Why you can set the clock by a cockerel
IF you have ever had an alarm clock fail to go off in the morning, it seems nature offers a much more reliable alternative.
Cockerels will crow at the same time every day regardless of whether they can see dawn breaking, according to scientists.
Until now, it has not been known whether roosters make a din in response to the morning light or their own body clock.
But scientists in Japan claim to have finally figured out what makes them tick. In a study, cockerels crowed just before dawn even when kept in constantly lit conditions – suggesting they instinctively know what time of day it is.
Scientists believe their behaviour is regulated by a circadian rhythm – the body’s own internal clock – rather than external triggers. ‘“Cock-a-doodle-do” symbol- ises the break of dawn in many countries,’ said researcher Dr Takashi Yoshimura, a professor of animal physiology at Nagoya University i n Japan. ‘ But it wasn’t clear whether crowing is under the control of a biological clock or is simply a response to external stimuli.’
During the study, which was published in the journal Current Biology, the researchers put a group of roosters in a sound- proofed, windowless room.
One group was observed under conditions of 12 hours of daylight and 12 hours of dim light. In the second group, they were exposed to constant dim light.
The report found: ‘Under 12 hours light and 12 hours dim light cycles, crowing was observed approximately two hours before the onset of light – anticipatory predawn crowing – consistent with observations of red jungle fowls in the wild.
‘Under round-the-clock dim lighting, the roosters kept right on crow- ing each morning just before dawn, proof that the behaviour is entrained to a circadian rhythm.’
The findings are just the start of the team’s efforts to unravel the meaning of roosters’ crows, which are not learned in the same way as human speech, the researchers say.
‘We still do not know why a dog says “bow-wow” and a cat says “meow”,’ Dr Yoshimura added. ‘We are interested in the mechanism of this genetically controlled behaviour and believe that chickens provide an excellent model.’