Emperor penguins recognize their chick thanks to an individual vocal signature: each cry has a unique acoustic structure, memorized by the parents, which allows them to find their young among several thousand individuals, even in the din of the Antarctic wind.
A two-voice song as an identity card
The emperor penguin emits a complex cry produced simultaneously by two sound sources in its syrinx, the vocal organ birds. This “two-voice” production creates a rich acoustic signature, combining several superimposed frequencies, much more difficult to confuse than a simple whistle. From the first days, the chick develops its own individual, structurally stable call, which its parents learn to distinguish among ambient noise.
Replay experiments (broadcast of recorded calls) carried out on colonies have shown that parents only respond to the call of their own chick, ignoring similar calls from neighbors located a few meters away. This mechanism is essential because the colony can include several tens of thousands of individuals crowded together, without territory or fixed nest.
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Unlike other colonial birds, the emperor penguin has no reliable visual cue: the chicks are very similar in plumage and constantly move within the crèche, a dense grouping formed to protect themselves from the cold. Identification therefore relies almost exclusively on hearing, a system which must remain effective despite winds that can exceed 100 km/h and the simultaneous cries of thousands of fellow creatures.
A mechanism shared with the king penguin
The king penguin, a close cousin living in equally dense colonies, uses a vocal system comparable to two voices. Comparative research between these two species has provided a better understanding of how the harmonic structure of the call encodes individual identity, a rare model in birds and particularly studied by biologists specializing in animal acoustics in polar environments.
