Scientists in the United States say they have solved the evolutionary mystery of why a peacock's tail fan is so large and elaborate.
Male birds grow their trains of iridescent feathers during the mating season, fanning them out and rattling them to attract a mate. Their eye-catching nature may have something do with the short attention span of female pea hens.
A team of biologists fitted peahens with eye-trackers to find out what they looked at during the male's display and reported their results in the Journal of Experimental Biology.
The footage revealed how difficult it is to keep a peahen's attention, which helps explain why such a large and elaborately decorated tail fan evolved.
It also gave clues about what a peahen looks for in the tail fan. Side-to-side eye movements suggested that females were gauging the fan's width and that they were most interested in the striking eyespots on the feathers.
Dr Jessica Yorzinski carried out the research project while based at the University of California Davis and Duke University in North Carolina.
She said there are quite a few species that have elaborate colourful traits that don't serve any survival function.
"(This long train) might actually make it very difficult to get away from a predator," she said
Dr Yorzinski said it was probably beneficial for peahens to divide their attention among potential mates and the environment. "If females are not alert and focus completely on a displaying male, they may end up as a tiger's dinner."
The peacock's tail is probably the most famous example of sexual selection - a phenomenon identified by Charles Darwin whereby animals evolve a trait because it is attractive to the opposite sex.
