The J-shaped notch on canine nostrils creates a physical airflow dynamic where inhaled odorants are retained and recirculated across space and time.
"Well, if you've ever seen that sort of J-shaped nostril on the dog's nose, it's kind of like little notches on the sides. It creates a physical environment where every inhale keeps the odor in and keeps it circulating. So, they're spending a lot of time with each odor, even if they smelled something a few seconds or even minutes ago." (said at 0:50:41)
The speaker misattributes the function of the lateral notch (alar slit) on the canine nostril and misstates the fluid dynamics of olfaction. Fluid dynamics and anatomical studies show that the external lateral nostril slit functions during expiration by directing expired air laterally and caudally away from the front of the snout, preventing exhaled air from blowing away the external odor plume. Odorant transport to sensory neurons occurs internally via a specialized anatomical olfactory recess located at the posterior nasal cavity. Canine sniffing occurs at high frequencies (roughly 3–7 Hz), and the external notch does not trap and recirculate inhaled odors across minutes.
- contradicts: The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of… (Journal of the Royal Society, Interface 2010)
"Inside the nose, the computation shows that a unique nasal airflow pattern develops during sniffing, which is optimized for odorant transport to the olfactory part of the nose. These results contrast sharply with nasal airflow in the human. We propose that mammalian olfactory function and acuity may largely depend on odorant transport by nasal airflow patterns resulting from either the presence of a highly developed olfactory recess (in macrosmats such as the canine) or the lack of one (in microsmats including humans)." (abstract, results, passage verified)
pubmedfull study (doi) - contradicts: A computational study of odorant transport and deposition in the canine nasal cavity: impl… (Chemical senses 2012)
"In the dog and other macrosmatic mammals, ORNs are relegated to a recess in the rear of the nasal cavity that is comprised of a labyrinth of scroll-like airways. Evidence from recent studies suggests that nasal airflow patterns enhance olfactory sensitivity by efficiently delivering odorant molecules to the olfactory recess." (abstract, results, passage verified)
pubmedfull study (doi)