The Copperhead () is found in 28 states throughout the central and eastern United States. Their geographic range extends from southern New England to the eastern parts of Kansas and Nebraska, and then south to eastern Texas to the Florida panhandle. They are also found in localized parts of western Texas and northern Coahuila and Chihuahua, Mexico.
Copperhead subspecies are recognized by slight changes in color pattern shape and hue. Five subspecies are recognized:
Northern Copperhead (A. c. mokasen) - Widely extends throughout the United States, southern New England (USA) to Coahuila and Chihuahua, Mexico.
Southern Copperhead (A. c. contortrix) - Extends through Massachusetts, westward to Texas and southeastern Nebraska.
Broad Banded Copperhead (A. c. laticinctus) - Confined to southern border of Kansas and Oklahoma, and central Texas.
Trans-Pecos Copperhead (A. c. pictigaster) - Confined to the Trans-Pecos (far west Texas) region as well as northeastern Mexico.
Osage Copperhead (A. c. phaeogaster) - Found in the central region of the United States, where they are most prominent in Missouri and eastern Kansas.
Recent molecular analyses using mitochondrial DNA however suggests that there are three clades within the species that have relatively low divergence and do not correspond to the above-mentioned subspecies designations. Additional analyses are needed to resolve genetic lineages within the species. (Conant and Collins, 1998; Douglas, et al., 2009; Gloyd and Conant, 1990)
The broad geographic range ofis associated with an array of habitats in which they occur. In the northeast and Appalachians they are typically found in deciduous forests and open woodlands with rock outcrops and hilly terrain. Areas with downed woody vegetation are also favored. On the southern coastal plain, they can be found in low, wet woodlands including the edges of swamps. Further west, they are associated with riparian areas in mixed woodlands with stream beds and arroyos. They also associate with man-made environments including construction areas, sawdust piles, and suburban neighborhoods. Their close proximity with humans likely contributes to their status as the snake species with the highest number of bites within the United States.
Overwintering sites are often south- or west-facing and include rock crevices, abandoned mines, caves, hollow logs, stumps, and building foundations. Gravid females also tend to use such sites and prefer microhabitats with higher temperature profiles. (Carter, 2013; Ernst and Ernst, 2011; Smith, et al., 2009; Szalay, 2014)
individuals are known for their distinctive reddish-brown bodies with a crossband pattern consisting of tan, copper, and rich brown colors that extend throughout the body. Adult copperheads average 76 cm in length and are normally described as heavy-bodied snakes. Copperheads are sexually dimorphic, as males tend to have longer bodies than females. The head is very distinct from the rest of the body and has a solid, rich brown color. Temperature-sensitive pit organs are present below the midline between the eye and the nostril. Although copperheads are venomous, their venom is somewhat mild compared to other snake species and is usually not fatal to healthy human adults.
Juveniles have very similar crossband patterns as adults but are much grayer in color. Besides their color differences, juveniles also have a yellow tinted tail tip until they reach the age of 3 to 4 years. The tinted tail is also found in other Agkistrodon species (Cottonmouth, Agkistrodon piscivorus, for example) and appears to be used to lure small prey within striking distance by mimicking caterpillar movements. Juveniles and adults have fully functioning fangs that can deliver proportionately equal amounts of venom to their prey. (Andrews and Wilson, 2014; Ernst and Ernst, 2011; Krysko and King, 2014)
Like other viperids, female copperheads are viviparous. Eggs are thought to be predominantly lecithotrophic (deriving a majority of energy from yolk), but there is recent evidence that amino acids can be transferred from the mother to the developing embryo. Upon parturition, the yolk sac membrane encasing a neonate is usually broken, releasing fully-developed young. Newborn copperheads are capable of finding and capturing their own prey at the time of birth. (Van Dyke and Beaupre, 2012)
While copperheads generally reproduce sexually, it has also been shown that it is one of a handful of vertebrates that can reproduce asexually through facultative parthenogenesis. Researchers have found that females kept in captivity in the absence of males periodically produce one fully developed neonate along with a group of aborted ova. It is hypothesized that parthenogenesis occurs via terminal fusion automixis, a mechanism whereby the reduced ovum combines with the second polar body following the second round of cell division in meiosis. Two primary lines of evidence support this interpretation. First, copperheads, and other advanced snakes, have a ZZ:ZW mode of genetic sex determination where males are the homogametic sex (ZZ). Observations of parthenogenesis within the group have so far found only male offspring. Second, molecular evidence shows that while the mother is heterozygous for neutral genetic loci (microsatellites), the parthenogens are homozygous across loci. These results make it highly unlikely that a captive female stored sperm from a mate prior to capture (see below) for fertilization. Notably, facultative parthenogenesis has also been documented in the wild which suggests that this reproductive mode is not a byproduct of captivity and may be fundamental to the species' reproductive biology. (Booth and Schuett, 2011; Booth, et al., 2012; Jordan, 2015; Schuett, et al., 1997)
Males search for mates during the breeding season by detecting pheromones in the air with their tongues. Males have longer tongues than females – a sexual size dimorphism that may aid in the search for a mate. Male to male competition can be fierce and involves various types of combat. Most combat occurs through the lifting of the anterior half of the body and is followed by a series of intertwined lunges and twirls. The male that is able to keep his head lifted and raised the longest is deemed the winner and gets access to the nearby female and courtship ensues.
After the male has earned the mating right to pursue the female, the male must participate in another intertwining battle with the female. Both sexes lift the anterior half of their bodies (similar to the male to male combat stance) and the male rubs his chin across the female's back while flicking his tongue. A receptive female will raise her tail and open her cloaca as an invitation for the male. Receptive females have been known successfully mate with multiple males resulting in multiple paternity of a litter. If a female is not interested, the female will swing her tail and continuously move to avoid copulation. (Schuett and Duvall, 1996; Schuett and Gillingham, 1988; Schuett and Gillingham, 1989; Smith, et al., 2008)
Mostpopulations that have been studied have two mating seasons: one from February to May and another from August to October. The latter mating season usually does not result in immediate fertilization, as females are capable of storing sperm over the winter for use in fertilization of ova in the subsequent spring. Research on a northern population at the edge of the geographic range do not show spring breeding.
Copperheads of both sexes reach sexual maturity at 3 to 4 years of age. Once reaching maturity, females may breed annually but it is also common for them to skip one or two seasons following parturition. It is hypothesized that this pattern depends on local food availability. Following a gestation period that averages 83 days, commonly 4 to 8 neonates are produced but litter size can range from 1 to 21 offspring with larger and older mothers tending to produce larger litters. Neonate size is correlated with maternal size, with total body length and body mass averaging 20.6 cm and 10.6 g, respectively. (Ernst and Ernst, 2011; Fitch, 1960; Schuett and Gillingham, 1986; Smith, et al., 2009)
The primary parental investment made by copperheads is the energy used by females to yolk eggs and carry embryos during gestation. Upon birth, neonates may stay with their mother for several days or until their first shed. Males show no parental investment. (Ernst and Ernst, 2011; Fitch, 1960; Greene, et al., 2002)
Records of captive copperheads suggest long lifespans, ranging from 20 to 29 years. Life table analysis using data from a wild population in Kansas projects a maximum lifespan of 15 years, while the oldest snake wild snake recorded lived 18 years. (Ernst and Ernst, 2011; Fitch, 1960; Vial, et al., 1977)
timber rattlesnakes, eastern racers, and eastern rat snakes). When emerging in the spring, individuals will tend to bask close to the hibernaculum for several weeks before becoming more active. Hibernacula are often outside the feeding range of the snake during the activity period, necessitating relatively long movements to and from hibernacula on a seasonal basis.is active from March or April to early November in the northern part of its range. During the winter, they have been observed to bask on warm days in December and January. Although copperheads have been shown to hibernate singly, communal hibernacula are common and may include other species (
On daily basis, copperheads are primarily active during daylight hours during the spring and fall. During the summer months, they become crepuscular or nocturnal to hunt during cooler evening hours. However, copperheads carefully select their resting habitats during daylight hours to ensure thermoregulation of preferred body temperatures of 23 to 31 degrees Celsius. Though they are most often found on the substrate surface, snakes have been observed up to 5 meters above-ground in shrubs and small trees to thermoregulate.
Males have been found to have larger activity ranges than females. This difference is most pronounced during the breeding season, and males often show an increase in aggression at this time. It is assumed that increased movement is associated with mate searching by males. Meanwhile, gravid females move shorter distances than non-gravid females and are often found in close proximity to the overwintering site in aggregations of 4 to 6 individuals. (Carter, 2013; Ernst and Ernst, 2011; Sanders and James, 1981; Schuett, et al., 2002; Smith, et al., 2009)
Radiotelemetry studies have indicated that home ranges are greatly influenced by habitat availability in likely association with thermoregulatory opportunities. In accordance with the discussion above on movement, males have larger home ranges (6.0 to 44.0 hectares) than females (0.01 to 15.7 hectares), with non-gravid females having larger home ranges than non-gravid females. (Carter, 2013; Fitch, 1960; Smith, et al., 2009)
Copperheads rely on olfaction for mate searching, and prey and predator detection. Their forked tongue collects chemical signals that are detected on chemoreceptors on the tongue and in the vomeronasal organ located in the dorsal region of the mouth.
In addition, they also use heat-sensitive facial pits to locate the position of primarily endothermic prey. The pits, located on either side of their face, allow estimation of the direction from which the heat source originates. (Ernst and Ernst, 2011; Zug, 2013)
Copperheads are carnivorous, with adults feeding primarily on rodents while juveniles feed on a range of prey items including salamanders, frogs, lizards, small snakes, and insects. Their diet is quite variable and depends on prey availability in different locations and seasons.
Adults rely on crypsis and ambush hunting to attack prey, and therefore do not travel far while hunting. Prey is detected through chemoreceptors in the tongue, heat-sensitive facial pits, and vision. Attacks are rapid with larger snakes able to deliver more venom to the prey. The venom is primarily hemolytic, causing massive hemorrhage and tissue lysis at the site of injection. Laboratory studies have reported that mice injected with copperhead venom are unable to move for 30 to 60 minutes. Large prey require tracking after they have been bit, while smaller prey can be held in the mouth of a copperhead until it dies. Juvenile copperheads differ from adults in predatory behavior by stalking prey but they have been reported to lure small animals with their yellow tail. (Conant and Collins, 1998; Ernst and Ernst, 2011)
Copperheads have many predators and are most vulnerable when young. Multiple snake taxa, including kingsnakes, racers, and cottonmouths prey on copperheads. They can also be preyed upon by bullfrogs, alligators, American crows, hawks, owls, opposums, coyotes, and feral cats.
To avoid predation, copperheads stay still and hide under leaves, brush, and cover, including man-made structures. When forced to expose themselves for thermoregulation, copperheads further rely on their markings for camouflage to avoid detection. If threatened, copperheads may vibrate the tip of their tail to mimic a rattlesnake, and will strike when sufficiently threatened. This can usually act as a sufficient deterrent from predation but kingsnakes and opossums are reported to be immune to their venom.
Copperheads play an intermediate role in food webs. They are both predators of many primary and secondary consumers and also prey to a range of secondary and tertiary consumers. Because they have been observed to prey on the most common rodents in their habitat, they may exert top-down control of rodent species diversity. (Ernst and Ernst, 2011)
The components of (Ernst and Ernst, 2011)venom have been frequently investigated for their potential use in pharmaceutical therapies and treatments. For example, contortrostatin, a derivative of copperhead venom, has been suggested to have anti-cancer properties by limiting metastasis and blood vessel development within a tumor.
Copperheads produce the largest number of venomous snake bites per year due in the United States to their association with human-modified habitats, and their ability to avoid detection through cryptic coloration and motionless behavior. Fortunately, their venom is one of the least toxic of all North American snake species. It is estimated that one third of bites produce effects requiring clinical treatment with approximately 10% considered serious. Among many reported symptoms, victims most often experience pain, edema, hemorrhage, fever, and lethargy. Bites very rarely lead to death in humans, children and older adults are considered most vulnerable. (Ernst and Ernst, 2011)
Because they live around people more than most other venomous snakes, copperheads produce the largest number of venomous snake bites per year due in the United States. Fortunately, their venom is one of the least toxic of all North American snake species. It is estimated that one third of bites produce effects requiring clinical treatment with about 10% considered serious. Bites very rarely lead to death in humans, children and older adults are considered most vulnerable. (Ernst and Ernst, 2011)
Copperheads are listed as a species of Least Concern (LC) on the IUCN Red List of Threatened Species as of 2007. Their placement of “Least Concern” can be due to their large population size and/or their large geographic distribution. However, certain areas of the United States are experiencing declines in populations and they are considered endangered in Iowa and Massachusetts. Threats that have been identified include habitat destruction, invasive plants, insecticide application, and road mortality. (Carter, 2013; Ernst and Ernst, 2011; Frost, et al., 2007)
Anna Hartsuff (author), Indiana University-Purdue University Fort Wayne, Mark Jordan (editor), Indiana University-Purdue University Fort Wayne.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
flesh of dead animals.
uses smells or other chemicals to communicate
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
(as keyword in perception channel section) This animal has a special ability to detect heat from other organisms in its environment.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
development takes place in an unfertilized egg
chemicals released into air or water that are detected by and responded to by other animals of the same species
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
mature spermatozoa are stored by females following copulation. Male sperm storage also occurs, as sperm are retained in the male epididymes (in mammals) for a period that can, in some cases, extend over several weeks or more, but here we use the term to refer only to sperm storage by females.
living in residential areas on the outskirts of large cities or towns.
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
an animal which has an organ capable of injecting a poisonous substance into a wound (for example, scorpions, jellyfish, and rattlesnakes).
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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