Window on Nature
By Lowell & Kaye Christie, F47246
This reptile with the notorious reputation would rather use its telltale tail to scare you away than fight.
Rattlesnakes are normally quiet creatures, usually staying out of sight and minding their own business. That business, in large part, is keeping the rodent population in check. But when surprised or threatened, a rattlesnake will usually shake its namesake rattle as a warning, and it’s a warning that must be respected, for the venom of a rattlesnake can be lethal.
But danger from rattlesnakes to campers and hikers is often exaggerated, both in news reports and in tales told around a campfire.
To put things in perspective, according to the Web site eMedicine.com, in 1989 fire ant stings accounted for the deaths of 32 people in four states. Wasps and bees account for between 30 and 120 deaths annually. But one source reported that rattlesnake bites are responsible for fewer than 12 fatalities per year. So although a close encounter with this fascinating reptile is to be avoided, its niche in the natural world is certainly worth exploring.
Rattlers are thought to be the most recently evolved creatures in the snake kingdom, and they exist only in the Americas. Numerous species and subspecies inhabit the United States, and they are found in almost all of the Lower 48 states. Although several characteristics distinguish them from other snakes, the one that’s most obvious from a safe distance is the rattle itself.
Within days after a rattlesnake is born (not hatched from eggs, but a live birth), it undergoes its first of many molts. These will later occur from one to four times a year, and each shedding of the snake’s old skin leaves an additional rattle segment. Once it has two segments, the snake can create the distinctive buzzing sound it uses as a warning. The rattle is caused by the segments hitting each other as the tail vibrates back and forth more than 50 times a second.
People once thought a rattler’s age could be determined by the number of rattle segments, but as the snake gets older, the end pieces often break off. Although a rattlesnake in the wild may live more than 20 years, you certainly won’t see that many segments on its tail.
The back end of the rattlesnake may be the noisemaker, but it’s the business end that folks need to be concerned about. Inside the snake’s mouth are hollow, curved fangs that lie parallel to the jaw. When the snake strikes at prey or in defense, muscles rotate these fangs into a perpendicular position. The hollow fangs act like hypodermic needles, injecting venom from special glands into the victim. According to one source, the entire strike and venom release takes only about 200 milliseconds “” faster than the eye can follow.
The snake immediately releases its victim and waits for the poison to take effect. Smaller creatures may be immobilized immediately. For larger prey, the snake will follow the animal until it collapses.
Not every snakebite is accompanied by a venom release. Evidently the snake has the ability to withhold the venom, since as many as 25 percent of the bites are “dry.” Perhaps this way the rattlesnake can use its fangs as a defensive weapon against larger creatures that it couldn’t hope to eat, while saving its venom for a later meal.
Rattlesnakes are very efficient hunters, conserving their energy by lying in wait along rodent paths. They will remain motionless for hours until a prey animal comes along and then strike at the last moment.
Although the rattlesnake has no ears, it has several ways of sensing danger or the availability of prey. It can detect ground vibration through its body, and it has a strong sense of smell. In addition to its nostrils, it uses its flexible forked tongue to “taste” the air, which it samples by way of organs located in the roof of its mouth.
The rattler has fairly good eyesight for nearby objects, but it also has the ability to “see” heat. Behind each nostril is a depression, or loreal pit, that can detect temperature variations. At very short distances, it is believed the rattler can detect differences of less than one degree. Since prey animals give off heat, this provides the snake an extra sense to use during the daylight hours, and even allows it to hunt in the blackness of underground burrows.
Rattlesnakes are cold-blooded animals, and they depend upon the heat from their environment to regulate their temperature. That’s why they can sometimes be seen sunning on rocky surfaces, or even lying in the center of hiking trails. This is a case where a little caution goes a long way.
Although rattlesnakes can move only approximately three miles per hour (less than a quick walking pace), they can strike from a coiled position faster than you can move. And contrary to common belief, they don’t have to be coiled to strike. They can surge forward between one-half and three-quarters of their length, so the safest observation distance is probably somewhere around 10 feet away or more. Don’t believe the old wives’ tale that they always rattle before they strike. And a pair of binoculars makes a great addition to your snake-watching kit.
Most of the sources we consulted agreed that more than 60 percent of the humans bitten by venomous snakes each year simply weren’t smart enough to leave them alone. They were bitten while trying to either capture or kill the snake. Unless you are in your own backyard, remember that you are invading their home territory.
When in rattlesnake habitat, keep your hands and feet out of places you can’t see into, be they gopher holes, piles of rocks, or fallen logs. If you’re crossing rocks or logs, step onto them so you can see the opposite side before you put your foot in the wrong place.
Now, with all those warnings, relax. As we said at the beginning, snakes tend to mind their own business and are just part of the wildlife you can enjoy seeing. After you’ve watched for a while, take a wide detour around the critter and enjoy the rest of your walk.