Why Do Dogs Sometimes Open Their Mouths While Sniffing?

Dogs have amazing noses. The dog's nose is more useful to the dog than its eyes when it comes to the information obtained via smelling. The scent receptors in the nose can detect and distinguish between tiny amounts of scents.

Sometimes dogs also open their mouths while sniffing. This is because they have evolved a special organ called the vomeronasal organ. The vomeronasal organ is like a cross between a nose and a tongue. Think of the nose as a specialized detector for scent molecules. The vomeronasal organ allows more access to the scent molecules to aid the nose in detecting and processing the scent.