Cock-A-Doodle-Doo! What Drives the Rooster to Crow at Dawn?

Roosters are known to crow "cock-a-doodle-doo" at the break of dawn. It was not clear whether the roosters crowed as a reaction to the environment or because they knew the time of the day.

Researchers Tsuyoshi Shimmura and Takashi Yoshimura of Nagoya University in Japan wanted to figure out what sets off the roosters to crow at dawn, because the rooters also crow when a car's headlights are turned on in the middle of the night. "'Cock-a-doodle-doo' symbolizes the break of dawn in many countries," said Takashi Yoshimura of Nagoya University. "But it wasn't clear whether crowing is under the control of a biological clock or is simply a response to external stimuli."

Yoshimura and his colleague have now found that the roosters' internal clocks, or circadian rhythms, are driving their crows at dawn.

For their study, the researchers put three different groups of roosters (four in each group) in constant light conditions and sound-tight rooms to record their "cock-a-doodle-doo"-ing (or "ko-ke-kok-koh" as they say in Japan) using sound recorders and video cameras.

The roosters were subjected to cycles of 12 hours of light and 12 hours of dim light for two weeks. The research team found that the birds crowed two hours before dawn - called predawn crowing. They carried out a second experiment, wherein the roosters were placed under 24 hours of dim light conditions for 14 days. The roosters continued to crow in the mornings, suggesting that internal clocks played a role in driving the birds to crow at dawn, reported Los Angeles Times.

The researchers then exposed the roosters to sound and light stimuli. They found that birds vocalized more in response to light and sound in the early mornings than during other times of the day. This also showed that the roosters' crow is driven by an internal clock rather than by external conditions.

The research team hopes to further study the innate vocalizations of other animals like dogs and cats. "We still do not know why a dog says 'bow-wow' and a cat says 'meow'", said Yoshimura. "We are interested in the mechanism of this genetically controlled behavior and believe that chickens provide an excellent model."

The findings of the study are published in the journal Current biology.