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IGUANA  •  VOLUME 14, NUMBER 2  •  JUNE 2007 119HISTORICAL PERSPECTIVES

itself by the destruction of the snake. But the certainty of the
effect of the poison serves as a warning and is advantageous, not
in defense after the attack is made, but in preventing an attack
from being made. If, then, the color of the rattlesnake were dif-
ferent from all harmless snakes, so much so as to render it con-
spicuous, this would be beneficial to it, by the readiness with
which all animals would recognize it, and thus protect the snake
by this notice of the deadly character of its weapons. If then a
conspicuous color would be of advantage, it seems to me that
any other means which it may be able to use in making known
its character to any animal that may come near it, would be
advantageous, and would be increased and preserved by natural
selection, and that the whirring noise which it produces, in this
view of the matter, admirably serves its purpose. In effect it
amounts to this, and by experience its enemies learn to under-
stand its language, “I am a rattlesnake, armed with what will be
death to you if you come too near; give me a wide berth!”

Prof. Shaler remarks that it is a fact well known doubtless
to those who have observed serpents, that many when in a state

of excitement vibrate the end of their tail just as the rattlesnake
does. This statement reminded me of a South American species
described by Darwin in his “Voyage of a Naturalist” (vol. i, p.
123, Harper’s ed.), where he says:—

“Of reptiles there are many kinds: one snake (a
Trigonocephalus, or Cophias), from the size of the
poison channel in its fangs, must be very deadly.
Cuvier, in opposition to some other naturalists, makes
this a sub-genus of the rattlesnake, and intermediate
between it and the viper. In conformation of this opin-
ion I observed a fact, which appears to me very curi-
ous and instructive, as showing how every character,
even though it may be in some degree independent of
structure, has a tendency to vary by slow degrees. The
extremity of the tail of this snake is terminated by a
point, which is very slightly enlarged; and as the ani-
mal glides along, it constantly vibrates the last inch;
and this part striking against the dry grass and brush-
wood, produces a rattling noise, which can be dis-
tinctly heard at the distance of six feet. As often as the
animal was irritated or surprised, its tail was shaken;
and the vibrations were extremely rapid. Even as long
as the body retained its irritability, a tendency to this
habitual movement was evident. The Trigonocephalus
has, therefore, in some respects, the structure of a
viper, with the habits of a rattlesnake; the noise, how-
ever, being produced by a simpler device.”

It was these remarks of Darwin that first suggested the problem
of the rattlesnake’s tail to my mind, and, as I had thought con-
siderably about the matter, of course I was deeply interested in
the paper by Prof. Shaler; but I must acknowledge that, while
many of his suggestions are correct and highly valuable, I was
disappointed to find that the only advantageous use, in his esti-
mation, of this tail appendage of the rattlesnake, is an imitative
call-note to allure birds within its reach, and that, otherwise, it
is rather a disadvantage than an advantage to be preserved and
perfected by natural selection. If it is useful for both purposes,
then there is a double reason for the action of natural selection.
If it is not used as an imitative call-note, but is useful in the man-
ner I have pointed out, then I have shown that it is explained by
natural selection.

Iwish to contribute my observations on the rattlesnake, having
been specially favored in opportunities for the study of this

reptile.
Of all the articles that have appeared on the subject in the

NATURALIST that by Mr. Putnam appears to me to present the
most satisfactory theory concerning the use of the rattles. I am
satisfied that one of their uses is to bring the sexes together.

In July, 1869, I was engaged in surveying along the Logan
river in Wayne County, Nebraska. After completing my contract
I devoted a day to investigating the natural history of the neigh-
borhood. While washing a collection of unios at the water’s
edge, I heard the familiar rattle of the Massasauga (Crotalophorus

The Rattle of the Rattlesnake6

Professor Samuel Aughey

6 Reprinted from The American Naturalist 7:85–86 (February 1873).

Prairie Rattlesnakes (Crotalus viridis) were locally abundant across the
Great Plains at the time these articles were written. Many of the rat-
tlesnake encounters reported by pioneers traversing the Oregon and
Mormon trails were with this species. This snake is in a classic “defen-
sive” position.

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120 IGUANA  •  VOLUME 14, NUMBER 2  •  JUNE 2007 AUGHEY

Editor’s Remarks

Rattlesnakes are iconic symbols of the American West.
During the 18th Century, rattlesnakes became symbols

of the American colonies and their fight for independence
from the British. For example, Paul Revere showed the
snake fighting a British dragon on the masthead of The
Massachusetts Spy in 1774. In 1775, a letter attributed to
Benjamin Franklin appeared in the Pennsylvania Journal,
calling for the adoption of the rattlesnake as the symbol of
the United States and saying, among other things, that the
rattlesnake “never begins an attack, nor, when once
engaged, ever surrenders: She is therefore an emblem of
magnanimity and true courage. ... she never wounds ’till
she has generously given notice, even to her enemy, and
cautioned him against the danger of treading on her,” lead-
ing to the motto “Don’t tread on me,” emblazoned on an
early revolutionary flag.

Yet today, rattlesnakes invariably appear as “bad guys”
in movies and books. Rattlesnake roundups still occur in
many places, and focus on killing as many of these useful
animals as possible. A proposed position paper from the
American Society of Ichthyologists and Herpetologists
“strongly opposes traditional rattlesnake roundups. Such
roundups promote overexploitation of natural populations
of wildlife, unnecessary killing and inhumane treatment of
individual animals, degradation of habitat, and promotion
of outdated attitudes toward important elements of
America’s natural heritage.” We strongly agree with this
statement.

Here we reprint several classic scientific papers focus-
ing on rattlesnakes. In 1872, N. Shaler published a piece
in the American Naturalist attempting to explain the func-
tion of the rattle. “For some years I have been teaching that
the tail appendage of the rattlesnake was not to be
explained on the doctrine of natural selection, inasmuch as
it could contribute in no way to the advantage of the ani-

mal.” However, having provided a “useful” purpose for the
“appendage,” he concluded that “it must be confessed that
the case of the rattlesnake seems to me no longer the bar to
the acceptance of the theory it once did.” Later that year,
and in the same journal, J. Henderson speculated on the
evolution of the rattle and its possible function. The fol-
lowing year, Samuel Aughey proposed yet another possible
explanation.

Today, these discussions, which occurred less than two
decades after publication of Charles Darwin’s On the Origin
of Species* in 1859, seem naïve. Even the language and the
methods are archaic. For example, the almost indiscrimi-
nant use of “theory” speaks eloquently to the evolution of
language (today we would substitute “hypothesis” for all
applications other than to Darwin’s theory of natural selec-
tion). Also, the heavy reliance on anecdotal observations
and a readiness to draw definitive conclusions from them
contradict modern scientific methods. Our knowledge has
greatly increased in the intervening years, and our ability
to test hypotheses about form and function is much more
sophisticated. Nevertheless, 134 years after the last of these
papers first appeared, many U.S. citizens still adamantly
cling to their opposition of evolution.

Gad Perry

* Complete title: On the Origin of Species by Means of Natural
Selection, or the Preservation of Favoured Races in the Struggle for Life.

Paul Revere showed an American snake fighting a British dragon
on the masthead of The Massachusetts Spy in 1774.

Benjamin Franklin at one time called for the adoption of the rat-
tlesnake as the symbol of the United States. That suggestion led
to the motto and image emblazoned on this Revolutionary War
era flag.

Western Diamondback Rattlesnakes (Crotalus atrox) are icons of
the American West. Yet today, these rattlesnakes invariably appear
as “bad guys” in movies and books. Rattlesnake roundups still
occur in many places, and focus on killing as many of these use-
ful animals as possible.

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tergeminus [= Sistrurus catenatus]). I quietly crept up the bank
and cautiously looking over the level bottom I saw, at the dis-
tance of about thirty feet, a rattlesnake coiled up with head erect
and gazing in an opposite direction from my position. Every
three or five minutes the snake would cease rattling for a minute
or more and then commence again. In about half an hour from
the time that I first saw the snake I observed another rattlesnake
approach the first one. Closer and closer the second one
approached, until at length they met and indulged in a sexual
embrace. I watched them for at least an hour and left them at
last without disturbing them.

The next year at the Bow river in the same state I saw the same
thing repeated under similar circumstances. In neither case could I
ascertain whether it was the male or female that give the call.

I am satisfied that the theory that the rattle resembles the
noise made by the Cicada, and that it is employed because of
this resemblance to entrap birds, etc., is a mistake. I have been
accustomed to the sound of the Cicada and the rattle of the rat-
tlesnake from my youth, and soon learned to distinguish them,
although there is betimes a striking resemblance between them.
My familiarity with them was gained in my native state amid the
Alleghanies of Pennsylvania. In the last week of June, 1869, I
was on the Missouri flood plain in a dense timber in Cedar
County, Nebraska. At the time there were many Cicadæ and
multitudes of birds in the timber. One day I was sitting on a log,
classifying a collection of flowers and plants. Suddenly I heard
the well-known rattlesnake rattle. The snake was not more than
forty feet from me. I could not have been the cause of its alarm
as a large log lay between us and I had been quiet for nearly an
hour. Even the Cicadæ were alarmed and disappeared, and soon
not a bird was to be seen, but the rattling continued.
Unfortunately, on the impulse of the moment, I killed the snake

without waiting to see or learn the purpose of its rattling. Again
I have noticed that the Massasauga, at least in Nebraska, is by
far the most abundant far away from the timber, where the
Cicadæ are rarely if ever seen. 

These observations seem to me to point to the theory that
the rattle calls the sexes together. In July, 1871, I was in the tim-
ber on the Missouri in Dakota County, Nebraska. I got sight of
a Baltimore oriole (rare in Nebraska) which I was following as it
flitted from twig to twig. As it swept near the ground a rat-
tlesnake struck his highest notes and seemed to paralyze the ori-
ole with fear. This snake was a Crotalus. The poor bird hovered
near the snake and fearing that it might fall into its jaws I shot
the reptile. This experience suggested the theory that perhaps an
additional purpose of the rattle was to frighten its victims into
submission and to protect itself by the terror it inspires from its
natural enemies. However that may be, is it not a mistake to
limit such a peculiar organ to any one single purpose? What is
needed to determine definitely the natural history of the rat-
tlesnake is closer and more accurate observation over a wide area,
and by persons who are fitted by nature and education for such
work. Unfortunately for science, the almost universal custom has
been to kill the rattlesnake as soon as found, without waiting to
learn its disposition and habits of life.

Once in the Dakota Nebraska timber I saw an attack of
hogs on a rattlesnake. In a few minutes after the snake com-
menced rattling, three others made their appearance. They
apparently came to the assistance of the first one, but all were
killed by the hogs in a few minutes. Seven hogs were more than
a match for four rattlesnakes. Here evidently the rattle was used
to call for help. These belonged to the genus Crotalophorus.

IGUANA  •  VOLUME 14, NUMBER 2  •  JUNE 2007 121HISTORICAL PERSPECTIVES

In 1873, Professor Samuel Aughey indicated that the rattle might also
be used to attract mates or allies in a struggle against predators. Like
Henderson, many of his observations were of Western Massasaugas,
although he also described an encounter with a Prairie Rattlesnake
(Crotalus viridis), illustrated here. 

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