Floppy Dog Ears

When it comes to genetics and artificial selection, domestic dog breeds are an exceptional example. We have dogs of many characteristics, which, for me, is a good thing; no dog can ever bore me with its appearance or personality because they are all so different.

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One quality that I am really curious about, though, is the flop of a dog’s ears–not how ear flop may affect our ideas of a dog’s “personality” but how, physiologically, some dogs’ ears are floppier than others’. Most are probably familiar with the big, droopy ears of a Basset Hound while the ears of, say, a German Shepherd  generally stand erect. And then, there are dogs like my Jack Russell Terrier that have one ear erect and the other that flops midway. How can this be explained?

I dug into some research, and found conclusions that provide an answer but are not altogether satisfying. In an interesting article, Boyko et al. (2010) examined how single nucleotide changes can drastically alter a dog’s phenotype. For instance, floppy ears can be seen in dogs with mutations in a small region on chromosome CFA10. Furthermore, species that are characteristically floppy-eared will tend to be homozygous for mutations in the region instead of heterozygous. However, we don’t know if this is due to the selection for floppy ears or the selection of another trait that also may be affected by the same region on CFA10. CFA10 has also been associated with a dog’s trainability, coat pattern, and size. I don’t know exactly how these play a role in the grand scheme of the animal, but I have heard that coat color may be an indicator of potential health problems in dogs, such as a correlation between spots and impaired vision or hearing.

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I am ultimately interested in finding the effects of mutations in the region of CFA10 on structure. Although I don’t have the answers, my immediate thought was that, somehow, a structural protein in upright-eared dogs has been mutated in floppy-eared dogs. Thus, upright-eared dogs have ears that are more stiff. I also want to know why some dogs, such as mine, will have one floppy ear and one upright ear. How does this work? Could there be some correlation between which ear is floppy and the color pattern on that ear?

I think this is an interesting examination of cells of the same animal (therefore, having the same DNA) can have different physical appearances due to the way that the genes are expressed in the cell. Not only may ears vary from breed to breed but may also have differences within a breed and even within a single animal. Interesting stuff.

In any readers know more why dogs may have floppy ears, I would love to hear about it. The physiology underlying the genetics is something I would like to know.