There are chemical signals all around the world that humans can barely notice. However, many animals are not only sensitive to these tastes and smells, but they are also able to secrete them as well. A scent known as a pheromone is one such chemical, given off by animals to influence the physical and mental behaviour of others in the same species. They are normally produced in microscopic amounts but their effect can be powerful.
Animals patrol a territory in which they plan to mate or inhabit and mark certain objects or the ground with their pheromone. Other animals arriving at the territory can detect the pheromone by smell. This lets them know the animal wants some privacy and may become aggressive if its living quarters are infringed upon.
There are many ways an animal can produce pheromones, such as glands on their body or leaving excretion in certain areas. Pheromones allow an animal to alert others of their readiness to breed.