The pigs are good at turning food into fat. "They're the fattest terrestrial mammal in the world," says ecologist Lehr Brisbin of the University of Georgia in Savannah. At their plumpest, they have more fat than lean tissue, and five times more fat than other breeds.
Spanish galleons visiting America left the pigs on Ossabaw Island about 500 years ago. Since then they have evolved to drink seawater, and adapted to a boom-and-bust food supply, gorging on acorns in autumn to survive the winter. Their fat stores last until the new spring's vegetation appears. But their crash diets and active lifestyles keep them in trim.
Put the pigs on a high-fat diet with little exercise for several months, Brisbin's team found, and they develop the precursors of diabetes and heart disease: raised levels of blood sugar and fat, increased blood pressure, and hardened arteries.
Lab animals such as mice get fat, as do commercial pig breeds, but these animals display a different range of symptoms to humans. Monkeys are more similar to us, but take several years to mature and are more difficult to work with.
"A lot of us are hoping that this turns out to be a good model," says diabetes researcher Jerry Nadler of the University of Virginia, Charlottesville. "It would be very exciting to have a large-animal model of what's happening very commonly in people."
About 150 million people worldwide have type II diabetes, in which the body fails to regulate its blood sugar levels. This is sometimes called adult-onset diabetes, although the number of childhood cases is increasing rapidly as waistlines widen. More than 80% of type II diabetes sufferers are obese.
Feast or famine
Humans are also thought to have evolved to cope with alternating feast and famine. Some groups, such as the Pima Native Americans of the southwestern United States, have developed especially high rates of obesity and diabetes over the past century as food has become constantly available. It's thought they have a thrifty biology, tuned to periodic starvation.
Ossabaw pigs are the first animal to be found to share this trait, Brisbin will tell this week's Ecological Society of America's annual meeting in Savannah. The team plans to investigate the genes and metabolic mechanisms that control Ossabaw pigs' fatty tendencies.
Others view the pigs as pests. Georgia's state government has begun an eradication plan, because the pigs supplement their diet with the young of loggerhead turtles that nest on the island.
The plan does not yet threaten the pigs' survival, says Brisbin, but he is concerned for their future. "We need a debate," he says. "I'm not against shooting the pigs, but I am against shooting the last ones."
The Ossabaw is one of only two feral pigs deemed worthy of protection by the World Conservation Union; the other is the babirusa of Indonesia.
Nature
6 August 2003
Original web page at Nature
