ِAnimals`sense of Smell
Humans and animals differ in the way they use their noses. Living things in the animal world generally use their scent perception to search for food, hunt, communicate amongst themselves, find their way, and to locate their mates and offspring. Birds, mammals, reptiles, fish, insects and other animals have been equipped with the olfactory systems most appropriate for the environments in which they live.
How did these living things all come by their scent-perception systems? To think that animals themselves constructed the perfect scent-perception systems in their own bodies—or that these perfect systems came into being by chance—is clearly irrational and illogical. Neither living things themselves nor chance can bring together such marvelous systems. Even under the advanced technology of the 21st century and despite all of scientists', researchers' and engineers' best efforts, nothing resembling these marvelous systems can be produced. As for how these living things came by their olfactory systems, there is only one logical reply: Creation.
It is revealed in the Qur'an that we need to learn from the creation of animals: There is instruction for you in cattle . . . . (Surat an-Nahl: 66)
And there is certainly a lesson for you in your livestock . . . . (Surat al-Muminun: 21)
Dogs: Olfactory Experts
The scents perceived by someone walking along the street and their dogs are hardly the same. Dogs obtain a great deal of detailed information about their surroundings from smells of which their owner is quite unaware. They collect information by analyzing scents left by other dogs and the individual scents of nearby human beings. They are able to analyze even the slightest smells in the air.
Dogs' noses are extraordinarily sensitive: Some breeds' scent sensitivity is up to a million times that of human beings'. A few statistics will help dramatize this special design. In the human nose, the scent region is 5 square centimeters (0.775 of a square inch), but as much as 150 square centimeter (23.25 square in) in dogs. And in the canine nose, there are many times more scent receptors. A fox terrier, for example, has 147 million, and a German shepherd, 225 million.
A photograph showing dogs' inhalation and exhalation, taken using the Schlieren technique.
Thanks to these properties, dogs are able to perform tasks way beyond human beings' most advanced technological devices. These animals' superior attributes are used in finding narcotics, contraband, missing people, explosives, criminals and the victims of catastrophes. For example, the bloodhound, a breed with an exceptionally well developed sense of smell, can follow tracks of which there are absolutely no visible traces. They can follow a track for as much as four days and follow the tracks left by a human for 80 kilometers (49.7 miles).
Strikingly, dogs do not make mistakes, despite the countless number of scents in their world. They are easily able to distinguish the particular smell they are looking for. Experiments have shown that a trained dog is able to locate what was expected of it from among items covered with highly pungent skunk scent.
The Schlieren photography technique revealed that dogs used a different method of inhalation: a dog smelling something twitches its nose when exhaling, and the air heads directly towards the two clefts on either side. Thanks to this special design, the dog's exhaled air flows in a different direction, and the air in its breath is thus prevented from combining with the scent.