About the Rattle
Rattles probably evolved as a warning device to protect the snake from being accidentally crushed by large, hoofed mammals. The rattle is composed of hollow, interlocking segments that click against each other when the tail is vibrated. Rattlesnakes gain a new segment to the rattle every time they shed their skin. Since they may shed from one to three times per year, one cannot accurately estimate the age of the snake simply by counting segments. Segments also break off as the snake grows older.
Two examples of rattles from deceased Eastern Diamondback rattlesnakes. Neither string is complete and contained more segments than shown. One can only imagine the age of a snake with this many segments. Photo by Paul Moody
The photo below shows a size comparison between the Eastern Diamondbacks rattle and the Dusky Pigmy rattlesnake’s rattle.
How the rattle is formed
Visualizing how the segments fit together is not as difficult as understanding how each one arises and how it joins the rattle string. This is best explained as a series of stages:
1. As the snake approaches the time when it will shed it’s skin (pre-shed), the horny layer covering the scale at the end of it’s tail becomes thickened. Figure A below
2. When the snake sheds, this horny layer cannot be completely discarded because of the constriction (Figure B below) and remains loosley in place over the end of the tail - it has now become a segment. The tip shrinks slightly, away from the inside of the old “shell”, and forms a new horny covering.
3. At the same time as the new tip is forming it’s horny layer, the part of the tail immediately in front of the rattle swells and becomes bulbous (Figure C below), in effect pushing the rattle (all the previous segments) further back, away from the scaly part of the tail. Now stage 1 is repeated.
Hear the rattle and hissing from a Eastern Diamondback rattlesnake.
