New study reveals

Do all dog noses sniff equally well?

Studies of the genetic material and the skull revealed no fundamental differences between sniffer dogs and other dogs, for example.(Bild: Pixabay)

Dog breeds known for their special smelling abilities may not have a better sense of smell than their conspecifics. A study by US researchers suggests that there are no fundamental differences between "sniffer dogs" and other dogs.

Dogs' sense of smell is considered to be outstanding. This is partly due to the high number of olfactory cells in the nasal mucosa, the special way they sniff and the processing of the odor in the brain. Humans make use of these special abilities by using dogs to search for people, drugs and explosives, as well as to detect diseases and for hunting. Beagles, bloodhounds and German wirehairs are considered to be particularly good sniffers. Greyhounds, border collies and pugs are considered to be particularly bad at this.

However, the group led by William Murphy from Texas A&M University now assumes that the known differences between breeds in scent detection tasks are due to inherited behavioral differences such as motivation and trainability. The German dog researcher Juliane Bräuer from the Max Planck Institute (MPI) for Geoanthropology conducts her own research into dogs' sense of smell and considers the results to be plausible.

Difficult to investigate
It is fundamentally difficult to study the olfactory abilities of dogs, says Juliane Bräuer. "We know extremely little about smelling in dogs." For example, it is unclear what a dog actually senses chemically when it follows a scent.

It is also difficult to use brain scans, for example, to investigate the processes in the brain during smelling, says Bräuer. The animals are then stressed and start panting. But this is a problem: "Anatomists are almost unanimous that sniffing and panting are not possible at the same time," says Bräuer. The number of olfactory cells in the dog, on the other hand, can be determined, but does not provide any reliable information about the dog's ability to smell.

Genetics are decisive
Murphy's group chose a different approach. They looked at the genetic material of 30 different dog breeds and specifically searched for genes for so-called olfactory receptors. They found that dogs have fewer such functional genes compared to wolves and coyotes.

However, the comparison between the dogs did not reveal any fundamental pattern that would explain the special olfactory abilities of sniffer dogs. A look at the so-called gene expression - i.e. the extent to which these genes are actually read and proteins are produced on this basis - also revealed no such differences.

Murphy's researchers also carried out measurements of the so-called lamina cribrosa on 103 skulls. This is part of the ethmoid bone, a bone at the end of the nasal cavity. The lamina cribosa is permeated by nerves that transmit olfactory information to the brain. The larger this structure is in relation to the size of a mammal's body, the better its sense of smell can be.

However, even in the lamina cribrosa, the researchers found no structural differences between breeds known for their excellent sense of smell and other dogs. "Our results call into question breeders' claims that olfactory traits are selected and controlled by strict reproductive controls in olfactory breeds," write the study authors.

Track recorded
Jeffrey Schoenebeck, a dog geneticist at the University of Edinburgh, is not entirely convinced, however, telling Science magazine. "I think there are other possibilities at play here," he said. More research is needed.

"I'm not surprised by the results," says dog researcher Bräuer. After all, most dog breeds are no more than 200 years old. In this comparatively short time, a better sense of smell does not necessarily develop despite breeding. Bräuer believes that tracking dogs such as bloodhounds were not bred for their special nasal abilities, but for their motivation to smell. The differences in smelling abilities could simply be due to how much certain breeds sniff - and how often their noses are on the ground.