Cats or dogs, who has a better sense of smell?

Cats or dogs, who has a better sense of smell?

Author: Xu Xuxu

When we describe a person as being sensitive to smell, we often say he has a "dog nose" because dogs have a very keen sense of smell. But have you ever thought about which of the two most popular pets, cats and dogs, has a more sensitive sense of smell?

To answer this question, first of all, we need to know why cats and dogs can smell. There is an area in the nose of mammals called the "olfactory epithelium", which is composed of many olfactory cells, and there is a structure on these cells called "olfactory receptors", which, as the name suggests, are responsible for smelling. When external odor molecules float into the nose of cats and dogs and contact these olfactory receptors, a series of reactions will be triggered, and finally the signal will be transmitted to the brain, and the cats and dogs will know what smell they just smelled. Therefore, the sensitivity of mammals' sense of smell is closely related to their olfactory receptors.

Why do dogs have such a strong sense of smell? One important reason is that their olfactory epithelium is a spiral structure. If it is unfolded, the area can reach more than 100 square centimeters, and there are hundreds of millions of olfactory receptors distributed in this area. You must know that some breeds of dogs are selected and trained specifically for search and rescue operations. In fact, one of the reasons why people choose these dogs is that they have a particularly large number of olfactory receptors. For example, bloodhounds have 300 million olfactory receptors, German shepherds have 225 million, and Labradors have 200 million.

In contrast, the olfactory epithelium of cats is much smaller, about 20 to 40 square centimeters. However, the number of olfactory receptors in cats is basically the same as that of dogs, about 200 million. However, the part of the cat's brain that processes olfactory information is smaller than that of dogs, so the cat's brain does not process olfaction as well as dogs.

Does this mean that cats' noses are not as sensitive as dogs'? Not necessarily. Cats also have their own auxiliary tool - the vomeronasal organ. The vomeronasal organ, also called the nasal organ, is an auxiliary olfactory sensory organ. It is located between the upper palate and the nasal cavity, supported by cartilage tissue. It is a tubular structure connected to the brain through nerves. If you find that your cat wrinkles its nose and opens its mouth to "make faces", it is probably using the vomeronasal organ to detect some irritating smells, such as... the smelly socks at home. Moreover, cats also use this vomeronasal organ to make friends and courtship. During the estrus period, cats will use the vomeronasal organ to receive special smells emitted by other cats. Although dogs also have this organ, it is not as developed as cats.

Overall, cats and dogs have about the same number of olfactory receptors. The part of the dog's brain that processes smell is larger, while the cat's vomeronasal organ is more developed, so there is not much difference in the sensitivity of their sense of smell.

So, compared with cats and dogs, how good is the human sense of smell? The area of ​​the human olfactory epithelium is basically about 10 square centimeters, and the number of olfactory receptors is only 50 million, which is far less than that of cats and dogs. In addition, as we all know today, a typical symptom of being infected with the new coronavirus is loss of smell. Scientists have found that this is because the new coronavirus can downregulate olfactory receptors, making it impossible for people to normally detect molecules related to taste [1].

References:

[1] https://m.chinacdc.cn/xwzx/gwxx/202203/t20220301_257262.html

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