There’s an old saying that the sun knows when to rise because the roosters crow to tell it. The sound of a rooster crowing has symbolized the crack of dawn for centuries. Cultures all over the world have relied on this avian alarm clock to start their days. Yet, how do roosters know exactly when to crow, and why do they do it? It’s not like roosters are on a schedule, or are they? You may be surprised by the answers. Keep reading to learn the science behind this early bird’s behavior.
Roosters Don’t Just Crow at Dawn
At close range, a rooster’s crow is as loud as a jet engine.
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Contrary to what most of us city-dwellers think, roosters crow throughout the day. Although crowing is most frequently heard just prior to dawn, it is a form of vocalization roosters use to communicate, regardless of the hour. These vocalizations are extremely loud, as anyone who has ever lived in proximity to a rooster can attest. At close range, roosters crow at 142.3dB, which is as loud as a jet engine from 100 feet away. Even at a distance of 0.5 miles, the sound can still measure 102dB, which is louder than city traffic. Scientists found that roosters’ auditory canals close when their beaks open, preventing hearing damage.
However, these loud calls are necessary for many reasons. Roosters crow to scare away predators or to warn them that the flock is protected. Crowing is a way to assert their dominance and proclaim their social status. They also crow to inform other roosters of the boundaries of their territory. Social stressors, such as hearing an unfamiliar bird crow, can also induce crowing. Roosters crow to attract the attention of hens or to signal that there is food nearby. They even have two types of alarm calls: one for aerial threats and another for ground-based threats. As the leaders and protectors of their flocks, roosters must ensure their vocalizations can be heard any time of the day or night.
How Do They Know When It’s Time to Crow?
The rooster’s circadian clock regulates the majority of its crowing.
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When it comes to their early morning wake-up calls, roosters crow not because of external cues, but because of an internal clock. Researchers found that in addition to crowing directly after light onset, the roosters in the study also crowed about two hours before sunlight, which is called anticipatory predawn crowing. Even in dim light conditions, most of the roosters’ crowing took place roughly 24 hours apart. When the roosters were exposed to artificial light and sound, researchers found that the birds crowed more often in response to stimuli during the morning. They concluded that roosters’ circadian clocks regulate the majority of their crowing.
The circadian system includes molecular, physiological, and behavioral components that synchronize with environmental light cycles. One of these elements is a neuroendocrine organ called the pineal gland. The pineal gland produces melatonin, a hormone that regulates sleep-wake cycles and other biological processes, such as reproduction and immunity. Melatonin production increases at night and decreases during the day. As melatonin levels begin to decrease as the night progresses, the rooster’s internal clock senses the approach of dawn. This prompts the rooster to crow, even before sunrise.
The Rooster Hierarchy
Chickens have a hierarchical society, and the dominant rooster always crows first.
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Birds, especially chickens, are known to have a strict hierarchical society, hence the phrase, “pecking order.” Even though crowing is primarily controlled by the circadian clock, there are also social implications. Scientists have found that when housed in small groups, the top-ranking rooster crows first, followed by its subordinates in order of rank. The subordinate birds typically follow the dominant rooster, even if the dominant rooster begins earlier or later than usual.
However, the researchers found that crowing in response to external stimuli was independent of a rooster’s social rank. Other roosters can still crow, but the initial call to signal the start of the day is the responsibility of the dominant rooster. The presence of this dominant rooster also reduces pre-dawn crowing in other birds, as they wait to crow until the top-ranking rooster begins, regardless of their own circadian rhythms.
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