By Ania Lichtarowicz BBC science reporter

Scientists in the United States have found that female lions prefer males with dark coloured, hairy manes.

According to work published in the journal Science, the females' preference for brunettes over blondes is not only cosmetic, as dark maned lions have high testosterone levels and seem to be in better health than their blond counterparts.

Female lions can be picky about who they mate with; as there are often more males than females, they have the luxury of choosing who will father their cubs.

It seems these girls know exactly what they want - a thick dark mane seems to be a very sexy and most attractive feature.

However the thick-maned males pay a price for their reproductive success - their body temperature is significantly higher.

Toy blokes

Hot beast

Scientists from the University of Minnesota took life-sized toy lions - some with dark manes and others with light coloured ones - left them in the Serengeti National Park, and observed which the females preferred.

Nine times out of ten the females chose the dark-maned lion.

Principal researcher Dr Peyton West said the females' preferences seem to reflect the fitness of the males.

"What we think is happening is that manes reflect what kind of condition a male is in," she said.

"If a male is healthy and hasn't been injured recently, then he can have a very long mane whereas if he's been injured or had some kind of infection their manes often become quite reduced."

Hard nuts

Mane men - dark hair brings success?

A male's colour, meanwhile, seems to be connected to his hormonal status.

According to Dr West, "males with more testosterone are more likely to be better fighters so they'll be more frightening to other lions, especially to males, and more attractive to females."

Male lions were clearly intimidated by both long and dark manes. The only males to approach the long-maned dummy had long, dark manes themselves.

The scientists suggest this is because males are sensitive to an opponent's mane length.

A survey of recently injured lions found most had shorter manes, suggesting they are weaker than individuals with long manes.