The domestic house cat (felis catus) has gone almost full circle in its development, from wild cat (felis sylvestris) to that that cuddly lap mop and back to a feral wild thing wreaking havoc all over the world.
Australia is particularly hard hit as an estimated six million feral cats roam the island continent killing native species and contributing to Australia’s shocking extinction rate in which four mammal species are lost a decade. Along with introduced European rabbits and other invasive species cats are now squarely in the sights of a beleaguered nation. Housecats, rabbits, dromedary camels, deer, horses, wild pigs, foxes and water buffalo all have been released in Australia causing various levels of destruction, with house cats among the most destructive.
Despite normal control efforts – catching, killing and poisoning, they seem to be getting ahead of control efforts. After all, a “Queen” can breed at six months, deliver two to three litters a year and breed for about ten years. Each litter contains three to five kittens on average. Although they are only mid-level predators with enemies including snakes, dogs, other canines, hawks owls and other creatures, the survival rate is good. Australia, with a long list of vulnerable endangered animals, is very worried. House cats are excellent hunters and prey on anything from insects up to prey slightly larger than rabbits. An estimated 1,000 species of prey, all told.
The worries have been worsened by the recent fires which authorities fear will benefit the cats because the burned over land will make it easier to find, kill and eat some of the more helpless animals on the island continent.
Australian scientists at CSIRO, Australia’s national science agency, are therefore sounding the alarm and looking into genetic control as a means of stopping the feline invasion and working to reduce the other invasive animals as well. A recent report by the organization highlights genetic control as a means of saving native species. Genetic control involves methods such as introducing genes to make the species more susceptible to disease, or sterilizing large numbers of individuals or causing all births to be of one gender. The CSIRO report thinks cats are a potential target of genetic control. The report stresses the long-term nature of the battle and the need for national commitment. Not an immediate fix
The technique of genetic control is probably most familiar due to work with insects. Starting in the 1930’s scientists Edward F Knipling and Raymond C. Bushland investigated ways to control the screw worm fly, which lays eggs in the flesh of living animals. The eggs are usually laid near an open wound or cut and the eggs hatch quickly and the larvae exploit the wound. The animals suffer enormously and can die if not treated. Treatment involved cleaning the wound, removing larvae with tweezers and continuing to treat the wound. The two men realized controlling the insects was the best strategy. After World War Two the scientists found ways to use radiation to sterilize the flies without killing them or otherwise changing their behavior. Millions of sterile flies were captive raised and then released. They mated with regular females who did not lay fertile eggs. Since the females only mated once, the number of fertile eggs laid eventually reached near zero. The method was tested in Florida and brought to Texas. Screwworms were eradicated in Texas by 1966 and have been eradicated in Mexico and several Central and South American countries since then. Their work has been hailed as one of the greatest success stories in insect control and the peaceful use of atomic power. Screw worms remain a problem in other parts of the world and veterinary scientists remain alert for outbreaks.
Whether Australians, or other people around the world will be as comfortable with genetic altering of cats, horses, foxes and rabbits remains to be seen. Other forms of genetic alteration technology, such as genetically altered food, have faced serious public criticism and many humans remain sceptical and wary of genetic alteration technology.