If you’re lucky enough, you may have seen a peacock displaying to a female. It’s an impressive event to witness: the peacock spreads and ruffles his enormous, brightly coloured tail feathers for a female, who, after checking him out, may choose to mate with him or not.
One of the most obvious features of the peacock’s appearance to us is the large ‘eyespots’ on his feathers. Indeed, we even have re-created these eyespots on human clothing, perhaps also as a visual signal, though I couldn’t presume what of.
Although you might guess that the females of the species (the peahens) would also pay attention to these striking eye spots, they surprisingly don’t seem to, instead more often looking below the neck of the peacock. It also seems that they are more likely to notice males that vibrate and shake their tail feathers more.
Recently, Angela Freeman and James Hare from the University of Manitoba asked whether peahens might pay attention to more than just what peacocks look like. Specifically, they wondered whether the shape the male makes with his feathers when displaying to a female might be important. When displaying with their tail feathers, peacocks curve them forwards into a concave shape. Could it be that they do this to actually create the effect of a cave; specifically, make any sounds they are making radiate more and therefore be more easily heard by a female?
What the scientists found was really quite remarkable. The peacocks produced very low ‘infrasonic’ sounds while displaying to peahens. Such sounds, at less than 20 Hz, typically cannot be heard by humans, which is why you won’t have noticed them in a peacock display before.
When the researchers played recordings of these infrasonic sounds to peacocks and peahens, the animals reacted, becoming more alert and running around more.
What exactly the purpose of the infrasonic sounds are isn’t yet clear, yet it seems very likely that it is used by these animals to communicate to each other. Perhaps males use such sounds to attract females to them before they can see the males’ impressive visual display. It is also possible that females might be able to judge the quality of a male, so that they can decide if they’re even going to bother to go and check him out. Finally, males might use thier ultrasonic sounds to tell other males to stay away. Hopefully more research on these intriguing birds will tell us the answer to these questions.
A great video of a male displaying to a female
Peacock: Kristine Deppe
Peacock with peahen: Raymond Bucko
Main article: Freeman, A.R. & Hare, J.F. (2015) Infrasound in mating displays: a peacock's tale. Animal Behaviour vol. 102 p. 241-250
Yorzinski, J. L., Patricelli, G. L., Babcock, J. S., Pearson, J. M., & Platt, M. L. (2013). Through their eyes: selective attention in peahens during courtship. Journal of Experimental Biology, 216, 3035-3046. http://dx.doi.org/10.1242/jeb.087338.