Is there a thermal camera in your dog’s nose?
Dogs are our closest companions, providing emotional support and company. Beyond that, and thanks to their extraordinary sense of smell and trainability, humans have used dogs for hunting, explosive and narcotic detection and assistance for persons with disabilities, among many other tasks. Their sensitive nose (~100.000 more sensitive than ours) allows them to detect certain tumors, COVID-19 infections and even the onset of seizures (1). In addition to this sophisticated sense of smell, a study in 2020 showed that dogs are also equipped with body-heat detection (2), a very rare and extraordinary ability.
Warm-bodied organisms (like all mammals) emit radiation, this energy travels in the form of waves, similar to the light emitted by the sun. However, this type of body-heat radiation, called infrared radiation, carries low energy and is not visible to our eyes. Indeed, this type of radiation is used in night vision and thermal imaging devices. The ability to detect infrared radiation is highly advantageous for nocturnal predators, allowing them to detect their prey’s body-heat in the dark. However, infrared detection is not very common in the animal kingdom and can represent challenges that require special adaptations.
One such adaptation would require the sensory organ to remain cold, in order to be able to detect modest changes in temperature from the distance. A dog’s nose could potentially serve this purpose, as it remains cool at different ambient temperatures. This observation led investigators to ask whether dogs can sense infrared radiation through their nose. The experiment consisted in training dogs to choose between two identical chambers, but one of them containing a weak thermal signal. From a distance over one meter, dogs were able to reliably identify the chamber with the thermal signal. This type of stimulus activated the area that represents tactile information from the nose in the dog’s brain. The authors of the study conclude that dogs are able to detect infrared radiation and point to the nose as the sensor organ.
Before this study, some species of snakes and vampire bats were the only vertebrates known to have infrared detection capabilities (3,4). In both cases, specialized structures in the face of the animals, called pits, are thermally isolated and contain a thin membrane that can get easily warmed. This membrane receives nerve endings extremely sensitive to temperature, allowing the animals to sense infrared radiation of prey. In the case of the dog’s nose, thermally isolated cavities as such are not present and the mechanism allowing infrared detection is unclear. But as direct descendants from wolfs, such adaptation would be a remnant of their past as nocturnal predators.
References:
1. Kokocinska-Kusiak, A., Woszczylo, M., Zybala, M., Maciocha, J., Barlowska, K., and Dzieciol, M. (2021). Canine Olfaction: Physiology, Behavior, and Possibilities for Practical Applications. Animals (Basel) 11. 10.3390/ani11082463.
2. Balint, A., Andics, A., Gacsi, M., Gabor, A., Czeibert, K., Luce, C.M., Miklosi, A., and Kroger, R.H.H. (2020). Dogs can sense weak thermal radiation. Sci Rep 10, 3736. 10.1038/s41598–020–60439-y.
3. Gracheva, E.O., Cordero-Morales, J.F., Gonzalez-Carcacia, J.A., Ingolia, N.T., Manno, C., Aranguren, C.I., Weissman, J.S., and Julius, D. (2011). Ganglion-specific splicing of TRPV1 underlies infrared sensation in vampire bats. Nature 476, 88–91. 10.1038/nature10245.
4. Gracheva, E.O., Ingolia, N.T., Kelly, Y.M., Cordero-Morales, J.F., Hollopeter, G., Chesler, A.T., Sanchez, E.E., Perez, J.C., Weissman, J.S., and Julius, D. (2010). Molecular basis of infrared detection by snakes. Nature 464, 1006–1011. 10.1038/nature08943.
