Breed standards continue to reinforce certain ear shapes, narrowing what dogs inherit and carrying those choices across generations. Researchers have now traced floppy ear length to specific inherited changes, revealing how human preference leaves lasting marks on canine biology and health.
Tracing inherited ear length
A recent genetic analysis across many dog breeds connected differences in drop-ear length to a small, shared stretch of DNA. At the University of Georgia (UGA), researchers refined that signal by comparing breeds with similar ear posture but different ear lengths.The work was led by Dr. Leigh Anne Clark, who studies canine genetics and inherited disease risk in many breeds. The findings give breeders and researchers a clearer target to watch as they compare traits across breeds.
Dogs, wolves, and coyotes
The researchers compared genomes from more than 3,000 dogs, wolves, and coyotes. They focused on dogs with floppy ears so that ear carriage – how ears sit on the head – stayed constant while ear length varied.“We only used drop-eared dogs in our study,” said Clark. This approach allowed the team to pinpoint DNA differences that affected ear length, even when all dogs shared the same ear type.
When DNA variants recombine
Differences in ear shape traced back to a small number of inherited DNA variants shared across breeds. Recombination brought together two DNA variants linked to ear posture on a single inherited block, and only that combination produced drop 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,” said Clark. That extra allele sat on the recombinant block, and it pushed ear tissue to keep growing longer.
How nearby DNA shapes ears
The strongest genetic signal appeared near a gene already linked to growth and maintenance of connective tissue in developing ears. The associated DNA did not change the gene directly, but sat nearby, where it could subtly affect how much the gene is used during development.Similar changes have been linked to larger ears in other animals, suggesting this region can influence how ear tissue expands over time.Because the signal lies outside the gene itself, the result points to regulation rather than structure as the likely driver.
Ear length and body size
The same stretch of DNA also sits close to a gene previously tied to overall body size in dogs. When traits sit near each other in the genome, selection for one feature can unintentionally carry another along with it. That overlap makes it harder to tell whether ear length reflects its own genetic cause or a side effect of selection for size. Sorting that out matters, especially when researchers try to separate harmless traits from ones linked to disease risk.
Breeds and hidden tradeoffs
Human breeding pushed certain ear shapes into breed standards, which raised the odds that specific DNA combinations became common. The three-allele package appeared most often in breeds selected for very long drop ears, where ear length defines the look. Breeds that kept the older, ancestral package usually carried smaller, upright ears, even when the head shape changed. Because breeders fix traits within a breed, those genetic packages can spread fast, leaving little diversity for future change.
How ears manage heat
Long ears do more than change appearance, as they help animals manage heat by exposing more skin. Classic rabbit research showed blood vessels in ears tighten in cool air and widen in warmth. When vessels widen, warm blood reaches the ear surface and sheds heat, while tightening keeps warmth inside the body. That biology helps explain why some animals evolve smaller ears in colder places, even before humans start selecting traits.
Breed genetics and health signals
Beyond looks, ear genetics matters to veterinarians because breed-linked DNA patterns can hide or mimic disease risks. In Clark’s UGA projects, strong selection can distort breed genetics, so the ear results add useful context. “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,” said Clark. Genetic tests could help avoid risky variants, but they work best when breeders balance health goals against narrow appearance rules.
A clearer view of dogs
The study relied on broad genetic comparisons across many dogs to narrow the search to promising regions. That approach highlights patterns of inheritance, but it cannot by itself prove which DNA change directly causes longer ears. Confirming the mechanism will require experiments that test how these nearby genetic changes affect ear development. Until then, the results serve as strong signals rather than final answers, shaped by both genetics and breeding history. Taken together, the results show how a small set of variants can shape ear posture and length across many dog breeds. Future genome-wide studies and lab work will test whether nearby DNA regions also influence hearing or other ear-related traits.
The study is published in the journal Scientific Reports.
Source: Earth.com
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