African penguins live on the rocky coasts of South Africa, Namibia and nearby islands. Like other types of penguins, the birds have white feathers covering their chests and black feathers covering their backs. They form lifelong pair bonds with mates, but they nest in huge colonies — so, scientists wondered how the birds were able to identify their partners among the sea of black-and-white birds. They wondered if their chest spots had something to do with it. To test this theory, they studied 12 African penguins at a zoo and marine park near Rome called Zoomarine Italia.
In one test, they hung two life-size photographs of the African penguins. One showed a random member of the colony, while the other showed the test subject's mate. The scientists recorded the birds' interactions with the photos: How long did they spend looking at each one, as well as how much time did they spend standing near each photograph? The penguins spent more time gazing at the photo of their partners — about 23 seconds longer, on average — than looking at the other photo. They also stood next to the image of their beaus for twice as long. Then, the researchers covered up the heads of the birds in the photographs, leaving only their speckled bodies visible, and the penguins still lingered near their partners' portraits.
In another experiment, the researchers hung up two photos of a bird's mate — but, in one, they had digitally removed its spots. In this case, the penguin again spent more time looking at the photo with the dots.
Finally, the researchers posted two photographs of penguins with digitally removed spots — one of the test subject's mate and the other of a random penguin from the colony. In this scenario（在这种情况下）, the penguins did not appear to recognize their partners. They spent roughly the same amount of time gazing at or standing near both photos.
Together, the results of these experiments suggest African penguins are zeroing in on their partners' spots and using them like name tags, scientists say.
"Our results provide the first evidence of a specific visual cue responsible for spontaneous individual recognition by a bird and highlight the importance of considering all sensory modalities in the study of animal communication," the researchers write in the paper.
