Follow Your Nose!

Translation: Denİz Candaş

Although we’ve known dogs, the so-called “man’s best friend” for thousands of years, we’ve only been pushing the limits of their olfactory abilities for the past hundred years. In addition to finding missing people and detecting illegal substances or explosives, we are now making use of their keen noses even for the early detection of diabetes and some cancer types.

Those living with a dog probably –regularly- witness the way how their friends tuck their noses everywhere. Because dogs trust their sense of smell, above everything else.

Dogs are said to have 300 million smell receptors in their nasal cavities, which makes their sense of smell 100,000 to 100 million times stronger than us (we, in comparison, are thought to have only about six million smell receptors). In addition, the brain region responsible for identifying smells is seven times larger in dogs than that of humans. Wing-like structures at the tip of their nostrils serve for determining the direction of air entering the nose. In other words, they are able to sense the source of a smell in “stereo”.

In short, there is no doubt that they are much better sniffers than us. And a new study now suggests that dogs can also detect heat emitting substances with the help of their noses.

In most mammals, a thin and smooth patch of skin covers the tip of the nose and around the nostrils. However, unlike many mammals, this area called the rhinarium is moist, cool, and full of rich neural network in dogs. And with this structure, they are believed to detect not only the origin and direction of smells, but also different heat sources. This is most likely an evolutionary feature that hunting animals have developed to find warm bodies. The ability to detect weak thermal radiation is thought to be limited to only a few animals: the black firefly, some vipers, and the vampire bat, that is, a single mammal.

In order to try this idea, researchers from Lund and Eötvös Lorand universities trained three dogs to choose one of two panels (one at ambient temperature, and the other heated to 10-14^oC above ambient temperature). Panels were kept at a distance of 1.6 metres each, in order to ensure the dogs wouldn’t be able to distinguish their smell or appearance. In double-blind experiments carried out after the trainings, all three dogs successfully detected the object emitting a weak heat.

The researchers also conducted functional MRI scans on 13 random pet dogs, while presenting them two objects, one of which was emitting weak heat. They observed that the left somatosensory cortex in their brains, delivering the signals from the nose, showed more response to objects emitting weak heat.

As a result of these two experiments, the researchers conclude that dogs can detect weak sources of heat, just like vampire bats do; and that this is probably an evolutionary ability from their ancestor, the grey wolf.

Even though it is still a little early to say that dogs can clearly distinguish heat over long distances, this may just be the explanation of how Buck, the sled dog in Jack London’s Call of the Wild, was able to hunt “not by sight or sound or smell, but by some other and subtler sense.”