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Reptiles of North America
By Hobart M. Smith, Edmund D. Brodie Jr., David M. Dennis, Sy Barlowe
St. Martin's PressCopyright © 1982 St. Martin's Press
All rights reserved.
This book is a guide to the identification of turtles, lizards, snakes, amphisbaenids, and crocodilians of North America north of Mexico. A total of 22 families, 109 genera, 278 species, and over 500 subspecies are treated. Among them are 18 exotic species that were introduced either intentionally or by accident and have now established resident populations in North America.
Like the amphibians from which they evolved, reptiles are air breathers and have little internal control of their body temperature (ectotherms), but the reptiles have advanced features that make their habitat less restrictive. All reptiles either give birth to their young (viviparous) or lay eggs (oviparous) on land. All reptiles also have an outer covering of scales or scutes enabling them to live away from the moist surroundings to which amphibians are confined. Temperature is thus the limiting factor in the distribution of reptiles as a group.
The diets and food habits of reptiles, as a group, are diverse. Some snakes, for example, feed exclusively on cold-blooded vertebrates; others primarily on worms, grubs, or insects; and still others make their meals mainly of mice or other rodents. Nearly all reptiles are predatory carnivores, or flesh eaters.
As a group, lizards are essentially insect eaters (insectivorous). Most turtles eat fish, frogs, crustaceans, and other small animals that live in or near water, but a few kinds of turtles and lizards eat both animals and plants (omnivorous) or are almost wholly vegetarian (herbivorous), particularly as adults. Those kinds of snakes that make their meals of rodents are obviously beneficial. The benefits of lizard predation on insects are less obvious but are also helpful. All reptiles play a role in the intricate web of life and are thus important elements in their particular habitats and ecosystems.
Nearly all reptiles are wary and secretive, their abundance often much greater than suspected. Most snakes and some lizards and turtles are active primarily at night (nocturnal) or only during evening and morning hours (crepuscular). Most lizards and turtles are active during daylight hours (diurnal). Turtles may bask in the sun but are quick to get out of sight at the slightest commotion. Snakes and lizards generally keep under cover, too, but lizards are the more conspicuous and can often be observed chasing and catching their insect prey. Male lizards may perform openly to attract females, and they chase after other males in territorial squabbles.
Where Reptiles Live
In North America, reptiles are most abundant in the warmer southern regions. Alligators do range as far north as South Carolina and Louisiana in resident populations, but they are by far most numerous in the near-subtropics of southern Florida. Snakes are most abundant both as individuals and in species in the southeastern United States, but some species range northward into Canada. A few species of lizards also occur as far north as Canada, but as a group, lizards are best represented in the warm and dry southwestern areas. Turtles, too, are widely distributed but are most abundant where it is warm. A few species — notably the tortoises — are adapted to dry (xeric) conditions, but as a group, turtles are most abundantly represented either in or near water.
When and Where to Look
In temperate climates, reptiles are dormant in winter. In extreme southern United States, it is warm enough for them to remain active throughout the year. Cool weather slows all reptiles, however, and they do not become active again until the weather warms. Male alligators, and also other crocodilians, roar or bellow in the spring to signal dominance of a territory, and both male and female alligators grunt, uttering a piglike noise that is apparently used as a "call" signal. Turtles, snakes, and lizards make sounds, but there are no vocal congresses to establish mating sites as there are in amphibians. Reptiles thus can be found, with the exception of crocodilians, only by seeing them, and for many species, the finds are as much by accident as by skill.
Knowing where the species lives has considerable bearing on the success of a reptile hunt, of course. To see aquatic turtles either feeding or basking, for example, approach a pond, lake, or stream cautiously. Expose as little of yourself as possible, do not make quick movements, and give all likely spots where the turtles might be sunning your special attention. Sometimes the turtles will bask at the surface with only their heads exposed. Softshell turtles bury themselves in the sand in shallow water and then stick their long, snakelike necks up to the surface, their tubelike snouts serving as snorkels. But even if no turtle is in sight at the moment, perhaps a vibration or some small noise has alerted them. If a turtle was active at a place, it will soon appear again if you wait quietly.
Lizards are the most conspicuous of the reptiles. While they will scurry out of sight — under a rock or log or onto the other side of a tree or limb — you will often hear their rustling even if you missed seeing them at first. Again, if your objective is watching them in nature, stand very quietly or find a good place to sit comfortably. Soon the lizards will be on the move again, accepting you as a part of their surroundings.
Most snakes are active at night and are only seen sunning during the day. It is difficult to observe them going about their daily lives. Aquatic snakes are the easiest of all to find because of their limited habitat. They are always either in the water or nearby. Terrestrial snakes are most easily found in their hiding places — under rocks, logs, bark, debris, or other movable objects. Do not, however, take this as a license to destroy habitats. Whatever is lifted or moved should be put back in place exactly as it was originally.
Reptile collecting is done almost totally in the daytime. Turtles are found in their hiding places — under rocks, in debris, or buried in sand or mud. Those that are buried leave small funnel-shaped depressions where they draw in their heads. With experience, you can recognize the approximate size of the turtle by the size of the funnel, then run your hands down into the sand or mud so that one is on each side of the turtle's carapace. Softshell turtles are commonly caught in this manner. Remember that they have extremely long and snakelike necks, sharp jaws, and vicious tempers. The bite of a large softshell can be severely painful, and the turtle is also reluctant to let loose. Snappers can also be dangerous, especially large ones. Be extremely careful in handling them. Turtles do not have teeth, but the edges of their jaws are sharp and their jaw muscles powerful.
All lizards can bite and are quick to do so, holding on tenaciously. Both the Gila Monster and the Mexican Beaded Lizard are poisonous, the only venomous lizards in the world. Their venom is primarily neurotoxic and can cause death. These lizards should be avoided, though they have only a primitive mechanism for injecting venoms and deaths from their bites are extremely rare. Bites of other lizards are harmless, but if the skin is broken, apply an antiseptic to curb any secondary infection. Do not grab a lizard by its tail, for in many species, the tail readily breaks off (autotomizes).
While most snakes are harmless, their bites no more dangerous than those from lizards, there are in North America a number of venomous species: the Copperhead, the Cottonmouth, coral snakes (2 species), and rattlesnakes (15 species). Snakes should not be handled unless you are absolutely sure of their identification. If you are picking up a snake of doubtful identity, use a noose on a long stick or a stick with a short fork to hold the snake behind its head. And pick up the snake by holding it behind its head so that it cannot bite. Hold the snake firmly. Snakes are difficult to restrain and can manage almost uncanny twists and turns. Snakes known to be harmless can be picked up by any part of their body, of course. But even harmless snakes can give painful bites. They strike and often draw back quickly, their back-curved teeth tearing the skin. Some snakes "chew" and are reluctant to release their hold.
Unbleached muslin bags of various sizes, double-sewed with rounded corners to eliminate loose, entangling threads, make excellent containers for reptiles. The bags should be at least twice as deep as wide and should have a tie string two inches (50 mm) or more from the top. These bags are strong and will not break even if moist litter is put in them. They can be carried looped over your belt, which makes them easy to get when they are needed.
Remember that venomous snakes have long fangs and can bite through the bags. Put the bags in a box or other container through which the snakes cannot bite or carry the bags at the end of a long stick or pole. Snappers and other turtles can also bite through a bag. This can be avoided, too, by carrying the bags properly.
Never put collected specimens in the sun. Many snakes succumb because collectors leave the bags exposed. Keep bags in the cool shade.
Leaving the habitat as nearly as possible exactly as you found it is a cardinal rule. Do not collect more specimens than you need for your study. Return the specimens alive to where they were collected after you have completed your observations. Because of habitat destruction — highways, housing developments, clearing for farming, and the like — a number of species of reptiles are now threatened with extinction.
Before you go collecting anywhere, check with state and federal wildlife representatives to learn what species are endangered and what can be collected. Never collect without first getting permission from the landowner. A refusal is rare, but if you do not have permission, you may be fined for trespassing, which can be both costly and embarrassing.
It has been the custom for herpetological hobbyists, and even some professionals, to express their interests by "going collecting" — merely trying to find and bag as many species or specimens (or both) as possible. Even though the specimens may be returned to their home territories later, the lives of many animals are unduly disrupted, often fatally, and seldom is as much learned about them as could be the case by simply observing the animals without disturbing them.
With the present increasing concern for our vanishing wildlife, the pursuit of herpetology should increasingly emphasize field observation with minimal disturbance. Astonishingly little is known about reptilian behavior under natural conditions — certainly a field of investigation that is destined to become popular in the future as students learn to "live and let live."CHAPTER 2
Bites of nonvenomous snakes can be treated with an antiseptic. The danger from these bites is secondary infection; some bites may warrant giving an antitetanus agent.
Venomous snakes, however, are indeed dangerous. Avoid picking up or handling poisonous snakes. (Of course, if you are collecting, this is sometimes unavoidable.) In areas where poisonous snakes live, wear boots, look before putting either your hands or your feet anywhere, and be very careful when you must cross fences or logs. Follow common sense precautions, and the chances of being bitten are extremely slim. It is also possible to be bitten by a venomous snake and not have poison injected. If you know the snake is venomous, keep calm and plan on how to get to a medical facility as quickly as possible.
The venom apparatus of snakes consists of large modified salivary glands connected by ducts to fangs on either side of the upper jaw. The snake controls the amount of venom ejected. A rattlesnake, for example, may release much or little of its available venom into a bite. If it bites several times it can inject venom with each bite.
In rattlesnakes and moccasins (viperids), the fangs are long modified front teeth that normally are held against the roof of the mouth. In their bite position, the bone to which they are attached is pivoted down so they are roughly perpendicular to the roof of the mouth. Each fang is hollow, like a hypodermic needle, and is connected to the duct from the poison gland located on that side of the head. Snakes can control the position of their fangs in striking or in biting. In elapids — the coral snakes — the fangs are short and fixed in an erect position at the front of the mouth. In both viperids and elapids, the fangs are shed periodically and replaced by reserve fangs.
Venoms are complex mixtures of proteins, many having enzyme action. They cannot be categorized simply as hemotoxins, neurotoxins, or cardiotoxins, as was often done in the past. Most venoms have elements with each of these properties. The venoms of a species of snake may differ in different areas and at different times of the year. The amount of venom injected also varies. Field determinations of the severity of a bite are precarious. For these reasons, it is important to get the snakebite victim to a medical facility as quickly as possible.
In general, the venom of rattlesnakes and other vipers of North America causes local swelling through destruction of the tissues exposed to it, including blood vessels and blood cells. Swelling is usually evident within 10 minutes and may increase and spread slowly for several days, with much edema and discoloration in the bite area. Pain may be intense.
Numbness around the mouth, weakness, sweating, and muscle twitches are also characteristic following some rattlesnake bites.
In contrast, the venom of coral snakes is primarily neurotoxic. The effect on the tissue in the bite area is minimal, but the venom may cause heart or respiratory failure. Although more lethal, drop for drop, than viperid venom, few deaths are now attributed to North American coral snakes. The symptoms and signs of poisoning, including pain, may be delayed for more than half an hour after the bite, and there may be little or no swelling. Within two hours the victim may become drowsy, have blurred vision, and find it difficult to speak distinctly. A collapse of the respiratory mechanism may follow, necessitating artificial respiration. Get the victim to a hospital quickly.
If a doctor or a hospital are not within 30 minutes distance, first aid must be administered either by the victim or a companion. Remain calm. Panic, exertion, and hysteria only help to spread the venom more rapidly. Remember, snakebite is rarely fatal.
Anyone who is collecting snakes or who is traveling where poisonous snakes occur should carry a snakebite first-aid kit. If one is not available, at-hand resources may be used.
First, at once place a constriction band immediately proximal to the bite. Then make a single, shallow, longitudinal (not cross) slit 1/8 to ¼ inch (3 to 6 mm) in length and depth over each fang wound, using a razor, knife blade, or other sharp object. Apply suction, preferably with a suction cup from a snakebite kit, but with the mouth, if necessary, if it has no lesions. These procedures must be started within 5 minutes of the bite to be effective, and the quicker the better. Suction should be carried out continuously for 30-60 minutes.
The longitudinal slit minimizes the chances of cutting vessels, nerves, tendons, and muscle fibers under the skin. A shallow cut is best because the venom generally at first pools in subcutaneous lymphatic channels. Rarely is the venom injected directly into a blood vessel, which would be followed almost immediately by alarming systemic signs and symptoms, or injected deep enough to pool between muscles or around bones where it would not be accessible to suction. The suction cups may need to be reapplied from time to time. The constriction band should be advanced ahead of the swelling.
If done well and promptly, this "cut and suck" first-aid treatment is of value. However, if the victim is within 30 minutes of medical care — rest, reassurance, immobilization of the injured part, and observation are all that is absolutely necessary. There is no harm in placing a constriction band just proximal to the wound site. However, a constriction band should only be tight enough to impede lymph flow. If swelling reaches the constriction band, move it farther away. When antivenin is given, the constriction band should be removed completely.
Excerpted from Reptiles of North America by Hobart M. Smith, Edmund D. Brodie Jr., David M. Dennis, Sy Barlowe. Copyright © 1982 St. Martin's Press. Excerpted by permission of St. Martin's Press.
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