Researchers have long thought that baboon males prefer females with bigger backsides as the mark of a good mother, but a new study suggests that the size of a female's swollen rump doesn't matter as much as previously thought. (CL Fitzpatrick, Duke University)

Female baboons are known for their distinct red bottoms, known to attract potential mates. But according to a new study, there's more to baboon courtship than these preposterous looking posteriors. In research published Monday in the journal Animal Behaviour, scientists report that the behind is less important than other indications of fertility.

A female baboon's backside will swell as she ovulates, so it follows that her suitors will take it as a cue of her fertility. And they do: The swelling brings all the baboons to the yard, as it were. Some females have more swelling than others, resulting in a bigger rear on display. But surprisingly, these larger ladies didn't get any more attention from the men.

[Why do men prefer certain female backsides? It may come down to an evolutionary push for curvy spines.]

It seems that the male baboons knew better: When the observations of swelling were compared with long-term data on offspring, the researchers found that more swelling during ovulation didn't correlate with more living children.

[Spring has sprung, so does science say love is in the air?]

But there was another sign of fertility that the male babooons seemed to rely on more: The number of menstrual cycles a female had been through since her last pregnancy.

"It's almost as if the males are counting," Duke University researcher Courtney Fitzpatrick said in a statement. "Our study suggests that, at least in part, males follow a rule along the lines of 'later is better' rather than 'bigger is better.'"

That's pretty smart: Baboons don't regain their fertility immediately after giving birth, especially when their offspring are still being weaned. So it's in a male's best interest to go after females who have had some time off from childbearing. In follow-up studies, Fitzpatrick and her colleagues will see whether this mating strategy actually leads to more surviving children for the males in question.

Want more science? Give these a click:

Why do seals keep trying to have sex with penguins?

Can menopausal killer whales have it all?

Long-forgotten secrets of whale sex revealed

Vampire squids have unusual reproductive habits that hint at longer lives