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Skewed sex ratio curbs courtship

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Researchers find that males spend less time in elaborate courtship displays such this peacock's feathers when males far out number females. Instead, they get sneaky to get a mate.

When a woman walks into a male-crowded bar she's unlikely to be showered with courtly attention — that is if findings about mating in the animal kingdom translate to the human realm.

"She might just be watching them fight it out and then have one particularly possessive one making sure others aren't getting access to her," Laura Weir, a postdoctoral fellow at Simon Fraser University in British Columbia, Canada, told me today. 


In other words, as the dudes duke it out with each other, one little weasel will sneak over and trap her in a corner and try to keep her all to himself?

"Exactly," she said, although she stressed her reluctance to take the analogy too far. The data, she noted, is compiled from the mating behaviors of the birds and bees … and alligators, fish, frogs, lizards and lobsters, too. 

Operational sex ratio
Her research focuses on the influence of the so-called operational sex ratio on competition for mates. Operational sex ratio is the ratio of males and females ready to get it on at any one time and place. 

In the animal kingdom, like at a bar, the ratio can often be heavily male biased. For example, in a lot of species, males are often first to arrive to the mating ground so they can establish territories.

The females will come afterward, and depending on the pace of female arrivals over  time, "you can have very biased sex ratios during some times of the mating season," Weir said.

When the first female arrives, the general thought is the males will get aggressive toward each other, fighting with each other to take out the competition. 

"We found that there is this increase in aggression to a point, but then they stop using aggression as a tactic to get females and they change to other tactics like sneaking in or scrambling around looking for females," Weir said.

Dying courtship
All this aggression and sneaking around comes at the expense of courtship, which is a costly, time-consuming investment. Think birds such as peacocks with their fabulous displays of feathers or sparrows constantly updating their playlists.  

Instead of investing in the displays and songs to attract the very best mate, the males put their energy into just trying to find a mate, any mate, which involves more covert sneaking around.

On the flip side, males in these situations tend to be more guarded of the mates they secure.

"If they've mated with her, they want to ensure they are the only one who's done it," Weir said. "And so, rather than go off and fight with other males or try to court another female, they'll just cling to the female that they've already mated with."

Overall, Weir and her colleagues note, the findings illustrate a considerable flexibility in the mating structure within species, which is likely related to the end goal of life: reproduction. 

At least, that's the next question they hope to tackle in their research. 

"If the goal of the biological world is to leave more offspring, are these changes in behavior beneficial to the males when they are actually competing for mates and competing to fertilize eggs?" asked Weir.

Weir is a lead author of a paper describing this research in the February issue of The American Naturalist. 

More stories on the science of animal sex:


John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).