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Rattlesnake, Crotalus horridus
Photo © 2004 Jim Jung. All rights reserved

A Natural History of the Timber Rattler

Crotalus horridus

Timber Rattlesnakes are one of those unfortunate species whose instinctual behavior has turned out to be particularly maladaptive when interacting with our culture. As a result the Timber Rattler has gained a tragically exclusive legal status - that of the endangered species.

The Timber Rattlesnake's year begins in April when the hibernating snakes stir from their long winter sleep and emerge from their communal dens to sun themselves on warm days around its mouth. These dens are nearly always located in steep, rocky terrain and are used year after year by the same group of snakes. It is here that mating takes place, either in the fall or spring, and males compete for the receptive females affections with a peculiar form of neck boxing.

Rattlesnake prey

With the warming days of May the rattlesnakes move off into the surrounding countryside to hunt for their favorite morsels of food: rodents. Most of their hunting takes place at night when their unique infrared-sensing pits can be put to use most effectively. These pits, located on the upper jaw halfway between their eye and nostril, are like a second pair of eyes and sense the heat emitted by their prey. Able to detect a difference in temperature of as little as .01° it enables the snake to strike unerringly even in total darkness.

Once prey is located the Rattlesnake moves slowly and cautiously to within striking distance and then, with blinding speed, strikes. The snake injects a small amount of venom via its needle sharp fangs, releases the prey, and waits for the poison to do its work. Within minutes the mouse, chipmunk, or vole is dead and the snake then swallows the prey whole, headfirst. Once it has eaten the Rattlesnake crawls out of sight and digests its meal - a process that takes two or three days. In the course of a season a Rattlesnake will only make 25 kills before returning to its den for wintering.

Reproducton

Pregnant females eat for as long as they are able, but as they retain their eggs instead of laying them, the rapidly growing young inside them quickly restrict their digestive tracts and force them to fast until their young are born. The pregnant females then return to the den site where they bask in the sun to raise their body temperatures and metabolism and hasten their youngsters' growth. This reproductive fast is hard on the female Rattlesnake. It will take at least two years of feeding before she has the fat reserves to carry another litter and often three years or more will pass before she becomes receptive again.

In August the heavily swollen females give birth. Unlike nearly all other reptiles baby rattlesnakes are born alive, not hatched from eggs. Once born, however, the mother Rattlesnake shows no more interest in her offspring and they're left to fend for themselves.

Just 16 inches or so at birth each of the four to ten baby rattlers in each litter is armed and dangerous from the moment it enters this world with a full (though proportionately small) complement of venom, a gray body, a bright yellow tail and a single button rattle. While the remnants of their yolk sac are being absorbed the babies crawl into the woods to hunt a meal or two before returning to the den for winter.

Youth

Adult rattlesnakes three to five feet long have little to fear - most potential predators give them a wide berth. Baby rattlesnakes, however, face a host of enemies: raccoons, hawks, bobcats, owls, skunks, coyotes and, of course, humans. If they can avoid predators, cars and the myriad other misfortunes the world offers the young rattlers can expect a life span of up to twenty five years. The vast majority though never see their second birthday.

The young rattlers grow quickly and soon outgrow their original gray skin which they shed to emerge with the adult pattern of diamond blotches they'll retain for the rest of their lives. With each shedding of the skin another rattle is added to the snake's tail. Since rattlers ordinarily shed their skin at least two or three times a year, counting the rattles on a snake is not a reliable indication of age. The rattles are brittle as well, breaking off easily, and a mature rattlesnake seldom has a complete set of rattles on its tail.

Denning

As August draws to a close the cooling nights signal the snakes that it's time to return to their ancestral den for the winter. Traveling mostly at night the rattlers eventually assemble at the den site where they can sometimes be seen on warm, sunny autumn days basking on rock ledges near the entrance to the den with the males anxiously scanning for receptive females with which to breed. The den proper is located some distance inside the bluff and is always reached by way of narrow crevices and cracks that preclude the entry of predators. In areas where den sites are rare or far between snakes of several different species will share the same space. Copperheads, Cottonmouths and even Garter Snakes have been found sharing dens with Rattlesnakes.

By the middle of September all the snakes are safely inside the den with the newly born young arriving last. Growing sluggish and sleepy they finally enter hibernation and sleep while winter's cold and storms rage outside. With the rising temperatures of spring the snakes begin to stir but don't really awaken until late April or early May when the cycle repeats itself and the snakes crawl away to forage. Of all our snakes, Rattlers are the last to leave hibernation and the first to enter it again in the fall.

Reproductive potential

Timber Rattlesnakes reach sexual maturity at six to eight years of age. Simple math shows that even under the most optimal of conditions (something which almost never happens) a female rattlesnake can only give birth to six litters. Recent research has shown that three or four litters is closer to the truth.

While being slow to mature sexually and possessing a low birth rate is bad enough, the rattlesnakes' habit of communal denning makes them particularly vulnerable to their human predators. Once located, whole populations of snakes can be exterminated in short order. Since dens are vital to this snake's survival as a species any one with knowledge of existing snake dens is urged to contact their local Department of Conservation.

Illinois Status

So rare have rattlesnakes become in most areas that Illinois has recently afforded them protected status. Anyone caught possessing, collecting, killing or molesting a rattlesnake in any manner is subject to a minimum $200 fine and possible jail time.

Hopefully, though I'm not particularly optimistic about it, our species will eventually realize (and that soon) what unique and interesting animals our Timber Rattlesnakes are. I've had the privilege of meeting and getting to know a few of our surviving fellow travelers and as snakes go they are gentle, inoffensive and meek creatures who only want to be left alone to live their lives and make their living - and while they differ from us in numerous and even radical ways - in that respect they're surprisingly very similar to ourselves.


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The information on this page is tailored to Southern Illinois, Southwest Indiana, Western Kentucky, and Southeast Missouri

Copyright © 2004 Jim Jung