The kangaroo shooter at work is one of the less palatable images of Australia. Using the door of his four-wheel-drive to steady his arms and his aim, he calmly cuts down the graceful, hopping creatures caught in his lights. He and his colleagues fill an annual quota set by the government at about three million red and grey kangaroos a year, for an industry that uses them mainly for leather and pet food.
The international response to this killing--campaigns in North America and Europe to place kangaroos on various lists of endangered species--never ceases to puzzle Australians. They know that a combination of the provision of well water for livestock in Australia's arid outback and the removal of dingos has increased kangaroo numbers. Although roo numbers vary greatly depending on rainfall, the long-term average population of reds and greys is about 20 million. And most marsupial biologists agree that figure is as high as it has ever been.
Perhaps some confusion over the status of the large kangaroos comes from the existence of the many other species of macropods inhabiting Australia and New Guinea--nearly half of which are considered vulnerable. At least six species are extinct. But none of the five large species open to roo shooters are in trouble.
The bigger kangaroos are little affected by predators. Relatively numerous, they are viewed by farmers and ranchers as pests that bash down fences, cause erosion and compete with stock for food. The extent and management of this kangaroo "problem" varies according to habitat and farming practice. In the arid rangelands of western Queensland and New South Wales, and in central and western Australia, for example, kangaroos tend to form a continuous population. The breeding of the dominant red kangaroo is aseasonal, with numbers geared to unpredictable rainfall. The traditional control method is to call in the shooters, who must be licensed and are allowed access only to five "commercial" species, for which quotas are set.
In national parks and the higher rainfall areas, the problem tends to be an abundance of grey kangaroos, which live in islands of woodland or bush interspersed with farmland, where they feed. Overpopulation impacts not only farm production but also the kangaroos themselves, causing increased starvation and disease.
"Shooting tends to remove adults, but the population quickly compensates," says zoologist Graeme Coulson at Melbourne University. "So you're looking at an ongoing process."
The alternative is to control fertility with options including sterilization by surgery, use of hormones to interrupt the breeding cycle, use of drugs to interfere with lactation--or even immunization of females against their own reproductive hormones, their own eggs or sperm from their own species.
So far in Australia, there has been only a single, high-profile case of broad-scale fertility control. Four years ago, 163 kangaroos were damaging the vegetation and soiling the lawns of Yarralumla in Canberra, the residence of the head of state. All the animals were captured, and 14 males were given vasectomies.
The other males and many of the females and young were removed, leaving 45 members of the present, stable, nonbreeding population. Researchers are hoping soon to begin a field trial of hormonal contraceptive implants in adult female grey kangaroos in the buffer zone parkland surrounding an aluminum smelter at Portland in western Victoria.