Chickens Gone Wild Did Not Go Through Reverse Domestication

October 3, 2016 | Erica Tennenhouse

Photo credit: Aaron Chenoweth/flickr (CC BY-NC-SA 2.0)

Study reveals the genetic path to feralization in Kauai chickens.

For thousands of years, humans have domesticated dogs, chickens, horses, and a host of other animals, by selecting the individuals with the most desirable traits to breed. Going from wild to tame has had dramatic effects on the genes of many domesticated species.

And then sometimes things go the other way, with domesticated animals readapting to life in the wild — these animals are referred to as feral.

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Becoming feral has always been considered as the reverse of domestication, but a new study published in Nature Communications concludes that adaptation back to the wild is a unique process involving a different set of genes.

The researchers focused on a group of feral chickens living on the island of Kauai in Hawaii. Tropical storms 30 years ago led to their accidental release into the wild, where these chickens proceeded to breed with wild red junglefowl.

Their re-adaptation to the wild has coincided with a number of changes with regards to the chickens’ egg production, brooding behavior, and appearance. For example, the feral chickens exhibited reductions in number and size of their eggs, increased time spent incubating their eggs, and smaller combs adorning their heads.

By pinpointing the gene regions responsible for these traits, the researchers were able to compare the genetic changes correlated with the transitions from wild to domesticated, and from domesticated to feral.

"We wanted to see whether feralization is the same process as domestication, but in the other direction,” says senior author Dominic Wright, from Linköping University in Sweden, in a press release.

“Our results show that this is not the case,” she explains. Rather, as the researchers found, it is “largely separate genes that are affected when domesticated chickens return to the wild.”

The findings close some gaps in our understanding of the mysterious process of feralization, and importantly, confirm that becoming feral is not simply a matter of reversing the changes that took place over the course of domestication.

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