A NATURAL HISTORY OF RATTLESNAKES
This is my second chapter on this blog of “Chris Mattison’s” excellent book on the rattlesnake of the America’s. Copyright date 1998, distributed by Sterling Publishing Co. of New York. Any one with a interest in rattle snakes would be well advised to secure a copy for its excellent photographs alone. Now on to the meat of the discussion
In review I should have pointed out that the Subcaudal scales mentioned on the tail are located on the lower side of the tail, the top has regular scales.
Rattlers shed their skin from time to time like all other snakes. the outer layer called the epidermis is a thin transparent layer that is supple when being shed but quickly becomes brittle after shedding. Juvenile snakes shed up to seven times in the first year. Adults can shed three times in a season. the first shed usually happens in the spring shortly after hibernation. shedding occurs when a new layer of epidermal is formed under the old one. They start by rubbing the nose against something hard and rough like a rock, to free the skin from around the jaw area. then they crawl over rough ground like rock or rouggh vegetaion until the entire skin is pulled away. Rattlesnakes differ from other snakes in that the skin that covers the scale of the tail does not shed.
The rattle sets the snake apart from all others, nothing like it is fond anywhere else. the rattle consists of a series horny shells which fit loosely over one another. They are made of keratin, the same material that form horn, claws, hair and finger nails.
Each segment of a rattle originates as the scale at the tip of the rattlers tail. I wish I had the skill to make a line drawing to illustrate this (but sadly I do not have the computer skill to do this). The first scale on a juvenile is called a bud and does not rattle, the scale covers the entire tip of the tail and has a bulb like tip. As the snake shed it’s first skin the bud does not fall off but remains stuck to the new scale.
In trying to think of a way to explain the construction of a rattle I remembered a magic trick I used to do(One of my many hobbies on days gone by, another chapter later on maybe). Somewhere around here I have a plastic shell of a thumb which I place over my thumb to do several different tricks. It fits snuggly over my thumb to the first knuckle, and slips off easily. This is much the same way the scale at the tip of the rattlers tail is. Imagine that we take a cord and wrap it around the thumb just below the nail and draw it tight enough to make a indentation all the way around, Now we have the segment of a rattle. As the old scale starts shed the base of the scale shrinks and catches in the groove of the new scale, now it is held in place and is a segment of the rattle, neat huh?
Now look at your thumb from the side and notice how the top is fairly flat and the bottom kinda slopes up to the tip. The scales that form the rattle are shaped much the same. the segments can flex up but not down. When the tail is moved up and down the snake achieves a rattling sound. However not being able to flex down the rattle does not drag on the ground as the snake crawls.
So as to the old tale about being able to tell a rattlesnakes age by the number of rattles on it’s tail, not true. A new segment is added each shed up to three a year after thee first year, and segment wear and fall or break off.
Rattlesnakes also have a armory of senses to enable them to interact with their surroundings. Some like the eyes are common to most other animals others such as the Jacobson’s organ are unique to snakes and some lizards. The heat pit is unique to the rattlesnake and other pit vipers.
Snake eyes are much simpler structures than in most other vertebrates and less efficient. the eyes of rattlesnakes have vertical pupils indicating they are primarily nocturnal by habit. The color of the iris usually match the stripe that passes through the eyes of most rattlers that help camougfage the eye. Snakes that do not have the eye stripe can be lighter to match the color of the head. Example the Tiger Rattlesnake has a pinkish iris and the Rock Rattlesnake has grey.
THE TONGUE AND JACOBSON’S ORGAN
Like all snakes the rattler uses its tongue to explore and identify their surroundings. Flicking its tongue the snake is “tasting” the air by picking up airborne molecules. Withdrawing it’s tongue into it’s mouth, it inserts each of it’s tips into a specialized organ embeded into the roof of its mouth the Jacobson’s organ. It is lined with nerve endings and is linked to the brain by a branch of olfactory nerves. The same nerves that connect the nostrils to the brain. Therefore the snake s literaly smelling the air with its tongue.
Rattlesnakes and the other pit vipers get their name from the pits located on either side of faces. The pits are sense organs used to detect radiant heat and exist in no other animal except for some boas and pythons which are slightly different.
the pits are located just below a imaginary line drawn between the eye and nostril. they look like a extra nostril, but are slightly larger. the pit points forward and has a inner and outer chamber separated by a diaphragm..
Heat entering the outer pit will fall on the diaphragm, which has many nerve endings leading to the brain. this allows the snake to detect at a distanece a object than it’s general surroundings. It is sensitive enough to distinguish between objects with a diffrence of less than 0.2 centigrade and 0.4 fahrenheit at close range.
Because of the extreme sensitivety of these pits and the fact that they are widely separated on the face the snake can determine the exact position of it’s prey. So effective are the pits that they enable the rattlesnake to judge the best place to sink it’s fangs. Rattlers “hit” the chest region of their prey almost every time.
THE VENOM APPARATUS
Rattlesnake fangs are long, curved hollow structures that inject venom deep into the body of their prey. When not in use they are hinged out of the way in the roof of the mouth and covered by a fleshy sheath so the snake can close its mouth. the fangs are attached to a bone called the Maxilla bone, which is shorter than those in other snakes, and can be rotated in a arc of about ninety degrees. When the snake strikes it normaly moves both fangs into the armed position but can move the independently of each other. It may do this when re-aliening it’s jaws after swallowing a meal. Each fang is connected to a venom gland by a narrow duct. The glands are located behind the eyes. Venom is forced along the duct by specialised muscles. The venom exits the fang through a small opening near the tip. Very occasionally the snake make make a dry bite in which no venom is injected.
from timt to time the fangs are replaced by new ones that grow next to the old ones. a snake may have two pair of fangs at the same time. the sheath covers both sets at the same time, both may secerete venom.
Some additional facts,
Of the thirty species of rattlesnakes, Mexico has the most with twenty-nine. and thirteen are found only in Mexico. Rattlesnakes are found in every main land state except for Alaska, Delaware, and Maine. Arizona has eleven, Texas eight, New Mexico seven and California has six.
I had a very sweet old Sophomore and Junior English teacher in high school named Goldia Stephens. She tried unsuccessfully to encourage me to write a decent book report. To her I offer up this effort , hopefully her efforts were not entirely in vane.
There is more such as habatit and locomation, the venom, mating (Iknow you want to know about the sex life of the rattlesnake,right?). maybe I’ll get the enegry to do more later, as it is I”ve made twellve pages of cramped berly eligebale note’s and am pretty tired of snakes at the present.