May 20, 2024

Research shows all dogs smell the same way

Certain dog breeds have a better sense of smell than others. That’s what you thought until now. But American researchers have made a surprising discovery.

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Dogs are thought to have an excellent sense of smell. This is due, among other things, to the large number of olfactory cells in the nasal mucosa.

Dogs are thought to have an excellent sense of smell. This is due, among other things, to the large number of olfactory cells in the nasal mucosa.
© Wolfgang Hoppe/dpa

Los Angeles/Jena. Dog breeds known for their special olfactory abilities may not have a better sense of smell than their relatives. At least that’s what a previously unpublished study by U.S. researchers suggests. When we looked at their genomes and skulls, we found no fundamental differences between sniffer dogs and other dogs, for example.

A group led by William Murphy at Texas A&M University hypothesizes that known differences between races in odor recognition tasks stem from differences in inbred behavior, such as motivation or training ability. This study has not yet been published in a peer-reviewed journal. Julian Breuer, a German dog researcher at the Max Planck Institute for Geoanthropology (MPI) in Jena, thinks this result is very plausible.

Highly regarded, but little understood

Dogs are thought to have an excellent sense of smell. This is due to, among other things, the large number of olfactory cells in the nasal mucosa, the unique way we smell, and the way odors are processed in the brain. People use dogs and other animals to use their special abilities to search for people, drugs, and explosives, detect diseases, and hunt. Beagles, bloodhounds, and German wirehaired pointers are thought to have particularly good senses of smell. Greyhounds, border collies, and pugs are thought to be particularly vulnerable to this.

As a general rule, it’s difficult to test a dog’s olfactory abilities, says Julian Breuer. “We know very little about dog smell.” Breuer is head of the Canine Research Research Group at the Jena Max Planck Institute, where he conducts research on dogs’ sense of smell. For example, it’s unclear what dogs actually recognize chemically when they follow a trail.

For example, Breuer says it’s also difficult to use brain scans to examine the brain processes involved in smelling. The animal then became stressed and began panting. But this is a problem. “Anatomists pretty much agree that it’s impossible to sniffle and pant at the same time,” says Breuer. Although the number of olfactory cells in a dog can be measured, this does not provide reliable information about a dog’s olfactory abilities.

Experiments with genetic material and skulls

Murphy’s group is now choosing a different approach. They looked at the genomes of 30 different dog breeds, looking specifically for genes for so-called olfactory receptors. They found that dogs have fewer such functional genes than wolves and coyotes.

However, comparisons between dogs did not reveal any underlying patterns that could explain the special olfactory abilities of sniffer dogs. Examination of so-called gene expression, how strongly these genes are actually read and proteins made based on them, revealed no such differences.

Murphy’s researchers also took measurements of the so-called lamina cribrosa in 103 skulls. This is part of the ethmoid bone, the bone at the end of the nasal cavity. The cribriform plate contains nerves that transmit olfactory information to the brain. The larger this structure is compared to the mammal’s body size, the better its sense of smell.

However, the researchers also found that there were no structural differences in the lamina cribrosa between dog breeds known for their excellent sense of smell and other dogs. “Our results refute breeders’ claims that olfactory traits were selected and controlled by strict reproductive controls in olfactory breeds,” the study authors wrote.

What do other experts say?

But Jeffrey Schoenebeck, a dog geneticist at the University of Edinburgh, told the journal Science that he wasn’t completely convinced. “I think there are other possibilities here,” he said. Further investigation is required.

“This result doesn’t surprise me,” says Breuer, the canine researcher. After all, the age of most dog breeds does not exceed 200 years. Despite breeding, they do not necessarily develop a better sense of smell during this relatively short period of time. Breuer believes that tracking dogs such as bloodhounds were not bred for special nasal abilities, but rather to be motivated by their sense of smell. Differences in smelling ability may simply be due to how well a particular breed smells and how often it puts its nose to the ground. (dpa)

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