Agkistrodon contortrix
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Agkistrodon contortrix is a venomous pit viper species commonly known as the copperhead. It is native to North America.
Description
Adult specimens have a coppery colored head and neck. They are not large snakes, generally about 50 cm long (1.5 ft), but specimens up to 1 m long (3 ft) have been encountered. The body is slender compared to most other pit vipers. There are five clearly defined subspecies. All subspecies have distinctive light and dark brown or redish banding. A. c. mokasen, A. c. contortrix and A. c. phaeogaster have bands that tend to narrow dorsally, giving them an hourglass shape, whereas A. c. laticinctus and A. c. pictigaster generally have bands of uniform width. Intergrading occurs in areas where the subspecies geographic ranges overlap, so pattern variations are commonplace. A. c. pictigaster is known especially for its distinctively patterned underside, with white and black banding.Behavior and reproduction
Like all pit vipers, A. contortrix is an ambush predator: it take up a promising position and waits for suitable prey to arrive. Roughly 90% of its diet consists of small rodents, such as mice and voles.A. contortrix breeds in late summer, but not every year: sometimes a female will produce young for several years running, then not breed at all for a time. They give birth to live young about 20 cm long: a typical litter is 4 to 7, but it can be as few as one or as many as 20. Their size apart, the young are similar to the adults, but lighter in color, and with a yellow-marked tip to the tail, which is used to lure lizards and frogs.
Venom
A. contortrix is venomous, but almost never deadly to humans and are generally non-aggressive. They have an efficient venom delivery system, with long fangs mounted at the front of the jaw which swivel back to allow the snake to close its mouth. The genus name Agkistrodon is derived from the Greek agkistron (fish-hook) and odon (tooth); a reference to the curved fangs. The primary role of the venom and fangs is to kill their food items quickly; the amount of venom a single copperhead can deliver is insufficient to kill an otherwise healthy adult human. It is capable of, however, producing intense pain, tingling, throbbing, swelling, and severe nausea. While rarely lethal, a copperhead bite can be damaging to muscle and bone tissue, especially when the bite occurs in the outer extremities such as the hands and feet, areas in which there is not a large muscle mass to absorb the venom. A bite from any venomous snake should be taken very seriously and immediate medical attention sought.In the state of Missouri about 200 people suffer from snakebite each year, mostly from copperheads, but there are no records of deaths resulting.[[Citing sources citation needed]] Although, technically the antivenom CroFab could be used to treat an envenomation from a copperhead, it is not typically administered as the risk of complications through an allergic reaction to the treatment is greater than the risk from the snakebite itself. Pain management, antibiotics, and medical supervision in the case of complications is typically the course of action.[link]
Frequency of Encounters
Commonly, the average person will assume any reddish or brownish snake is a copperhead. This is far from the case. Many harmless snakes, such as the brown snake (genus Storeria), or water snake (genus Nerodia) are frequently mistaken for copperheads. Copperheads are primarily a terrestrial species, and though quite capable swimmers, they are rarely found swimming.
The easiest way to tell venomous snakes from non-venomous in North America is by the shape of their pupils. All dangerously venomous snakes in North America, with the exception of the coral snake, are pit vipers and have a vertical type pupil, like a cat's eye. Most non-venomous snakes in North America have a round pupil like a human. However, some harmless, nocturnal Colubrids have vertical elliptical pupils.
Safety
The best way to avoid being bitten when in the outdoors in copperhead country is to be aware of their typical behavior and habitats and take appropriate precautions. Like most North American vipers, copperheads prefer to avoid humans and, given the opportunity, will leave the area without biting; however, unlike the rattlesnake, they are unable to make an audible warning of their presence.Copperheads often tend to "freeze" instead of slithering away; thus, many bites come from people unknowingly stepping on or near them. This tendency to freeze likely evolved because of the extreme effectiveness of their camouflage. When laying on dead leaves or red clay they can be almost impossible to notice. They will frequently stay still even when approached closely, and will only generally strike if physically harassed or trod upon.
Small hiding places such as niches in rock walls, woodpiles, etc., should be examined before hands or feet are placed in them, and one should stand on or bend over a fallen log to look for a snake instead of blindly jumping over. Favorite habitats include rocky hillsides above wooded streams. In the south, copperheads are nocturnal during the hot summer months, but are commonly active during the day during the spring and fall. A pair of stout leather hiking boots might blunt the strike of a snake. Heavy tramping of feet will cause vibrations in the ground that can alert snakes to peoples' presence, giving them time to quietly escape. The majority of snakebite incidents are the result of attempting to handle the snake or attacking it with an object.
If bitten, one should not apply a tourniquet or suck blood from the bite — the victim should be kept calm and be transported to a hospital as quickly as possible. A tourniquet will increase tissue damage in the area of the bite and may even create the need to amputate a bitten limb that may have otherwise been saved. Never cut where the bite is.
Subspecies
- The Northern copperhead (Agkistrodon contortrix mokasen, is found throughout the northeastern United States It is reddish brown overall, with a number of chestnut-colored "hourglass" markings running down its back. Also called Upland moccasin.
- The Southern copperhead (Agkistrodon contortrix contortrix) of the south-eastern United States is generally paler and has more clearly defined markings, sometimes including a row of dark triangular marks the sides of the body.
- The Broad-banded copperhead (Agkistrodon contortrix laticinctus) of Kansas, Oklahoma and Texas tends to be smaller than the Northern and Southern races, rarely being longer than about 75 cm, and has wide bands across the back which are not narrowed at the spine.
- The Trans-Pecos copperhead (Agkistrodon contortrix pictigaster) is similar to the Broad-banded, is of equal size, and has slightly hourglass-shaped markings, usually with a lighter patch at the base of each band.
- The Osage Copperhead (Agkistrodon contortrix phaeogaster) of the mid-west has the same typical reddish-brown coloring and dark bands as the other subspecies.
See also
External links
- [EMBL Reptile Database - Family Viperidae]
- Species [Agkistrodon contortrix] at the [EMBL Reptile Database]
Gallery
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