Dogs' Amazing Cold Noses Detect Heat as Well as Odors
fMRIs show they do this by using their left somatosensory association cortex.
Posted Feb 29, 2020
I recently read an extremely interesting and important essay involving scientists at Lund University in Sweden and Eötvös Loránd University in Budapest, published in Scientific Reports and available online. It's written by Anna Bálint and seven colleagues and titled, "Dogs can sense weak thermal radiation." 1 The results of this research have generated a good deal of interest in popular media.
An excellent essay that explains more about this project by science writer Virginia Morell called "New sense discovered in dog noses: the ability to detect heat" makes clear what this research is all about. She begins, "Dogs' noses just got a bit more amazing. Not only are they up to 100 million times more sensitive than ours, they can sense weak thermal radiation—the body heat of mammalian prey, a new study reveals. The find helps explain how canines with impaired sight, hearing, or smell can still hunt successfully." While we know just how sensitive dogs' noses truly are, the ability to sense heat hasn't previously been shown in carnivores.
Here's a general summary of what this fascinating research uncovered. (Details about the methodology can be read in the research essay.) At Lund University, using double-blind experiments, three dogs (Kevin, Delfi, and Charlie) were asked to distinguish between two objects radiating heat, a neutral object that approximated ambient temperature, and a warm object (31°C) that approximated the surface temperature of a furry mammal. All three were able to detect the warm object.
In addition, at Eötvös Loránd University, the brains of 13 awake dogs were studied using functional magnetic resonance imaging (fMRI) while they were exposed to objects giving off the same amount of heat as the neutral and warm objects used at Lund. The results showed that the warm stimulus caused the left, but not the right, somatosensory association cortex to fire. This part of the brain received input from dogs' noses and responded more to the warm object than to the neutral object.
Morrel writes, "Together, the two experiments show that dogs, like vampire bats, can sense weak hot spots and that a specific region of their brains is activated by this infrared radiation, the scientists say. They suspect dogs inherited the ability from their ancestor, the gray wolf, who may use it to sniff out warm bodies during a hunt." The researchers note, "Our results demonstrate a hitherto undiscovered sensory modality in a carnivoran species."
The only other mammal known to be able to detect radiation is the common vampire bat who "can detect skin areas richly perfused with blood and thus suitable for biting after landing on a host animal." One fact that amazes me is that snake pit-organs are sensitive to temperature changes as tiny as 0.001 degrees, and maybe even smaller ones.
The research under discussion provides yet another window into the sensory worlds of dogs' highly evolved cold noses. Stay tuned for more discussion about the amazing sensory capacities of dogs and other animals.
It seems inevitable that future research will show that we've only discovered the tip of the "nasal iceberg" of dogs and their sensory organs and those of other animals. It's a very exciting time to study and to learn about how other animals sense the worlds in which they live. This information tells us more about the choices they make, and how distinct their sensory capacities are from one another's, and how foreign they are from ours.
1) The abstract for "Dogs can sense weak thermal radiation" reads, "The dog rhinarium (naked and often moist skin on the nose-tip) is prominent and richly innervated, suggesting a sensory function. Compared to nose-tips of herbivorous artio- and perissodactyla, carnivoran rhinaria are considerably colder. We hypothesized that this coldness makes the dog rhinarium particularly sensitive to radiating heat. We trained three dogs to distinguish between two distant objects based on radiating heat; the neutral object was about ambient temperature, the warm object was about the same surface temperature as a furry mammal. In addition, we employed functional magnetic resonance imaging on 13 awake dogs, comparing the responses to heat stimuli of about the same temperatures as in the behavioural experiment. The warm stimulus elicited increased neural response in the left somatosensory association cortex. Our results demonstrate a hitherto undiscovered sensory modality in a carnivoran species."
Bekoff, Marc. Secrets of the Snout: A Dog's Nose Is a Work of Art.
_____ and Jessica Pierce. Unleashing Your Dog: A Field Guide to Giving Your Canine Companion the Best Life Possible. Novato, California, New World Library. 2019.