Why dogs sniff each other: the mystery is solved

When two dogs meet, they often try to sniff each other from behind. Cats behave similarly, as confirmed by those who have several pets at home.

It turns out that there is a good reason behind the sniffing habit, LiveScience writes. In this way, four-legged animals learn about the health of another animal.

"Dogs can determine the reproductive status of another dog, what it has been eating, and generally get 'news' by sniffing each other's hindquarters," says Ellen Furlong, an associate professor of psychology who specializes in animal cognition at Transylvania University in Lexington, Kentucky.

The instinct to reproduce also plays a role. To this end, males can spend more time sniffing females.

But how do dogs manage to get all this information? One of the first clues to solving this mystery appeared in 1976 when a study on dogs and coyotes was published.

It showed that two small pouches, one on each side of a dog's anus (anal pouches), secrete a cocktail of smelly chemicals, including fishy-smelling trimethylamine and caustic propionic and butyric acids. According to a study published in 2021, these anal sac secretions may serve as chemical communication signals.

Each chemical probably conveys some information to another dog, but scientists have yet to crack this code of odors. A 2023 study compared the anal sac secretions of male and female dogs. It turned out that certain chemicals are released only by females, while others are released only by males.

The researchers also noted that even in same-sex individuals, the chemicals, their composition, and concentration differ. So, in addition to gender, other parameters affect a dog's scent profile.

So dogs sniff out the existing chemical composition. Thanks to their much better sense of smell, dogs can identify individual odors in a mixture and detect them in much lower concentrations than humans.

"A dog's sense of smell is 10,000 to 100,000 times better than ours. Dogs can smell out of a trillion others," Furlong said.

Cats can do it too

Cats' sense of smell is also much more developed than humans'. Research shows that scent recognition plays a central role in the behavior and overall well-being of cats, Christine Vitale, an assistant professor of animal health and behavior at the University of the Environment in Maine, told Live Science in an email.

Like dogs, cats have small glands that produce chemicals with distinct odors.

"By smelling the back of another cat's body, a cat can determine whether it is familiar with it or not, as well as its gender and even possibly its reproductive capabilities," Vitale says.

"Both male and female cats use scent to identify and communicate with social partners," she added.

In 2023, researchers from the University of California, Davis, studied 23 domestic cats. It was found that the anal glands of animals are home to bacteria that are likely involved in the production of foul-smelling anal gland secretions. Different cats had different bacteria in their anal glands, and the types of bacteria varied depending on the age and weight of the cat.

Scientists believe that these bacteria help cats and dogs communicate. This hypothesis is supported by a similar study conducted on hyenas.

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