One of the first things many people think of when talking about dogs is their wet nose. It is often said that a wet nose is a sign of a healthy dog, and this is true to some extent. But there is another reason why dogs have wet noses.
Smell is very important to dogs. The part of a dog’s brain dedicated to processing scent is proportionally 40 times larger than ours, and they have 300 million scent receptors in their noses. In general, compared to humans, their sense of smell is at least 10,000 times better than ours.
Research has found that dogs can use their scent to create a mental picture of the world around them, so keeping this sense sharp is crucial to their success. However, as you can guess from the course of this article, a dry nose drastically reduces a dog’s sense of smell.
To keep these 300 million olfactory receptors working properly, dogs secrete mucus to move through the nasal cavity to coat the rinarium (the mobile outer part of the nose that their owners are so familiar with poking at their face). Smell is a result of these receptors picking up chemicals entrained in the air, and when a dog’s nose is wet, they are better able to capture and process chemicals.
Given that dogs use the olfactory factor to identify and communicate with prey and predators, having a functional mucus is really a matter of life and death for them. It is not surprising, therefore, that they have developed a robust sense of smell and physiological responses to keep it sharp. Behaviorally, they lick their noses frequently to help coat the mucus evenly across the nose and add an additional layer of moisture.
Another reason: Sweating structures
Another reason why dogs’ noses are constantly wet is related to their sweating structure. Because they are covered with fur, sweating from the skin, like humans, is not very effective for dogs. Instead, they sweat from their paws and a small amount of sweat is also released by their noses.
This not only helps keep a dog’s nose wet but also keeps him cool. Research has shown that regardless of smell, dogs can also use their noses to sense heat.
A 2020 study investigated the noses of dogs to check the hypothesis that the cooler noses of carnivores such as dogs (compared to the warmer noses of herbivores) may have evolved as a type of infrared sensor. In this study, three dogs were trained to recognize hot objects and they were able to distinguish between hot and cold objects even when they could not detect any smell.
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