#currentbiology

It’s often something that most people are aware of – a rooster crowing as day breaks. It is a familiar sound, and often is an annoying one if you are not ready to be woken up yet. It has become such a well known trait of the rooster that it is not often that we think about why it crows every morning. But according to research, it now suggested that it is not just a coincidence, roosters really do know the time of day.

Image courtesy of Juan Tello

The study, which can be found in the journal Current Biology, found that roosters put into a situation of constant light conditions will still crow at the crack of dawn. It has never been clear whether the crowing of a cockerel was due to a response to external stimuli such as the growing of light, or under the control of a biological clock. It has been known that the stimulus of a light, such as the appearance of car headlights, has set off a rooster’s crow at any time of the day. And so it was naturally assumed that increasing light was the trigger for a cockerel’s crowing.

In order to find out if this was the case, or if cockerels have an inbuilt clock that tells them when to crow, Takashi Yoshimura of Nagoya University and his colleagues put 40 roosters in a setting with constant light, with cameras set up to record when they crowed. They were surprised to find that as dawn broke, despite being in a situation where they had been exposed to light for many hours, the still roosters crowed at the right time. The cameras also recorded the chickens crowing at other times of the day, in response to light and also in response to the crows of others, but the crowing and the sudden act of crowing was much more obvious at daybreak. Thus, the findings suggest that an internal clock does indeed take precedence over any external cues.

The researchers also found that a social ranking system exists among the birds, and affected the timing of when they would crow.  “Crowing is a warning signal advertising territorial claims. Our preliminary data suggest that they highest ranked rooster has priority in breaking the dawn, and lower [ranking] roosters are patient enough to wait and follow the highest ranked rooster each morning,” said Yoshimura. 

The scientists and researchers involved in this study are curious as to why no one has ever really looked into this before, as it is such an interesting subject and fascinating to find that roosters have an internal clock that drives their crowing. But perhaps the fact that it hasn’t been looked into before, just goes to demonstrate how familiar the early morning crowing of a rooster is.

By Ellie Cambridge

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