Cock-a-doodle-do: It’s in me!

April 11, 2013 · by · in

Be it alarm tones of roosters crowing or even the nursery rhyme “Cocks crow in the morn”  –roosters’ crows are often associated with the break of dawn or a new day. Previous studies have shown that crowing occurs throughout the day but with higher frequencies in the morning. One study even attributed the stimulus of roosters’ crow to pineal opsin, a chemical produced by the brain.

Contrary to popular literature, a recent study by two researchers concluded that predawn crowing and even crowing caused by external stimulus such as light and other roosters’ crows – are under the control of a circadian (internal biological) clock.

Experimental process and results

First, roosters were placed separately in a light-and-sound tight room. After 28 days of observations, it was noted that  roosters would crow frequently about two hours before dawn everyday even without exposure to sunlight.

Then, the researchers varied the light and sound intensities as opposed to the actual time outside the experimental room. The roosters crow at high frequency before the actual daylight and there were halfhearted crowings when the stimulated conditions resembled the actual sunrise.

Also, they noticed that crowing is a social behaviour regulated by the circadian clock. Roosters crow more when there are higher testosterone levels (before daylight), thereby promoting competitive behaviour as a display of fitness to attract females.

Significance

Thus, apart from pre-dawn crowing, social behaviour and external stimuli such as light and crowing of other roosters which were previously thought to be responsible for inducing roosters’ crow are also regulated by a circadian clock.  This study is part of an ongoing investigation of rooster vocalisations, which are not learned like bird song or human speech. Also, it is interesting how we can draw parallels to human beings’ experiences of jet-lag when we travel to different time zones.

Here’s a video that sums it up! Enjoy!

“How do roosters know it is dawn” by geobeats. Geobeats Youtube Channel, 20 March 2013. URL: http://www.youtube.com/watch?v=9BBp7Y0uzQE (accessed 28 March 2013).

Sources:

Aschoff, Jürgen, 1989. Temporal orientation: circadian clocks in animals and humans. Animal Behaviour, 37(6): 881-896.

Shimmura, Tsuyoshi & Yoshimura, Takashi, 2013. Circadian clock determines the timing of rooster crowing. Current Biology, 23(6): 231-233.

“Why rooster crowing isn’t that impressive, and chickens get jet lag like the rest of us,” by Bouckau. Animal Science Review, 19 March 2013. http://blogs.oregonstate.edu/abouck/2013/03/19/why-rooster-crowing-isnt-that-impressive-and-chickens-get-jet-lag-like-the-rest-of-us/ (accessed on 1 April 2013)

“Before the rooster crows,” by Rooster Weathervane. Flickr, 1 July 2011. URL: http://www.flickr.com/photos/4thglryofgod/8611513114/ (accessed on 1 April 2013)

 

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