A theory for the existence of the feline Henry’s pocket

Some time ago I proposed that a domestic feline’s Henry’s pocket enhanced the reception of high pitched sounds in the interests of refined hunting skills (read the theory by clicking on this link). An anonymous and educated visitor disagreed. I did not however mix up longer paths with longer frequencies as he states. Although his theory is very neat and deserves to be published as an article rather than a comment. His theory is probably better than mine. Here it is…..

Henry's pocket a theory for its existence

Henry’s pocket a theory for its existence


Your observations are very good, however they not quite correct because you are mixing up the concept of ‘longer paths’ with ‘longer frequencies’. What happens in fact (and this has been well studied in humans) is that, as you observed, an incoming sound wave (of whatever frequency) impinges directly on the eardrum.

Simultaneously the same sound wave, again as you observe, bounces off the tragus (Henry’s pocket) and it’s folds, taking a longer path to the eardrum. However we are still talking about the same frequency, as it is not the wavelength that changes but rather the time it takes for those waves to get to the eardrum. In other words: as the sound bounces off the pina and tragus it is delayed.

So then it is the difference between the first arriving wave that directly hits the eardrum, and the subsequent ones delayed by the tragus, which creates a phase (not frequency) difference within the ear.

This then works in conjunction with the fact that we (and our cats) have two ears, just like we have two eyes, and so we/they have binaural hearing just like having binocular vision. In other words: having two ears allows us to have stereo hearing just as having two eyes allows us stereo vision (seeing in 3D).

This means then that the structure of our feline friends ears (as well as other animals, most notably owls) gives them an ability to ‘localize’ sound (knowing where they are coming from in 3d space) much better than us.

As for them being able to hear frequencies higher than we do? That’s not so much about the structure of the outer ear as it is the inner ear and it’s attached nervous system.

So Yes our fuzzy friends not only hear but localize (know physically in space) where that mouse is long before we do!


My comment: this theory is good because cats do isolate prey very accurately at a distance using sound. It is a hunting refinement. My theory was also related to hunting skills. The Fennec fox also has a very noticeable Henry’s pocket. This animal lives in the Sahara of North Africa and hunts at night. Hearing must play a huge part in hunting.

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