The Kangaroo industry
In North America, the feral cat poses no threat to the native ecosystem because predation from the Coyote has kept it confined to urban areas. In Australia, the feral cat inhabits the entire continent from the snowy highlands to the arid interior and is pushing Australian birds, reptiles and marsupials towards extinction. It is only in Tasmania (where the Devil controls it like a Coyote) where the cat is not a huge ecological threat
But Australia was not always the cat paradise that it is today. It is quite probable that over the last 10,000 years, the cat was introduced by successive waves of Indonesian, Chinese, Portuguese and Dutch mariners. However, it seems that the cat found it difficult to take hold in an ecosystem containing Devils, Dingos, Thylacines (Tasmanian Tigers) and nomadic Humans.
Aside from being small, the cat's main disadvantage was that it had very little endurance. Any Devil, Thylacine or Dingo that followed their trail would have found it easy to either catch them or at least, chase them off their kills. Even humans have found them easy to track. Today, Aboriginal groups have shown how easy they are to catch. If the land is flat, they simply follow their prints. Once they draw close, the cat makes a sprint but then gives up. They are then easily clubbed and turned into a delicious meal.
When the English introduced the cat in 1788, it was into an ecosystem in which Devils and Thylacines had recently become extinct, and the local Humans were soon to stop living a nomadic existence. This allowed the cat to enter near the top of the food chain with few competitors or other animals hunting it.
As well as being aided by a lack of competitors, the cat was aided by Humans deliberately releasing them into the wild in order to control rabbits and mice. Although the cats did quite a good job keeping the rabbits and mice under control, they also preyed upon native birds, marsupials and lizards that had not evolved defences to it. This led to mainland Australian suffering a significant decline in ecological biodiversity.
Thankfully, the island state of Tasmania had the Devil, and this helped the local ecosystem resist some of the negative attributes of the cats. The Devil is primarily a scavenger. It has evolved a good sense of smell to find dead animals, and powerful jaws to chase any other carnivore off the carcass. In Tasmania, Tiger Quolls do most of the hunting of live animals, only to then find the Devil following their trail, and then chasing them off their kills. Since being introduced to Tasmania, the cat has found itself in a similar position to the Quoll. It hunts, and is then chased off its kill by Devils. Cat remains have also been found in Devil stomachs. This may indicate that the cat's lack of endurance has been exploited by Devils.
Being constantly chased off their kills, and/or eaten, has resulted in Tasmania having by far the lowest cat concentrations in Australia. As a consequence, Tasmania has not lost a single marsupial, with the exception of the Thylacine, since colonisation. (Fortunately for the cat, Tasmania has lots of trees that allows it to escape. Cats on the Australian plains would really struggle against a Devil.)
On mainland Australia, significant money has been spent on Cat eradication programs. The use of 1080 is a favoured method. 1080 is a synthetically produced substance that is a replication of a naturally occurring poison found in plant species such as poison bush, kite leaf poison bush, poison pea, and wallflower poison bush. Although native animals can eat the foliage, seeds and flowers of the plants with no ill effect, it is deadly on the feral animals that have not evolved alongside it.
Despite the impressive science behind it, it is very expensive, and for a country of 7,600,000 square kilometres, it has zero chance of success because it can't overcome the vacuum effect. Once Cats are removed from a region, more simply migrate in. For this reason, using it just slows the process of an ecosystem reaching a sustainable balance with the change.
There are also large areas of Australia where poisoning can not be used. These areas include farming land, urban communities and any area when poison bush doesn’t occur naturally. Farmers don't want local Cat populations eradicated because to do so would result in plague populations of rabbits and mice. Although constant poisoning and warren ripping regimes are in an ecologist's interests for they bring with them funding, they are not in a farmer's interests as they are expensive and time consuming. The Cats do a better, cheaper, and more sustainable job. As is to be expected, different agendas have led to some heated division between ecologists and farming communities. Ecologists refer to the farmers with all manner of unsavoury insults, while farmers tell the ecologists to do something useful with their lives.
In defence of farmers, sometimes ecologists really act like idiots as they implement their ideologies. The removal of feral species from Macquarie Island is one of the best examples of ecologists wrecking the ecosystem in the process of trying to turn it back to 1788. Cats, rabbits, and rats were first introduced in the 1860s. Although the cats hunted some native birds, a new balance was formed in which all species were relatively assured of survival. Almost a century later, the myxomatosis virus was introduced to eliminate rabbits. As Rabbit numbers fell, Cats turned to native birds. With each new myxomatosis outbreak, the ecosystem was pushed into chaos, with cat numbers exceeding available prey. Some native birds were then hunted to extinction by the starving Cats.
To deal with the problem of cats, scientists asked for $500,000 to eliminate a feral population of around 500 cats. Meanwhile, rabbits were building up their immunity to myxomatosis. When the final cat was removed in 2000, rabbit numbers were between 4,000 and 20,000. Within 6 years, the population had reached 130,000. To make matters worse, the elimination of cats also led to population explosions of rats, which in turn ate the bird eggs and chicks.
Land slip caused by exploding rabbit populations
Recognising the futility of the poisoning regimes promoted by some ecologists, some scientists have taken a more holistic approach to the issue. Professor Chris Johnson, from James Cook University, has argued in favour of reintroducing Dingos, Quolls and the Devils to the various mainland ecosystems that humans have eradicated them from. Professor Johnson has stressed that native predator communities need to be rebuilt because they have the ability to remain in balance with native prey. As native predators replace the feral predators, or reduce their numbers, native prey is able to rebound.
Wednesday, 11 July 2007
In regards to how the Dingo would go against the Fox and the cat, Professor Johnson has some interesting research backing up his proposal. He has found that in places where Dingoes are rare or absent, and foxes and cats are abundant, 50 per cent of ground-living mammals have vanished. Where Dingoes remain abundant, the rate of local disappearance is 10 per cent or less.
Even though Devils would be more than capable of holding their own in a fight against a dog, fox or cat, some concerned citizens fear that if the Devils were reintroduced, they would prey on native fauna. One of these concerned citizens is Sarah Hartwell, who wrote:
As Hartwell quite rightly feared, a wild animal can’t be trained to kill one animal and not another. It will kill what it is capable of killing. In Tasmania, Devils are scavengers because they are slow and cumbersome. They do; however, have powerful jaws and a keen sense of smell. Contrary to stereotypes, the cat fares poorly when compared to native predators. It has very weak jaws and very little endurance. Furthermore, whereas the pouch allows marsupial predators to be very mobile with their young, the cat is forced to leave their kittens unprotected as it goes to hunt. The cat’s main advantage is a symbiotic relationship with humans. Because it lives in the family home, or on the family farm, if it is ever eradicated from the wild due to a drought or other changes in conditions, the urban landscape acts as an oasis until the good times return. It can then recolonise. Furthermore, the urban cats can breed with the feral cats to increase genetic diversity and strengthen the species as a whole. On the other hand, the marsupial predators do not have a symbiotic relationship with humans thus do not have an urban oasis to retreat to in times of difficulty or gain access to fresh genetics.
Bush fire prevention