Why is your dog always sniffing other dogs' rear-ends? He's not being rude — he's collecting important information.

When a dog sniffs another dog's bottom, he's actually gathering information about the other dog's gender, diet and emotional state.

As the narrator in the American Chemical Society video below explains it, "Think of it kind of like speaking with chemicals."

A dog's sense of smell is 10,000 to 100,000 times better than our own, so canines can glean a lot of details from another dog's aroma.

In 1975, Dr. George Preti of the Monell Chemical Senses Center studied this sniffing behavior by analyzing the anal secretions of dogs and coyotes.

He found that the animals' rear-ends have several glands that secrete chemicals containing information about the animals' gender and diet, among other things.

The primary chemical compound released from these glands is trimethylamine, an organic compound with an odor often associated with bad breath or rotting fish.

But how can a dog's nose sniff out a canine's identifying information without other anal smells getting in the way?

Dogs have a second olfactory system known as the Jacobson's organ, a patch of sensory sells located in the main nasal chamber. This organ's nerves direct detected chemical information directly to the brain so other odors can't interfere.

To learn more about what your dog is sniffing down there, watch the video below.

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