Why some dogs have long ears and others have short ears

Dogs have a variety of ear shapes - standing, button, rose, bat and long floppy ears. Now scientists have found out what it is in the DNA that is responsible for how long these very "signature" ears will be in some breeds.

Researchers from the University of Georgia (USA) analysed the genetic data of more than 3000 animals - domestic dogs, as well as wolves and coyotes - and found that the length of ears is associated with differences in the genome near the MSRB3 gene. The results are published in the journal Scientific Reports.

The surprise is that the work focused specifically on dogs with floppy ears. According to the authors, with such selection, the "signal" in this part of the genome should not seem to stand out, because all the dogs in the sample have ears no longer standing. However, the analysis revealed a more subtle adjustment: a combination of DNA variants in the MSRB3 region helps to "divide" the type of ears (standing versus floppy), and an additional variant on top of this combination already affects whether the ears will be short or long.

The MSRB3 gene is known to be associated not only with ear characteristics in dogs, but also appears in studies of human hearing: mutations in it have been associated with hearing impairment. Therefore, the authors note that the finding may be useful not only for understanding the appearance of breeds, but also for future genetic work on inherited diseases.

A separate finding relates to breeding. Many features of canine exteriors once arose naturally, but purposeful selection by humans has reinforced contrasts between breeds. Understanding which parts of the genome are 'illuminated' by selection is important for veterinary genetics: it helps to better account for background mutations when searching for the causes of inherited diseases and, in the long term, to develop tests that will reduce the frequency of undesirable variants in the population.