Secret revealed how peacocks hypnotize their mates —

Male peacocks fan their colourful rear feathers and shake them, but somehow keep their plumes’ iridescent circles, or eyespots, nearly still, like a fixed stare. It’s a trick that is known to work with the ladies, who are known as peahens.Courtship - Peacock courting peahen (publi domain)

Now a team of US and Canadian scientists has captured the secret to their success. “This ‘train-rattling’ display attracts the peahen’s visual attention and always precedes copulation,” they wrote in new study in the journal PLOS ONE.

Charles Darwin first noted this chase-and-dance behaviour a century and a half ago, but researchers have never fully understood how the biomechanics work.

So the team, led by Dr Roslyn Dakin from the University of British Columbia, Canada, studied the mating dance, in which the male shakes dozens of train feathers — each up to 1.5 metres long — and holds them erect for hundreds of hours of display each breeding season, which may last two to three months.

They used high-speed video to analyse the train-rattling movements in 14 adult peacocks. It was found that the feathers vibrated on average around 25 beats per second, generating a pulsating low-frequency sound that is hard for humans to hear, but in the perfect range for peahens.

Previous research has also shown peacocks that display eyespots with greater iridescence are more successful at wooing the ladies.

The researchers found that rapid shaking of the peacock’s tail feathers created a dynamic iridescence around the eyespot. “It is possible that this motion also influences how peahens perceive the eyespot colours that are important for mate choice,” they wrote.

Using scanning electron microscopy the researchers found the eyespots stay so still during displays because they are locked together with microhooks much like those on flight feathers.

This gives each eyespot greater density than the surrounding loose barbs, keeping it essentially in place as the loose barbs shimmer in the background, the researchers said.

The researchers also found that the longer a male’s tail feathers, the faster he was able to shake them.

This effort would require more muscular strength, and might be a powerful signal of fitness to the females.

“We often video-recorded peacocks train-rattling for more than 25 minutes, suggesting that this behaviour may pose a considerable challenge to metabolic stores and short-term muscle power output,” the researchers said.

The researchers said their study countered Darwin’s view the peacock’s dance served “merely to make noise”.

“On the contrary, our results suggest the possibility that sexual selection via female choice has shaped both the biomechanical design of the eyespot feathers and the behaviours that produce visual and audio cues,” they wrote.

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