snakes‎ > ‎

North America's most venomous snakes


Surveys disagree on the number of venomous snake bites recorded every year in North America - between 1400 and 8000 - and on the number of deaths resulting from these bites - between 1 and 5.
Statistics also suggest that only about 18 percent of snake bites in the USA are from venomous species.
Of course even 1 death is always 1 too many for the person concerned, but if put into perspective or compared to all the other possible causes of death, one can consider that human deaths caused by snake bites are virtually non existent in North America.
In fact, few venomous species occur in North America and only 4 of them pose a hazard to humans - though none of them would rank among the most venomous in the world.

North America's venomous snakes fall into two groups: Coral Snakes and Pit Vipers (which include Rattlesnakes, Cottonmouth, Copperhead)


1) CORAL SNAKES (Micrurus)

Coral snakes are related to the cobra family and can potentially be extremely venomous though they are generally shy and slow to bite. Coral snakes thus account for fewer than 1% of venomous snakebites in the United States with most people bitten while handling the snakes intentionally. On top of all, Coral Snakes cannot strike quickly and must hang on for a brief period to achieve significant envenomation in humans. Because of this relatively primitive venom delivery apparatus, it is estimated that 60% of those bitten by North American coral snakes are not envenomed.
There has been no deaths from Coral Snake bites in the United States since antivenin became available. Before, bites killed 10% of the victims from respiratory or cardiovascular failure. People who survive the bite may need respiratory support for up to a week and may suffer persistent weakness for weeks or even months.

Those pretty snakes are rather short - usually less than 40 inches or 1 meter - and easy to recognize with their distinctive alternating black, red and yellow bands.

Though Coral Snakes are often confused with a number of harmless species, notably the Kingsnakes - that mimic their coloration-, the Coral Snake's colored bands are arranged in a unique sequence, which can be remembered with these lines: "Red on yellow, will kill a fellow. Red touches black, venom lack" -Unfortunately, if this saying works well for North American species is must be taken with caution for snakes occurring further South as some non-venomous species also have red bands touching yellow bands, and some Corals only have two colors-.

There are only three species of Coral Snakes in North America:

- Eastern Coral Snake (Micrurus fulvius)

Common throughout most of its range, the Eastern Coral Snake is, nevertheless secretive and therefore seldom seen. It can be found in west central Mississippi and North Carolina and south to the Florida Keys.
It frequents a variety of habitats, such as wooded and scrub areas, palmettos and swamps, likes Coral Snakes like to hide in protected places such as beneath debris or flatwood, and it even ventures into residential locations.
The Eastern Coral Snake has short fangs that are fixed in an erect position and often has to chew to release its venom into a wound. Its neurotoxic venom is very powerful, causing respiratory paralysis in the victim, who succumbs to suffocation.

- Coral Snake (Micrurus tener)

Found in Texas, Louisiana and Arkansas. It is not always considered a seperate species from Micrurus fulvius,which is found on the other side of the Mississippi river.

- Arizona Coral Snake or Sonoran Coral Snake or Western Coral Snake (Micruroides euryxanthus)

It occurs in arid and semiarid areas of central and southern Arizona, extreme southwestern New Mexico and southward to western Mexico (where it is called Corallilo). It occupies different types of habitat: thornscrub, desert-scrub, woodland, grassland, farmland and especially rocky areas from sea level to 5800 feet (1770 m).
This mostly nocturnal species is also active on overcast days and feeds essentially on other snakes.

The venom of the Arizona Coral Snake is similar to that of the cobra. However, due to the small size of the snake - it measures 13 to 21 inches, or 33-53 cm which translates into less venom-, its smaller mouth, and small fangs -less effective means of delivery-, its bite is not as dangerous to humans as that of rattlesnakes. In facr, no deaths have been attributed to this snake.



2) PIT VIPERS

Pit Vipers can be found throughout most of the United States. That group - which includes rattlesnakes, copperheads and cottonmouths - have in common a "pit", or hole, between their eyes and nostrils which is heat-sensitive and enables the snake to locate warm-blooded prey in total darkness.

2.1 Rattlesnakes (Crotalus, Sistrurus)

Rattlesnakes are a truly American family of pit vipers since they are not found in the Old World and all but two of the existing 27 species are found in the U.S. or Mexico.
They are divided between two genera based on their head scales: "Crotalus" have numerous small scales on their heads while "Sistrurus" have large scales (plates) on their heads.
Rattlesnakes vary in size from the 18 inches or 45 centimeters of the Pygmy rattler to the 84 inches or more than 2 meters of the Eastern Diamondback. Rattlesnakes possess a unique rattle although many snakes have the tail vibrating behavior.

Rattlesnakes can be anything from mildly venomous to extremely venomous. Bites from some Rattlesnake can be deadly to humans.

- Eastern Diamondback Rattlesnake (Crotalus adamanteus)

This species inhabits the coastal areas of North and South Carolina, Louisiana and Florida (including the Keys). It is found in pine woods, flatwoods, scrubs, palmettos or swamps, and it is capable of swimming many miles out in the Gulf of Mexico, to reach some of the islands off the Florida coast.

The Eastern Diamondback can reach up to 84 inches - 2.4 meters - which makes it the largest venomous species in North America. It has no natural enemies and is the top of the food chain. This species can be quite irritable and readily defends itself if it feels threatened. Its venom is potent and haemotoxic, causing great pain and damage to tissue.

The Eastern Diamondback was almost selected as the National Animal of the U.S, instead of the Bald Eagle.

- Western Diamondback Rattlesnake (Crotalus atrox)

This very aggressive rattlesnake is found from Arkansas to southern California, in Oklahoma, Texas, New Mexico, and Arizona, and is very common over its range. It lives in grasslands, deserts, woodlands, and canyons.
The Western Diamondback is known to stand its ground and defend itself vigorously, the first step being when it coils and rattles. This rattlesnake is responsible for many bites and injects a large amount of venom when it does bite. It is therefore considered one of the most dangerous snakes in North America. Its venom is haemotoxic and causes considerable pain and tissue damage.

- Mojave Rattlesnake (Crotalus scutulatus)

This rattlesnake can be found in arid regions, deserts and rocky hillsides from sea level to 2400-meter elevations, in the Mojave Desert in California, as well as in Nevada, southwest Arizona, Texas and Mexico.
Despite its moderate size, it delivers a very serious bite - and have caused death - with a mostly neurotoxic venom which affects the central nervous system.

Other species of North American rattlesnakes include Sidewinder (Crotalus cerastes), Lower California rattlesnake (Crotalus enyo), Timber Rattlesnake (Crotalus horridus), Rock Rattlesnake (Crotalus lepidus), Speckled Rattlesnake (Crotalus mitchellii), Blacktail Rattlesnake (Crotalus molossus), Twin-spotted Rattlesnake (Crotalus pricei), Red Diamond Rattlesnake (Crotalus ruber), Tiger Rattlesnake (Crotalus tigris), Western Rattlesnake (Crotalus viridis), Ridgenose Rattlesnake (Crotalus willardi), Massasauga (Sistrurus catenatus), Pigmy Rattlesnake (Sistrurus miliarius).

2.2 Cottonmouths or Water Moccasins

The name cottonmouth comes from the fact that their opened mouths bear a resemblance to cotton. These 30 to 48 inches - 75 to 120 centimeters - snakes are usually thought to be aggressive but studies have shown that this is not really true.

- Cottonmouth (Agkistrodon piscivorus)

Located in the southeast United States - Southeast Virginia, west central Alabama, south Georgia, Illinois, east central Kentucky, south central Oklahoma, Texas, North and South Carolina, Florida, and the Florida Keys -, this snake is one of the most common snakes in Florida. It a semi-aquatic species living in swamps, lakes, rivers, ditches and brackish waters where it is easily mistaken for other harmless water snakes.
A Cottonmouth often stands its ground and is famous for flashing the inside of its mouth as a warning sign - hence the name 'Cottonmouth'. If harassed it will deliver a fairly potent bite with a haemotoxic venom. Bites are prone to gangrene.

2.3 Copperheads or Highland Moccasins

These short snakes are especially found in Eastern parts of the United States-where they are the most common venomous snakes -, notably Alabama, Missouri and Arkansas.
They derive their name from the copper-like coloring of their head.

Copperheads rely upon camouflage and cover for safety. In case of a danger, they usually freeze and remain motionless until the threat has passed. Unless a person steps on them, grasps them, or otherwise comes in very close contact with them, Copperheads will not usually bite.
The relative abundance of Copperheads and their occurrences near human habitations is the reason bites from Copperheads are the most numerous among snake bites in the Eastern United States. Luckily this snake is mildly venomous and bites are very seldom fatal. However, a bite may still have serious consequences.

There are 5 species of Copperheads in North America. Western species seem to have a higher venom toxicity and are much smaller than the Northern and Southern Copperheads.

- American Copperhead (Agkistrodon contortrix)

This snake is very common over much of its wide range: Eastern Gulf States, Texas, Arkansas, Maryland, North Florida, Illinois, Oklahoma, Kansas, Ohio, New York, Alabama, Tennessee, and Massachusetts.
It is found in wooded and rocky areas as well as in mountainous regions where it is well camouflaged and hard to spot.
Tough Copperheads are not known for their aggressive nature, they will defend themselves vigorously and bite when stepped on or if someone accidentally lies down next to them. Their venom is haemotoxic.

Sources:

http://www.backyardnature.net/snakvenm.htm

http://www.venomous.com/
North American Venomous

http://www.venomoussnakes.net/
Venomous snakes - poisonous snakes

http://www.wilderness-survival.net/snakes-5.php
POISONOUS SNAKES OF THE AMERICAS

http://www.desertmuseum.org/books/nhsd_coral_snake.php

http://www.snakesandfrogs.com/scra/snakes/copperh.htm
VENOMOUS SERPENTS and HUMANS

http://www.pitt.edu/~mcs2/herp/SoNA.html

http://emedicine.medscape.com/article/771701-overview
Snake Envenomation, Coral

Comments