 Different hormones are secreted when a dog is angry, fearful or confident, and some chemical signatures identify the sex and age of the dog, and if a female is in the estrus cycle, pregnant or recently given birth.Many of the pheromone chemicals can be found dissolved in a dog's urine, and sniffing where another dog has urinated gives the dog a great deal of information about that dog.Male dogs prefer to mark vertical surfaces and having the scent higher allows the air to carry it farther.