Opossums living on an island off Georgia are giving scientists information on how competition for survival influences aging.
For about 9,000 years, the opossums on Sapelo Island have enjoyed life without predators. As a result, they live longer than their counterparts that have to face the "dog-eat-possum" rigors of the mainland.Steven Austad, a Harvard University biologist, has discovered another difference: The easy island life seems to keep them fertile longer, too.
Ordinarily, animals - people included - produce fewer babies as they get older. Opossums normally live only two or three years, and 2-year-old females have fewer and smaller offspring than 1-year-olds. But on Sapelo, the situation is reversed. Two-year-olds have larger litters.
That's like a 45-year-old woman being more fertile than a 25-year-old, said Austad.
He suggests that taking ecology into consideration can shed light on why some species live much longer than others.