Mar. 18, 2013 — Of course, roosters crow with the
dawn. But are they simply reacting to the environment, or do they really know
what time of day it is? Researchers reporting on March 18 in Current
Biology, a Cell Press publication, have evidence that puts the clock in
"cock-a-doodle-doo" (or "ko-ke-kok-koh," as they say in the
research team's native Japan
"'Cock-a-doodle-doo' symbolizes the break of dawn in
many countries," says Takashi
Yoshimura of Nagoya
University
That's because other things -- a car's headlights, for
instance -- will set a rooster off, too, at any time of day. To find out
whether the roosters' crowing is driven by an internal biological clock,
Yoshimura and his colleague Tsuyoshi Shimmura placed birds under constant light
conditions and turned on recorders to listen and watch.
Under round-the-clock dim lighting, the roosters kept
right on crowing each morning just before dawn, proof that the behavior is
entrained to a circadian rhythm. The roosters' reactions to external events
also varied over the course of the day.
In other words, predawn crowing and the crowing that
roosters do in response to other cues both depend on a circadian clock.
The findings are just the start of the team's efforts to
unravel the roosters' innate vocalizations, which aren't learned like songbird
songs or human speech, the researchers say.
"We still do not know why a dog says 'bow-wow' and a
cat says 'meow,' Yoshimura says. "We are interested in the mechanism of
this genetically controlled behavior and believe that chickens provide an
excellent model."
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