced in the 1970s and early 1980s and the numbers of feral water buffaloes in the wild has severely declined.

Many smaller introduced species have also been incredibly destructive. Foxes and cats devastate populations of native wild life, and mice and rats get into grain stores, destroy crops and compete with native species for food and space.

Rabbits have spread across most of Australia, despite the 1700 kilometre Rabbit-Proof fence being constructed in Western Australia. Rabbits destroy plants and shrubs; compete with the native species and cause soil erosion.

Probably the newest arrival is the Cane Toad, which was introduced in the 1930’s to eat the beetles that were ravaging the sugar cane crops in Queensland. They failed to contain the beetles and are now spreading over ever growing swathes of Australia. They are harmful to native species as they are highly venomous and when another animal attempts to eat them they die of poisoning, they also prey on native species and compete with native amphibians for living and breeding space in ponds and water courses.

Feral animals in Australia are controlled by a number of methods including traditional methods such as fencing, shooting, poison baits and trapping and using biological controls such as introducing species-specific diseases and using contraception to slow down breeding. Much emphasis is now placed on control programmes being humane and causing as little suffering to the animals as possible, and also taking into consideration how they may be now important in the ecosystem or economy in some local areas. After all, it is not their fault that they are there!

Not all attempts at control work, for example an attempt to control rabbits with a disease called mxyomatosis was attempted in the 1950s, which proved to be initially successful but resistance to the disease has built up in the rabbit population. Great attempts are now made to preserve existing pristine ecosystems, such as those on islands; as these are often the last colonies of some native species. There are also some big projects, such as Project Eden on the Peron Peninsula in the Shark Bay area, where major attempts are being made to root out all feral animal and plant species and return the area to an entirely native ecosystem. An electric fence has been built at the neck of the peninsula to stop any more feral animals gaining entry and human traffic enters over a cattle grid that emits the sound of a dog barking when weight is placed on it to deter feral animals from crossing the grid. Existing native species are now thriving and other native species are slowly being re-introduced. You can even join in and experience feral animal control as there are tour companies that take tourists out trapping feral pigs or even shooting feral bulls!

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