Given that they have the largest nose in the world, it is perhaps not surprising that elephants are thought to have the best sense of smell of all animals. The sense of smell is probably the most important of their senses. If you observe elephants for any length of time, you will notice that the tip of their trunks are constantly moving, testing the smells in the air in every direction as we might perhaps use our eyes.
Monitored wild elephants have shown that they are able to pick up smells over distances of several miles, giving them a useful early warning system of approaching danger. Elephants also commonly smell each other and each other's body secretions to obtain valuable chemical knowledge about their companions.
When something more than smell is required, elephants use the trunk tip as a chemical receptor - allowing them to obtain information about other elephants. They gather chemical information by touching the trunk tip against a substance, commonly urine, faeces or temporal glad secretions. The trunk tip is then pressed against the roof of the mouth to the vomeronasal or Jacobson's organ where the chemical is analysed for the information it possesses. This is known as the Flehmen Response.