Planet Earth

Penguins Find Each Other's Beaks Sexy

InkfishBy Elizabeth PrestonSep 16, 2015 2:26 PM

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If Tinder for penguins existed, birds with the best beak spots would get swiped right. King penguins are attracted to the colors on each other's beaks, scientists have found—including colors we clueless humans can't see. King penguins (Aptenodytes patagonicus) live near the bottom of the world and are monogamous for about a year at a time. They're a little smaller than emperor penguins, the ones you saw in March of the Penguins, and have a less arduous lifestyle. In the spring, they gather on the shore in massive breeding colonies. Individuals on the edges of the colony flirt with each other and form tentative pairs. Once two penguins have committed, they move farther into the colony and get down to business. Earlier research suggested that the king penguin's "beak spot" might be important to how it chooses mates. This is the vivid orange area on either side of the bottom of the beak. It's really a vivid orange-and-ultraviolet area, if you have a penguin's eyes. Penguins have cone cells that let them see UV, like many other birds, in addition to all the colors a human sees. Ismaël Keddar of France's Centre d’Ecologie Fonctionnelle et Evolutive and his colleagues went to the Kerguelen Islands, also called the Desolation Islands, to learn more. There, about 200,000 king penguins had come together to breed. The researchers observed penguins at the periphery of the group and selected 75 pairs* who were in the flirting stage. They gently captured both members of a pair so they could weigh the penguins, measure the colors of their beaks and chest patches with a spectrophotometer, and take other vital stats. Then they released the birds where they'd captured them. (Even at this early relationship stage, penguin partners can find each other by their voices.) Afterward, the researchers kept monitoring these penguin pairs. Some committed and laid eggs, while others broke apart to seek better prospects. Even though humans can't see a penguin beak in all its UV glory, the scientists could use information about the light-sensing cells in penguins' eyes to model how their beak colors looked to other penguins. They saw that relationship success was tied to beak color. Penguins that formed committed pairs had similar beak colors to each other. The other factors that researchers measured, including the orange patches on penguins' chests and the sides of their heads, didn't matter. Only beak color seemed important to penguins trying to choose a mate. It's more common in birds for males to be flashy, and for drab females to choose among them. But in king penguins, each sex may be judging the other. The authors say this makes sense because both partners need to contribute heavily to raising young. The parents take turns incubating the egg, then balancing the newly hatched chick on their feet, while the other parent looks for food. If either parent is a deadbeat, the chick won't make it. So both male and female king penguins have to be picky. And looking for a partner with a beak like theirs is apparently a system that works—at least until penguins hear about Match.com. *Two of the pairs were left out of the results because they turned out to be same-sex—one pair of females and one of males.

Image: by David Cook (via Flickr)

Keddar, I., Altmeyer, S., Couchoux, C., Jouventin, P., & Dobson, F. (2015). Mate Choice and Colored Beak Spots of King Penguins Ethology DOI: 10.1111/eth.12419

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