杏吧原创

Some penguins match the vocal calls of fellow penguins to their faces or other aspects of their physical appearance, making them the first birds besides crows known to have this double-sense recognition ability.

African penguins (Spheniscus demersus) 鈥� which have unique, individualised spotted markings on their chests and which are found in southern Africa 鈥� may have evolved this voice-plus-image recognition ability in order to improve communication in their rocky and windswept coastal setting, says at the University of Turin in Italy.

鈥淚magine a large [penguin] colony in this really challenging environment, with a lot of wind noise, background noise,鈥� he says. 鈥淎nd potentially, they鈥檙e relying on vocal communication, calling to each other as they鈥檙e coming back from a hunting trip, for example. But also, their unique pattern of black spots [could become difficult to decipher] amongst the waves and rocks. So the ability to integrate both visual and auditory identifiers can be necessary when one of the cues is not available.鈥�

Baciadonna and his colleagues worked with 10 adult penguins living in captivity in a colony of 17 individuals at , a park in central Italy. They placed the penguins in pairs, then each pair was placed in a separate enclosure for about a minute before one of the two penguins was herded out through a wooden door. Twenty seconds later, the scientists played a pre-recorded audio file of a penguin squawk from a speaker above the wooden door.

Each penguin underwent testing six times on six different days. Sometimes the squawk they heard was from the partner penguin that had just left the enclosure; sometimes it was a squawk from a randomly chosen penguin from the same colony.

The lone penguin in the enclosure 鈥� the tested penguin 鈥� always responded to the audio recordings by looking at the door, says Baciadonna. But if the call came from a randomly chosen penguin, the tested penguin looked at the door more than twice as quickly as it did when the audio recording was from the penguin that had just passed through the door.

鈥淓ssentially, if you hear the call from the same guy who just left a few seconds ago, it鈥檚 more likely that the call belongs to that guy, not some random [guy],鈥� he says, adding that this implies the animals create a 鈥渕ental picture鈥� of the individual making the call. 鈥淪o when there鈥檚 a mismatch between the visual and acoustic input, we call this a 鈥榲iolation of expectation鈥�, and they react more quickly.鈥�

In other words, this behaviour indicates that the tested penguins weren鈥檛 expecting to hear the randomly chosen penguin鈥檚 call because it conflicted with their mental image of the penguin that had just passed through the door, says Baciadonna.

This association between an individual鈥檚 appearance and their vocalisations is unusual in birds, but it has been reported in mammals including African lions, goats, horses and rhesus macaques 鈥� with the macaques even showing an ability to .

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