"Garrison Hilliard" <
[email protected]> wrote in message news:<
[email protected]>...
>
[email protected] (mark freedman) wrote:
>> >
> > Proper technique is to stare directly into it's eyes while saying in your best stern father
> > voice
> >
> > "BAD rattlesnake. BAD rattlesnake. Go home ......"
>
> Actually, snakes are deaf (no external ears) and respond only to ground vibrations - so the
> stomping thing should work.
>
> p.s. Yes, I know that your post is a parody of the standard anti-dog dictum.
Thank you. I was hoping somebody would say that
from
http://www.anapsid.org/torrey.html
Melissa Kaplan's Herp Care Collection Last updated August 11, 2002
Shhh! The snake may hear you
©1998 John Carson. Torrey Pines State Park
Can snakes hear, you ask?
A few decades ago the answer was no, for - obviously - snakes don't have external ears. And any way,
snakes don't appear to respond to loud noises. Further support for this view is found in some
current zoology texts, which still report that snakes lack the sense of hearing. But research begun
about 35 years ago, especially the extensive investigations over many years by E.G. Wever and
associates at Princeton University, has shown that snakes have a hearing capability(at least in an
electrophysiological sense) comparable to that of lizards.
This should not be too surprising, for snakes and lizards share some common features and are thought
to have common ancestors.
So how can a snake hear, lacking external ears? By having equivalent structures on each side of its
head. The skin and muscle tissue on each side of the head cover a loosely suspended bone, called the
quadrate, which undergoes small displacements in response to airborne sound. The quadrate motion is
transferred by intermediate structures to the cochlea, which produces electrical signals on its hair
cells that correlate with the airborne sounds (within a range of intensity and frequency determined
by the ear system) and are transferred to the brain.
Cochlear signals are present in functioning ears of all classes of vertebrates from fish to mammals,
while animals that are congenitally deaf produce no such signals, so their presence in response to
sound is taken as an indication of the hearing sense. Wever and co-workers
[1] developed techniques to measure the hair-cell signals in lizards, snakes, and amphibians, which
involved anesthetizing the specimen, inserting a very thin wire probe into contact with a hair
cell, and measuring the acoustic signal level needed to produce a specified hair-cell signal
(typically 0.1 microvolt). Various experiments were performed to demonstrate that the hair-cell
signals were in direct response to airborne sound and not to mechanical vibrations from the
medium on which the specimens were placed.
According to Porter [2], the auditory response of snakes in the range of 200 to 300 Hz is superior
to that of cats. Hartline and Campbell
[2] investigated the transmission of airborne sound through the snake's skin and lung into the inner
ear. Wever's results show that this type of transmission, called the somatic mode, is much
reduced compared to that through the skin to the quadrate, which is the main mode of hearing.
How are the cochlear responses to be interpreted? Wever points out that it is often difficult to
determine the role of hearing in lower forms such as reptiles. It is possible that snakes make less
use of the auditory sense than other animals. He notes that the maximum sensitivity occurs in the
frequency range of noise made by movements of large animals, so detection of such sounds could
function as a warning to snakes to be motionless, a common defensive action with animals. (Although
not discussed in the references I was able to check, there is also the question of how the cochlear
signals are used in the snake brain. Is it possible that the ability to process this information has
been or is being lost?) So the next time you meet a snake on the Reserve trails, be careful what you
say to it, for the snake may hear you.
Acknowledgements - My thanks to R. Haase, research associate with the UCSD Biology Dept., for
informative discussions and reviewing this article.
References
[3] Wever, E.G., The Reptile Ear, Princeton University Press, 1978
[4] Porter, K.R., Herpetology, Sanders Co., 1972
[5] Hartline, P.H., and Campbell, H.W., "Auditory and Vibratory Responses in the Midbrains of
Snakes, " Science, vol 163, 1221, (1969)
