Rattlesnakes are a group of venomous snakes of the
generaGenera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...
CrotalusCrotalus is a genus of venomous pit vipers found only in the Americas from southern Canada to northern Argentina. The name is derived from the Greek word krotalon, which means "rattle" or "castanet", and refers to the rattle on the end of the tail which makes this group so distinctive...
and
SistrurusSistrurus is a genus of venomous pit vipers found in Canada, the United States and Mexico. The name is a Latinized form of the Greek word for "tail rattler" and shares its root with the ancient Egyptian musical instrument, the sistrum, a type of rattle...
of the subfamily
CrotalinaeThe Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...
("pit vipers"). There are 32 known
species of rattlesnake, with between 65-70 subspecies, all native to the
AmericasThe Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, ranging from southern
AlbertaAlberta is a province of Canada. It had an estimated population of 3.7 million in 2010 making it the most populous of Canada's three prairie provinces...
and southern
British ColumbiaBritish Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
in
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
to Central
ArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
Rattlesnakes are predators who live in a wide array of habitats, hunting small animals such as birds and rodents. They kill their prey with a venomous bite, rather than by
constrictingConstriction is a method used by various snake species to kill their prey. Although some species of venomous and mildly-venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. The snake initially strikes at its prey and holds on, pulling the prey...
. All rattlesnakes possess a set of fangs with which they inject large quantities of hemotoxic venom. The venom travels through the bloodstream, destroying
tissueTissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
and causing swelling, internal bleeding, and intense pain. Some species, such as the Mojave Rattlesnake, additionally possess a neurotoxic component in their venom that causes
paralysisParalysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
and other
nervousThe nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
symptoms.
The threat of envenomation, advertised with the shaking of the rattle, deters many predators. However, rattlesnakes fall prey to hawks, weasels, king snakes, and a variety of other species. Rattlesnakes are heavily preyed upon as neonates, while they are still weak and mentally immature. Very large numbers of rattlesnakes are killed by humans. Rattlesnake populations in many areas are severely
threatenedThreatened species are any speciesg animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future.The World Conservation Union is the foremost authority on threatened species, and treats threatened species not as a single category, but as a group of three categories,...
by
habitat destructionHabitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
,
poachingPoaching is the illegal taking of wild plants or animals contrary to local and international conservation and wildlife management laws. Violations of hunting laws and regulations are normally punishable by law and, collectively, such violations are known as poaching.It may be illegal and in...
, and extermination campaigns.
Rattlesnake bites are the leading cause of snakebite injuries in North America, and cause approximately 82% of fatalities. However, rattlesnakes rarely bite unless provoked or threatened; and if treated promptly, the bites are rarely fatal.
Names
Rattlesnakes receive their name from the rattle located at the end of their tails which, when shaken,it makes a loud rattling noise that deters predators or serves as a warning to passersby. The scientific name
Crotalus derives from the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
,
κρόταλον, meaning "
castanetCastanets are a percussion instrument , used in Moorish, Ottoman, ancient Roman, Italian, Spanish, Sephardic Music, and Portuguese music. The instrument consists of a pair of concave shells joined on one edge by a string. They are held in the hand and used to produce clicks for rhythmic accents or...
". The name
Sistrurus is the Latinized form of the
GreekGreek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
word for "tail rattler" (
Σείστρουρος, Seistrouros) and shares its root with the ancient
EgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
ian musical instrument, the
sistrumA sistrum is a musical instrument of the percussion family, chiefly associated with ancient Iraq and Egypt. It consists of a handle and a U-shaped metal frame, made of brass or bronze and between 76 and 30 cm in width...
, a type of rattle.
Range and habitat
Rattlesnakes are native to the
AmericasThe Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
, living in diverse habitats from Southwestern
CanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
to Central
ArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. The large majority of species live in the
American SouthwestThe Southwestern United States is a region defined in different ways by different sources. Broad definitions include nearly a quarter of the United States, including Arizona, California, Colorado, Nevada, New Mexico, Oklahoma, Texas and Utah...
and
MexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Four species may be found east of the
Mississippi riverThe Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
, and two in
South AmericaSouth America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. In the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, the state with the most forms of rattlesnakes is
ArizonaArizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
, with seventeen species and subspecies.
Rattlesnakes are found in almost every type of habitat that is capable of supporting terrestrial ectothermic vertebrates; but individual species can have extremely specific habitat requirements, only able to live within certain plant associations in a narrow range of altitudes. Most species live near open, rocky areas. Rocks offer them cover from predators, plentiful prey (e.g. rodents, lizard, insects, etc. that live amidst the rocks), and open basking areas. However, rattlesnakes can also be found in a wide variety of other habitats including prairies, marshes,
desertsDéserts is a piece by Edgard Varèse for brass , percussion , piano, and tape. Percussion instruments are exploited for their resonant potential, rather than used solely as accompaniment...
, and forests. Rattlesnakes prefer a temperature range between 80 and 90°F (26-32°C), but can survive temperatures below
freezingFreezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....
, recovering from brief exposure to temperatures as low as 4°F, and surviving for several days in temperatures as low as 37°F.
Evidence has been collected to show the most probable ancestral area of rattlesnakes is the
Sierra Madre OccidentalThe Sierra Madre Occidental is a mountain range in western Mexico.-Setting:The range runs north to south, from just south of the Sonora–Arizona border southeast through eastern Sonora, western Chihuahua, Sinaloa, Durango, Zacatecas, Nayarit, Jalisco, Aguascalientes to Guanajuato, where it joins...
region in Mexico. This same study found the most probable vegetation or habitat of the ancestral area to be pine-oak forests.
Prey
Rattlesnakes consume mice, rats, small birds and other small animals, playing an important ecological role by limiting the size of rodent populations, which prevents crop damage and stabilizes ecosystems.
Rattlesnakes lie in wait for their prey, or hunt for it in holes. The prey are killed quickly with a
venomVenom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous bite as opposed to
constrictingConstriction is a method used by various snake species to kill their prey. Although some species of venomous and mildly-venomous snakes do use constriction to subdue their prey, most snakes which use constriction lack venom. The snake initially strikes at its prey and holds on, pulling the prey...
. If the bitten prey moves away before dying, the rattlesnake can follow it by its scent. When it locates the fallen prey, it checks for signs of life by prodding with its snout, flicking its tongue, and using its sense of smell. Once the prey has become incapacitated, the rattlesnake locates its head by odors emitted from the mouth. The prey is then ingested head-first, which allows wings and limbs to fold at the joints in a manner which minimizes the girth of the meal. The gastric fluids of rattlesnakes are extremely powerful, allowing for the digestion of bone as well as flesh. Optimal digestion occurs when the snake maintains a body temperature of between 80 and 85°F (25-29°C). If the prey is small, the rattlesnake will often continue hunting. If it was an adequate meal, the snake will find a warm, safe location in which to coil up and rest until the prey is digested.
Rattlesnakes are believed to require at least their own body weight in water annually in order to remain hydrated. The method in which they drink depends on the water source. In larger bodies of water (streams, ponds, etc.) they will submerge their head and ingest water by opening and closing their jaw, which sucks in water. If drinking dew, or drinking from small puddles, they will sip the liquid either by capillary action or by flattening and flooding the lower jaw.
Predators
Newborn rattlesnakes are heavily preyed upon by a variety of species including ravens, crows, roadrunners, raccoons, opossums, skunks, coyotes and weasels, whipsnakes, kingsnakes, and
racersRacers may refer to:* Lego Racers, a product range of the Lego construction toy* Akron Racers, a women's softball team* Elgin Racers, a franchise of the International Basketball League* Harringay Racers, a British ice hockey club...
. Neonates of the smaller Crotaline species are frequently killed and eaten by small predatory birds such as jays, kingfishers, and shrikes. Some species of ants in the genus
FormicaFormica is a genus of ants of the family Formicidae, commonly known as wood ants, mound ants, or field ants. Formica is the type genus of the Formicidae, and of the subfamily Formicinae...
are known to prey upon neonates, and it is very likely that
Solenopsis invicta (fire ants) do as well. On occasion, hungry adult rattlesnakes will cannibalize neonates. The small proportion (often as few as 20%) of rattlesnakes that make it to their second year are heavily preyed upon by a variety of larger predators including coyotes,
eaglesThe Eagles are an American rock band formed in Los Angeles, California in 1971 by Glenn Frey, Don Henley, Bernie Leadon, and Randy Meisner.With five number one singles, six Grammys, five American Music Awards, and six number one albums, the Eagles were one of the most successful musical acts of the...
, hawks,
owlsOWLS is a mnemonic used by general aviation airplane pilots to assess an unprepared surface for a precautionary landing.Like all mnemonics this check has become part of aviation culture and folklore.OWLS:* Obstacles* Wind direction...
, feral pigs, badgers, indigo snakes, and kingsnakes.
The common
kingsnakeKingsnakes are a type of colubrid snake that are members of the Lampropeltis genus, which also includes the milk snake along with another four species and 45 sub-species....
(
Lampropeltis getulaLampropeltis getula is a harmless colubrid species found in the United States and Mexico. A distinct color pattern and the common belief that this species actively hunts for venomous snakes helps to protect them from people. It has long been a favorite among collectors...
), a
constrictorConstrictor may refer to:Biology:* Any snake that kills its prey by constriction* A boa constrictor, a large non-venomous boas found primarily in Central and South America.* A taxonomic synonym for Python, a.k.a...
, is immune to the venom of rattlesnakes and other
viperThe Viperidae are a family of venomous snakes found all over the world, except in Antarctica, Australia, Ireland, Madagascar, Hawaii, various other isolated islands, and above the Arctic Circle. All have relatively long, hinged fangs that permit deep penetration and injection of venom. Four...
s, and rattlesnakes form part of its natural diet. Rattlesnakes sense kingsnakes' presence by their odor. When they realize a kingsnake is nearby, they begin enacting a set of defensive postures known as "body bridging". Unlike its normal erect and coiled defensive-striking posture, the rattlesnake keeps its head low to the ground in an attempt to prevent the kingsnake from gaining a hold of it (the head being the first part of the rattlesnake that is ingested). The rattlesnake jerks its body about, while bridging its back upwards, forming an elevated coil which faces the kingsnake. The elevated coil is used to strike the attacker, and is also used to shield the head from the kingsnake.
Sensory organs
Like all pit vipers, rattlesnakes have two organs that can sense
radiationIn physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
: their eyes, and a set of heat-sensing "pits" on their face that enable them to locate prey and strike towards it, based on the prey's
thermal radiationThermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....
signature. These pits have a relatively short effective range of approximately 1 ft, but nevertheless give the rattlesnake a distinctive advantage in hunting for warm-blooded creatures at night.
Rattlesnake eyes, which contain a large number of rod cells, are well adapted to nocturnal use. However rattlesnakes are not exclusively nocturnal, and their
visionThe visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...
is more acute during daylight conditions. Rattlesnakes also possess cone cells, which means that they are capable of some form of color vision. The rattlesnake eye lacks a
foveaThe fovea centralis, also generally known as the fovea , is a part of the eye, located in the center of the macula region of the retina....
making it impossible for them to see sharply defined images. Instead, they mostly rely on the perception of movement. Rattlesnake eyes are capable of horizontal rotation, but they do not appear to move their eyeballs to follow moving objects.
Rattlesnakes have an exceptionally keen sense of
smellSmell may refer to:* Olfaction, sense of smell, the ability of humans and other animals to perceive odors* Odor, the percept resultant from the sense of smell...
. They can sense olfactory stimuli both through their nostrils, and by flicking their
tongueThe tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
, which carries scent-bearing particles to the Jacobson's organ in the roof of their mouth.
Like all snakes, rattlesnakes do not have external
earThe ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....
openings, and the structures of their
middle earThe middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
is not as highly specialized as those of other vertebrates, such as mammals. Thus their sense of
soundSound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing and of a level sufficiently strong to be heard, or the sensation stimulated in organs of hearing by such vibrations.-Propagation of...
is not very effective. However, they are capable of sensing vibrations in the ground, passed via the skeleton to the auditory nerve.
Fangs
Rattlesnake fangs are connected by venom ducts to large poison glands near the outer edge of the upper jaw, towards the rear of the head. When the rattlesnake bites, muscles on the sides of the venom glands contract, which squeezes the venom through the ducts and into the fangs. When the fangs are not in use, they remain folded against the palate.
Rattlesnakes are born with fully functioning fangs and venom, and are capable of killing prey at birth. Adult rattlesnakes shed their fangs every 6–10 weeks. At least 3 pairs of replacement fangs lie behind the functional pair.
Venom
Most species of rattlesnakes have
hemotoxicHemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells , disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term hemotoxin is to some degree a misnomer since toxins that damage the blood also damage other tissues...
venom, destroying tissue, causing
necrosisNecrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
and
coagulopathyCoagulopathy is a condition in which the blood’s ability to clot is impaired. This condition can cause prolonged or excessive bleeding, which may occur spontaneously or following an injury or medical and dental procedures.The normal clotting process depends on the interplay of various proteins in...
(disrupted blood clotting). In the U.S., some varieties of the Mojave rattlesnake (
C. scutulatus) have a presynaptic neurotoxic venom component known as Mojave Type A toxin, which can cause severe
paralysisParalysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
.
C. scutulatus is widely regarded as producing one of the most toxic snake venoms in the Americas, based on studies in laboratory mice.
Rattlesnake venom is a mixture of 5-15 enyzmes, various metal ions, biogenic amines, lipids, free amino acids, proteins, and polypeptides. It contains components designed to immobilize and disable the prey, as well as digestive enzymes which break down tissue to prepare for later ingestion. The venom is very stable, and retains its toxicity for many years in storage.
Older snakes possess more potent venom, and larger snakes are frequently capable of storing larger volumes of it.
Rattle
According to Rubio, "The most widely accepted hypothesis for the evolution of the rattle is that the rattle is a warning device for predatory animals that might be a threat to the rattlesnake. It produces a signal to drive them away."
The rattle is composed of a series of hollow, interlocked segments made of
keratinKeratin refers to a family of fibrous structural proteins. Keratin is the key of structural material making up the outer layer of human skin. It is also the key structural component of hair and nails...
, which are created by modifying the scales that cover the tip of the tail. The contraction of special "shaker" muscles in the tail causes these segments to vibrate against one another, making the rattling noise (which is amplified because the segments are hollow). The muscles that cause the rattle to shake are some of the fastest known, firing 50 times per second on average, sustained for up to three hours.
Each time the snake sheds its skin, a new rattle segment is added. They may shed their skins several times a year depending on food supply and growth rates. Rattlesnakes travel with their rattles held up to protect them from damage, but in spite of this precaution, their day-to-day activities in the wild still cause them to regularly break off end segments. Because of this, there is no way to determine the age of a rattlesnake based on the number of rattles on its tail.
One of the differentiating features of males and females is that males have a thicker and longer tail. The tails of males also taper gradually from the body, whereas female tails narrow sharply at the vent.
Skin and circulation
Rattlesnake skin is composed of a set of overlapping scales which cover the entire body, providing protection from a variety of threats including
dehydrationIn physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...
and physical trauma. The skin of snakes is highly sensitive to contact, tension, and pressure; and they are capable of feeling
painPain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
.
An important function of the skin is the sensation of changes in air temperature, which can guide the snakes towards warm basking/shelter locations. All snakes are ectotherms. In order to maintain a stable body temperature, they exchange heat with their external environment. Snakes often move into open, sunny areas to absorb heat from the sun and warmed earth - a behavior known as basking. Nerves in the skin regulate the flow of blood into the veins near the surface. Rubio states that "The skin's acceptance of radiant energy, its ability to determine the temperature, and the snake's ability to move toward or away from one
temperature gradientA temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. The temperature gradient is a dimensional quantity expressed in units of degrees per unit length...
to another are among the most important behavioral actions in its daily life."
The skin of rattlesnakes is intricately patterned in a manner that camouflages them from their predators. Rattlesnakes do not generally have bright or showy colors (reds, yellows, blues etc.), instead relying on subtle earth tones that resemble the surrounding environment.
There are creases in the epidermal tissue which connects the scales of rattlesnakes. When ingesting large prey, these creases can unfold, allowing the skin to expand to envelop a much greater volume. It appears that the skin is tightly stretching to accommodate the meal, but in reality, the skin is simply smoothing out from its creased state and is not under very high tension.
Reproduction
Most rattlesnake species mate during the summer or fall, while some species mate only in the spring, or during both the spring and fall.
Females secrete small amounts of sex pheromones, which leave a trail that males follow by using their tongue and Jacobson's organ as a guide. Once a receptive female has been located, the male will often spend several days following her around (a behavior that is not common outside of the mating season), frequently touching and rubbing her in an attempt to stimulate her.
The males of some species, such as timber rattlesnakes (
C. horridus), will fight each other during the mating season, in competition over females. These fights known as "combat dances" consist of the two males intertwining the anterior portion of their bodies, often with the head and neck held vertically. The larger males usually end up driving the smaller males away.
Although many kinds of snakes and other reptiles are oviparous (lay eggs), rattlesnakes are viviparous (give birth to live young). The female produces the ova ("eggs") in her ovaries, after which they pass through the body cavity and into one of her two oviducts. The ova are arranged in a continuous chain in a coiled section of the oviduct, known as the "tuba". Male rattlesnakes have sexual organs known as hemipenes, located in the base of the tail. The hemipenis is retracted inside of the body when mating is not occurring. Unlike a
penisThe penis is a biological feature of male animals including both vertebrates and invertebrates...
, where
semenSemen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...
travels through an internal seminal duct, the semen in a hemipenis travels via a groove into the female's oviduct. Females can store semen for months in internal recesses known as spermathecae, which permits them to mate during the fall, but not fertilize the ova until the following spring.
Rattlesnakes generally take several years to mature, and females usually reproduce only once every three years.
Hibernation
Some rattlesnake species hibernate in the colder winter months. They often gather together for hibernation in very large numbers (sometimes over 1,000 snakes), huddling together inside of underground "rattlesnake dens" or
hibernacula. Rattlesnakes will regularly share their winter
burrowsBurrows is a provincial electoral division in the Canadian province of Manitoba. It was created by redistribution in 1957, and formally came into existence in the provincial election of 1958. The riding is located in the northern part of Winnipeg....
with a wide variety of other species (such as turtles, small mammals, invertebrates, and other types of snakes).
Rattlesnakes often return to the same den, year after year, sometimes traveling several miles to get there. It is not known exactly how the rattlesnakes find their way back to the dens each year, but it has been hypothesized that they use a combination of
pheromoneA pheromone is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting outside the body of the secreting individual to impact the behavior of the receiving individual...
trails and visual cues (e.g.
topographyTopography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...
,
celestial navigationCelestial navigation, also known as astronavigation, is a position fixing technique that has evolved over several thousand years to help sailors cross oceans without having to rely on estimated calculations, or dead reckoning, to know their position...
, and
solarThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
orientation).
Species with long periods of hibernation tend to have much lower reproductive rates than those with shorter hibernation periods, or those that don't hibernate at all. Female timber rattlesnakes in high peaks in the
Appalachian MountainsThe Appalachian Mountains #Whether the stressed vowel is or ,#Whether the "ch" is pronounced as a fricative or an affricate , and#Whether the final vowel is the monophthong or the diphthong .), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians...
of
New EnglandNew England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
reproduce every three years on average; the lance-headed rattlesnake (
C. polystictusCrotalus polystictus is a venomous pitviper species found in central Mexico. No subspecies are currently recognized.-Description:Adults usually grow to 60-70 cm, although exceptionally large specimens may be as much as 100 cm in length....
), native to the warm climate of Mexico, reproduces annually.
Like most other snakes, rattlesnakes aestivate during very hot or dry periods, which is why they are very rarely seen during the hottest and driest months of summer.
Conservation status
Rattlesnakes tend to avoid developed areas, preferring undisturbed, natural habitats. Rapid habitat destruction by humans, mass killings during events like rattlesnake round-ups, and deliberate extermination campaigns all pose severe threats to rattlesnake populations in many areas. Several species of rattlesnakes, such as the timber rattler, massasauga, and canebrake rattlesnake are listed as threatened or endangered in many U.S. states.
A very large number of rattlesnakes die from being run over by cars.
In more heavily populated and trafficked areas, there have been increasing reports of rattlesnakes that do not rattle. This phenomenon is commonly attributed to selective pressure by humans, who often kill the snakes when they are discovered. Non-rattling snakes are more likely to go unnoticed, and therefore survive to reproduce offspring who, like themselves, are less likely to rattle.
Safety and first aid
Rattlesnakes are the leading cause of snakebite injuries in North America, and are a significant cause in Central and South America.
Avoiding bites
Rattlesnakes tend to avoid wide open spaces where they cannot hide from predators, and will generally avoid humans if they are aware of their approach. Rattlesnakes rarely bite unless they feel threatened or provoked. A large majority of victims (~ 72%) are males, often young and intoxicated. Approximately half of bites occur in cases where the victim saw the snake, yet made no effort to move away.
Hikers and campers should avoid contact with rattlesnakes by remaining observant and not approaching the animals. Hikers are advised to be particularly careful when negotiating fallen logs or boulders and when near rocky outcroppings and ledges where rattlesnakes may be hiding or sunning themselves - however, snakes will occasionally sun themselves in the middle of a trail, so such areas are not the only places where they are encountered. When encountering a rattlesnake on a trail, hikers are advised to keep their distance and allow the snake room to retreat.
Caution is advised even when snakes are believed to be dead; rattlesnake heads can see, flick the tongue, and inflict venomous bites for up to an hour after being severed from the body.
Effect of bites on humans
Rattlesnake bites are rarely fatal to humans, if treated promptly. Between 7,000 and 8,000 people are estimated to have been bitten by venomous snakes in the United States each year, and about five of those die. The most important factor in determining survival following a severe envenomation is the amount of time elapsed between the bite and treatment. Most deaths occur between 6 and 48 hours after the bite. However, if antivenom treatment is given within 1–2 hours of the bite, the probability of recovery is greater than 99%.
When a bite occurs, the amount of venom injected is under voluntary control by the snake. The amount released is dependent on a variety of factors including the condition of the snake (e.g. having long, healthy fangs and a full venom sack) and its temperament (an angry, hungry snake that has just been stepped on vs. a satiated snake that was merely surprised by walking near it). Approximately 20% of bites result in no envenomation at all. A lack of burning pain and
edemaEdema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
1 cm away from the fang marks after 1 hour, suggests that either no or minimal envenomation occurred. A lack of edema or
erythemaErythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
in the area of the bite after 6–8 hours indicates a lack of envenomation for most rattlesnake bites.
Common symptoms include swelling, severe pain, weakness, anxiety,
nauseaNausea , is a sensation of unease and discomfort in the upper stomach with an involuntary urge to vomit. It often, but not always, precedes vomiting...
and
vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
, hemorrhaging, perspiration, and eventually
heart failureCardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
. Local pain following envenomation is often intense, increasing with the ensuing edema. In general, children experience more severe symptoms because they receive a larger amount of venom per kilogram of body mass.
Emergency response
Data on the effectiveness of first aid techniques for rattlesnake bites is limited. However, general recommendations for first aid in the field are as follows:
- Remain calm, and retreat from the snake at least 10–15 feet. Arrange to have the victim transported to a medical facility as soon as possible.
- Remove restrictive clothing items (rings, bracelets, watches, buttoned shirts, etc.) from the victim.
- Splint or otherwise immobilize any bitten limbs, and keep them below heart level. If (and only if) the victim is more than 1–2 hours away from a medical facility, it is recommended to place a lightly constricting band (that admits one finger beneath it) above the bitten area to prevent the systemic spread of the venom.
- Keep victims calm; put them at rest; keep them warm and give them comfort and reassurance (which will lower their heart rate, slowing the spread of the venom). However, keeping a victim's heart rate
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per minute . Heart rate can vary as the body's need to absorb oxygen and excrete carbon dioxide changes, such as during exercise or sleep....
down should never interfere with getting him or her to a medical facility.
In no case should tourniquets be used, nor should any incisions or suction be applied to the wound.
Antivenom
Crotaline antivenom (or "antivenin") is commonly used to treat the effects of local and systemic pit viper envenomations. The first step in the production of crotaline antivenom is collecting ("milking") the venom of a live rattlesnake - usually from the Western Diamondback (
Crotalus atroxCrotalus atrox, the "western diamondback rattlesnake", is a venomous rattlesnake species found in the United States and Mexico. It is likely responsible for the majority of snakebite fatalities in northern Mexico and the second greatest number in the USA after C. adamanteus. No subspecies are...
), Eastern Diamondback (
Crotalus adamanteusCrotalus adamanteus is a venomous pit viper species found in the southeastern United States. It is the heaviest venomous snake in the Americas and the largest rattlesnake. It featured prominently in the American Revolution, specifically as the symbol of what many consider to be the first flag of...
), South American rattlesnake (
Crotalus durissis terrificus), or fer-de-lance (
Bothrops atroxBothrops atrox is a venomous pitviper species found in the tropical lowlands of northern South America east of the Andes. No subspecies are currently recognized.-Description:...
). The extracted venom is then diluted and injected into horses, goats, or sheep, whose immune systems produce antibodies that protect from the toxic effects of the venom. These antibodies accumulate in the blood, which is then extracted and centrifuged to separate the red blood cells. The resulting serum is purified into a lyophilized powder, which is packaged for distribution and later use by human patients.
Because antivenom is derived from animal antibodies, people generally display an allergic response during infusion, known as
serum sicknessSerum sickness in humans is a reaction to proteins in antiserum derived from an non-human animal source. It is a type of hypersensitivity, specifically immune complex hypersensitivity . The term serum sickness–like reaction is occasionally used to refer to similar illnesses that arise from the...
.
Veterinary care
In the United States, more than 15,000 domesticated animals are bitten by snakes each year. Rattlesnake envenomations account for 80% of the deadly incidents.
Dogs are most commonly bitten on the front legs and head. Horses generally receive bites on the muzzle, and
cattleCattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
on their tongues and muzzles. If a
domesticatedDomestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...
animal is bitten, the hair around the bite should be removed, so that the wound can be clearly seen. The crotaline Fab antivenom has been shown to be effective in the treatment of canine rattlesnake bites.
In human culture
Indigenous Americans
AztecThe Aztec people were certain ethnic groups of central Mexico, particularly those groups who spoke the Nahuatl language and who dominated large parts of Mesoamerica in the 14th, 15th and 16th centuries, a period referred to as the late post-classic period in Mesoamerican chronology.Aztec is the...
paintings, Central American temples, and the great burial mounds in the southeastern U.S. are frequently adorned with depictions of rattlesnakes, often within the symbols and emblems of the most powerful deities. The
Feathered Serpent deityThe Feathered Serpent was a prominent supernatural entity or deity, found in many Mesoamerican religions. It was called Quetzalcoatl among the Aztecs, Kukulkan among the Yucatec Maya, and Q'uq'umatz and Tohil among the K'iche' Maya...
of the preclassic
OlmecThe Olmec were the first major Pre-Columbian civilization in Mexico. They lived in the tropical lowlands of south-central Mexico, in the modern-day states of Veracruz and Tabasco....
was depicted as having the combined features of the quetzal bird and rattlesnake. The
Ancient MayaThe Maya is a Mesoamerican civilization, noted for the only known fully developed written language of the pre-Columbian Americas, as well as for its art, architecture, and mathematical and astronomical systems. Initially established during the Pre-Classic period The Maya is a Mesoamerican...
considered the rattlesnake to be a "vision serpent" that acted as a conduit to the "otherworld".
Christian snake handling sects
Members of some
ChristianA Christian is a person who adheres to Christianity, an Abrahamic, monotheistic religion based on the life and teachings of Jesus of Nazareth as recorded in the Canonical gospels and the letters of the New Testament...
sects in the southern United States are regularly bitten while participating in "
snake handlingSnake handling or serpent handling is a religious ritual in a small number of Pentecostal churches in the U.S., usually characterized as rural and Holiness. The practice began in the early 20th century in Appalachia, spreading to mostly coal mining towns. The practice plays only a small part of...
" rituals. Snake handling is when people hold venomous snakes, unprotected, as part of a religious service inspired by a literal interpretation of the
BibleThe Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...
verse Mark 16:17-18 which reads "In my name ... they will pick up snakes with their hands".
As a food
Journalist
Alistair CookeAlfred Alistair Cooke KBE was a British/American journalist, television personality and broadcaster. Outside his journalistic output, which included Letter from America and Alistair Cooke's America, he was well known in the United States as the host of PBS Masterpiece Theater from 1971 to 1992...
claims that rattlesnake tastes "just like chicken, only tougher." Others have compared the flavor to a wide range of other meats, including veal, frog, tortoise, quail, fish, rabbit, and even canned tuna.
Video
See also