86-410: The subfamily also includes many genera of pit vipers that are not rattlesnakes. Rattlesnakes are venomous snakes that form the genera Crotalus and Sistrurus of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers . Rattlesnakes are predators that live in a wide array of habitats, hunting small animals such as birds and rodents. Rattlesnakes receive their name from
172-421: A bite, sting, or similar action. The toxin is delivered through a specially evolved venom apparatus , such as fangs or a stinger , in a process called envenomation . Venom is often distinguished from poison , which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen , which is actively transferred to the external surface of another animal via
258-428: A chemical arms race. Predator/prey pairs are expected to coevolve over long periods of time. As the predator capitalizes on susceptible individuals, the surviving individuals are limited to those able to evade predation. Resistance typically increases over time as the predator becomes increasingly unable to subdue resistant prey. The cost of developing venom resistance is high for both predator and prey. The payoff for
344-551: A comparatively low venom yield, the venom toxicity of C. tigris is considered to be among the highest of all rattlesnake venoms, and among the highest of all snakes in the Western Hemisphere based on LD 50 studies conducted on laboratory mice. C. scutulatus is also widely regarded as producing one of the most toxic snake venoms in the Americas, based on LD 50 studies in laboratory mice . Rattlesnake venom
430-490: A few species of crotalines are highly active by day, such as Trimeresurus trigonocephalus , a bright green pit viper endemic to Sri Lanka, most are nocturnal, preferring to avoid high daytime temperatures and to hunt when their favored prey are also active. The snakes' heat-sensitive pits are also thought to aid in locating cooler areas in which to rest. As ambush predators, crotalines typically wait patiently somewhere for unsuspecting prey to wander by. At least one species,
516-698: A narrow range of elevations. Most species live near open, rocky areas. Rocks offer them cover from predators, plentiful prey (e.g. rodents, lizards, 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 , deserts , and forests . Rattlesnakes prefer a temperature range between 80 and 90 °F (26 and 32 °C), but can survive temperatures below freezing, recovering from brief exposure to temperatures as low as 4 °F (−16 °C), and surviving for several days in temperatures as low as 37 °F (3 °C). The most probable ancestral area of rattlesnakes
602-436: A paper proposing behavioral plasticity as the mechanism by which the rattling system evolved in rattlesnakes. In the case of rattlesnakes, Allf et al. proposed that tail vibration in response to predator threat could be the precursor for the rattling system in rattlesnakes, an example of behavioral plasticity . To investigate this hypothesis, the researchers analyzed tail vibration and relatedness to rattlesnakes among snakes in
688-594: A person lingers too long or gets too close. Rattlesnakes are the leading cause of snakebite injuries in North America and a significant cause in Central and South America. Rattlesnakes tend to avoid wide-open spaces where they cannot hide from predators, and generally avoid humans if they are aware of their approach. Rattlesnakes rarely bite unless they feel threatened or provoked. A majority of victims (about 72%) are males. Around half of bites occur in cases where
774-625: A physical delivery mechanism. Venom has evolved in terrestrial and marine environments and in a wide variety of animals: both predators and prey, and both vertebrates and invertebrates . Venoms kill through the action of at least four major classes of toxin, namely necrotoxins and cytotoxins , which kill cells; neurotoxins , which affect nervous systems; myotoxins , which damage muscles; and haemotoxins , which disrupt blood clotting . Venomous animals cause tens of thousands of human deaths per year. Venoms are often complex mixtures of toxins of differing types. Toxins from venom are used to treat
860-520: A rattlesnake bite although they can be vaccinated against them. Pit viper The Crotalinae , commonly known as pit vipers , or pit adders , are a subfamily of vipers found in Asia and the Americas. Like all other vipers, they are venomous . They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on both sides of the head. Currently, 23 genera and 155 species are recognized: These are also
946-523: A separate family : the Crotalidae. Today, however, the monophyly of the viperines and the crotalines as a whole is undisputed, which is why they are treated here as a subfamily of the Viperidae . *) Not including the nominate subspecies. ) Type genus . Venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of
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#17327759205881032-425: A small, underdeveloped rattle early in the evolution of the rattling system could have been advantageous if tail vibration was an ancestral behavior. At birth, a "prebutton" is present at the tip of the snake's tail; it is replaced by the "button" several days later when the first skin is shed. However, no sound can be made by the rattle until a second segment is added when the skin is shed again. A new rattle segment
1118-526: A stable body temperature, they exchange heat with their external environments. 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. 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
1204-464: A sting. In bees and wasps , the stinger is a modified ovipositor (egg-laying device). In Polistes fuscatus , the female continuously releases a venom that contains a sex pheromone that induces copulatory behavior in males. In wasps such as Polistes exclamans , venom is used as an alarm pheromone, coordinating a response from the nest and attracting nearby wasps to attack the predator. In some species, such as Parischnogaster striatula , venom
1290-406: A variety of larger predators, including coyotes, eagles , hawks , owls , falcons , feral pigs , badgers , indigo snakes , and kingsnakes. The common kingsnake ( Lampropeltis getula ), a constrictor, is immune to the venom of rattlesnakes and other vipers , and rattlesnakes form part of its natural diet. Rattlesnakes sense kingsnakes' presence by their odor. When they realize a kingsnake
1376-470: A wide range of diseases, explored in over 5,000 scientific papers. In medicine, snake venom proteins are used to treat conditions including thrombosis , arthritis , and some cancers . Gila monster venom contains exenatide , used to treat type 2 diabetes . Solenopsins extracted from fire ant venom has demonstrated biomedical applications, ranging from cancer treatment to psoriasis . A branch of science, venomics , has been established to study
1462-422: A wide range of medical conditions including thrombosis , arthritis , and some cancers . Studies in venomics are investigating the potential use of venom toxins for many other conditions. The use of venom across a wide variety of taxa is an example of convergent evolution . It is difficult to conclude exactly how this trait came to be so intensely widespread and diversified. The multigene families that encode
1548-420: A wide variety of “chemical cocktails” in rattlesnake venoms. The prevailing theory for the driving force of this evolution is directional selection , where efficacy on prey is selected for. Diversity in prey leads to less specificity in toxins, while highly specialized toxins are more likely to develop when there are few key prey species. However, recently, balancing selection has been indicated to better explain
1634-498: Is a mixture of five to fifteen enzymes , various metal ions , biogenic amines , lipids , free amino acids , proteins , and polypeptides . More specifically, there are three main families of toxins in rattlesnakes: phospholipases A2 (PLA2s), snake venom metalloproteinases (SVMPs), and snake venom serine proteinases (SVSPs). It contains components meant to immobilize and disable the prey, as well as digestive enzymes, which break down tissue to prepare for later ingestion . The venom
1720-414: Is added each time the snake sheds its skin, and the snake may shed its skin several times a year, depending on food supply and growth rate. 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, the number of rattles on its tail is not related to
1806-426: Is among the most prolific of all live-bearing snakes. Many young crotalines have brightly coloured tails that contrast dramatically with the rest of their bodies. These tails are known to be used by a number of species in a behavior known as caudal luring; the young snakes make worm-like movements with their tails to lure unsuspecting prey within striking distance. In the past, the pit vipers were usually classed as
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#17327759205881892-539: Is applied all over the body as an antimicrobial protection. Many caterpillars have defensive venom glands associated with specialized bristles on the body called urticating hairs . These are usually merely irritating, but those of the Lonomia moth can be fatal to humans. Bees synthesize and employ an acidic venom ( apitoxin ) to defend their hives and food stores, whereas wasps use a chemically different venom to paralyse prey, so their prey remains alive to provision
1978-558: Is derived from the Greek κρόταλον, meaning " castanet ". The name Sistrurus is the Latinized form of the Greek word for "tail rattler" (Σείστρουρος, seistrouros ) and shares its root with the ancient Egyptian musical instrument the sistrum , a type of rattle. Rattlesnakes are native to the Americas from southern Canada to central Argentina, with the majority of species inhabiting arid regions. The large majority of species live in
2064-534: Is found in a few other reptiles such as the Mexican beaded lizard , the gila monster , and some monitor lizards, including the Komodo dragon . Mass spectrometry showed that the mixture of proteins present in their venom is as complex as the mixture of proteins found in snake venom. Some lizards possess a venom gland; they form a hypothetical clade, Toxicofera , containing the suborders Serpentes and Iguania and
2150-403: Is higher. Rattlesnakes have responded locally by increasing the effectiveness of their venom. The kingsnakes of the Americas are constrictors that prey on many venomous snakes. They have evolved resistance which does not vary with age or exposure. They are immune to the venom of snakes in their immediate environment, like copperheads, cottonmouths, and North American rattlesnakes, but not to
2236-607: Is more acute during daylight conditions. Rattlesnakes also possess cone cells , which means they are capable of some form of color vision. The rattlesnake eye lacks a fovea , making vision of sharply defined images impossible. 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 smell . They can sense olfactory stimuli both through their nostrils and by flicking their tongues , which carry scent-bearing particles to
2322-435: 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 on it (the head being the first part of the rattlesnake to be ingested). The rattlesnake jerks its body about, while bridging its back upwards, forming an elevated coil that faces
2408-460: Is proven that reptile and platypus venom have independently evolved, it is thought that there are certain protein structures that are favored to evolve into toxic molecules. This provides more evidence of why venom has become a homoplastic trait and why very different animals have convergently evolved. Envenomation resulted in 57,000 human deaths in 2013, down from 76,000 deaths in 1990. Venoms, found in over 173,000 species, have potential to treat
2494-607: Is similar to the human penis . 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. The Arizona black rattlesnake ( C. oreganus cerberus ), has been observed to exhibit complex social behavior reminiscent of that in mammals. Females often remain with their young in nests for several weeks, and mothers have been observed co-operatively parenting their broods. Rattlesnakes generally take several years to mature, and females usually reproduce only once every three years. In
2580-606: Is the Sierra Madre Occidental region in Mexico. The most probable vegetation or habitat of the ancestral area appears to be pine-oak forests. Rattlesnakes typically consume mice , rats , rabbits , squirrels , small birds , and other small animals . They lie in wait for their prey , or hunt for it in holes . The rattlesnake's defence and hunting mechanisms are bound to its physiology and its environment. More importantly environmental temperature can influence
2666-434: Is thought that they did not expand further into Europe. The subfamily Crotalinae is found from Central Asia eastward and southward to Japan , China , Indonesia , peninsular India , Nepal , and Sri Lanka . In the Americas, they range from southern Canada southward to Central America to southern South America. Crotalines are a versatile subfamily, with members found in habitats ranging from parched desert (e.g.,
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2752-432: Is very stable, and retains its toxicity for many years in storage. Snake venom , in general, has a complex and ongoing evolutionary process, and rattlesnake venom is no different. The primary mechanisms of evolution are both gene duplication and gene loss events. The duplication events provided material for neofunctionalization to create the novel toxin genes, while gene loss influenced speciation and helped lead to such
2838-719: The American Southwest and Mexico. Four species may be found east of the Mississippi River , and two in South America. In the United States, the state with the most types of rattlesnakes is Arizona, with 13. Rattlesnakes are found in almost every habitat type capable of supporting terrestrial ectothermic vertebrates , but individual species may have extremely specific habitat requirements, living where certain plant associations occur or within
2924-740: The Appalachian Mountains of New England reproduce every three years on average; the lance-headed rattlesnake ( C. polystictus ), 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 rarely seen during the hottest and driest months of summer. Rattlesnakes tend to avoid developed areas, preferring undisturbed, natural habitats. Rapid habitat destruction by humans, mass killings during events such as rattlesnake round-ups , and deliberate extermination campaigns all pose threats to rattlesnake populations in many areas. Several species, such as
3010-1006: The Cnidaria , sea urchins among the Echinodermata , and cone snails and cephalopods , including octopuses , among the Molluscs . Venom is found in some 200 cartilaginous fishes, including stingrays , sharks , and chimaeras ; the catfishes (about 1000 venomous species); and 11 clades of spiny-rayed fishes ( Acanthomorpha ), containing the scorpionfishes (over 300 species), stonefishes (over 80 species), gurnard perches , blennies , rabbitfishes , surgeonfishes , some velvetfishes , some toadfishes , coral crouchers , red velvetfishes , scats , rockfishes , deepwater scorpionfishes , waspfishes , weevers , and stargazers . Some salamanders can extrude sharp venom-tipped ribs. Two frog species in Brazil have tiny spines around
3096-522: The Jacobson's organs in the roof of their mouths. Like all snakes, rattlesnakes lack external ear openings, and the structures of their middle ear are not as highly specialized as those of other vertebrates, such as mammals. Thus, their sense of hearing is not very effective, but they are capable of sensing vibrations in the ground, passed by the skeleton to the auditory nerve . Rattlesnake fangs are connected by venom ducts to large venom glands near
3182-487: The eastern diamondback , can measure up to 2.4 m (7.9 ft) in length. Rattlesnakes are preyed upon by hawks , weasels , kingsnakes , and a variety of other species. Rattlesnakes are heavily preyed upon as neonates , while they are still weak and immature. Large numbers of rattlesnakes are killed by humans. Rattlesnake populations in many areas are severely threatened by habitat destruction , poaching , and extermination campaigns. The scientific name Crotalus
3268-400: The ova ("eggs") in her ovaries , after which they pass through her 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. The hemipenis
3354-439: The phosphodiester bonds of DNA ; and neurotoxins, which disrupt signalling in the nervous system. Snake venom causes symptoms including pain, swelling, tissue necrosis, low blood pressure, convulsions, haemorrhage (varying by species of snake), respiratory paralysis, kidney failure, coma, and death. Snake venom may have originated with duplication of genes that had been expressed in the salivary glands of ancestors. Venom
3440-536: The rattle located at the end of their tails, which makes a loud rattling noise when vibrated that deters predators. Rattlesnakes are the leading contributor to snakebite injuries in North America, but rarely bite unless provoked or threatened; if treated promptly, the bites are seldom fatal. The 36 known species of rattlesnakes have between 65 and 70 subspecies, all native to the Americas , ranging from central Argentina to southern Canada. The largest rattlesnake,
3526-431: The ability of ectotherms. The prey is killed quickly with a venomous bite as opposed to constriction . 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
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3612-546: The age of a rattlesnake. Compared to females, males have thicker and longer tails (because they contain the inverted hemipenes ). Also, the tails of males taper gradually from the body, whereas the tails of females narrow abruptly at the vent. Rattlesnakes, like other members of the Squamata order, have a circulatory system that is powered by a three-chambered heart composed of two atria and one ventricle. The right atrium receives deoxygenated blood from veins coming from
3698-422: The arboreal Gloydius shedaoensis of China, is known to select a specific ambush site and return to it every year in time for the spring migration of birds. Studies have indicated these snakes learn to improve their strike accuracy over time. Many temperate species of pit vipers (e.g. most rattlesnakes) congregate in sheltered areas or "dens" to overwinter (brumate, see hibernation ), the snakes benefiting from
3784-439: The bushmaster, Lachesis muta , a species known to reach a maximum total length of 3.65 m (12.0 ft) in length. This subfamily is unique in that all member species share a common characteristic – a deep pit, or fossa, in the loreal area between the eye and the nostril on either side of the head. These loreal pits are the external openings to a pair of extremely sensitive infrared -detecting organs, which in effect give
3870-479: The colder winter months, some rattlesnake species enter a period of brumation , which is dormancy similar to hibernation . They often gather together for brumation in large numbers (sometimes over 1,000 snakes), huddling together inside underground "rattlesnake dens" or hibernacula. They regularly share their winter burrows with a wide variety of other species (such as turtles , small mammals, invertebrates , and other types of snakes). Rattlesnakes often return to
3956-490: The combined heat. In cool temperatures and while pregnant, pit vipers also bask on sunny ledges. Some species do not mass together in this way, for example the copperhead, Agkistrodon contortrix , or the Mojave rattlesnake, Crotalus scutulatus . Like most snakes, crotalines keep to themselves and strike only if cornered or threatened. Smaller snakes are less likely to stand their ground than larger specimens. Pollution and
4042-473: The cost of physiological resistance is an increased chance of survival for prey, but it allows predators to expand into underutilised trophic niches. The California ground squirrel has varying degrees of resistance to the venom of the Northern Pacific rattlesnake . The resistance involves toxin scavenging and depends on the population. Where rattlesnake populations are denser, squirrel resistance
4128-406: The crown of their skulls which, on impact, deliver venom into their targets. Some 450 species of snake are venomous. Snake venom is produced by glands below the eye (the mandibular glands ) and delivered to the target through tubular or channeled fangs. Snake venoms contain a variety of peptide toxins, including proteases , which hydrolyze protein peptide bonds; nucleases , which hydrolyze
4214-453: The destruction of rainforests have caused many pit viper populations to decline. Humans also threaten pit vipers, as many are hunted for their skins or killed by cars when they wander onto roads. With few exceptions, crotalines are ovoviviparous , meaning that the embryos develop within eggs that remain inside the mother's body until the offspring are ready to hatch, when the hatchlings emerge as functionally free-living young. In such species,
4300-431: The eggshells are reduced to soft membranes that the young shed, either within the reproductive tract, or immediately after emerging. Among the oviparous (egg-laying) pit vipers are Lachesis , Calloselasma , and some Trimeresurus species. All egg-laying crotalines are believed to guard their eggs. Brood sizes range from two for very small species, to as many as 86 for the fer-de-lance, Bothrops atrox , which
4386-555: The eyes with these thermal images from the pit organs to more accurately visualize their surroundings in low levels of light. Research conducted recently on the molecular mechanism of this ability suggests the temperature sensitivity of these pit organs is closely linked to the activity of transient receptor potential ankyrin 1, a temperature-sensitive ion channel saturated in the pit membrane. Rattlesnake eyes, which contain many rod cells , are well adapted to nocturnal use. Rattlesnakes, though, are not exclusively nocturnal, and their vision
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#17327759205884472-538: The families Varanidae , Anguidae , and Helodermatidae . Euchambersia , an extinct genus of therocephalians , is hypothesized to have had venom glands attached to its canine teeth. A few species of living mammals are venomous, including solenodons , shrews , the European mole , vampire bats , male platypuses , and slow lorises . Shrews have venomous saliva and most likely evolved their trait similarly to snakes. The presence of tarsal spurs akin to those of
4558-401: The families Viperidae and Colubridae . Their results demonstrated that the more closely related a species was to rattlesnakes, the more similar that species was to rattlesnakes in both duration and rate of tail vibration. These results strongly support the hypothesis that tail vibration preceded the rattling system as a behavior and allowed for the rattle to be selected for once developed. Even
4644-521: The food chambers of their young. The use of venom is much more widespread than just these examples; many other insects, such as true bugs and many ants , also produce venom. The ant species Polyrhachis dives uses venom topically for the sterilisation of pathogens. There are venomous invertebrates in several phyla , including jellyfish such as the dangerous box jellyfish , the Portuguese man-of-war (a siphonophore) and sea anemones among
4730-504: The functional pair. Rattlesnake venom is hemotoxic, destroying tissue, causing necrosis and coagulopathy (disrupted blood clotting). In the U.S., the tiger rattlesnake ( C. tigris ) and some varieties of the Mojave rattlesnake ( C. scutulatus ) also have a presynaptic neurotoxic venom component known as Mojave type A toxin, which can cause severe paralysis . However, most North American rattlesnakes are not neurotoxic. Although it has
4816-460: The kingsnake. The elevated coil is used to strike the attacker, and is also used to shield the head from the kingsnake. Like all pit vipers, rattlesnakes have two organs that can sense radiation ; their eyes and a set of heat-sensing "pits" on their faces that enable them to locate prey and move towards it, based on the prey's thermal radiation signature. These pits have a relatively short effective range of about 1 ft (0.30 m) but give
4902-478: The maintenance of adaptive genetic diversity in venom-related genes, potentially allowing for the rattlesnakes to better keep up in the evolutionary arms race with their prey. Older snakes possess more potent venom, and larger snakes are frequently capable of storing larger volumes of it. The rattle serves as a warning for predators of the rattlesnake. The rattle is composed of a series of hollow, interlocked segments made of keratin , which are created by modifying
4988-637: The many toxins that they contain; some venoms are complex mixtures of toxins of differing types. Major classes of toxin in venoms include: Venom is widely distributed taxonomically, being found in both invertebrates and vertebrates, in aquatic and terrestrial animals, and among both predators and prey. The major groups of venomous animals are described below. Venomous arthropods include spiders , which use fangs on their chelicerae to inject venom , and centipedes , which use forcipules — modified legs — to deliver venom, while scorpions and stinging insects inject venom with
5074-464: 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 their heads and necks 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 ovoviviparous (give birth to live young after carrying eggs inside). The female produces
5160-416: The meal was adequate, the snake finds a warm, safe location in which to coil up and rest until the prey is digested. Feeding habits play an important ecological role by limiting the size of rodent populations, which prevents crop damage and stabilizes ecosystems. Rattlesnakes are believed to require at least their own body weight in water annually to remain hydrated . The method by which they drink depends on
5246-407: The membrane allows the snake to determine its direction. Having one of these organs on either side of the head produces a stereo effect that indicates distance, as well as direction. Experiments have shown, when deprived of their senses of sight and smell, these snakes can strike accurately at moving objects less than 0.2 °C (0.36 °F) warmer than the background. The paired pit organs provide
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#17327759205885332-436: The mouth. The prey is then ingested head first, which allows wings and limbs to fold at the joints in a manner that minimizes the girth of the meal. The gastric fluids of rattlesnakes are extremely powerful, allowing for the digestion of flesh and bone. Optimal digestion occurs when the snake maintains a body temperature between 80 and 85 °F (25 and 29 °C). If the prey is small, the rattlesnake often continues hunting. If
5418-557: The muscularis compressor glandulae, forces venom out of the gland. The earliest known fossil pit viper remains are from the Early Miocene of Nebraska . As pit vipers are thought to have had an Asian origin before eventually colonizing the Americas, this suggests that they must have originated and diversified even earlier. During the Late Miocene, they reached as far west as eastern Europe, where they are no longer found; it
5504-452: The only viperids found in the Americas. The groups of snakes represented here include rattlesnakes , lanceheads , and Asian pit vipers . The type genus for this subfamily is Crotalus , of which the type species is the timber rattlesnake , C. horridus . These snakes range in size from the diminutive hump-nosed viper, Hypnale hypnale , that grows to a typical total length (including tail) of only 30–45 cm (12–18 in), to
5590-549: The organ. Due to the high density of heat-sensitive receptors innervating this membrane, the rattlesnake can detect temperature changes of 0.003 °C or less in its immediate surroundings. Infrared cues from these receptors are transmitted to the brain by the trigeminal nerve, where they are used to create thermal maps of the snake's surroundings. Due to the small sizes of the pit openings, typically these thermal images are low in resolution and contrast. Nevertheless, rattlesnakes superimpose visual images created from information from
5676-482: 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 to squeeze 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 three pairs of replacement fangs lie behind
5762-443: The platypus in many non- therian Mammaliaformes groups suggests that venom was an ancestral characteristic among mammals. Extensive research on platypuses shows that their toxin was initially formed from gene duplication, but data provides evidence that the further evolution of platypus venom does not rely as much on gene duplication as was once thought. Modified sweat glands are what evolved into platypus venom glands. Although it
5848-414: The proteins associated with venom and how individual components of venom can be used for pharmaceutical means. Venom is used as a trophic weapon by many predator species. The coevolution between predators and prey is the driving force of venom resistance, which has evolved multiple times throughout the animal kingdom. The coevolution between venomous predators and venom-resistant prey has been described as
5934-429: The rattlesnake a distinct advantage in hunting for warm-blooded creatures at night. Aside from their eyes, rattlesnakes are able to detect thermal radiation emitted by warm-blooded organisms in their environment. Functioning optically like a pinhole camera eye, thermal radiation in the form of infrared light passes through the opening of the pit and strikes the pit membrane located in the back wall, warming this part of
6020-497: The same den, year after year, sometimes traveling several miles to get there. How the rattlesnakes find their way back to the dens each year is unknown, but may involve a combination of pheromone trails and visual cues (e.g., topography , celestial navigation , and solar orientation). Species with long periods of brumation tend to have much lower reproductive rates than those with shorter brumation periods or those that do not brumate at all. Female timber rattlesnakes in high peaks in
6106-462: 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, thus making the rattling noise (which is amplified because the segments are hollow) in a behavior known as tail vibration . The muscles which cause rattling are some of the fastest known, firing 50 times per second on average, sustainable for a duration of up to three hours. In 2016, Allf et al. published
6192-487: The sidewinder, Crotalus cerastes ) to rainforests (e.g., the bushmaster, Lachesis muta ). They may be either arboreal or terrestrial , and at least one species (the cottonmouth, Agkistrodon piscivorus ) is semiaquatic. The altitude record is held jointly by Crotalus triseriatus in Mexico and Gloydius strauchi in China, both of which have been found above the treeline at over 4,000 m above sea level. Although
6278-457: 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 Formica are known to prey upon neonates, and Solenopsis invicta (fire ants) likely do, as well. On occasion, hungry adult rattlesnakes cannibalize neonates. The small proportion (often as few as 20%) of rattlesnakes that make it to their second year are heavily preyed upon by
6364-419: The snake with thermal rangefinder capabilities. Clearly, these organs are of great value to a predator that hunts at night, as well as for avoiding the snake’s own predators. Among vipers, these snakes are also unique in that they have a specialized muscle, called the muscularis pterigoidius glandulae, between the venom gland and the head of the ectopterygoid. Contraction of this muscle, together with that of
6450-401: The snakes a sixth sense to help them find and perhaps even judge the size of the small, warm-blooded prey on which they feed. The pit organ is complex in structure and is similar to the thermoreceptive labial pits found in boas and pythons . It is deep and located in a maxillary cavity. The membrane is like an eardrum that divides the pit into two sections of unequal size, with the larger of
6536-562: 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 the males follow using their tongues and Jacobson's organs as guides. Once a receptive female has been located, the male often spends several days following her around (a behavior 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 ), fight each other during
6622-421: The surrounding environment. Creases in the epidermal tissue connect the scales of rattlesnakes. When ingesting large prey, these creases can unfold, allowing the skin to expand to envelop a much greater volume. The skin appears to tightly stretch to accommodate the meal, but in reality, the skin is simply smoothing out from its creased state and is not under very high tension. Most rattlesnake species mate during
6708-420: The systemic circuit. The left atrium receives oxygenated blood from the lungs in the pulmonary circuit and pumps it to the ventricle and through the systemic circuit via capillaries and arteries . Rattlesnake skin has a set of overlapping scales that cover the entire body, providing protection from a variety of threats, including dehydration and physical trauma. The typical rattlesnake, genus Crotalus , has
6794-527: The tentacles of venomous sea anemones (an obligatory symbiosis for the fish), and are resistant to their venom. Only 10 known species of anemones are hosts to clownfish and only certain pairs of anemones and clownfish are compatible. All sea anemones produce venoms delivered through discharging nematocysts and mucous secretions. The toxins are composed of peptides and proteins. They are used to acquire prey and to deter predators by causing pain, loss of muscular coordination, and tissue damage. Clownfish have
6880-648: The timber rattlesnake, massasauga , and canebrake rattlesnake, are listed as threatened or endangered in many U.S. states. Many rattlesnakes die from being run over by cars. In more heavily populated and trafficked areas, reports have been increasing of rattlesnakes that do not rattle. This phenomenon is falsely attributed to selective pressure by humans, who often kill the snakes when they are discovered. However, snake experts have dismissed this theory, stating that snakes simply do not rattle as often as laymen expect them to, and that snakes that live near populated areas simply get used to people passing by, only rattling when
6966-421: The top of its head covered with small scales, except, with a few species, a few crowded plates directly over the snout. The skin of snakes is highly sensitive to contact, tension, and pressure; they are capable of feeling pain. 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 . To maintain
7052-403: The toxins of venomous animals are actively selected , creating more diverse toxins with specific functions. Venoms adapt to their environment and victims, evolving to become maximally efficient on a predator 's particular prey (particularly the precise ion channels within the prey). Consequently, venoms become specialized to an animal's standard diet. Venoms cause their biological effects via
7138-576: The two facing forwards and exposed to the environment. The two sections are connected via a narrow tube, or duct, that can be opened or closed by a group of surrounding muscles. By controlling this tube, the snake can balance the air pressure on either side of the membrane. The membrane has many nerve endings packed with mitochondria . Succinic dehydrogenase, lactic dehydrogenase, adenosine triphosphate , monoamine oxidase , generalized esterases , and acetylcholine esterase have also been found in it. When prey comes into range, infrared radiation falling onto
7224-433: The venom of, for example, king cobras or black mambas. Among marine animals, eels are resistant to sea snake venoms, which contain complex mixtures of neurotoxins, myotoxins, and nephrotoxins, varying according to species. Eels are especially resistant to the venom of sea snakes that specialise in feeding on them, implying coevolution; non-prey fishes have little resistance to sea snake venom. Clownfish always live among
7310-405: The victim saw the snake, yet made no effort to move away. Harassing or attacking a rattlesnake, illegal in some jurisdictions, puts one at much higher risk of a bite. Rattlesnakes seek to avoid humans and other predators or large herbivores that themselves pose lethal danger. Dogs , often much more aggressive than humans, are much more likely to experience a snakebite, and are more likely to die of
7396-532: The water source. In larger bodies of water ( streams , ponds , etc.), they submerge their heads and ingest water by opening and closing their jaws, which sucks in water. If drinking dew or small puddles, they sip the liquid either by capillary action or by flattening and flooding their lower jaws. Newborn rattlesnakes are heavily preyed upon by a variety of species, including cats , ravens , crows , roadrunners , raccoons , opossums , skunks , coyotes , weasels , whipsnakes , kingsnakes , and racers . Young of
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