"What great big ears you have!"

Researchers at the University of Georgia have identified the genetic basis behind ear size in dogs, following an analysis of more than 3,000 canines. The findings were published in Scientific Reports, a Nature journal, and mark the first time specific DNA variants linked to ear length have been pinpointed.

The research team analysed genetic data from dogs, wolves and coyotes to identify the region of the genome responsible for ear size. The study found that ear length is influenced by genomic differences near the gene MSRB3 – a result the researchers did not initially expect.

MSRB3 plays a role in determining whether a dog has upright ears, such as those seen in German shepherds, or drop ears, such as those of bloodhounds. Mutations in the same gene are also associated with hearing loss in humans.

“We only used drop-eared dogs in our study,” said Leigh Anne Clark, corresponding author of the study and an associate professor in the UGA College of Veterinary Medicine. “There shouldn’t have been differences at that location in the genome because they all had floppy ears.

“What we learned is that there’s a combination of alleles, or different DNA sequences, at this locus that dictates whether a dog has prick ears like a husky versus drop ears like a cocker spaniel. But then there is an extra allele on top of that combination that determines if the ear will be short or long.”

The study was inspired by undergraduate researcher Anna Ramey’s cocker spaniel and represents the first clear identification of the genetic mechanisms underlying ear size in dogs.

Dogs display a wide range of ear shapes. These variations can serve different purposes, from hearing and scent detection to appearance. For example, the upright ears of a Belgian Malinois assist with detecting distant sounds, while the long ears of a beagle help concentrate scents by limiting external noise.

Some ear traits evolved naturally, while others have been emphasised through selective breeding. Although Clark’s laboratory primarily focuses on inherited diseases in dogs and their genetic causes, the findings may help support future research into canine health.

“It’s important for us to understand what genes and genomic regions are being selected for in breeds, especially when we’re thinking about genetic disorders.”

With greater understanding of how this area of the genome is affected by breeding decisions, researchers can take these factors into account when mapping disease-related genes.

“If we can identify the alleles that underlie disease, then we can develop a genetic test that breeders can use to avoid the allele or reduce its frequency in the population. Ultimately, our goal is to reduce disease incidence, or in some cases, eliminate it all together.”

The study was co-authored by Tori Rudolph from the UGA Department of Pathology and Jonah Cullen and Steven Friedenberg from the University of Minnesota.