Why do peacocks looking for mates hang out together like buddies at a singles bar, even when many are never lucky enough to find the perfect peahen?
For sound evolutionary reasons, according to research published Tuesday.Scientists have long wondered why the unsuccessful peacocks stick around the same group year after year when the hens tend to select the same few males each breeding season.
Research published in the journal Nature suggests an evolutionary reason: Many of the bird buddies within individual groups are brothers. By working together, they increase the odds that their genes will be passed to another generation.
"By helping your relatives to attract mates, your genes are spread," said Marion Petrie, a researcher at Britain's University of Newcastle, Newcastle-upon-Tyne.
The research sheds light on why some peacocks seem unconcerned with sex and are content to be hangers-on in the animal singles scene: Larger groups of peacocks attract more females, so some of the peacocks are there just to make the group bigger.
"The benefits of helping closely related dominants to attract more females may outweigh the subordinate males' own meager mating opportunities," said Cornell University researcher Paul Sherman in an accompanying Nature commentary.
Petrie and her colleagues studied about 200 free-ranging peafowl in Whipsnade Park north of London. Using DNA fingerprinting, the researchers found birds inside the strutting groups are more likely to be related to each other than those outside the group.
But how do the related birds find each other? That's unclear, but it is not because the peacock brothers grew up together.
In fact, the researchers found that when peacock brothers were separated before hatching and then were released into Whipsnade Park when they were yearlings, the brothers still tended to group together.
The mechanism by which the birds found their relatives is unknown. It could be by odor, feather patterns or the sounds the birds make.
"There is some way in which kin can be associated, which doesn't require learning or environmental clues," Petrie said. "They didn't know their fathers or mothers. They could not possibly learn who their brothers were. They had no reference points to where they were born, but they still found each other."