Domestic Dog

A Nose Wired for Airflow

Size and genes are the usual explanation for a Domestic Dog’s (Canis lupus familiaris) sharp nose, but they leave out how air moves through it. Its nasal cavity holds hundreds of millions of scent-sensing cells in the olfactory epithelium, a lining over the convoluted nasal turbinates at the back of the nose. Scientists built a three-dimensional computer model of a dog’s nasal passages from MRI scans and found that sniffing draws a separate sample of air into each nostril, which may let a dog compare the smell’s strength on each side and locate its source. The airflow pattern inside the nose contrasts sharply with a human’s. The researchers propose that a dog’s sense of smell may depend largely on that airflow, shaped by a highly developed olfactory recess that humans lack.

The Wolf Behind the Wag

The domestic dog was the first animal humans domesticated, though scientists are still not sure when the process began. Its wild ancestor is the grey wolf, the first species to give rise to a domestic population. Domestication reshaped more than behavior. Dissections of six dogs and four wolves found that a muscle called the levator anguli oculi medialis was routinely present in the dogs, while in the wolves it was typically only scant fibers. The muscle raises the inner eyebrow intensely. Filmed as a stranger approached, 27 shelter dogs made that movement more often and more intensely than nine wolves from wolf parks, and the researchers suggest human preference selected for these “puppy dog eyes”.

One Species, Countless Shapes

Selective breeding has produced dogs weighing anywhere from under 1 kilogram to 70 kilograms. Dogs are omnivores: their diet includes birds, mammals, amphibians, reptiles, fish and eggs, along with seeds, grains, nuts and fruit. They live alongside people worldwide, in cities, suburbs and farmland, across habitats from tundra and desert to forest and rainforest.

A Dog’s Clock, and a Built-In Compass

A Built-In Compass Off the leash in open fields, dogs in one study preferred to line up north-south to go to the bathroom, but only while Earth’s magnetic field was calm.

A UK study of 30,563 dogs that died between 2016 and 2020 put life expectancy at birth at 11.23 years. Breed changed that a lot: among the breeds studied, the Jack Russell Terrier had the longest at 12.72 years and the French Bulldog the shortest at 4.53. AnAge, a longevity database, puts the maximum dog lifespan at 27 years. An Australian cattle dog named Bluey was reported to have lived 29.5 years, but AnAge calls that record unverified.