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Does a Dog's Size Predict Its Hearing Sensitivity?

Dogs with wide heads have a different sensitivity to high-frequency sounds.

Key points

  • Dogs have greater sensitivity to high-frequency sounds than human beings.
  • A reduced sensitivity to higher-pitched sounds occurs in dogs with wider heads.
  • Larger dogs are more susceptible to age-related hearing loss.
Zulema Ortega/Flickr
Source: Zulema Ortega/Flickr

Most people believe that, in comparison to humans, dogs have exceptionally acute hearing. However, there are individual differences, and some dogs have better hearing abilities than others. One of the interesting findings concerning canines is that we can predict certain aspects of their hearing sensitivity by simply looking at their physical characteristics, such as their body size.

How Does the Hearing of a Dog and a Human Differ?

One of the reasons that people believe that dogs' hearing is so good is that they seem to react to sounds that are often too faint for the average person to hear. We now know that this is because dogs are particularly sensitive to sounds in the high-frequency range. While human hearing sensitivity reaches its limit at around 20,000 Hz, dogs can hear up to 45,000 Hz.

To give you an idea of what this means in practical terms, the highest note on a piano is 4,186 Hz. To reach the highest note that a human can hear, the right side of the piano would have to be extended by 28 keys. To reach the highest note that a dog can hear, the keyboard would have to be extended by 52 keys—while the last 24 of these keys' notes would all be completely beyond human hearing ability.

A Big Head Might Mean More Limited Hearing Range

While it is obvious to scientists that some dogs have the capability to hear higher frequencies than other dogs, the surprising thing is that a dog's ability to hear such high sounds may be predicted by his head size. In this case, head size is measured from ear to ear as if we were going straight through the head. Based on data gathered in other species, this is not a surprise to sensory researchers, since it has been demonstrated that larger-headed animals in general have lower high-frequency sound sensitivity as you can see in the figure below.

 Courtesy of SC Psychological Ltd.
Source: Courtesy of SC Psychological Ltd.

These findings were specifically confirmed for dogs ranging in head size from a small Chihuahua to a broad-headed St. Bernard, and the data show quite clearly that the dogs with wider heads have lower sensitivity for higher-frequency sounds.

Source: Courtesy of SC Psychological Ltd. redrawn from data from McMahon (2015)
Source: Courtesy of SC Psychological Ltd. redrawn from data from McMahon (2015)

Now the Matter Gets Hairy

Of course, generally speaking, a big head on an animal suggests that the animal is big overall. A larger-sized individual means that everything in the animal's body would be larger including all of the components in the dog's ear. In the inner ear of the dog (which is a snail shell–shaped structure called the cochlea) fluid is moved back and forth in response to sound waves reaching the individual. Ultimately, those fluid movements bend tiny hair cells embedded in the inner ear. You can see those hair cells in the magnified section in figure below. Those hair cells have to bend to produce the neural response that sends information to the brain indicating that a sound has arrived.

 Courtesy of SC Psychological Ltd.
Source: Courtesy of SC Psychological Ltd.

The quirk involved here is that if the animal is bigger, its hair cells are also bigger. Thick hair cells will not vibrate as easily or as rapidly, which means that they are simply not as capable of responding to high-frequency sounds. This alone can limit the dog's ability to hear those high-frequency signals that require rapid hair movements. Without the flexing of the hair cells, no information gets passed on to the higher brain centers.

Age Also Matters

There is another problem that a dog's larger size brings to its hearing ability. As dogs (and also humans) age, there is a gradual loss in hearing ability. This again has to do with the hair cells in the inner ear. Imagine flexing a wire hanger back and forth many times. Ultimately, you have material fatigue, and the metal hanger will break. This is what happens to the hair cells in the inner ear. All of that vibration and bending causes the hair cells to break, simply as a function of wear and tear over time. When the hair cells in the inner ear break, they do not regenerate, which means we lose the ability to hear the sounds that those particular hair cells normally responded to.

Now imagine that you have two different wire coat hangers. One of them is thicker than the other. That means that it is less flexible. It also means that if you force it to bend back and forth it will break more easily and more quickly than one composed of a thinner wire. This is exactly what is going on in the inner ear of a larger dog compared to its smaller cousin. For both animals, the high-frequency vibrations cause rapid flexing of the hair cells in the ear, but for the larger dogs, their thick hair cells are more apt to break more quickly and the dog will lose the corresponding auditory sensitivity. Ultimately, this causes large dogs to be more likely to show earlier age-related hearing losses.

The effect a dog's size has on its age-related hearing loss is really quite large. For a small dog, the first signs of hearing loss are not apt to appear before the dog is 9 years of age, while for a larger dog, signs of probable loss of hearing sensitivity might begin to appear as early as 6 years of age. It is rare to find a large dog who is not showing some evidence of hearing loss at 10 years of age, while smaller dogs seem to be blessed with a grace period of two or three years of better hearing. You can see that in the table below.

 Courtesy of SC Psychological Ltd.
Source: Courtesy of SC Psychological Ltd.

So, the upshot of all of this is that body size, and very particularly head size, is related to a dog's hearing ability. Smaller dogs hear a larger range of high-frequency sounds overall and enjoy better hearing over a larger span of their life. It appears that when it comes to auditory function, for dogs, as for other mammals, size matters.

Copyright SC Psychological Enterprises Ltd. May not be reprinted or reposted without permission.

References

Barber, A. L. A., Wilkinson, A., Montealegre-Z, F., Ratcliffe, V. F., Guo, K., & Mills, D. S. (2020). A comparison of hearing and auditory functioning between dogs and humans. Comparative Cognition & Behavior Reviews, 15, 45–80. https://doi.org/10.3819/CCBR.2020.150007

Coren, S. (2004). How dogs think: Understanding the canine mind. New York: Free Press (pp. i – xiv, 1-351).

McMahon, D. H. (2015). Investigating the relationship between the frequency ranges a dog can hear compared to its head size. Unpublished BSc (Hons) thesis, College of Life Sciences, University of Lincoln, Lincoln, UK.

Strain G.M. (2012). Canine Deafness. Veterinary Clinics: Small Animal Practice, 42 (6), 1209-1224, DOI:https://doi.org/10.1016/j.cvsm.2012.08.010

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