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robertogreco : feralization   1

When chickens go wild : Nature News & Comment
"The feral chickens of Kauai provide a unique opportunity to study what happens when domesticated animals escape and evolve."



"Chicken and egg

“You won't see a bird as healthy-looking as that,” Wright says of the hen that he and Henriksen had captured at Opaekaa Falls. “Her plumage is perfect.” In the basement of a rented house on Kauai, the researchers have set up a makeshift laboratory where they photograph the bird, draw its blood and then kill it and prepare it for dissection. Wright starts with the hen's Brazil-nut-sized brain.

Their unpublished research has shown that the brains of domestic chickens are smaller than those of junglefowl, relative to their body size, and organized differently. The team hopes to identify the genes responsible for these changes and others, such as the diminished visual-processing systems of domestic birds. Life in the wild has also altered the reproductive systems of the feral chickens. Domestic breeds lay eggs almost daily, but breeding seasonally could allow feral chickens to reapportion the minerals devoted to eggs (which come from spongy tissue in the centre of their bones) to making their skeletons more robust. The researchers sample the hen's femur and also find that its ovaries are empty of egg follicles, which could be a sign of seasonal breeding.

Feralization has garnered much less attention from scientists than domestication (which gets a nod in chapter one of Charles Darwin's 1859 On the Origin of Species). But swapping of domestic and wild genes has been happening all over the world for thousands of years. A feral-sheep population that has lived on the island of St Kilda in the Scottish Outer Hebrides for as long as 4,000 years acquired beneficial alleles that determine coat colour from a modern domestic sheep breed some 150 years ago2. A 2009 study in Science3 found that some wolves in Yellowstone National Park, Wyoming, carry a domestic-dog version of a gene linked to dark coats that shows hallmarks of positive selection, possibly helping wolves from the Arctic to adapt to forested environments. “People would have thought that genes to live in a farm and house aren't going to be any good in the wild, but that's not necessarily true,” says Jonathan Losos, an evolutionary ecologist at Harvard University in Cambridge, Massachusetts.

And like Kauai's feral chickens, other feral animals such as dingoes in Australia and urban pigeons practically everywhere have not evolved back to the state of their wild ancestors — even if certain traits may trend in that direction.

Like chickens, other domesticated animals tend to have smaller brains than their wild cousins, relative to body size (see 'Free bird'). And brain regions involved in processing things such as sight, sound and smell are among the most diminished, perhaps because humans bred animals to be docile and less wary of their surroundings. Feral pigs in Sardinia seem to have regained large brains and high densities of neurons involved in olfaction, but not the abilities that come with them: their neurons do not express a protein that has been linked to the exquisite sense of smell in closely related wild boars4. Likewise, feral dogs, cats and pigs often lack the savvy of their wild brethren and still depend on human niches for their survival, notes Melinda Zeder, an archaeologist at the Smithsonian Institution's National Museum of Natural History in Washington DC. Packs of feral dogs, for instance, do not form the complex hierarchies that make wolves such fearsome predators. “There's no leadership the way you get in a wolf pack. It's just a bunch of shitty friends ,” says Greger Larson, an evolutionary geneticist at the University of Oxford, UK, who is part of a team examining the mixed ancestry of Kauai's feral pigs."
feral  chickens  kauai  nature  birds  anthropocene  science  evolution  2016  ewencalloway  feralization  via:anne 
february 2016 by robertogreco

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