A team of researchers has revealed a unique trick that male peacocks use to court females, also known as "peahens": fanning their colorful rear feathers and shaking them while keeping their plumes' eyespots almost completely still.
"This 'train-rattling' display attracts the peahen's visual attention and always precedes copulation," the researchers wrote.
Charles Darwin was the first to notice this unique chase-and-dance behavior around 150 years ago, although scientists have never completely grasped the biomechanics of the trick, until now.
Led by Roslyn Dakin from the University of British Columbia, Canada, the team examined the mating dance in detail. During the dance, males shake dozens of their train feathers, each measuring up to 1.5 meters long, and hold them erect. Over the course of each breeding season, which last two to three months, male peacocks log hundreds of hours of time using this trick.
"When the peahen is close to a peacock, his huge fan of feathers could practically fill her field of view," Dakin said. "And when he starts to wiggle those feathers, most of what she would see is moving, except for the eyespots floating on top."
Using high-speed video, the team was able to carefully analyze these unique movements in 14 adult peacocks. In combination with individual feather studies in the lab, they were able to get a better grasp of how the process works.
The results revealed that peacocks' eyespots are able to stay still during these courting displays thanks to microhooks that hold them together in the same manner as 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," Dakin and her team wrote.
The team also discovered that longer tail feathers enable males to shake them faster, a feat that requires more muscular strength and thus could be a signal of power and fitness to females.
The majority of peacock train feathers possess a single eyespot, and previous studies have shown that the increased iridescence of these eyespots is connected to more mating.
The findings were published in the April 27 issue of the journal PLOS ONE.