The loss of a single snake, or a dozen snakes, or even a hundred in one year will probably not seriously impact the balance of a particular ecosystem, at least not in the long term. Most natural changes occur slowly, over prolonged periods, like the rhythm of the seasons or the process of aging, so that their effects are usually not immediately apparent. But it is clear that over time the cumulative consequences of snake bashing, coupled with habitat destruction and environmental pollution, have taken a heavy toll of most native serpents, as probably has the insidious and sometimes equally devastating damage inflicted by the imported fire ant. Although habitat degradation and pollution are the chief causes of decline in local serpent populations statewide, it is not our intention to address these issues at length, since the resolution of such threats resides largely in the political arena and is therefore beyond the scope of this book. This is not to suggest, however, that interested persons should avoid becoming involved with local or national conservation groups to influence government policy makers in wildlife conservation matters. Indeed, doing so is often the best way to achieve significant and lasting results.
But to anyone with a clutching fear of snakes (which includes most of us), any idea of conserving these creatures will seem ludicrous or, at the very least, a misplaced priority. What is the compelling reason for this antiserpent bias? If we can accept that the great majority of snakes are incapable of causing us serious harm and that by reason of their feeding habits most of them are beneficial to our interests, by what logic do we feel obliged to destroy them on sight? The obvious answer is that a great majority of us lack even a basic understanding of these essentially timid and benign animals.
Our information about them often comes from those whose bias, like our own, is based primarily on the same myths and misconceptions that have confounded the subject since ancient times. Although erroneous, such implausible tales pique our interest, and their telling makes for lively after-dinner conversation. Unfortunately, however, by masking the truth they make more difficult the task of getting to the facts. The challenge then is to present the facts about these generally innocuous animals in such a way that even the snake haters among us will see these reptiles for what they really are—not vengeful creatures lurking in the brush to ambush the next human victim but another life form no more villainous than any of the others. Indeed, the life of a snake is basically not much different from that of other animal species. Like them it must find food, reproduce, protect itself from its enemies, and maintain a comfortable body temperature in the face of the changing seasons. How serpents fulfill these life functions can be as interesting as the bizarre snake stories we often hear and accept as fact. Only when we can cast aside such misinformation and replace it with an objective view of our subjects aye we likely to entertain the idea of conserving snakes. That, it seems to us, is where the conservation ethic begins.
Myths and Other Misinformation
Most of the fictitious snake stories and misconceptions that follow have been part of our culture since at least colonial times, having been chronicled as fact in newspapers, magazines, books, and even in state publications. Others not listed here (but mentioned in the main text under the appropriate species or subspecies accounts) include those of the hoop snake (under western mud snake), spreading adder (under eastern hog-nosed snake), milk snake (under Central Plains milk snake), and whipsnake (under eastern coachwhip). Finally, the erroneous belief that one can determine the age of a rattlesnake by the number of segments in its rattle is discussed under the account for the western diamond-backed rattlesnake.
- Snakes are slimy.
- Unlike fish, whose slimy bodies help to reduce resistance as they move through the water, snakes have skin that is quite dry. Since they have no internal resource with which to control their body temperature, snakes often feel cold to the touch, a condition that may be misconstrued as sliminess.
- The snake's forked tongue is a venomous stinger.
- Nothing could be farther from the truth, since the soft, fleshy tongue—a delicate organ associated with the snake's senses of taste and smell—is no more dangerous than our own. It is found in all snake species, even those that are nonvenomous.
- Snakes have hidden legs.
- A male snake that is thrown into a fire may evert its hemipenes in agony. During its frantic attempts to escape the flames, these exposed, paired copulatory organs will probably be perceived as legs.
- Snakes do not die until sundown.
- A wounded snake, even a seriously injured one, may hold on to life for hours or even days before succumbing to its wounds, though it will quickly die if decapitated, cut in two, or crushed under a large rock.
- Snakes always travel in pairs.
- During the breeding season, which generally occurs in the spring, male and female snakes of the same species can be found together during the short time it takes them to consummate the mating act. After that, they usually go their separate ways. According to this myth, a snake whose mate is killed as the two are traveling together will avenge the act by attacking the perpetrator. Although none of that is true, it has been confirmed that a male racer, particularly of the northeastern subspecies, Coluber c. constrictor, when interrupted during courtship or mating, sometimes vigorously attacks a human interloper. Such an assault should be of little concern, however, for a snake of this kind is incapable of inflicting serious injury.
- Snakes chase people without provocation.
- It is true that some native snakes defend themselves aggressively when they are provoked and unable to flee, but none is known to pursue a human being. When, as occasionally happens, an intruder comes between a snake and its refuge, the snake may dash right by the startled onlooker to reach its nearby shelter. In these circumstances, it would be difficult to convince anyone that the snake was not making a direct attack.
- Snakes routinely crawl into sleeping bags.
- Although snakes have been known to enter sleeping bags to escape the chill of evening, such events are extremely uncommon. To avoid this possibility it is suggested that the sleeping bag be placed on a cot or used inside a tightly zippered tent.
- Snakes will not cross a horsehair rope.
- The belief, once common in the Southwest, that a rattlesnake will not crawl over a horsehair rope placed around a campsite can be dangerously misleading. As the story goes, the stiff protruding hairs of the rope stick the snake's belly as it attempts to cross, causing the reptile enough discomfort or pain to make it turn back. Yet most rattlesnakes are desert dwellers that live among spiny plants, including cactus, over which they sometimes crawl without hesitation. A snake that is not deterred by cactus spines will hardly be discouraged by the presence of a horsehair rope.
- A snake's detached fang can kill.
- This legend, dating back to at least the early 1700s, describes the death of a man who was struck through one of his boots by a rattlesnake. The same boot was later worn by the victim's son, who was pricked by a fang still embedded in the leather and suffered the same fate that befell his father. After his death, a second son eventually put on the fatal boot, only to succumb to the poisonous fang as well. While it is true that when quickly dried and properly stored, the venom of a rattlesnake can maintain its potency for many years, the small amount of venom, if any, that would reside in the detached fang under the circumstances described above would hardly be enough to cause death in even one person, let alone three. Moreover, in an actual rattlesnake bite, the venom is forced under pressure through the hollow fang and into the victim. In the case of a detached fang, any small amount of venom that may still reside in the fang would simply remain there, unable to be expelled, since there is no mechanism to force it out through the orifice near the fang's pointed tip. On the other hand, there is a real danger in handling the recently severed head of a venomous snake, since it can still see, flick its tongue, and inflict a poisonous bite for up to an hour after having been separated from its body.
- Mother snakes swallow their young to protect them.
- One of the oldest of all snake myths, this one has been traced back to the early Egyptians (about 2500 BC), though it is among the most incredible stories of snake behavior repeated in the United States today. It details how a mother snake, confronted by danger, emits a warning hiss or whistle to alert her young, whereupon she opens her mouth and allows the infants to enter and hide in her throat. If such an event is as common as the many eyewitness accounts would have us believe, why has it not been observed by even one herpetologist, professional or amateur? After all, many hundreds of snakes are born in captivity every year, yet not one of the female parents of these broods has ever been seen to swallow her young. Nor has this behavior been observed in the wild by trained field zoologists, either in this country or elsewhere. One likely explanation for this popular myth is that when a female snake carrying nearly full-term young is killed, the infant snakes, still alive, may be expelled through her cloaca or escape from her ruptured body. To some, this confirms the notion that just before her death, the mother snake senses the potential danger, prompting her to swallow the young as a way to protect them.
For further information about this topic, we suggest the following books and pamphlets: L. M. Klauber, Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind (1956); C. H. Curran and C. F. Kauffeld, Snakes and Their Ways (1937); K. P. Schmidt, The Truth about Snake Stories (1929); J. A. Oliver, Snakes in Fact and Fiction (1958); J. K. Strecker, Reptiles of the South and Southwest in Folklore (1926b); and E. Wigginton, The Foxfire Book (1972), especially the chapter on snake lore.
The Snakebite Hazard
To a large extent, our fear of snakes is based on the knowledge that a few of them are venomous and capable of causing us serious bodily injury and sometimes even death. This fear, while logical enough when based on the facts of the matter, is usually so exaggerated that it can become unreasonable or, in the extreme, even grotesque, leaving little or no opportunity for rational dialogue. Some people have such an overwhelming fear of snakes that getting them to talk about the animals that cause them so much mental anguish may be impossible without professional help. Psychologists explain that ophidiophobia is among the more difficult fears to overcome. Such practitioners estimate that more than 50 percent of our population experience some anxiety in the presence of snakes, and another 20 percent are terrified by them. Extreme examples of the latter include those who become terror-stricken when they so much as see the picture of a snake in a magazine, a book, or on television, and others who avoid outdoor activities altogether for fear of encountering a snake, even a harmless one. Sadly, most of these people retain their morbid fear for life. But there are hopeful signs that the 50-plus percent— those with only a moderate fear of serpents —are slowly but surely being reduced in number as both public and private institutions and organizations concerned with natural history education reach ever more people with their hands-on programs. Probably at the forefront in molding such attitudinal changes are the country's zoological parks (and aquariums), which, through live exhibits and informal teaching programs, annually expose their nearly 120 million visitors to wildlife conservation messages. Science museums, nature centers, and wildlife organizations are fulfilling a similar role. As a direct result of such efforts, one encouraging sign of the change taking place in our attitude about snakes is the phenomenal growth of the pet-snake hobby; having gained prominence only about 20 years ago, it continues to expand at an accelerated pace, with devotees nationwide numbering in the many thousands.
Despite such progress, a great deal of apprehension and misunderstanding still exist among Texans about their native serpents. In the minds of most persons, snakes are still the enemy. They are seen as mysterious and menacing, to be killed wherever and whenever they are encountered. The truth is that snakes—even the dangerous ones—are fundamentally shy and retiring, more than willing to avoid a confrontation with mankind by fleeing when given the chance. Only as a last resort will they bite in self-defense. The notable exceptions are assignable not to our native serpents but to a few exotic species such as the giant king cobra of southeastern Asia, the deadly black mamba of Africa, and the fearsome taipan of Australia—all highly dangerous venomous snakes whose occasional lack of tolerance for man's intrusion into their territory can result in an aggressive confrontation.
Our native venomous serpents do not display such overtly offensive behavior; they nevertheless pose a potential risk for those engaged in outdoor activities. This is, after all, a large state with a diverse snake fauna, consisting of 72 species (by our count), 11 of which are considered dangerous to man. Ranking the states by raw figures, Parrish (1964) estimated that Texas suffered more venomous snakebites in a single year than any other state nationwide, although when the number of such accidents was calculated per 100,000 residents, Texas ranked third, with an incidence rate of 14.70 percent, trailing behind North Carolina at 18.79 percent and Arkansas at 17.19 percent. Moreover, based on actual and projected snakebite incidents for 1958 and 1959, he estimated that approximately 1,408 snakebite victims were treated in Texas in each of those years, consisting of 784 inpatients and 624 outpatients. An average of only 2.4 fatalities occurred annually—a mortality rate of just one-fourth of one percent of those bitten. Even more encouraging are the mortality figures for the last 18 years (1978 through 1995), which according to the Texas Department of Health, Bureau of Vital Statistics, averaged only one death a year. These figures hardly classify venomous snakebite as a high-mortality occurrence, at least in the United States. Outdoor hazards more likely to cause human death in Texas are the stings and bites of insects and arachnids, lightning strikes, hunting accidents involving firearms, and drownings.
Among our dangerous snake species, two in particular are responsible for the greatest number of bites inflicted on humans. They are the copperhead and the western diamondbacked rattlesnake, both abundant and wideranging in the state. Although copperheads accounted for 22 percent of the bites reported by Parrish, they caused no fatalities, whereas the western diamondback, which was blamed for nearly all of the bites included in the rattlesnake category (47 percent of the bite total), was responsible for some human deaths. The cottonmouth ranked next in order of frequency but inflicted only 7 percent of the bites.
Reducing the risk of snakebite is largely a matter of learning to recognize the dangerous species in your part of the state, becoming familiar with their habits, and observing some commonsense safety practices, a few of which are listed below.
- The first rule should be, never handle a venomous snake unless you are qualified by training or experience to do so. This admonition, while it may seem self-evident, deserves emphasis, for an ever-increasing number of snakebites are being inflicted on inexperienced amateur herpetologists and reckless adventurers. Other bites are the result of mistaken identification. In one such incident, a Houston radio announcer encountered a coral snake on a city jogging trail. Believing the snake to be a harmless species, he picked it up and was promptly bitten on the hand, whereupon, momentarily startled by the reptile's reaction, he quickly dropped it to the ground. Still not convinced that the snake was dangerous, he handled it a second time and was bitten again. Also to be carefully avoided is a dead venomous snake, for such a creature often can bite reflexively for periods lasting up to an hour after death, as can its decapitated head, a reaction Klauber (1956) elicited many times from experimentally beheaded rattlesnakes. One of the most sobering examples of such an accident is the case reported by Kitchens and his colleagues (1987) in which a Florida man died after having been bitten by the severed head of a large canebrake rattlesnake.
- Since nearly all snakebites occur on the arms and legs of human victims, avoid placing your hands in places where you cannot see, and wear protective footwear on the lower half of your legs when venturing into areas known to harbor venomous snakes. Be particularly alert when climbing rocky ledges or when walking near old logs and decaying tree stumps, places often favored by certain venomous species. It also makes sense when crossing a log to first step onto it in order to see what is behind it, then to step down on the other side when it appears safe to do so. Never reach into mammal burrows, especially in arid habitats where aboveground shelters are scarce, for such tunnels are frequently occupied by rattlesnakes. Since one of the leading causes of snakebite is the practice of lifting or turning surface objects with the bare hands, a sensible rule to follow is to move these items (rocks, boards, logs, brush, construction debris, etc.) with a long-handled tool such as a hoe, shovel, axe, or broomstick.
- To discourage snakes from maintaining permanent residence close to a home or vacation cottage, it is advisable to keep the premises free of debris. Rock piles, trash piles, stacked lumber, and various forms of junk not only provide the serpents with shelter but also often harbor the rats and mice that constitute the principal food of most venomous species. Removing such debris helps to eliminate the snake's cover and that of its rodent prey.
- If you must kill a venomous snake that is a threat to human safety, do so out of range of the snake's strike, which ordinarily is less than its own body length. To attack the reptile with a short-handled weapon such as a knife, hatchet, or hammer is simply to invite an accident. Although this word of caution may seem too obvious to bear mentioning, it is clear from our review of Texas snakebite cases that accidents from this cause happen with some frequency.
For most people, snakebite is a terrifying experience that finds the victim both emotionally and intellectually unprepared to deal with such an emergency. Usually fear and extreme apprehension result from such an accident, when what is most needed at this time is a sense of calm. Despite the rarity of human death from envenomation in the United States, convincing a fearful snakebite victim that he or she has an excellent chance to recover from such a mishap is difficult. Nevertheless, every attempt should be made to convey this information to the victim, since to do so may relieve his or her anxiety and thereby expedite the victim's recovery.
Reaching medical aid as quickly as possible should be the first objective, but with a minimum amount of physical exertion on the part of the victim, who, if alone and on foot, should not run. If the bite is on an extremity, immobilize the bitten limb or at least avoid moving it, since muscular activity hastens the spread of venom through the lymphatic channels. Moreover, when the bite is on a hand or arm, take off any rings and tight bracelets before swelling makes their removal difficult.
Other, more aggressive first-aid measures—including incision and suction, with or without a constricting band or tourniquet; application of cold to the bite site; compression wrapping of the extremity; or stun gun electroshock—may or may not be used, depending on the knowledge and decision of the victim. However, such procedures, some of which are potentially harmful, have not been embraced with equal enthusiasm among the best-informed medical specialists, although the same experts agree that the several preliminary steps mentioned earlier (reassurance, prompt transport to medical aid without undue exertion, immobilization of the bitten limb, and removal of rings and tight bracelets) are beneficial. One expert, Dr. D. L. Hardy (1992), reviewed several commonly recommended first-aid methods for North American pit viper bites and presented his evaluation of their effectiveness. Anyone with a serious interest in snakebite first aid is encouraged to read this article.
Early native Americans were well acquainted with their local snake fauna, but their interest in them appears to have been more a matter of veneration than of specific knowledge about their behavior. The Spanish explorers who encountered reptiles in Texas during the period from about 1650 to 1700 were especially impressed with the large and dangerous noise-making snake they called the cascabel (meaning tinkle bell or jingle bell). Since the classification scheme of Linnaeus was not published until 1758, there was no formal designation of snake names. To the Spaniards, however, "vibora," or viper, was the name for any snake believed venomous, and "culebra" was any nonvenomous species. These terms are still widely used by Spanish-speaking native Texans. Perhaps the first European to have written scientific articles about Texas amphibians and reptiles was Jean L. Berlandier, a French botanist who, as he traveled across the state between 1828 and 1834, recorded his encounters with snakes in his field journal.
Prior to 1900, the collection of Texas amphibians and reptiles for scientific study was accomplished primarily by professional employees of the United States government, particularly those whose duties involved land exploration and survey work in the then largely unfamiliar territories of the Southwest, including Texas. Two such pioneers, John Russell Bartlett and William Emory, who conducted a railroad survey for the U.S. Army from 1850 to 1854, amassed a rather significant study collection of amphibians and reptiles from across the state (between Indianola in Calhoun County and El Paso), which was the source for most Texas-related herpetological publications issued between 1852 and 1854. During the next 15 years, because of the difficulties of conducting faunal surveys, little fieldwork was accomplished; hostile native forces, the distractions of the Civil War, and the stresses that followed the war were all contributing factors
Dr. Benno Matthes, a German physician who had traveled to Texas on several occasions before settling here in 1865, was described by Geiser (1941) as one of the state's earliest resident herpetologists. The results of his studies, mostly published in German scientific journals, included a monograph of North American salamanders and the osteology and natural history of certain Texas snakes, especially those from Central Texas, where he lived.
By the late 1870s, following that period of inactivity, the acquisition of specimens for study collections was again being actively pursued. Most of the material acquired during this period was forwarded to some of the leading herpetologists in the northeastern states, resulting in the publication of approximately 40 scientific papers between 1876 and 1899. In 1895, John K. Strecker, who was to become the father of Texas herpetology, began his field surveys in the state, eventually producing 60 articles dealing with the state's herpetofauna, among which was his 1915 checklist of Texas reptiles and amphibians, the first such comprehensive summary to be published. His work continued until 1935. Despite the creation of the Texas Herpetological Society in 1937, little fieldwork or other herpetological research was conducted in Texas between 1935 and 1946, partly as a result of the Second World War and the restrictions it had placed on automobile travel. After the war there was a renewed interest in the subject. A number of Texas universities appointed appropriate professors of zoology to inaugurate doctoral programs with an emphasis on herpetology. Among them were W. Frank Blair at the University of Texas and Hobart M. Smith and William B. Davis at Texas A&M University. Since then, generations of doctoral students in herpetology have walked the halls of Texas universities. Some have pursued their professional careers in the state or have left and returned to do so later. Among those still involved in the science of herpetology, either in Texas or elsewhere, are Ralph W Axtell, Royce E. Ballingel, James P. Bogart, Lauren E. Brown, Jeffrey D. Camper, William G. Degenhardt, Benjamin E. Dial, James R. Dixon, Robert R. Fleet, Alvin G. Flury, M. Jack Fouquette, Daniel S. Gallagher, William Garstka, Brian D. Greene, Sheldon H. Guttman, Louise Hayes, Fred S. Hendricks, David L. Jameson, Jerry D. Johnson, Frank Judd, J. Patrick Kennedy, Christopher P. Kofron, Chris T. McAllister, Wayne McAllister, John S. Mecham, William W Milstead, Craig E. Nelson, David Pettus, Kenneth R. Porter, William F. Pyburn, Carlos Rivero-Blanco, Richard D. Sage, Joseph J. Schall, James F. Scudday, Kyle W Selcer, Jack W. Sites, Robert A. Thomas, R. Kathryn Vaughan, Aron 0. Wasserman, and probably others.
Largely because of the work of many zoologists, our knowledge of Texas amphibians and reptiles has expanded at an accelerated pace over the past four decades. Each new book on the subject, particularly if it contains species distribution maps, invariably leads to additional short notes on distribution or natural history by those who can add to this body of knowledge with contributions of their own. During the 45 years prior to Strecker's Reptiles and Amphibians of Texas, issued in 1915, only 85 articles had been published about the state's amphibians and reptiles. Yet, from 1915 until the appearance in 1950 of An Annotated Checklist of the Reptiles and Amphibians of Texas, by Bryce Brown, 453 articles concerning these animals appeared in print. From 1950 to 1994, 2,116 additional works were published, many of them no doubt inspired by several recent books: Raun and Gehlbach's Amphibians and Reptiles in Texas (1972), Tennant's Snakes of Texas (1984), Dixon's Amphibians and Reptiles of Texas (1987), Vermersch and Kuntz's Snakes of South-central Texas (1987), and Garrett and Barker's A Field Guide to Reptiles and Amphibians of Texas (1987).
Much of the recent increase in the publication of locality reports and brief natural history notes can be attributed to the relative ease with which such information can be published in national and state journals, as well as in regional herpetological society newsletters. As examples of this incessant growth, Raun and Gehlbach's 1972 book referenced 1,108 articles about Texas amphibians and reptiles published through 1967. Dixon's 1987 volume contained an additional 990 articles, and by the middle of 1996 there was a total of 2,769 separate articles spanning 146 years of herpetological investigation in Texas. References to individual species of Texas snakes, published between 1828 and 1996, number 4,736 citations, representing an average of 66.7 references per species.
The five snakes most frequently mentioned in these reports, in descending order of frequency, are the western diamond-backed rattlesnake, coachwhip, Texas rat snake, copperhead, and plain-bellied water snake, followed by the bull snake, ribbon snake, racer, common king snake, and checkered garter snake. Discounting any recent name changes, those mentioned least often include the Trans-Pecos black-headed snake, red-bellied snake, worm snake, plains garter snake, and Mexican black-headed snake. Venomous snake species represent only 15.5 percent of the Texas snake fauna but are mentioned in 21.6 percent of the literature, whereas aquatic and semiaquatic snakes comprise 21.1 percent of the Texas serpent fauna and are mentioned in 20.6 percent of the Texas snake literature. Coachwhips, racers, rat snakes, king snakes, and bull snakes together amount to 18.3 percent of the snake fauna and are mentioned in 23.3 percent of the literature. The seven snakes found most commonly in yards represent 9.8 percent of the state's snake fauna but are noted in 13.4 percent of the articles, whereas the ten rarest and most secretive serpents—those with a limited Texas distribution—represent 13.4 percent of the serpent fauna but are included in only 3.5 percent of the literature.
Those wishing to pursue their interest in reptiles may join one of several state, regional, or local herpetological societies scattered throughout the state. Catering to mixed groups of amateur, student, and professional members, such nonprofit organizations promote the study and conservation of amphibians and reptiles through regular meetings and newsletters. One of them, the Texas Herpetological Society, established in 1937, sponsors an annual spring field trip within the state at a different site each year, as well as an annual fall meeting of speakers, most of them specialists in their field. For anyone with a serious interest in herpetology, participation in these meetings is indispensable.
The principal Texas herpetological organizations are the Texas Herpetological Society, the East Texas Herpetological Society, the El Paso Herpetological Society, the North Texas Herpetological Society, the South-central Texas Herpetological Society, and the South Texas Herpetological Society. Since most, if not all, of these groups frequently change officers by due process of periodic elections, changes of address are not unusual. To obtain current names and addresses, contact the nearest museum, zoo, nature center, or university biology department.
In addition, the serious student and the professional may wish to belong to one or more of the following North American herpetological organizations, each of which provides regular issues of its scientific journal as a benefit of membership: American Society of Ichthyologists and Herpetologists, publishers of Copeia; Herpetologists League, publishers of Herpetologica; Society for the Study of Amphibians and Reptiles, publishers of Journal of Herpetology and Herpetological Review.
Texas universities offering both graduate and undergraduate courses in herpetology include the University of Texas colleges at Arlington, Austin, El Paso, and Tyler; Texas A&M University colleges at College Station and Kingsville (formerly Texas A&I); Baylor University; Texas Tech University; Southwest Texas State University; Sul Ross State University; Angelo State University; and Midwestern State University. Lower-division (two-year) colleges with herpetologists on staff include El Paso Community College, Hill Junior College, Temple Junior College, and Navarro Junior College.
Biotic Provinces of Texas
By our count, 72 snake species inhabit Texas, more than reside within the borders of any other state in the Union. This is not surprising, since Texas is so large, is located far enough south to enjoy a relatively warm year-round climate, and contains a wide diversity of environments ranging from moist East Texas pine-oak forest, which receives an annual 40 to 55 inches (102—140 cm) of rainfall, to the arid Trans-Pecos region in the west, some parts of which normally get as little as 8 inches (20 cm) of precipitation a year. Elevation, which also affects the distribution of Texas snakes, varies from sea level to as high as 8,749 feet (2,667 m) at Guadalupe Peak, though much of the state is relatively flat or consists of rolling prairies. To help define the distribution of small vertebrate animals (including snakes) within this mosaic of diverse climatic, physiographic, and vegetational conditions, biologists have divided the state into several rather distinct natural regions called biotic provinces.
One of the first to define such regions in Texas was L. R. Dice (1943), who described a biotic province as "a considerable and continuous geographic area... characterized by the occurrence of one or more ecologic associations that differ, at least in proportional area covered, from the associations of adjacent provinces. In general, biotic provinces are characterized by peculiarities of vegetation type, ecological climax, flora, fauna, climate, physiography, and soil." In his review he recognized seven provinces. Not long thereafter, W. F. Blair (1949), using terrestrial vertebrate animals (including snakes) as indicator species, refined Dice's arrangement but did not change the number of provinces. He did, however, change the name of one of Dice's provinces, in part, from the Comanchian to the Kansan.
Much of the following information is based on Blair's study. We have also referred to Richard Phelan's book, Texas Wild. For an interesting and easy-to-read introduction to Texas' wilderness areas, their effect on mankind, and humanity's impact on them, we recommend this publication.
Blair recognized seven biotic provinces in Texas, only six of which were large enough to have been adequately defined by their faunal elements. The seventh, the Navahonian, was later invalidated by Mecham (1979), who demonstrated that the overwhelming majority of reptile and amphibian species in this region inhabiting elevations below 6,000 feet (1,829 m) actually belong in the Chihuahuan biotic province, mixed with some Texan and Balconian forms. Of the small number of reptiles and amphibians identified as belonging in the Navahonian biotic province, only a few occur in the Guadalupes above 6,000 feet (1,829 m). Since at best this province represents a transitional zone in the state, we support Mecham's suggestion that it not be recognized as a legitimate Texas biotic province.
Blair listed the following numbers of snake species in each of the six biotic provinces described in this section (the numbers known from these regions today appear in parentheses): Chihuahuan, 38 (40); Balconian, 36 (40); Tamaulipan, 36 (38); Kansan, 31 (35); Texan, 39 (41); and Austroriparian, 29 (33)
However distinct these provinces, none is inhabited exclusively by a unique set of animals, for many species occur in two or more such regions. Unlike the narrow lines used to separate these regions on a physiographic map, the real boundaries are ordinarily wide and inexact, the product of intermingling ecological conditions between adjacent provinces. Thus, some snakes that are confined largely to one region often cross over into another without having to forsake suitable habitat. Certain other species, such as garter, ribbon, and water snakes, which ordinarily thrive in the wetter provinces, sometimes manage to make their way into an adjacent drier region by following the edges of rivers or streams that flow from one into the other. One biotic province in particular, the Kansan, serves as a broad distributional crossroads for eastern and western species, whose ranges fall chiefly in other provinces. Despite the inexact nature of these somewhat artificially defined natural regions, they serve as useful tools to help us more easily visualize the overall, sometimes complex distributions of Texas snakes.
The Chihuahuan Province
Beginning west of the Pecos River and including all of the Big Bend region of Texas, this is physiographically the most diverse of all Texas biotic provinces. It is essentially an arid region of dry, rocky mountains, separated by hot desert plains and basins, whose soils range from igneous and basaltic to sedimentary. Its mountain ranges—more than 30 in all—reach a maximum elevation of 8,749 feet (2,667 m) on Guadalupe Peak in the Guadalupe Mountains, 8,381 feet (2,554 m) on Mount Livermore in the Davis Mountains, 7,730 feet (2,356 m) on Chinati Peak in the Chinati Mountains, and rise to just over 6,000 feet (1,829 m) in a few of the remaining mountain groups. Some of the highest elevations, whose north-facing slopes receive about twice as much rainfall as the surrounding lowlands, support cool, alpine forests of juniper, Ponderosa pine, and oak, although such tree growth, more sparse than at the top, extends down the slopes of some mountains to approximately 4,500 feet (1,371 m). On the mountain foothills, at and below 3,500 feet (1,064 m), grow mostly desert plants including dense stands of sotol, yucca, lechuguilla, agave, and various cacti, as well as creosote bush, leatherstem, and blackbrush. There are also grasslands in the Trans-Pecos, which occur most conspicuously at elevations between 3,500 and 5,200 feet. According to Powell (1988), the best stands of grass, consisting mainly of blue grama, can be found in the Davis Mountains around the towns of Valentine, Marfa, Alpine, and Fort Davis, where soils are rather deep and fertile.
The Balconian Province
Situated in the south-central part of the state, this is a limestone plateau with elevations ranging between 1,500 feet (457 m) and 3,000 feet (914 m). Its most clearly defined boundary is the Balcones Escarpment, a wide, ragged band of exposed limestone that forms the canyons and breaks along the southern and eastern edge of the Edwards Plateau from Del Rio to Austin. Elements of these limestone extrusions also appear sporadically from Austin to Dallas, with a rather large outcrop within the city of Dallas itself, which lies outside the Balconian province. Throughout the province, the southeastern part of which is often called the Hill Country, the soil is primarily of limestone origin, with some igneous extrusions and sediments. Since it rests on solid rock, the soil is usually only a few inches deep, except where it has accumulated in cracks, depressions, and low-lying areas. Despite its sparse rainfall and resulting aridity, the region has an abundance of underground water, which surfaces as springs and rivers, with tall sycamore and cypress trees typically lining the banks of the latter. Where surface water is absent, the vegetation consists chiefly of short-tree forest—oak, cedar, ash, hickory, cedar elm, hackberry, and mesquite, with an understory of arid-resistant grasses, catclaw, agarita, Texas persimmon, and cactus.
The Tamaulipan Province
An essentially dry, rocky, low-lying region characterized by flat or only slightly rolling terrain, this province covers nearly all of South Texas from the Balcones Escarpment to the southernmost tip of the state. Its northeast boundary lies along an indistinct transition zone where the aridland brush intermingles with the sacahuista grass of the adjoining coastal marshes. Its eastern border is the Gulf of Mexico; its western, the Rio Grande. The region's soils are mostly sedimentary, with some Cretaceous limestone outcroppings along the upper Rio Grande Valley, but in Kenedy, Brooks, and parts of some neighboring counties the substrate is predominantly sand, some of it reaching a depth of 6o feet (18.3 m). Rainfall in the Tamaulipan province is scarce, annually averaging about 25 inches (63.5 cm) in counties remote from the Gulf, though the hurricanes and violent storms that occasionally sweep across South Texas can cause severe flooding in low-lying areas, adversely affecting the local fauna. In response to the region's semiarid climate, the native vegetation consists largely of droughtresistant species armed with needle-sharp spines or thorns, hence the term "thornbrush." The predominant species include catclaw acacia, mesquite, huisache, Texas ebony, white brush, prickly pear, tasajillo, cenizo, wild olive, retama, and granjeno, with grasses growing in the open spaces. The Chihuahuan province also contains a wide variety of spiny plant species, but those in the Tamaulipan province frequently grow close together to form large, tangled masses of impenetrable brush that may stand as much as 20 feet (6.1 m) tall. Such thornbrush reaches its greatest luxuriance on the floodplain of the lower Rio Grande Valley, where, in addition to the typical plant species seen elsewhere in the province, large elms occur in places. The sabal palm, a typically Mexican species, reaches the northernmost end of its range along the Rio Grande in the vicinity of Brownsville.
The Kansan Province
The largest and one of the most varied of all such regions in Texas, this province extends across the entire Panhandle, then continues eastward through the Rolling Plains of north-central Texas to the western edge of the Cross Timbers, its southern boundary more or less following the course of the Colorado River. To a large extent it is a region of transition in which woodland species from the east intermingle with western grassland forms. Responsible for this faunal mixing are the region's rather diverse environmental components of physiography, vegetation, and climate, which have prompted ecologists to divide the province further into three subregions called biotic districts. From west to east, they are as follows:
- Short-grass Plains District. Better known as the High Plains or the Llano Estacado, this western portion of the Texas Panhandle, the driest of the three, is situated at elevations between 3,000 feet (912 m) and 4,000 feet (1,219 m) above sea level. It was formed by the action of rainwater and melting snow that over time systematically washed away sand, gravel, shale, and clay from the slopes of New Mexico's adjacent Rocky Mountains and left the displaced material on the flatter Texas plains. Over these deposits lies several feet of rich soil, blown there by southwest winds, once covered with native grass but now supporting mostly a variety of agricultural crops. Along the eastern edge of this district is the Caprock Escarpment, a natural, uneven boundary between it and the mixed-grass plains district immediately to the east. The leading edge ascends from 200 to 800 feet or more above the base. Its scalloped outline, made jagged by the forces of erosion, is also dissected by the region's major streams, which have cut canyons back into the Caprock. The most notable is Palo Duro Canyon, carved out of the Caprock by a tributary of the Red River. In it grow juniper, mesquite, and cottonwood trees.
- Mixed-grass Plains District. Bounded on the west by the Caprock Escarpment and on the east by the mesquite plains district, this division of the Kansan province is characterized by rolling hills. In many places it is covered with grama grass, beardgrass, and buffalograss, though the floodplains of streams that drain southeast through the district support stands of oak, elm, hackberry, and maple. Those moist woodlands create habitable avenues for the westward dispersal of moisture-dependent reptiles and amphibians from the east.
- Mesquite Plains District. This, the easternmost district in the Kansan province, borders the Texan province on the east and the Balconian on the south. Its most common plant association is mesquite and a few shrubs, which grow in clusters and alternate with open areas of grass, mostly grama and threeawn. In many instances, the same stream systems that occur in the mixed-grass plains district also pass through this one, creating continuous corridors of streamside woodland that facilitate the dispersal of moistureloving reptiles and amphibians into the drier parts of the Kansan province from the east.
The Texan Province
In Texas, this variable region, trending from north to south, extends all the way from the Red River to the Gulf Coast. It is bounded on the west by the Kansan, Balconian, and Tamaulipan provinces and on the east by the moist pine-oak forests of the Austroriparian province. It includes both the East and West Cross Timbers, whose essentially sandy soils support the growth of post oak—blackjack oak—hickory savannahs interspersed among tallgrass prairies. The Grand Prairie, which lies between the two, has thinner, rockier soil, exposed limestone hills, and cedar brakes but also contains significant areas of tallgrass prairie, as do both the Blackland and Coastal prairies. The Texan province additionally includes some of the state's better interior wetlands, with numerous freshwater marshes and peat bogs scattered along a line stretching from Leon County to Gonzales County, where some typically eastern species of reptiles and amphibians occur. A number of moisture-dependent reptiles and amphibians have entered the drier parts of the province from the east by moving along the major river systems, whose wet woodlands of oak, hackberry, elm, and pecan trees provide the necessary moisture and leaf-litter shelter that are necessary to the survival of such species. Their overland entry into or through the province would otherwise be unlikely.
The Austroriparian Province
Because of its sandy soils and high annual rainfall—conditions that promote tree growth—this province contains the largest, most luxuriant woodlands in the state, the pine and pinehardwood forests of East Texas. Its western boundary in Texas runs approximately along a line drawn from the western end of Red River County in the north to Harris County in the south; its eastern boundary in the state is the Louisiana border. The southernmost part of the province is coastal prairie. To describe the region simply as a pine and pinehardwood forest is to understate the spectacular diversity of this most complex mosaic of plant life. While the northern upland part of the province contains fewer kinds of trees per acre (mostly longleaf pine together with some oaks and sweet gum) than the southern, the region to the south, particularly in the Big Thicket, is believed to contain more separate ecosystems than any other area of similar size in North America. Altogether, the bountiful flora of this province comprises hundreds of plant species, some derived from eastern and northern forests and a few whose origins are represented in the barren deserts to the west. Oaks, hickories, and sweet gums, with some ash, sycamore, alder, river birch, black willow maple, water hickory, and swamp tupelo, grow in the bottomlands; bald cypress and swamp tupelo, together with some water hickory and water elm, constitute the region's cypress sloughs; dwarf palmettos growing among hardwood trees in wet flatlands characterize the palmetto swamps; American beech and southern magnolia, along with a few white oak and loblolly pine, grow on the drier slopes and ridges, as do some prickly pear cactus and yucca; and there are even more plant associations that form additional biotic subdivisions.
Neither the Chihuahuan nor the Balconian biotic province contains a characteristic group of snakes within its borders, but together they share the following 12 species: Baird's rat snake, Trans-Pecos rat snake, Trans-Pecos blind snake, Central Texas whipsnake, gray-banded king snake, Big Bend patch-nosed snake, Trans-Pecos blackheaded snake, Texas lyre snake, northern black-tailed rattlesnake, Mojave rattlesnake, banded and mottled rock rattlesnake, and western and eastern black-necked garter snake. The Tamaulipan biotic province, where part of the serpent fauna is of tropical origin, includes a number of snakes that in Texas are found only in this region: indigo snake, speckled racer, black-striped snake, Mexican hook-nosed snake, northern cateyed snake, Schott's whipsnake, and Mexican black-headed snake. Although the Kansan biotic province contains a large complement of snakes (35 species), only the western plains garter snake is confined to this province in Texas. The Texan biotic province contains an even greater number of serpent species (41), of which only the midland water snake is restricted to it in Texas. The Austroriparian biotic province contains only three characteristic serpents—Louisiana pine, Florida red-bellied, and Gulf crayfish snakes. When combined with those of the Texan province, the following six serpents can be added— western mud snake, canebrake rattlesnake, western pygmy rattlesnake, Mississippi green water snake, broad-banded water snake, and western earth snake.
We would be remiss if we did not discuss aquatic habitats in Texas, for no less than 24 Texas snake species and subspecies (22 percent) are aquatic or semiaquatic. Texas contains nine major river basins: the Rio Grande, Nueces, San Antonio — Guadalupe, Colorado, Brazos, Trinity, Neches-Sabine, Canadian, and Red River systems. The Canadian and Red rivers drain most of North Texas; the Trinity and Neches-Sabine basins drain East Texas; the Brazos basin drains central and northwestern Texas; the San Antonio, Guadalupe, and Nueces basins drain southern Texas; and the Colorado and Rio Grande basins drain parts of central and western Texas.
Only two native aquatic serpents, the Brazos and Concho water snakes, are narrowly restricted to limited sections of particular river systems, whereas each of the others is distributed between and among two or more river systems. All of the garter snakes are semiaquatic, and although several of them are found in very dry habitats, they seldom stray far from moisture. The checkered garter snake, which seems able to tolerate arid conditions for relatively long periods, is the single exception. On the other hand, the Gulf salt marsh snake, which is restricted to the Gulf coastal marshes, is the only native serpent wholly adapted to a saltwater existence, although even the cottonmouth demonstrates a degree of tolerance for brackish and saltwater Gulf Coast marshes. Most of the aquatic snakes are habitat generalists, in that they occur in aquatic conditions but these conditions can occur from eastern to southern Texas and from the Sabine system to the Pecos River and Rio Grande.
Snake Classification and Identification
Taxonomy is the science of classifying and naming animals and plants—the foundation for the development of biological knowledge. The history of classifying animals is perhaps nearly as old as man himself. Even natives of various primitive tribes were good naturalists, with specific names for local trees, flowers, mammals, birds, fishes, and other species. Their health—sometimes even their lives—depended on their ability to distinguish between harmless and venomous (or toxic) plants and animals. To survive in nature, they frequently learned the subtle differences between such things as edible mushrooms and deadly toadstools, milk snakes and coral snakes, and a host of other "good-bad" species that they encountered in the wild.
Perhaps the first modern taxonomist was Aristotle (384-322 BC), who brought together the knowledge of his time and formulated it into the beginnings of a science of classification. He categorized animals by larger groupings and even classified them according to their actions, habits, and where they lived. But the real father of taxonomy is considered to be Carolus Linnaeus, a Swedish naturalist who in the mid-1700s consistently used the binomial system of nomenclature in his pioneer work; that is, he assigned both a generic and specific name to each animal. In those days, taxonomy was a relatively simple science that required only a careful examination of the organism's body parts and a comparison of such features with those of other closely related animals. Since then, however, the science of taxonomy has changed dramatically. Today, instead of relying only on morphological characters to compare species, the taxonomist uses a variety of other, more sophisticated, tools to accomplish the task. Among them are biochemistry, histology, cytology, genetics, and, in the case of venomous snakes, analysis of their venoms by electrophoresis and chromatography.
Beginning at the highest level of animal classification, snakes are grouped with the vertebrates, since they have a backbone consisting of individual segments, or vertebrae. Together with the crocodilians, turtles, lizards, and tuataras (all of which are cold-blooded and share the characteristic of dry, scaly skin), they are included in the class Reptilia. Defining their taxonomic status even more narrowly, snakes are sorted with lizards in the order Squamata, then placed in their own suborder, Serpentes. This suborder is generally considered to be divisible into 13, 14, or 15 living families (depending on which authority one follows), 4 of which occur in Texas. In the main body of this book, the species and subspecies accounts are grouped by family, and each of the four groups is preceded by a brief definition of the relevant family.
The most prominent feature of this glossy, smooth-scaled little snake is the sharp, horizontal line of demarcation on the third row of dorsal scales, where the uniformly dark gray or purplish black body hue meets the contrasting salmon-pink belly color. Just days before the snake sheds its skin and until the epidermis is discarded, the dark dorsal tone fades to ashen gray, masking its true color. The serpent's bluntly pointed head is no wider than its neck, its eyes are small, and its short tail ends in a sharp little spine. There are but 13 midbody rows of dorsal scales, and the anal plate is divided.
When first hatched, the mud snake is nearly the same length as an adult worm snake, but with a much thicker body. Although both species are shiny and blackish on the back and sides, the red color of the mud snake's belly extends up along the lower sides of the body as vertical bars instead of terminating in a sharp, horizontal line of demarcation. The ring-necked snake, whose slate gray to blackish dorsum is similar to that of a worm snake, has a narrow, pale-colored ring on the neck and black spotting on its yellowish belly. The Florida red-bellied snake may have a pale orange abdomen, but its color does not extend upward to the third row of body scales. Moreover, it has 15 rows of keeled dorsal scales at midbody and a conspicuous pale spot covering all of the fifth upper lip scale.
Although the known record length for this snake is 14 3/4 inches (39.5 cm), most adults are between 7 1/2 and 11 inches (19-27.9 cm) long.
In northeastern Kansas, according to D. R. Clark (1970), the snake's distribution is closely tied to stream valleys adjacent to forested or grassy hillsides where elevations generally rise above 100 feet (30.5 m). Such areas, while damp, contain well-drained, organically rich soils littered with rocks or logs, under which the snake can take cover, and are shaded either by trees or dense ground cover, leafy umbrellas that help to conserve soil moisture. Black, clay-loam soils containing from 10 to 30 percent water, by weight, are preferred, whereas neighboring patches of more cohesive, light-brown clay substrate are avoided. Some open habitats near Lawrence, Kansas, characterized by sparse ground cover as the result of moderate cattle grazing, actually attracted greater numbers of worm snakes than did other, more natural, nearby habitats.
An altogether harmless reptile, the worm snake neither strikes nor bites when handled. Like many other snake species, it does employ a defensive strategy that may repel small predators, although the same tactic probably has limited success against larger adversaries. Combining musk from its scent glands with waste from its cloacal opening, it smears the smelly material over its captor as it struggles to free itself. Meanwhile, it may firmly press its sharp tail tip into one part of a person's hand while its head is busily probing in another. To the captor, such persistent poking can be alarming, for when the snake's terminal tail spur is unexpectedly forced against the skin, the sensation is like the jab of a dull needle. This strange feeling, while not painful, may nevertheless be startling enough to cause the handler to pull back suddenly and drop the snake to the ground. Since the serpent's tail-tip maneuver ordinarily is not directed at the part of the hand grasping the snake, the tail thrusts are perhaps intended to find an escape route or to assist the snake's forward motion. Almost nothing is recorded about the western worm snake's natural history in Texas, for the serpent is rare in the state, having been reported so far in only two northeastern counties, Bowie and Red River. Consequently, most of the data presented below are from field studies conducted by D. R. Clark in northeastern Kansas, where the snake occurs so commonly that it is often found there at the rate of 150 to 300 individuals per acre. The study, from which we have drawn freely, remains the primary source of information about the snake's natural behavior.
The worm snake's small narrow head, smooth glossy scales, and short pointed tail all suggest a fossorial existence, yet this reptile has no outstanding physical or behavioral attributes that would allow it to bore easily into packed soil, although it can readily penetrate loose substrate. When approached, a worm snake usually tries to escape by quickly crawling under a rock or some other form of surface debris. In the absence of such cover, it places its snout against the loose soil, if there is any, seeking some small opening into which it can poke its snout. By rotating its head from side to side, up and down, in a rolling motion, or in a combination of such movements, it makes a hole large enough for its body to enter, then soon disappears below the surface.
Above ground it can be found wandering about either by day or at night, so long as the air temperature is between 58 and 78 degrees F and the ground is warm and damp. This small serpent normally travels over surprisingly short distances. One marked specimen was recaptured nearly two and a half years later just 12 feet from the same spot where it was initially liberated. There are also records of unusually long treks. One, involving an adult female worm snake that wandered 410 feet in only 19 days, represents a record travel distance for this species. In northeastern Kansas the male occupies a home range estimated to be approximately one-sixth of an acre maximum, minuscule compared to the large home territories inhabited by the males of other species living in the same region: copperhead, 24.4 acres; racer, 26.3; rat snake, 29; and garter snake, 35. (Females occupy smaller home ranges.)
The snake's annual activity cycle is infiuenced largely by temperature and precipitation. Thus, when rising spring temperatures and increased rainfall accelerate the decomposition of leaf litter deposited the previous fall, earthworms rise to the surface and are soon followed by the worm snakes that feed on them. Later in the year (notably in August), as temperatures rise and the surface mulch dries, the earthworms move deeper into the ground, and the worm snakes follow them. This is illustrated by Clark's comment that 94 percent of all C. vermis he discovered during the year in an Osage County, Kansas, field survey were encountered in March, April, and May. Before the end of October, the serpent's wanderings are over and it prepares for winter. In most cases the worm snake hibernates in minute burrows whose entryways are located under rocks, although it also seeks winter refuge in ant mounds, rock crevices, rotting logs,, and tree stumps, or even under loose tree bark. Johnson (1987) mentioned hibernacula in which the snakes crawled into deep accumulations of leaf litter that filled the basins of dark, steep-sided ravines, and he noted that other worm snakes found winter shelter in a cave.
Though it sometimes consumes other small invertebrate prey, earthworms constitute the primary diet of this leaf-litter inhabitant of the forest floor. The ringnecked snake, another small serpent living in the same damp woodlands, hides under the same logs, rocks, and pieces of loose bark with its smaller neighbor and even competes with it for the same annelid prey.
Two mating periods occur in this species, one in April and May and another in September and October. The fall copulation results in the storage of viable sperm in the female's body until the following spring, when the eggs are fertilized and embryonic development begins. Sometime between mid-June and early July the female lays 1 to 8 (normally 2 or 3) oval eggs, 1 to 1 1/2 inches (2.5-3.8 cm) long, beneath rocks or in tiny underground burrows. They incubate over the next seven weeks, hatching during the period of mid-August to early September. The baby snakes, which measure 3 1/2 to 4 inches (8.9-10.2 cm) long, look much like the adults but show more contrast between the dark dorsal hue and the reddish pink undercolor.