In certain species, the top boys fight to restrict access to females, preventing subordinate males from mating. This can help pass on qualities such as strength to the next generation. But having only a few breeding males has its drawbacks. It also limits genetic variety in the population, making it more vulnerable to sudden changes in the environment-especially if numbers shrink. "With just 200 individuals you're really starting to worry about genetic diversity," says Peter Tolson from the Toledo Zoo in Ohio.
This has prompted Allison Alberts and colleagues at the San Diego Zoo to propose a new method of conservation: temporarily kidnapping the dominant males. Removing them should give other males a shot at reproduction and maximise the genetic diversity of a population. This would give the population a better chance of surviving a new disease or a sudden change in climate. "When you consider the benefit I think it is a feasible strategy," says Tolson.
The team tested the idea on a population of Cuban iguanas (Cyclura nubila) at Guantnamo Bay in Cuba. These iguanas are not endangered, but many of their sister species are. The researchers removed the five highest-ranking males for six weeks during the breeding season. Other males quickly seized their chance and began breeding. When the dominant males were brought back they fought with the usurpers to regain supremacy.
"This is very much an emergency measure," cautions Alberts. The scheme would be labour intensive and costly. But most of the population would remain in the wild, sustaining the impetus to conserve the habitat.