Pheromones

Whilst pheromone is a well known term it is often used to refer merely to sex attractants. They actually comprise a sub-class of semiochemicals which comprise two classes of signalling chemicals that birds, fish and mammals can detect in their environment and which may modify  their behaviour.  The other sub-class of semiochemicals are allelochemics which are described, briefly, first before the focus of this text changes to the subject of this text, pheromones. 

Any dog walker will observe that the animal will follow a trail sniffing the ground as s/he proceeds whilst the odour is rarely apparent to the dog walker.   This is because dogs have many thousand more odour receptors in their noses than do humans.  The odour receptors do not duplicate themselves and are respond to different odours hence dogs are much more sensitive to the environment than are humans even if inhabiting the same space.  This also explains why some dogs are so effective at detecting drugs, dead bodies and even explosives.

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