Why penguins trade pebbles? Inside the sweet courtship ritual that builds their future

Recently, a video caught the fancy of internet users where school students were seen painting pebbles for the penguins in the Edinburgh zoo. The video further shows that the penguins take their own sweet time to find out the best pebble to gift their mate.

This tradition popularly known as ‘pebbling’ is not new. It is an essential tradition followed every mating season.

Scientists who study penguin colonies have found that these pebbles play an essential role in nesting, reproduction, and competition among birds.

This tradition is particularly common in species such as Gentoo and Adélie penguins.

BBC Wildlife reports, “The story goes that males try to woo a female by presenting her with a pebble, and she chooses the suitor that brings her the smoothest one. It’s a lovely idea, and easy to imagine that such a ritual might give females clues about a male’s potential as a provider, but any evidence that it’s actually true is hard to come by.”

It has been discovered that these fascinating birds perform a courtship ritual similar to that traditionally performed by people to get engaged to each other.

In their case, instead of the usual engagement ring, the penguins give a pebble or polished rock to the female in their group with whom they hope to build a nest and mate. Surprisingly, this coincides with the symbolism that since ancient times has represented the love between two people and their commitment to join in marriage.

Why pebbles?

Although scientific information on this phenomenon is not very abundant, recent research on penguin behaviour has led to the inference that, due to the conditions of their habitat, the small rocks they collect are intended to cover the ground on which they build their nests.

These stones keep the eggs above the water surface once their colonies are invaded by rapidly melting snow.

Observation of this habit highlights the time a penguin spends collecting the stone that brings it close to its partner’s feet, as they are intensely dedicated to finding the “ideal” stone within all the possibilities of their habitat.

A 2016 research concludes that the female is the one who chooses her mate, being the one who imposes the conditions for courtship to begin.

In other words, it is she who triggers the situation that results in both of them leaning in, grooming each other and familiarising themselves with the sounds the other makes. In this way, they can recognise each other and find each other easily in the crowd.

What is the Edinburgh Zoo tradition?

Children being supported by Edinburgh Children’s Hospital Charity paint special pebbles to celebrate the beginning of penguin breeding season at the Royal Zoological Society of Scotland’s Edinburgh Zoo.

Discovery and community officers from the wildlife conservation charity delivered the pebbles as part of their weekly interactive sessions at the Royal Hospital for Children and Young People. This aims to bring children closer to nature and the animals at Edinburgh Zoo and Highland Wildlife Park.

The penguins are incredibly popular with children at the hospital who regularly watch them on live webcams. They will now be able to keep up with all the breeding activity and watch the penguins pick up their painted pebbles as they use them to build their nests.