26 November 2023

We humans recognize each other by face and can sometimes recognize individuals in other species as well. For instance, African penguins (Spheniscus demersus) have unique patterns of dots on their chests that zookeepers use to tell them apart. Psychologist Luigi Baciadonna wondered if the dots functioned the same way for the penguins themselves so he ran an experiment at Zoomarine Italia in Rome.

In the experiment individual penguins were herded into a small corral with life-size portraits of two group members, at least one of which was his/her mate. African penguins like to hang out near their mates so if the visiting bird stared at the mate’s portrait and gravitated toward it, he/she was recognizing the mate. The experiment had three variations:

Test #1: Accurate photos: one of the mate, one of another member of the colony. Result: In this video of Test#1 a male penguin, Gerry, is presented with an image of his partner, Fiorella, on the left and one of group member Chicco on the right. Notice what he does.

Test 2: Two photos of the mate: one accurate, one with dots digitally removed. Result: The birds spent more time looking at the mate photo with dots.

Test 3: Dots digitally removed from both photos: mate and another member of the group. Result: The birds no longer seemed to recognize their mate. There was no difference in how long they gazed at the mysteriously spotless portraits.

Quiz! Now that I know African penguins have unique chest dots I discovered that the penguin pictured below is also in a photo above. Which one is he?

Visit the National Aviary in Pittsburgh to check out the African penguins’ dotted chests at Penguin Point.

Read more about the study at Science Direct: African penguins utilize their ventral dot patterns for individual recognition

(credits are in the captions)