Henderson, J. G.

English

The University of Kansas: Journals@KU

IGUANA  •  VOLUME 14, NUMBER 2  •  JUNE 2007 117HISTORICAL PERSPECTIVESto which they belong. It is natural enough that a part of thebody situated at one of the regions of manifold relations as thetail is, and unappropriated to any special function, should be putto use in various ways, as a prehensile instrument by some mon-keys and other animals, or a building tool by the beavers, as afly-brush by many others, etc.Mr. Herbert Spencer has already suggested that the wag-ging of the dog’s tail and similar movements of that appendageis in fact an escape of nervous force restrained from other modesof expression at the moment. Looking at the matter from thispoint of view, which is doubtless quite satisfactory, we may rec-oncile it perfectly with the views which have just been presentedby supposing that the ancient and no longer functional channelof escape for nervous force, the tail, has remained the way ofoutlet for the suppressed energy of the animal. The older thechannel the less easy it is to close it either by volition or by nat-ural selection.Be the cause of the persistence of the tail and its movementwhat it may, we are still justified in assuming as the startingpoint, that the progenitor of the rattlesnake had the alternatingmotion of the tail common among snakes. It is the opinion ofsome herpetologists that the rattles are the remains of the skinssuccessively shed by the animal. The rate of development of therattles, together with the fact that the skins of some serpents aremore imperfectly detached from the region about the tail thanat other parts of the body, makes this view very probable. Let ussuppose that we had a group of poison-fanged serpents, acciden-tally tending to keep the tail skin in the peculiar fashion of rat-tlesnakes and that in some of these it was persistent enough tomake the whirring sound of the Cicada when the tail was rap-idly moved under excitement. These would survive and breedthe most surely and so that feature would become hereditary.The great variability in the number of rattles in the differentforms of rattlesnakes and the late time of their development,even among those which differ in no other regard, would seemto indicate that this structure has not yet been firmly fixed bylong inheritance.The reader will please not suppose that because I haveboldly followed the lead of the most advanced of the championsof natural selection that I am convinced of its sufficiency as anexplanation of the great diversities which exist among animalsor of its being sufficient basis for an explanation of the snake’srattle. But having been driven step by step from a decided oppo-sition of the whole theory and compelled to accept it as a veracausa, though I think one much more limited in its actionamong animals than Mr. Darwin believes, I feel it to be my dutyto examine every one of those points upon which I have reliedfor evidence against it.It must be confessed that the case of the rattlesnake seems tome no longer the bar to the acceptance of the theory it once did.It seems that the singular structure from which the subject ofthese notes derives its name, was intended as a special stum-bling block in the path of antidarwinists, or to intensify the“struggle for existence” which the Darwinian theory, like allother theories must undergo.In most notices I have seen of the rattles of the rattlesnake,they have been mentioned as though they were of no advantageto the possessor, and that natural selection would never producethem but on the contrary would weed them out, if that theorywere correct. It seems to me that the whole trouble in the matterarises from the assumption that the sound of the rattles, as a war-cry, is a disadvantage to the reptile, by calling the attention of itsenemies to it and thus inviting its own destruction, and that con-sequently the only way to reconcile the existence of the rattles withthe theory of Darwin, is to show that there is some other use madeof them and that in striking the balance between the profit andloss sides of the ledger, the line falls on the side of the former andfor that reason natural selection produced and retains the rattles.If I understand him rightly, this is the view of the matter taken byProf. N. S. Shaler in his paper in the January NATURALIST. He saysthat for some years he has “been teaching that the tail appendageof the rattlesnake was not to be explained upon the theory of nat-ural selection, inasmuch as it could contribute in no way to theadvantage of the animal; that is seemed to him quite clear that itwas rather calculated to hinder than to help the creature in the raceof life by warning its prey of its presence.” But he intimates thathe is now ready to say, that this appendage can be explained uponUse of the Rattles of the Rattlesnake5J. G. Henderson5 Reprinted from The American Naturalist 6:260–263 (May 1872).J. G. Henderson, also in 1872, disputed Shaler’s assumption that rat-tles were used to attract prey and proposed instead that they serve as awarning directed at potential predators. Many of his observations wereof Western Massasaugas (Sisturus catenatus tergeminus), at that timeplaced in the genus Crotalophorus. SUZANNE L. COLLINS, CNAHthe theory of natural selection. He considers the idea that it mightbe used as a sexual call as untenable, but that the whirring soundof the rattles closely imitates the sound made by the Cicada andfor this reason is used as a call-note, as a hunter uses his bone-turkey-caller, to induce the bird to come within the range of hisweapon. Now the first question which naturally arises is this: Doesthe snake sound its rattles when seeking to capture its prey? I havealways understood that it is only when it throws itself upon thedefensive and prepares for battle that the rattles are sounded; thatit is an alarm note, a war-cry, and not a gentle, deceptive invita-tion to the victim. I have never seen a rattlesnake, and know ofcourse nothing personally of its habits. But if this use is not madeof the rattles as suggested by Prof. Shaler, and the sound onlyserves to call the attention of its enemies and thus invite destruc-tion, then indeed is the theory of natural selection nonplussed.But as I view the matter, instead of inviting his destruction bysounding the rattles, it is one of the most effective means of selfprotection and is as useful to it in the race for life as is the growlof the tiger when threatened with danger. The snake does notsound its rattles until it considers itself discovered, and not thenunless it apprehends danger. It throws itself in position to strikeand says in unmistakable language, “Look out, I am ready foryou!” If pushed upon, it makes its leap at its antagonist, and againthrows itself in position to renew the conflict, and again soundsthe note of defiance; a note calculated to alarm and, like the war-whoop of the Indian, strike terror to the heart of the assailant; butit may be said that the Indian only utters his yells when rushingon his enemy, or when actually engaged in the conflict, and thesounding of the rattles upon the first approach of danger is a dis-advantage. Now it seems to me, if this were true and if it be a pieceof rashness upon the part of the snake thus early to exhibit hiscombatativeness, that natural selection would cure the matter byselecting and preserving the more timid, and that, eventually, rat-tlesnakes would only sound their tail-bells when it would best pro-mote their interests.We are not to judge of the advantage or disadvantage of therattles by their effect upon the nerves of man alone, though nodoubt many a man has turned his back and been deterred frommaking an attack by the sound of these rattles and the defiantattitude of their possessor.The ability of the snake to defend itself does not consist inits strength or size, or in its power of overcoming its adversaryby a prolonged conflict, for most of its enemies are its superiorin size and strength. Nor does its deadly poison act quicklyenough to secure its own safety when it is attacked, but, in mostcases, the victim, after the deadly stroke is given may still revenge118 IGUANA  •  VOLUME 14, NUMBER 2  •  JUNE 2007 HENDERSONThis Western Massasauga (Sisturus catenatus tergeminus) is initiating a strike from a coiled “ambush” position. Rattlesnakes use a sit-and-wait for-aging strategy, contradicting the contention that the rattles were disoperative because the sound would “warn” potential prey as the snakeapproached. Instead, the distinctive “buzz” appears to serve as a warning directed not only at potential predators, but at large grazing mammalsthat might inadvertently step on an undetected snake. JACK GOLDFARB, WWW.JACKGOLDFARB.COMIGUANA  •  VOLUME 14, NUMBER 2  •  JUNE 2007 119HISTORICAL PERSPECTIVESitself by the destruction of the snake. But the certainty of theeffect of the poison serves as a warning and is advantageous, notin defense after the attack is made, but in preventing an attackfrom 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 withwhich all animals would recognize it, and thus protect the snakeby this notice of the deadly character of its weapons. If then aconspicuous color would be of advantage, it seems to me thatany other means which it may be able to use in making knownits character to any animal that may come near it, would beadvantageous, and would be increased and preserved by naturalselection, and that the whirring noise which it produces, in thisview of the matter, admirably serves its purpose. In effect itamounts to this, and by experience its enemies learn to under-stand its language, “I am a rattlesnake, armed with what will bedeath to you if you come too near; give me a wide berth!”Prof. Shaler remarks that it is a fact well known doubtlessto those who have observed serpents, that many when in a stateof excitement vibrate the end of their tail just as the rattlesnakedoes. This statement reminded me of a South American speciesdescribed 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 (aTrigonocephalus, or Cophias), from the size of thepoison channel in its fangs, must be very deadly.Cuvier, in opposition to some other naturalists, makesthis a sub-genus of the rattlesnake, and intermediatebetween 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 ofstructure, has a tendency to vary by slow degrees. Theextremity of the tail of this snake is terminated by apoint, 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 theanimal was irritated or surprised, its tail was shaken;and the vibrations were extremely rapid. Even as longas the body retained its irritability, a tendency to thishabitual movement was evident. The Trigonocephalushas, therefore, in some respects, the structure of aviper, 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 problemof the rattlesnake’s tail to my mind, and, as I had thought con-siderably about the matter, of course I was deeply interested inthe paper by Prof. Shaler; but I must acknowledge that, whilemany of his suggestions are correct and highly valuable, I wasdisappointed to find that the only advantageous use, in his esti-mation, of this tail appendage of the rattlesnake, is an imitativecall-note to allure birds within its reach, and that, otherwise, itis rather a disadvantage than an advantage to be preserved andperfected 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 bynatural selection.Iwish to contribute my observations on the rattlesnake, havingbeen specially favored in opportunities for the study of thisreptile.Of all the articles that have appeared on the subject in theNATURALIST that by Mr. Putnam appears to me to present themost satisfactory theory concerning the use of the rattles. I amsatisfied that one of their uses is to bring the sexes together.In July, 1869, I was engaged in surveying along the Loganriver in Wayne County, Nebraska. After completing my contractI devoted a day to investigating the natural history of the neigh-borhood. While washing a collection of unios at the water’sedge, I heard the familiar rattle of the Massasauga (CrotalophorusThe Rattle of the Rattlesnake6Professor Samuel Aughey6 Reprinted from The American Naturalist 7:85–86 (February 1873).Prairie Rattlesnakes (Crotalus viridis) were locally abundant across theGreat Plains at the time these articles were written. Many of the rat-tlesnake encounters reported by pioneers traversing the Oregon andMormon trails were with this species. This snake is in a classic “defen-sive” position.JACK GOLDFARB, WWW.JACKGOLDFARB.COM

Use of the Rattles of the Rattlesnake

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Use of the Rattles of the Rattlesnake

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