Predatory Dingoes Promote Diversity

June 30, 2009 -- The world's longest fence stretches for 5,000 kilometers (more than 3,000 miles) from one side of southern Australia to another. The fence was designed to keep sheep-eating dingoes out of a third of the country, but the barrier has had some other surprising consequences.

On the dingo-free side of the fence, according to a new study, overall biodiversity is actually lower than it is on the side where dingoes are free to roam. The research suggests that invasive predators, once they've established themselves, play an important role in the food web and might actually be good for conservation.

The finding could affect efforts to both control and reintroduce predators in other parts of the world, too, including wolves in the western United States.

"There's an idea that introduced predators are altogether bad and cause these catastrophic extinctions," said Mike Letnic, an ecologist at the University of Sydney in Australia. "Our results clearly show that this introduced predator species has a positive ecological role that is contrary to its classification as a pest."

Dingoes were introduced to Australia 5,000 years ago and promptly replaced the Tasmanian Wolf, a marsupial, as top predator. From 1900 to the 1960s, the country built a six-foot tall wire fence through deserts and mountains, from the southern coast to the northeast of Brisbane, to keep the dogs away from sheep and other livestock. Since then, ecosystems on either side of the fence have diverged in striking ways.

Related Content:

• Evolutionary Experiments Gone Wild
• Treehugger.com: Australia: The Politics of the Environment
• HowStuffWorks.com: Dingo
• More Discovery News

Some of those differences are obvious. There are noticeably more kangaroos, for example, inside the fence, where there are no dingoes, than there are outside the fence, where dingoes are plentiful and eager to eat the hopping marsupials.

During his years out in the field, Letnic also noticed other, more intangible differences.

"Something about areas with dingoes... felt totally different," he said. "I worked long enough as a naturalist to feel there was something significant going on."

With his colleagues, Letnic spent two weeks surveying eight sites on both sides of the fence. Pairs of sites were located in similar landscapes.

At each site, the researchers used traps, counted tracks and scat, and watched for animals, including dingoes, kangaroos, foxes, cats, rabbits and rodents. The scientists also looked at dung samples to see what animals from each group were eating.