Why female lemurs are dominating

Most males rule the animal kingdom, but when it comes to lemurs -- primates that look like cats -- the trend is upturned. Lemur females behave more like males, thanks to the presence of slight testosterone, says a new study.

It's not uncommon for female lemurs to bite their mates, snatch a piece of fruit from their hands, whack them on the head or shove them out of prime sleeping spots.

Females mark their territories with distinctive scents just as often as the males do. Males often don't take their share of a meal until the females have had their fill.

"If a male lemur is enjoying a patch of sunlight, for example, a female is likely to push him aside and take his spot," said Joseph Petty from Duke University.

Most female mammals that get their way over males are well armed to be bullies. Dominant female spotted hyenas, for example, are bigger and heavier than males.

But female dominance in lemurs remains a puzzle. Female lemurs are no bigger than males, and they don't have antlers or bigger fangs to give them a physical edge over their mates.

Researchers at the Duke Lemur Centre say females have significantly lower testosterone levels than the males across the board. But when they compared six lemur species, they found that females of some species have higher testosterone levels than others.

Petty and Duke professor of evolutionary anthropology Christine Drea examined behaviour and hormone profiles in nearly 30 animals representing six closely-related species in the genus Eulemur.

In four of the species, females are at the top of the pecking order, and in the other two species the sexes have equal status. The dominant females had significantly higher male hormone levels than the females from the two more egalitarian species.

"It's strong evidence that hormones are playing a role. It could be that females are more sensitive to the effects of testosterone than males, stimulating aggressive behaviour even though males still have more of the hormone," said Petty.