Don’t throw away the dog that’s destroying your house. Maybe it’s a walking “heat detector”.

Author: Su Chengyu

The article comes from the Science Academy official account (ID: kexuedayuan)

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I don't need to tell you how amazing a dog's nose is, but scientists have recently discovered that dogs not only have a keen sense of smell, but they can also be heat detectors.

When it comes to heat detectors, the most famous one is the thermal infrared life detector. The reason why it can detect life is that it can judge different targets by sensing temperature differences. Any object with a temperature above absolute zero will generate infrared radiation, and the human body is naturally an infrared radiation source. The infrared life detector uses the temperature difference between the human body and other objects to separate the target to be searched from the background in an imaging manner.

There are many animals in nature that can detect temperature, such as cockroaches, click beetles, vampire bats and pitted snakes... Snakes' pits have a unique sensory system that can detect infrared light, allowing them to create a thermal image of a predator or prey.

Snake pits Source: Wikipedia

A new member of the heat detection family: Dogs

Biologists from Lund University in Sweden conducted an experiment.

The researchers designed a device divided into two enclosed compartments, which were completely wrapped with black insulating tape. One of the compartments was at a high temperature (about 11 degrees higher than the room temperature and could emit micro-heat radiation, that is, infrared radiation) and contained food, which could be pushed open by a sliding rod; the other compartment was at about the same temperature as the room and also contained food, but it could not be pushed open.

The left side has no temperature and cannot be opened at all, while the right side has temperature and can be opened. Source: Document 1

The device makes no sound or smell except for the temperature difference, so there is only one factor that affects the dog's judgment: temperature.

Then, the researchers found three pet dogs from ordinary people's homes, and after a certain amount of training, they made the dogs associate the warm compartment with food.

Under infrared detection, the temperature of the compartment on the left is the same as the room temperature, while the temperature on the right is higher than the room temperature and has a certain amount of infrared radiation. Then let the golden retriever make a judgment on the temperature of the compartment at a certain distance. Image source: Document 1

Next came the formal experiment. The researchers removed the food from the compartment and asked the dogs to choose between the two compartments from 1.6 meters away. The dogs could not return to the original path and make a new choice, as there was a baffle separating them. Through the double-blind test, all three dogs successfully detected the compartment with the higher temperature.

In order to more accurately illustrate that dogs can detect heat, and that the detector is the dog's nose, scientists conducted further experiments. Scientists found 13 pet dogs, including 5 golden retrievers, 4 border collies, 1 Australian shepherd, 1 Chinese crested dog and 2 mixed breeds. Scientists first placed some objects in front of the dogs (at a certain distance), with the temperature difference between the objects being the same as in the previous experiment, and scanned their brains with a functional magnetic resonance imaging scanner.

The results showed that the left somatosensory cortex in the dog's brain, which is responsible for transmitting information from the nose, reacted more strongly to warm thermal stimuli than to neutral (room temperature) thermal stimuli. When a hot object appeared in front of the dog, a cluster of 14 voxels (3D pixels) appeared in the left hemisphere of the dog's brain, but there was no such cluster in the right hemisphere of its brain, which means that the brain felt the temperature stimulus and felt it at a distance with the nose. When a room temperature object appeared in front of the dog, there was no reaction at all.

Under the stimulation of thermal radiation, there are 14 voxels in the left somatosensory association cortex. Source: Reference 1

Through these two experiments, scientists have proved that dogs' noses can sense heat sources at a long distance, and the left area of ​​their brains will be activated by infrared radiation.

Why can dogs detect heat?

As for the reason, the researchers only made a simple analysis. Because the dog's nose is normally damp and cold, only about 22 degrees, which makes its nose particularly sensitive to the surrounding temperature.

Under infrared observation, the temperature of the dog's nose is relatively low, only about 22 degrees. Source: Document 1

Therefore, dogs can use their noses as heat detectors to assist in finding specific targets, such as prey to be caught. However, how a dog's nose detects and converts infrared signals into nerve impulses is still unclear and requires further research.

Now, "dog nose" not only means a keen sense of smell, but also the ability to detect heat.

References:

Bálint, A., Andics, A., Gácsi, M., Gábor, A., Czeibert, K., Luce, CM, … Kröger, RHH (2020). Dogs can sense weak thermal radiation. Scientific Reports, 10(1). doi:10.1038/s41598-020-60439-y

Gracheva, EO, Ingolia, NT, Kelly, YM, Cordero-Morales, JF, Hollopeter, G., Chesler, AT, … Julius, D. (2010). Molecular basis of infrared detection by snakes. Nature, 464(7291), 1006–1011. doi:10.1038/nature08943