Pecking Order Determines Which Rooster Crows First

Less dominant roosters only crow after the most dominant male has decided to announce the break of dawn, researchers say.

AsianScientist (Aug. 3, 2015) – Not only do top ranked roosters have priority when it comes to eating and mating, but they also get to perform the morning’s first crow, according to research published in Scientific Reports.

Since the period of the Indus Valley Civilization (around B.C. 2600-1800), the rooster’s ‘cock-a-doodle-do’ has been used to announce the time. In 2013, researchers from Nagoya University led by Professor Takashi Yoshimura discovered that how each individual rooster decides when to crow is governed by their internal biological clock, rather than external factors such as light.

In the present study, they have found that roosters follow a systematic rule when it comes to who crows first: the pecking order.

Chickens are known to be highly social creatures and develop a dominance hierarchy known as the ‘pecking order.’ The pecking order starts with the dominant chicken pecking all the chickens, the second dominant chicken pecking all the chickens apart from the dominant chicken and with the least dominant chicken remaining harmless.

The researchers first observed that the highest ranking rooster among a group of chickens was always the first one to crow in the morning. The crowing was followed by the second, third and fourth ranking roosters, showing that roosters crow in descending order of their social ranking.

In addition, the time that the dominant rooster started to crow varied from day to day, but the crowing of the lower ranking roosters always started right after the crowing of the highest ranking rooster, suggesting that the most dominant rooster was able to determine the timing of crowing within the group. Upon removing the highest ranking rooster from the group, the second ranking rooster became the first to crow, showing that the second ranking rooster can also take the role of the most dominant rooster.

Along with these results, they also showed that the frequency of voluntary crowing was lower for subordinate roosters compared to dominant roosters. On the other hand, upon stimulating the roosters to crow using light and/or sounds, they found that the subordinate roosters crowed as much as the dominant roosters. This indicates that although the subordinate roosters have the ability to crow, they have the patience to wait every morning for the most dominant rooster to crow before crowing themselves.

“We have discovered that roosters live in a strictly linear hierarchy, where social ranking reflects the order to announce the break of dawn,” says Yoshimura, who is a principal investigator at the Institute of Transformative Bio-Molecules (ITbM) in Nagoya University.

The article can be found at: Shimmura et al. (2015) The Highest-Ranking Rooster has Priority to Announce the Break of Dawn.

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Source: Institute of Transformative Bio-Molecules; Photo: Tom Woodward/Flickr/CC.
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