Ecology of the Sierra Nevada
See Sierra Nevada for general information about the mountain range in the United States. The ecology of the Sierra Nevada, located in the U. S. state of California, is diverse and complex: the plants and animals are a significant part of the scenic beauty of the mountain range. The combination of climate, topography and soils influences the distribution of ecological communities across an elevation gradient from 1,000 to 14,500 feet. Biotic zones range from scrub and chaparral communities at lower elevations, to subalpine forests and alpine meadows at the higher elevations. Particular ecoregions that follow elevation contours are described as a series of belts that follow the length of the Sierra Nevada. There are many hiking trails and unpaved roads, vast public lands in the Sierra Nevada for exploring the many different biomes and ecosystems; the western and eastern Sierra Nevada have different species of plants and animals, because the east lies in the rain shadow of the crest. The plants and animals in the east are thus adapted to much drier conditions.
The altitudes listed for the biotic zones are for the central Sierra Nevada. The climate across the north-south axis of the range varies somewhat: the boundary elevations of the biotic zones move by as much as 1,000 feet from the north end to the south end of the range; the lowest-elevation biotic zone in the Sierra Nevada is found along the boundary with the Central Valley. This zone, stretching in elevation from 500 to 3,500 feet, is the foothill woodland zone, an area, hot and dry in the summer with little or no snow in the winter; the foothills are vegetated with grasslands of non-native grasses, mixed grasslands and woodlands savanna, a foothill woodland community of blue oak and gray pine, chaparral. Many of the plant communities are similar to those found on the inner California Coast Ranges. Animals typical of this zone include black bear, ringtail cat, gray squirrel, California mule deer, skunk. In the foothills of the northern portion of the Sierra Nevada and chamise co-dominate certain open serpentine chaparral communities.
Beginning near the 3,000-foot elevation, the hot, dry summers and cool, moist winters of the Mediterranean climate give rise to the lower montane forest zone. This zone is known as the yellow pine forest zone; the accumulation of several feet of snow during the winter is not uncommon and can stay on the ground for several months. The diversity of tree species found in this zone make this a beautiful and interesting forest to explore; the indicator species for the lower montane forest are the ponderosa pine and the Jeffrey pine: the ponderosa pine occurs on the west side of the Sierra, while the Jeffrey pine occurs on the east. The lower montane forests include trees such as California black oak, sugar pine, incense-cedar, white fir. Animals that may be found in this zone include the dark-eyed junco, mountain chickadee, western gray squirrel, mule deer, American black bear; the endangered Yosemite toad is found in montane forests of the central Sierra Nevada, at elevations of 4,790 to 11,910 feet.
The character of the Lower Montane Forest changes with latitude. North of Grass Valley, the lower montane forest ranges from 2,000 to 4,000 feet, with less ponderosa pine and more Douglas-fir. In the middle Sierra, south to the Merced River, the lower montane forest has the same elevation, but precipitation decreases and the forest mixes with chaparral. In the southern Sierra, the lower montane forest occurs between 3,000 to 5,000 feet, but can range as high as 6,000 feet, with ponderosa pine dominating the landscape. Unlike further north, the geology of the southern lower montane forest is dominated by granite; the mid-montane forest grows on the western slopes of the Sierra Nevada at moderate elevations. North of Lake Tahoe, the mid-montane forest occurs from 3,000 to 6,000 feet. Between Tahoe and Yosemite, the forest ranges from 4,000 to 6,000 feet, while south of Yosemite, it occurs between 5,000 to 7,000 feet; the mid-montane zone has a mixed forest of white fir, Douglas-fir, ponderosa pine, Jeffrey pine, live oak, black oak, tanoak, depending on location.
North of Tahoe, the mid-montane forest has more white fir and Douglas-fir, less ponderosa pine than further south. Jeffrey pine occurs on ultramafic lava soils. In Yosemite and points south, giant sequoia occurs in wetter locations; the upper montane forest begins at higher elevations near 7,000 feet, where the montane climate is characterized by short, cool summers and cold, wet winters. Snow may accumulate to depths up to 6 feet and remain until June. Pure stands of red fir and lodgepole pine are typical of this forest. Jeffrey pine, which has bark that smells like vanilla, the picturesque western juniper can be found in this zone. Wildflowers bloom in meadows from June through August. Common animals in this zone include the hermit thrush, dusky grouse, great grey owl, golden-mantled ground squirrel, the marten. Upper montane forests may be viewed from the Tioga Pass Road east of Crane Flat, Glacier Point Road, State Route 108; the elevation of the upper montane zone shifts with latitude: it occurs from 6,000 to 8,000 feet north of Yosemite, 7,000 to 9,000 feet to the south.
The upper montane forest is replaced by the subalpine forest near 9,000 feet, where the climate is cooler with an shorter growing season due to long and snowy winters. Accumulations of three to ni
Clark's nutcracker, sometimes referred to as Clark's crow or woodpecker crow, is a passerine bird in the family Corvidae. It is smaller than its Eurasian relative the spotted nutcracker, it is ashy-grey all over except for central tail feathers. The bill and feet are black; this bird derives its name from the explorer William Clark. It can be seen in western North America from British Columbia and western Alberta in the north to Baja California and central New Mexico in the south. There is a small isolated population on the peak of Cerro Potosí, elevation 3,700 metres, in Nuevo León, northeast Mexico, it is found in mountains at altitudes of 900–3,900 metres in conifer forest. Outside the breeding season, it may wander extensively to lower altitudes and further east as far as Illinois following any cone crop failure in its normal areas; the most important food resources for this species are the seeds of pines, principally the two cold-climate species of white pine with large seeds P. albicaulis and P. flexilis, but using other high-altitude species like P. balfouriana, P. longaeva and P. monticola.
During migrations to lower altitudes, it extensively uses the seeds of pinyon pines. The isolated Cerro Potosí population is associated with the local endemic Potosi pinyon Pinus culminicola. All Clark's Nutcrackers have a sublingual pouch capable of holding around 50–150 seeds, depending on the size of the seeds. Clark's nutcrackers store seeds in the ground for consumption, in caches of 1–15 seeds. Depending on the cone crop as well as the tree species, a single Clark's nutcracker can cache as many as 98,000 seeds per season; the birds store more than they need as an insurance against seed theft by other animals, as well as low availability of alternative foods. Through this activity of caching and over-storing, the bird is perpetuating its own habitat. Tied in with this storage behavior is the bird's remarkable long-term spatial memory; the diet includes a wide range of insect prey and other fruits, small mammals and flesh from carcasses. Eggs and nestlings are sometimes devoured, peanuts and suet have become a favorite at bird tables.
Food is taken both from the ground and from trees, where the nutcrackers are agile among the branches. The birds are able to extract food by clasping pine cones in such a way that the cones are held between one or both feet; the birds hack the cones open with their strong bills. Rotten logs are hacked into in order to locate large beetle grubs, animal dung may be flipped over in search of insects. Clark's nutcrackers can be opportunistic feeders in developed areas, are known to some as "camp robbers"; the species nests in pines or other types of conifers during early spring. Two to four eggs are laid, incubation occurring in 16–18 days. Incubation is performed by both the male and female parents, the young are fledged by around the 22nd day; the fledglings follow their parents around for several months in order to learn the complex seed storage behavior. Clark's nutcracker is the primary seed disperser for whitebark pine. Whitebark pine is in decline throughout its range, due to infection by white pine blister rust, widespread outbreaks of mountain pine beetle, the long-term effects of fire suppression.
The Clark's nutcracker is an integral part of the whitebark pine restoration process: the Clark's nutcracker must remain in whitebark pine forests and cache the seeds in excess, so that healthy trees will continue to grow. If whitebark pine declines into extinction, the Clark's nutcracker will lose an important source of food and may no longer be seen in areas where the tree is the primary source of seed, such as Glacier National Park; the voice of this bird is varied and produces many different sounds. However, the most frequent call is described as khraaaah-khraaaah. Clark's nutcracker Clark's nutcracker photo gallery VIREO Clark's nutcracker on the Internet Bird Collection Clark's nutcracker at All About Birds Whitebark Pine Ecosystem Foundation
The bobcat is a North American cat that appeared during the Irvingtonian stage of around 1.8 million years ago. Containing 2 recognized subspecies, it ranges from southern Canada to central Mexico, including most of the contiguous United States; the bobcat is an adaptable predator that inhabits wooded areas, as well as semidesert, urban edge, forest edge, swampland environments. It remains in some of its original range, but populations are vulnerable to local extinction by coyotes and domestic animals. With a gray to brown coat, whiskered face, black-tufted ears, the bobcat resembles the other species of the midsized genus Lynx, it is smaller on average than the Canada lynx, with which it shares parts of its range, but is about twice as large as the domestic cat. It has distinctive black bars on its forelegs and a black-tipped, stubby tail, from which it derives its name. Though the bobcat prefers rabbits and hares, it hunts insects, chickens and other birds, small rodents, deer. Prey selection depends on location and habitat and abundance.
Like most cats, the bobcat is territorial and solitary, although with some overlap in home ranges. It uses several methods to mark its territorial boundaries, including claw marks and deposits of urine or feces; the bobcat has a gestation period of about two months. Although bobcats have been hunted extensively by humans, both for sport and fur, their population has proven resilient though declining in some areas; the elusive predator features in the folklore of European settlers. There had been debate over whether to classify this species as Lynx rufus or Felis rufus as part of a wider issue regarding whether the four species of Lynx should be given their own genus, or be placed as a subgenus of Felis; the genus Lynx is now accepted, the bobcat is listed as Lynx rufus in modern taxonomic sources. Johnson et al. reported Lynx shared a clade with the puma, leopard cat, domestic cat lineages, dated to 7.15 million years ago. The bobcat is believed to have evolved from the Eurasian lynx, which crossed into North America by way of the Bering Land Bridge during the Pleistocene, with progenitors arriving as early as 2.6 million years ago.
The first wave moved into the southern portion of North America, soon cut off from the north by glaciers. This population evolved into modern bobcats around 20,000 years ago. A second population arrived from Asia and settled in the north, developing into the modern Canada lynx. Hybridization between the bobcat and the Canada lynx may sometimes occur. Thirteen bobcat subspecies have been recognized based on morphological characteristics: L. rufus rufus – eastern and midwestern United States L. r. gigas – northern New York to Nova Scotia and New Brunswick L. r. floridanus – southeastern United States and inland to the Mississippi valley, up to southwestern Missouri and southern Illinois L. r. superiorensis – western Great Lakes area, including upper Michigan, southern Ontario, most of Minnesota L. r. baileyi – southwestern United States and northwestern Mexico L. r. californicus – California west of the Sierra Nevada L. r. mohavensis – Mojave Desert of California L. r. escuinapae – central Mexico, with a northern extension along the west coast to southern Sonora L. r. fasciatus – Oregon, Washington west of the Cascade Range, northwestern California, southwestern British Columbia L. r. oaxacensis – Oaxaca L. r. pallescens – northwestern United States and southern British Columbia and Saskatchewan L. r. peninsularis – Baja California L. r. texensis – western Louisiana, south central Oklahoma, south into Tamaulipas, Nuevo León, CoahuilaThis subspecies division has been challenged, given a lack of clear geographic breaks in their ranges and the minor differences between subspecies.
The latest revision of cat taxonomy in 2017, by the Cat Classification Taskforce of the Cat Specialist Group recognises only two subspecies, based on phylogeographic and genetic studies, although the status of Mexican bobcats remains under review: Lynx rufus rufus – east of the Great Plains, North America Lynx rufus fasciatus – west of the Great Plains, North America The bobcat resembles other species of the genus Lynx, but is on average the smallest of the four. Its coat is variable, though tan to grayish-brown, with black streaks on the body and dark bars on the forelegs and tail, its spotted patterning acts as camouflage. The ears are pointed, with short, black tufts. An off-white color is seen on the lips and underparts. Bobcats in the desert regions of the southwest have the lightest-colored coats, while those in the northern, forested regions are darkest. Kittens are born well-furred and have their spots. A few melanistic bobcats have been captured in Florida, they may still exhibit a spot pattern.
The face appears wide due to ruffs of extended hair beneath the ears. Bobcat eyes are yellow with black pupils; the nose of the bobcat is pinkish-red, it has a base color of gray or yellowish- or brownish-red on its face and back. The pupils are round, black circles and will widen during nocturnal activity to maximize light reception; the cat has sharp hearing and vision, a good sense of smell. It is an excellent climber, swims when it needs to, but avoids water. However, cases of bobcats swimming long distances across lakes have been rec
The wolverine, Gulo gulo referred to as the glutton, skunk bear, or quickhatch, is the largest land-dwelling species of the family Mustelidae. It is a stocky and muscular carnivore, more resembling a small bear than other mustelids. A solitary animal, it has a reputation for ferocity and strength out of proportion to its size, with the documented ability to kill prey many times larger than itself; the wolverine is found in remote reaches of the Northern boreal forests and subarctic and alpine tundra of the Northern Hemisphere, with the greatest numbers in Northern Canada, the American state of Alaska, the mainland Nordic countries of Europe, throughout western Russia and Siberia. Its population has declined since the 19th century owing to trapping, range reduction and habitat fragmentation; the wolverine is now absent from the southern end of its European range. Genetic evidence suggests that the wolverine is most related to the tayra and martens, all of which shared a Eurasian ancestor. Within the Gulo gulo species, a clear separation occurs between two subspecies: the Old World form Gulo gulo gulo and the New World form G. g. luscus.
Some authors had described as many as four additional North American subspecies, including ones limited to Vancouver Island and the Kenai Peninsula in Alaska. However, the most accepted taxonomy recognizes either the two continental subspecies or G. gulo as a single Holarctic taxon. Compiled genetic evidence suggests most of North America's wolverines are descended from a single source originating from Beringia during the last glaciation and expanding thereafter, though considerable uncertainty to this conclusion is due to the difficulty of collecting samples in the depleted southern extent of the range. Anatomically, the wolverine is muscular animal. With short legs and rounded head, small eyes and short rounded ears, it more resembles a bear than it does other mustelids. Though its legs are short, its large, five-toed paws with crampon-like claws and plantigrade posture enable them to climb up and over steep cliffs and snow-covered peaks with relative ease; the adult wolverine is about the size of a medium dog, with a length ranging from 65–107 cm, a tail of 17–26 cm, a weight of 5.5–25 kg, though exceptionally large males can weigh up to 32 kg.
Another outsized specimen was reported to scale 35 kg. The males can be twice the females' weight. According to some sources, Eurasian wolverines are claimed to be larger and heavier than North American with average weights in excess of 20 kg but this may refer more to areas such as Siberia, as data from European wolverines shows they are around the same size as their American counterparts; the average weight of female wolverines from a study in the Northwest territories of Canada was 10.1 kg and that of males 15.3 kg. In a study from Alaska, the median weight of ten males was 16.7 kg while the average of two females was 9.6 kg. In Ontario, the mean weight of males and females was 9.9 kg. The average weights of wolverines were notably lower in a study from the Yukon, averaging 7.3 kg in females and 11.3 kg in males because these animals from a "harvest population" had low fat deposits. In Finland, the average weight was claimed as 11 to 12.6 kg. The average weight of male and female wolverines from Norway was listed as 10 kg.
Shoulder height is reported from 30 to 45 cm. It is the largest of terrestrial mustelids. Wolverines have thick, oily fur, hydrophobic, making it resistant to frost; this has led to its traditional popularity among hunters and trappers as a lining in jackets and parkas in Arctic conditions. A light-silvery facial mask is distinct in some individuals, a pale buff stripe runs laterally from the shoulders along the side and crossing the rump just above a 25–35 cm bushy tail; some individuals display prominent white hair patches on their chests. Like many other mustelids, it has potent anal scent glands used for marking territory and sexual signaling; the pungent odor has given rise to the nicknames "skunk bear" and "nasty cat." Wolverines, like other mustelids, possess a special upper molar in the back of the mouth, rotated 90 degrees, towards the inside of the mouth. This special characteristic allows wolverines to tear off meat from prey or carrion, frozen solid. Wolverines are considered to be scavengers.
A majority of the wolverine's sustenance is derived from carrion, on which it depends exclusively in winter and early spring. Wolverines may find carrion themselves, feed on it after the predator has finished, or take it from another predator. Wolverines are known to follow wolf and lynx trails, purportedly with the intent of scavenging the remains of their kills. Whether eating live prey or carrion, the wolverine's feeding style appears voracious, leading to the nickname of "glutton". However, this feeding style is believed to be an adaptation to food scarcity in winter; the wolverine is a powerful and versatile predator. Prey consists of small to medium-sized mammal
The gray fox, or grey fox, is an omnivorous mammal of the family Canidae, widespread throughout North America and Central America. This species and its only congener, the diminutive Channel Island fox, are the only living members of the genus Urocyon, considered to be the most basal of the living canids. Though it was once the most common fox in the eastern United States, still is found there, human advancement and deforestation allowed the red fox to become more dominant; the Pacific States still have the gray fox as a dominant. It is the only American canid, its specific epithet cinereoargenteus means "ashen silver". The gray fox is distinguished from most other canids by its grizzled upper parts, black stripe down its tail and strong neck, while the skull can be distinguished from all other North American canids by its separated temporal ridges that form a U-shape. There is little sexual dimorphism, save for the females being smaller than males; the gray fox ranges from 76 to 112.5 cm in total length.
The tail measures 27.5 to 44.3 cm of its hind feet measure 100 to 150 mm. The gray fox weighs 3.6 to 7 kg, though exceptionally can weigh as much as 9 kg. It is differentiated from the red fox by the lack of "black stockings" that stand out on the latter and the stripe of black hair that runs along the middle of the tail as well as individual guard hairs being banded with white and black; the gray fox displays white on the ears, chest and hind legs. In contrast to all Vulpes and related foxes, the gray fox has oval pupils; the dental formula of the U. cinereoargenteus is 18.104.22.168.1.4.3 = 42. The gray fox appeared in North America during the mid-Pliocene epoch 3.6 million years ago with the first fossil evidence found at the lower 111 Ranch site, Graham County, Arizona with contemporary mammals like the giant sloth, the elephant-like Cuvieronius, the large-headed llama, the early small horses of Nannippus and Equus. Genetic analyses of the fox-like canids confirmed that the gray fox is a distinct genus from the red foxes.
Genetically, the gray fox clusters with two other ancient lineages, the east Asian raccoon dog and the African bat-eared fox. The chromosome number is 66 with a fundamental number of 70; the autosomes include one only pair of metacentrics. Faunal remains at two northern California cave sites confirm the presence of the gray fox during the late Pleistocene. Genetic analysis has shown that the gray fox migrated into the northeastern United States post-Pleistocene in association with the Medieval Climate Anomaly warming trend. Recent mitochondrial genetic studies suggests divergence of North American eastern and western gray foxes in the Irvingtonian mid-Pleistocene into separate sister taxa; the gray fox's dwarf relative, the Channel Island fox, is descended from mainland gray foxes. These foxes were transported by humans to the islands and from island to island, are descended from a minimum of 3–4 matrilineal founders; the genus Urocyon is considered to be the most basal of the living canids. The species occurs throughout most rocky, brushy regions of the southern half of North America from southern Canada to the northern part of South America, excluding the mountains of northwestern United States.
It is the only canid whose natural range spans both South America. In some areas, high population densities exist near brush-covered bluffs; the gray fox's ability to climb trees is shared only with the Asian raccoon dog among canids. Its strong, hooked claws allow it to scramble up trees to escape many predators, such as the domestic dog or the coyote, or to reach tree-bound or arboreal food sources, it can jump from branch to branch. It descends by jumping from branch to branch, or by descending backwards as a domestic cat would do; the gray fox is nocturnal or crepuscular and makes its den in hollow trees, stumps or appropriated burrows during the day. Such gray fox tree dens may be located 30 ft above the ground. Prior to European colonization of North America, the red fox was found in boreal forest and the gray fox in deciduous forest, but now the red fox is dominant in most of the eastern United States since they are the more adaptable species to development and urbanization. In areas where both red and gray foxes exist, the gray fox is dominant.
The gray fox is assumed monogamous. The breeding season of the gray fox varies geographically; the gestation period lasts 53 days. Litter size ranges with a mean of 3.8 young per female. The sexual maturity of females is around 10 months of age. Kits begin to hunt with their parents at the age of 3 months. By the time that they are four months old, the kits will have developed their permanent dentition and can now forage on their own; the family group remains together until the autumn, when the young males reach sexual maturity they disperse. Out of a study of nine juvenile gray foxes, only the males dispersed up to 84 km; the juvenile females stayed within proximity of the den within 3 km and always returned. On the other hand, adult gray foxes showed no signs of dispersion for either gender; the annual reproductive cycle of males has been described through ep
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae. The scientific name Crotalus is derived from the Greek κρόταλον, meaning "castanet"; the name Sistrurus is the 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. The 36 known species of rattlesnakes have between 65 and 70 subspecies, all native to the Americas, ranging from southern Alberta and Saskatchewan and southern British Columbia in Canada to central Argentina. Rattlesnakes are predators that live in a wide array of habitats, hunting small animals such as birds and rodents. Rattlesnakes receive their name from the rattle located at the end of their tails, which makes a loud rattling noise when vibrated that deters predators or serves as a warning to passers-by. However, rattlesnakes fall prey to hawks, king snakes, a variety of other species. Rattlesnakes are 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 threatened by habitat destruction and extermination campaigns. Rattlesnakes are the leading contributor to snakebite injuries in North America. However, rattlesnakes bite unless provoked or threatened. Rattlesnakes are native to the Americas, living in diverse habitats from southwestern Canada to central Argentina; the large majority of species lives in Mexico. Four species may be found east of the Mississippi River, two in South America. In the United States, the states with the most types of rattlesnakes are Arizona. Rattlesnakes are found in every type of habitat capable of supporting terrestrial ectothermic vertebrates, but individual species can have specific habitat requirements, only able to live within certain plant associations in a narrow range of altitudes. Most species live near rocky areas. Rocks offer them cover from predators, plentiful prey, open basking areas. However, rattlesnakes can be found in a wide variety of other habitats including prairies, marshes and forests.
Rattlesnakes prefer a temperature range between 80 and 90°F, but can survive temperatures below freezing, recovering from brief exposure to temperatures as low as 4°F, surviving for several days in temperatures as low as 37°F. The most probable ancestral area of rattlesnakes is the Sierra Madre Occidental region in Mexico; the most probable vegetation or habitat of the ancestral area appears to be pine-oak forests. Feeding habits play an important ecological role by limiting the size of rodent populations, which prevents crop damage and stabilizes ecosystems. Rattlesnakes consume mice, small birds, other small animals, they lie in hunt for it in holes. The prey is killed 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, 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 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 powerful, allowing for the digestion of flesh, as well as bone. Optimal digestion occurs when the snake maintains a body temperature between 80 and 85 °F. If the prey is small, the rattlesnake continues hunting. If it was an adequate meal, the snake finds 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 to remain hydrated; the method in which they drink depends on the water source. In larger bodies of water, they submerge their heads and ingest water by opening and closing their jaws, which sucks in water. If drinking dew, or drinking from small puddles, they sip the liquid either by capillary action or by flattening and flooding their lower jaws. Newborn rattlesnakes are preyed upon by a variety of species, including ravens, roadrunners, opossums, coyotes, whipsnakes and racers.
Neonates of the smaller crotaline species are killed and eaten by small predatory birds such as jays and shrikes. Some species of ants in the genus Formica are known to prey upon neonates, Solenopsis invicta do, as well. On occasion, hungry adult rattlesnakes cannibalize neonates; the small proportion of rattlesnakes that make it to their second year are preyed upon by a variety of larger predators including coyotes, hawks, falcons, feral pigs, indigo snakes, kingsnakes. The common kingsnake, a constrictor, is immune to the venom of rattlesnakes and other vipers, 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 on it; the rattlesnake jerks its body about, while bridging its back upwards, fo