Can a dog see its own nose?

Dogs can "smell" thermal radiation

The cold, wet nose is a dog's most important sense organ. Their mucous membrane houses up to 300 million olfactory cells and makes the dog a so-called macrosmate. This is the name given to animals whose sense of smell is particularly well developed and plays a central role in perception. For comparison: the human nose has just five million olfactory cells, so we are microsmats.

The extraordinary smell performance of dogs cannot be determined by the number of these specific cells alone. The four-legged friends also have an enormous area in the brain that is responsible for processing olfactory signals. Researchers estimate that dogs can smell about a million times better than we can. But that's not all: As an international research team reports in "Scientific Reports", dogs can apparently also register weak heat radiation with their olfactory organs - and not just by touch, but over a distance of one and a half meters.

Highly sensitive snout

The biologists around Anna Bálint from the Eötvös-Loránd University of Budapest and Ronald Kröger from the University of Lund got the cold snout of animals on the hot trail of this ability: the so-called nasal mirror (rhinarium), i.e. the black, hairless area around the nostrils, is much colder in dogs and some other predators than in herbivores such as the ungulates. "Our hypothesis was that the dogs' nasal mirror could be particularly sensitive to heat radiation due to the cold," the study says.

To test this assumption, the scientists first carried out experiments with three dogs. They taught the animals to distinguish between two objects that were identical in appearance and smell. But the objects were not exactly the same: thanks to built-in heat sources, one was 20 degrees Celsius (corresponding to the ambient temperature), the other was eleven degrees warmer and corresponded to the body surface temperature of a hairy mammal.

The researchers themselves could only determine the temperature difference by touch, but the dogs were made more difficult in the subsequent double-blind experiments. You should identify the warmer object from a distance of 1.6 meters. The result: All three dogs were able to track down the warmer object from this distance, write the scientists.

Activated brain region

In a second experiment, brain activity in dogs was examined using functional magnetic resonance imaging. This imaging method makes it possible to observe changes in blood flow in different areas of the brain, from which conclusions can be drawn about the neural activity in these areas. Specifically, Bálint and colleagues looked into the brains of 13 dogs of different races while they also presented them with objects that were either at ambient temperature or around 31 degrees Celsius.

It was shown that the area of ​​the cerebral cortex that is centrally involved in the processing of perceptual stimuli in dogs was activated significantly more strongly by the warmer test objects. According to the researchers, the results suggest that dogs can sense weak thermal radiation through their noses.

They suspect that our domestic dogs have this ability from their wild ancestral form: Thanks to their thermosensitive noses, wolves could track down prey even better. And maybe that will also indirectly benefit people - with rescue dogs looking for victims. (David Rennert, March 3rd, 2020)