Why roosters don't go deaf from their own loud crowing

January 30, 2018 by Bob Yirka, Phys.org report

A team of researchers with the University of Antwerp and the University of Ghent, both in Belgium, has uncovered the means by which roosters prevent themselves from going deaf due to their own loud crowing. In their paper published in the journal Zoology, the group outlines their study of the birds and what they found.

Anyone who has ever lived on a farm has heard the familiar sound of the crowing rooster (male chicken). Few likely realize, however, just how loud that crowing can be. In this new effort, the researchers sought to measure how loud the crowing is, and how the rooster avoids deafness from hearing itself every morning.

The team placed a tiny microphone near the ears of sample roosters to measure how loud the crowing would sound to them. They found it was louder than thought—averaging over 100 decibels, which is roughly the same as running a chainsaw. People who regularly use chainsaws without ear protection, it should be noted, go deaf over time due to damage to the tiny hair cells in the inner ear. Chickens of both genders also have such hairs in their ears, and the team wondered why they weren't damaged. To find out, they performed micro-computerized tomography scans on the skulls of the birds.

They discovered that half of the birds' eardrum was covered by a bit of soft tissue that dampened incoming noise. They also found that when the rooster tilted its head back to crow, another bit of material covered the ear canal completely, serving as a built-in ear-plug. Thus, for the rooster, it is as if someone were sticking their fingers in their ears while they are crowing. The researchers noted the birds also have another advantage—unlike humans, birds can regrow damaged hair cells. As for why the hens and chicks do not suffer hearing damage from the male crowing, though not mentioned in the research, it is well known that roosters tend to seek a vantage point offering maximum reach when they crow (away from the hens and chicks), making sure everyone within earshot knows that the hens that live there are his.

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Roosters are nicer to their relatives than to other males

Date: March 29, 2017

Source: Linköping Universitet

Male domestic fowl are less aggressive towards related males than to unrelated males when competing for copulations, according to a new study from Linköping University in Sweden. This finding, which has been published in the scientific journal Behavioral Ecology, suggests that domestic fowl can recognise their kin among individuals in a group, and that their behaviour is different towards kin and non-kin.

Domestic fowl in groups form a strict hierarchy, with one rooster being dominant over the others. The roosters compete for access to hens to mate with, and in this way produce offspring and transmit their genes to the next generation. If a rooster that is lower in the ranking attempts to mate with a hen, the dominant male will often interrupt and abort the mating attempt.

The researchers who conducted the study investigated if roosters not only attempt to produce offspring themselves but also to help relatives to do so. From an evolutionary perspective, this would be a way of ensuring that at least some of the male's genes are transmitted to the next generation. Particularly older males, with reduced reproductive capacity, may be more accepting towards younger relatives mating attempts. Thus, the researchers wanted to determine whether dominant roosters are more permissive towards the attempted matings of subordinate relatives than to those of unrelated lower-ranked males. They divided the chickens into groups with one dominant male and two roosters of lower rank; one of which was brother or son of the dominant male, and one that was unrelated to him. The three roosters were released together with four hens, and the researchers observed their mating behaviour.

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Bossy rooster takes lead vocal of cock-a-doodle-do

Date: July 24, 2015

Source: Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University

Summary:  From ancient times, people have been aware of the rooster's "cock-a-doodle-do" that marks the break of dawn, but has anyone wondered who crows first? In a new study, biologists have revealed that there is actually a systematic rule based on social ranking that determines the order of crowing in roosters.

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To keep peace, Bristol considers ban on roosters

OCTOBER 1, 2013 : Updated: October 1, 2013 6:00am

BRISTOL, Conn. (AP) — Bristol officials are considering banning roosters to end the birds' early-morning wake-up calls.

The Bristol Press reports (http://bit.ly/18o2UlS ) that the city's Zoning Commission is responding to a rising number of complaints. It's considering the ban in residential areas.

Farmers would not be affected by new rules being considered. And those who now own roosters would be allowed to keep the birds, but not replace them when they die.

The city lets residents keep up to a dozen chickens in many residential areas with no specific wording in regulations about roosters.

City Planner Alan Weiner said the zoning enforcement officer typically speaks with the owner of a rooster subject of complaints. He said most understand the problem and get rid of the bird, but some refuse.

http://www.mysanantonio.com/news/article/To-keep-peace-Bristol-considers-ban-on-roosters-4858959.php

Roosters Prefer Mates That Have The Biggest Comb Size

Size matters, and bigger is always better, at least when it comes to what roosters want when looking at possible mates.

New research published in the journal PLoS Genetics suggests that roosters select the girl with the largest hairdo, or “comb.”

The scientists, from Linköping Universitet, say that the larger the comb of a hen, the bigger dose of sperm she will receive from the rooster, which leads to more eggs.

Domestic hens have larger combs, as well as denser bones, when compared to wild hens. According to the research, this feature can be changed through human manipulation.

The scientists say that the greater the bone mass a hen has, the more eggs she is able to lay. They have spotted a clear correlation between comb size and bone mass in chickens from a cross between red jungle fowl and domestic chicken.

After spotting this correlation, the team set up a study to determine where these chickens were crossed for several generations, allowing them to “map” the functions of individual genes.

After the eighth generation, the team found an area that had a strong effect on the weight of the comb, as well as bone mass and fertility.

The genetic variation has gradually decreased over the course of domestication, according to the findings.

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Putting the Clock in 'Cock-A-Doodle-Doo'

Mar. 18, 2013 — Of course, roosters crow with the dawn. But are they simply reacting to the environment, or do they really know what time of day it is? Researchers reporting on March 18 in Current Biology, a Cell Press publication, have evidence that puts the clock in "cock-a-doodle-doo" (or "ko-ke-kok-koh," as they say in the research team's native Japan).

"'Cock-a-doodle-doo' symbolizes the break of dawn in many countries," says Takashi

Yoshimura of Nagoya University. "But it wasn't clear whether crowing is under the control of a biological clock or is simply a response to external stimuli."

That's because other things -- a car's headlights, for instance -- will set a rooster off, too, at any time of day. To find out whether the roosters' crowing is driven by an internal biological clock, Yoshimura and his colleague Tsuyoshi Shimmura placed birds under constant light conditions and turned on recorders to listen and watch.

Under round-the-clock dim lighting, the roosters kept right on crowing each morning just before dawn, proof that the behavior is entrained to a circadian rhythm. The roosters' reactions to external events also varied over the course of the day.

In other words, predawn crowing and the crowing that roosters do in response to other cues both depend on a circadian clock.

The findings are just the start of the team's efforts to unravel the roosters' innate vocalizations, which aren't learned like songbird songs or human speech, the researchers say.

"We still do not know why a dog says 'bow-wow' and a cat says 'meow,' Yoshimura says. "We are interested in the mechanism of this genetically controlled behavior and believe that chickens provide an excellent model."

http://www.sciencedaily.com/releases/2013/03/130318132625.htm