Domestic breeds: Fancy Traits Come at a Price

Afroduck swimming in Mirror Lake at OSU
(©Abigail Smith)

Afroduck was Ohio State’s beloved unofficial mascot because of a unique trait that set him apart from the other ducks, a crest of feathers on his head that looked like an afro. Many have wondered if this is a kind of rare genetic mutation never before seen in ducks. As it turns out, his fluffy little afro is a genetic mutation, but it is far from rare.

Many duck varieties can have the crested trait, like this Mallard Duck. (©Heather Paul, 2011)

Afroduck was a breed of domestic Crested Duck. This means that he was specifically bred to have a fluffy crest atop his head. The crest trait has been selected for by breeders in many different duck species. These ducks are considered ‘fancy breeds’ and are bred for show, not for their eggs or meat.

Breeders have been selecting for this trait for centuries. Crested ducks even appear in 17th century Dutch paintings.

Melchior d’ Hondecoeter. A Hunter’s Bag near a Tree Stump with a Magpie, 1678. Rijksmuseum, Amsterdam, www.rijksmuseum.nl

When humans breed animals for a specific trait we call this  artificial selection. Artificial selection has allowed us to domesticate wild animals into livestock like pigs, cows, and sheep. Unfortunately, selecting for a certain trait and attempting to exaggerate that trait as much as possible can have unintended consequences. For example, dog breeds with smashed-in faces, like bulldogs and pugs, have respiratory problems because of their small nostrils, elongated soft palate, and narrow trachea. Selectively breeding for a crest in ducks also comes with negative consequences.

The crest forms on the head of the duck because of a malformation in the skull. These ducks develop with a gap in their skull which is filled in with a mass of fatty tissue. The feathers growing from this area of the head are fluffy and create the crest. Studies have found that the fat bodies cause motor incoordination in some ducks. A 2009 study conducted by J. Mehlhorn and G. Rehkämper tested coordination in crested ducks by placing them on their backs and timing how long it took for them to right themselves. Ducks with larger fat bodies were more likely to have bad coordination

This diagram shows where the fat body develops inside the skull. (Julia Mehlhorn and G. Rehkämper, Brain alterations, their impact on behavior and breeding strategy in Crested Ducks (Anas platyrhynchos f. d.), 2010)

The crested gene is potentially a lethal gene as well. If two ducks with the crested trait are bred there is a 25% mortality rate for the ducklings. Ducklings who receive the crested gene from both parents are likely to die in the shell. The gap in the skull will cause the duckling’s brain to develop outside of the skull.

Humans have used artificial selection for hundreds of years to genetically modify and domesticate plants and animals. In the case of Afroduck and other fancy ducks, humans have selected unusual genetic mutations that they find visually pleasing. Breeding animals in order to exaggerate a single trait often creates unintended and detrimental side-effects. While we might consider Afroduck’s best phyiscal trait to be his fully afro, he might not agree.

Chelsea is one of our student workers and does general collection work

About the Author: Chelsea Hothem is a 3rd year majoring in Evolution & Ecology at The Ohio State University and works as a Research Assistant at the Museum of Biological Diversity in the Tetrapod Collection.