Dogs have an incredibly powerful sense of smell that they use to communicate with other dogs and with humans. Here are FOUR ways that dogs use their sense of smell to communicate:   Marking their territory: Dogs mark their territory by urinating or defecating in specific locations. This leaves a scent that other dogs can detect, letting them know that the territory is already claimed. Identifying other dogs: Dogs can recognize other dogs by their scent, just as humans can recognize each other by their faces. They use their sense of smell to identify familiar dogs and to detect the presence of unfamiliar dogs in their territory.  Communicating emotions: Dogs can detect the emotional state of other dogs by their scent. For example, a dog that is feeling anxious may give off a specific scent that other dogs can detect, indicating that it may need comfort or reassurance. Tracking: Dogs have been used for centuries to track humans and animals, thanks to their powerful sense of smell.