How light and sound affect how much roosters crow. Image: Shimmura and Yoshimura, Curr Bio, 2013.
Why do roosters crow before dawn . . . really?
This is Sandra Tsing Loh with the Loh Down on Science.
Crowing behavior interests Japanese biologist Takashi Yoshimura. It’s because he studies circadian rhythms, or body clocks. They control biological processes—like sleep—that occur every twenty-four hours.
He wondered: Do roosters crow because of an internal body clock? Or in reaction to external stimuli?
To find out, he brought twelve roosters into a windowless lab. He put them on a lighting schedule. Twelve hours light, twelve hours dim.
And? As in the outside world, the roosters crowed two hours before the light got bright! Next, he switched to dim light round the clock. The roosters crowed at the same time at first, but eventually stopped altogether.
When he exposed the birds to external light and sound they also crowed. Just more enthusiastically at their regular morning time.
Yoshimura says this shows circadian rhythms do control crowing. But it's also influenced by factors like daylight and other roosters sounding off.
So that’s why roosters crow. As to why chickens . . . cross the road? More research is needed.
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Thursday, from 2-3 p.m. on the LDOS blog: Sandra chats with author Deborah Fallows about her book Dreaming in Chinese.
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