Researchers from Nagoya University in Japan have shown that roosters crowing at dawn are regulated by circadian rhythms and internal genetic body clocks.
Takashi Yoshimura of Nagoya University, who worked on the study, said: "it wasn't clear whether crowing is under the control of a biological clock or is simply a response to external stimuli."
The reason behind roosters crowing had never been studied before.
The researchers found that even without the light of the sun, roosters still crowed at around the same time everyday.
They performed two experiments, using different lighting conditions.
The roosters in the first experiment were exposed to 12 hours of bright light and 12 hours of less light on the same schedule for 14 days.
And the roosters consistently would crow 2 hours before the light got brighter.
The second experiment had the roosters in a dimly lit area 24 hours a day for 14 days.
The birds still created their own schedule that revolved around a 23 point 8 hour time period, and the roosters would crow when they thought it was supposed to be dawn.
The researchers believe it is a genetic predisposition for the roosters to crow every 24 hours.
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