Those also who have carefully watched rattlesnakes under various circumstances, must perceive that timidity is one of the strongest features in this reptile. In chap. xxx. I will give examples of this. Already convinced by observation, I attributed to excessive timidity the chief agitation of the rattle, when writing on the Ophidia in the Dublin University Magazine, December 1875, and again in Aunt Judy’s Magazine, July 1877. Fear causes some snakes to puff themselves; others to expand or flatten the body; fear excites the cobra to erect its anterior ribs and display its ‘hood;’ and, above all, fear causes most snakes to hiss. Fear is coupled with anger, in these attempts to do their best towards repelling the offender. Dr. E. Coues, in speaking of the rattle, supposes it to have possibly ‘resulted in the course of time from the continual agitation of the caudal extremity of these highly nervous and irritable creatures.’ Dr. Weir Mitchell has known captive snakes to vibrate the rattle for hours at a time; and probably, if there were opportunities of becoming more intimately acquainted with crotaline idiosyncrasies, we should discover some snakes to be more or less afflicted with temper, nervousness, terror, or other emotions which induce an animal to express its feelings in its own way.
But the most remarkable peculiarity in this snake is that no other way is in its power: a rattlesnake never hisses. Throughout the numerous arguments, theories, explanations, and suggestions, there is such an absence of allusion to this fact that we must suppose it to be very little known. Says Dumeril in describing les petits étuis cornés, comparé à celui que feraient plusieurs grelots peu sonorés: ‘Les Crotales diffèrent de tous les autres serpents connus par la faculté qu’ils ont de produire des sons sourds et rapides, cu plutôt des bruits continus et prolongés à l’aide d’un organe spécial, qui supléerait—pour ainsi dire—à la voix, dont ces serpents sont toujours privés.’[89] But the sibilations of the rattle are often so like hissing that they have been compared to the whistling of wind among the leaves, to the escape of water through a pipe, to the whizzing of insects, the rattling of seed pods, and many similar sounds, showing at the same time the character of the noise and its variability.
Concisely recapitulating what this rattle does, we understand that in the first place it is a substitute for the voice—so far as hissing can be called voice; and that what would cause other excessively nervous, timid, terrified snakes to hiss, causes the rattle to vibrate. It may attract insectivorous birds; it may alarm other timid creatures; it may summon its mate; and, as is well known, it has sympathy with its mate; for a second rattle is almost sure to be sounded, and they have been observed to sound in pairs or numbers responsively—it may be to express anger, fear, and for aught we know pleasure, in a state of liberty and enjoyment, feelings expressed by the tail of other creatures.
Why it is formed as it is, so wholly different from all other tails; from what it has been evolved; and how long in evolving,—all these are problems to be solved by future Darwins and future Evolutionists.
This chapter, therefore, closes with only feeble speculations after feeble attempts to explain an inexplicable phenomenon. The simplest and truest solution seems to be found in those few words, ‘qui supléerait à la voix, dont ces serpents sont toujours privés.’
Again, we wonder whether in the non-hissing serpents any peculiarity of trachea may be observed.
