Copperhead

## Description

The copperhead (Agkistrodon contortrix) is a venomous pit viper endemic to eastern North America; it is a member of the subfamily Crotalinae in the family Viperidae. As a common species within its range, it may be encountered by humans. Unlike other viperids, copperheads often "freeze" instead of slithering away, due to their habit of relying on excellent camouflage, rather than fleeing. Bites occur due to people unknowingly stepping on or near them.

## Appearance

The body of this snake is relatively stout and the head is broad and distinct from the neck. The skin is pale tan to pinkish-tan in color and becomes darker towards the foreline, overlaid with a series of 10-18 crossbands. These crossbands are light tan to pinkish-tan to pale brown in the center, but darker towards the edges. A series of dark brown spots are also present on the flanks, next to the belly, and are the largest and darkest in the spaces between the crossbands. At the base of the tail are one to three (usually two) brown crossbands followed by a gray area. In juveniles, the pattern on the tail is more distinct: 7-9 crossbands are visible, while the tip is yellow. Males in this species are usually larger than females.

## Distribution

Copperheads are found in North America; their range within the United States is in Alabama, Arkansas, Connecticut, Delaware, Northern Florida, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Mississippi, Missouri, Nebraska, New Jersey, New York, North Carolina, Ohio, Oklahoma, Pennsylvania, South Carolina, Tennessee, Texas, Virginia, and West Virginia. In Mexico, they occur in Chihuahua and Coahuila. These snakes occupy a variety of different habitats. In most of North America, they favor deciduous forests and mixed woodlands. They are often associated with rock outcroppings and ledges but are also found in low-lying, swampy regions. In the states around the Gulf of Mexico, however, copperheads are also found in coniferous forests. In the Chihuahuan Desert of West Texas and northern Mexico, they occur in riparian habitats, usually near permanent or semipermanent water and sometimes in dry arroyos (brooks).

## Lifestyle

Copperheads are highly terrestrial but may also climb trees to gorge on cicadas. These snakes hunt alone but during the winter, they hibernate in dens, caves, or limestone crevices, often together with Timber rattlesnakes and Black rat snakes. They also can be found in groups near den sites, while basking in the sun, drinking, eating, and during the breeding season. During hot summer months, copperheads are active during the night but in the spring and fall, they become diurnal. These snakes are ambush predators and hunt by waiting for prey to arrive. However, when hunting insects, copperheads actively pursue their prey. Juveniles use a brightly colored tail to attract frogs and perhaps lizards; this behavior is called caudal luring. Copperheads prefer to avoid humans and leave the area without biting. They often "freeze" instead of escaping, most likely due to their camouflage. When lying on dead leaves or red clay, they can be almost impossible to notice. They frequently stay still even when approached closely, and generally strike only if physical contact is made. When feeling threatened copperheads will vibrate their tail. They are capable of vibrating their tail in excess of 40 times per second - faster than almost any other non-rattlesnake snake species.

## Venom

Although venomous, copperheads are generally not aggressive and bites are rarely fatal. Their venom has an estimated lethal dose of around 100 mg, and tests on mice show its potency is among the lowest of all pit vipers, and slightly weaker than that of its close relative, the cottonmouth. Copperheads often employ a "warning bite" when stepped on or agitated and inject a relatively small amount of venom, if any at all. "Dry bites" involving no venom are particularly common with the copperhead, though all pit vipers are capable of a dry bite. Pit vipers that are dead are still dangerous and capable of producing venom in amounts that necessitate the use of antivenom.

Bite symptoms include extreme pain, tingling, throbbing, swelling, and severe nausea. Damage can occur to muscle and bone tissue, especially when the bite occurs in the outer extremities such as the hands and feet, areas in which a large muscle mass is not available to absorb the venom. A bite from any venomous snake should be taken very seriously and immediate medical attention sought, as an allergic reaction and secondary infection are always possible.

The venom of the southern copperhead has been found to hold a protein called "contortrostatin" that halts the growth of cancer cells in mice and also stops the migration of the tumors to other sites. However, this is an animal model, and further testing is required to verify safety and efficacy in humans.

The antivenom CroFab is used to treat copperhead envenomations that demonstrate localized or systemic reactions to the venom. As many copperhead bites can be dry (no envenomation), CroFab is not given in the absence of a reaction (such as swelling) due to the risk of complications of an allergic reaction to the treatment. The antivenom can cause an immune reaction called serum sickness. Pain management, tetanus immunization, laboratory evaluation, and medical supervision in the case of complications are additional courses of action. In 2002, an Illinois poison control center report on the availability of antivenom stated it used 1 Acp to 5 Acp depending on the symptoms and circumstances.

## Diet

The copperhead is a carnivorous species. Most of its diet consists of small rodents, such as mice and voles. It also hunts insects, frogs, lizards, salamanders, and other small creatures.

## Reproduction

Copperheads have a polygynandrous (promiscuous) mating system in which both sexes have multiple partners. Males have longer tongue tine lengths than females during the breeding season, which may aid in the chemoreception of males searching for females. These snakes breed in the spring and fall but not every year; sometimes females produce young for several years running, then do not breed at all for a time. Females give birth to live young, each of which is about 20 cm (7.9 in) in total length. The typical litter size is 4 to 7, but as few as one, or as many as 20 may be seen. The gestation lasts 3 to 9 months. Snakelets are independent at birth and ready to fend for themselves. Their size apart, the young are similar to the adults but lighter in color, and with a yellowish-green-marked tip to the tail, which is used to lure lizards and frogs. Copperheads become reproductively mature when they are 3 to 4 years old.

## Population

### Population threats

Copperheads don't face any major threats at present. However, locally they suffer from habitat loss and degradation, collection for the pet trade, and killing by humans.

### Population number

According to IUCN, the Copperhead is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.

### Ecological niche

Like all snakes, Copperheads play a very important ecological role in their environment. Due to their diet, they help control populations of small rodents they prey on.