Studies have shown that some birds have the capacity to identify their own relatives.
A new study from Linköping University in Sweden has found that this ability extends to male domestic fowl as well, and that bonds of kinship result in less aggressive behavior among individuals.
The study was designed to investigate whether roosters who attempted to mate would also help their relatives attempt to do so. In evolutionary terms, any kind of kin-to-kin assistance would be a good way to ensure that at least a portion of the male's genes would be passed on to the new generation. This would be especially important for older males with a less robust reproductive capacity.
Researchers wanted to find out if dominant roosters would be more tolerant of mating attempts by their younger, subordinate relatives as opposed to attempts by lower-ranking males to whom they were not related.
In order to conduct the study, researchers divided the birds into groups. Each contained one dominant male and two lower-ranking roosters, one who was either the brother or son of the dominant male and one who was unrelated. The researchers released the roosters together into a group of four hens and studied the mating attempts.
According to Hanne Løvlie, lead researcher and professor in the University's Department of Physics, Chemistry, and Biology, "We saw that related males interrupt each other's mating attempts less frequently, and are in this way more tolerant towards kin. The dominant rooster interrupted unrelated males' mating attempts more frequently."
This finding, according to the study's lead author, Charlotte Rosher, suggests that chickens can identify their relatives and bonds of kinship lead to less aggressive behavior among related birds in a competitive setting.
The researchers also observed that older males did not demonstrate a higher level of tolerance than younger males did, and that on the whole, all roosters were friendlier to their relatives than to strangers, regardless of age.
"The finding demonstrates how complex evolutionary processes and finely tuned individual behaviour can be. Animals in a group behave differently towards other individuals depending on who they are related to," says Løvlie.
What remains unclear is exactly how the birds are able to recognize their relatives. Researchers suspect that olfactory cues could play a role.
The study was published in the journal "Behavioral Ecology" and you can check it out here.
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