Australia has a problem with many introduced species.
Here are a a few.
They arrived in Australia with the First Fleet in 1788, but then more were deliberately released for hunting in the 1800s. The rate of spread of the rabbit in Australia was the fastest of any colonizing mammal anywhere in the world
It is estimated that their presence reduces Australia’s agricultural
productivity by over $200 million each year. Rabbits also have a direct
impact on over 300 threatened species nationally.
Land owners are required by law to keep rabbits under control. We do this by poisoning, shooting and gassing and ripping warrens. Many years ago myxomatosis was released as a biological control. It was effective for a while but then the rabbit population became resistant.
This was followed up by the release of the calicivirus RHDV 1 in 1996. It had a devastatingly successful affect on the rabbit population. But again, resistance began to surface.
Early this year a new strain, RHDV1 - K5, variant was released.
Foxes were originally introduced to mainland Australia in the 1850s for recreational hunting and spread rapidly.
They have few natural predators in the country and pose a threat to livestock, as they prey on poultry, calves, lambs and goat kids.
They are controlled by shooting and poisoning.
We give permission to licensed shooters to come onto our property annually to try to take care of the problem. Being almost surrounded by a National Park, we have a thriving population of foxes around here. It is not unusual to see one blithely trot through our backyard.
The dingo is considered a native dog. They originated in Asia where they were present possibly 10 000 to 14 000 years ago and were derived from wolves. Aboriginal people brought the dingo to Australia approximately 4000 years ago. It is the largest animal predator on the continent and considered a pest by many in the rural community.
But of more concern are domestic dogs that have gone feral. They hunt in packs and can do considerable damage to livestock. They are known to have interbred with the dingo.
Control is by trapping, baiting and shooting. We have a had a few packs around here at times but haven't seen them for some years now.
Cats probably arrived in Australia as pets of European settlers and were later deliberately introduced in an attempt to control rabbits and rodents. Cats now occupy 99% of Australia, including many offshore islands.
Feral cats live, hunt and reproduce in the wild and have adapted to some of Australia’s harshest conditions and invade almost all parts of the continent.
They mainly eat small native and exotic mammals, birds, lizards and insects. About 80 endangered and threatened species are at risk from feral cat predation in the country.
There was quite a colony of them when we moved into this area. Some were very large and aggressive. We eventually got rid of them by shooting (before very strict gun laws came into force in 1996).
Biological control seems out of the question because of the huge number of domestic cats. However we have seen with the rabbit problem pet rabbits can be vaccinated against the calicivirusso maybe there is a similar argument for feral cat control.
One of the most ill conceived biological control plans ever!
The cane toad was introduced into Australia in 1935 to control the native cane beetle in sugar cane which is a major agricultural crop. 102 were released in northern Queensland
It was a complete failure.
The cane beetle remained a pest and the cane toads thrived. Today the population is estimated at 200 million. They are making their way across northern Australia in a westerly direction at a rate estimated at 60km per year.
Cane toads naturally generate potent toxins (bufodienolides)
throughout their bodies, which act by stopping the heart of most animals
that attempt to eat them.
The cane toad is often cited in surveys
as Australia’s most hated invasive animal taking over from the rabbit.
They are listed as a ‘key threatening process’ under Australia’s
Environment Protection and Biodiversity Conservation Act 1999 as they
adversely impact native species via predation, competition and poisoning
by lethal toxin ingestion.
The Department of the Environment and Energy has stated "There
is unlikely to ever be a broad scale method available to control cane
toads across Australia. Researchers are beginning to understand the
toad’s impact on native fauna and to appreciate the ways in which native
species are adapting to the presence of cane toads and recovering from
the impact of their arrival."
It is likely that the lessons
from the cane toad debacle have influenced the strict quarantine laws
and risk assessment procedures Australia has in place today as anyone arriving at our international airports would know.
They have yet to arrive in our part of the country. But I have seen seething masses of them in suburban backyards in my old stomping ground Brisbane.
And then Australia also has problems with camels (yes, really!), wild goats, wild pigs, deer, water buffalo, wild horses (brumbies), carp, rats and mice.
But we might leave some of those for another time.