Kamis, 28 Mei 2015

Crotalus horridus, commonly known as timber rattlesnake, canebrake rattlesnake or banded rattlesnake, is a species of venomous pit viper found in the eastern United States. This is the only rattlesnake species in most of the populous northeastern United States. No subspecies is currently recognized.


Crotalus horridus

Adults usually grow to total length of 91â€"152 cm (35.8â€"59.8 in). Most adult timber rattlesnakes found measure less than 100 to 115 cm (39 to 45 in) in total length and weigh on average between 500 and 1,500 g (1.1 and 3.3 lb), often being towards the lower end of that weight range. The maximum reported total length is 189.2 cm (74.5 in) (Klauber, 1956). Holt (1924) mentions a large specimen caught in Montgomery County, Alabama, which had a total length of 159 cm (62.6 in) and weighed 2.5 kg (5.5 lb). Large specimens can reportedly weigh as much as 4.5 kg (9.9 lb).

The dorsal scales are keeled and arranged in 21â€"26 scale rows at midbody (usually 25 rows in the southern part of its geographic range, and 23 rows in the northern part). The ventral scales number 158-177 in males and 163â€"183 in females. Males have 20â€"30 subcaudal scales, while females have 15â€"26. The rostral scale is normally a little higher than it is wide. In the internasal-prefrontal area there are 4â€"22 scales that include 2 large, triangular internasal scales that border the rostral, followed by 2 large, quadrangular prefrontal scales (anterior canthals) that may contact each other along the midline, or may be separated by many small scales. Between the supraocular and internasal, only a single canthal scale is present. There are 5â€"7 intersupraocular scales. The number of prefoveal scales varies between 2 and 8. Usually the first supralabial scale is in broad contact with the prenasal scale, although slightly to moderately separated along its posteroventral margin by the most anterior prefoveals.

Dorsally, they have a pattern of dark brown or black crossbands on a yellowish brown or grayish background. The crossbands have irregular zig-zag edges, and may be V-shaped or M-shaped. Often a rust-colored vertebral stripe is present. Ventrally they are yellowish, uniform or marked with black. Melanism is common, and some individuals are very dark, almost solid black.

Geographic range

Crotalus horridus

Found in the eastern United States from southern Minnesota and southern New Hampshire, south to east Texas and north Florida.

Its historic range includes southern Ontario and southern Quebec in Canada, but in May 2001, the Canadian Species at Risk Act listed it as extirpated in Canada. A Canadian government sponsored recovery strategy is currently under study to support the reintroducing of this predator of many pests to its former Canadian habitat.

Although several experts disagree, many were found in some of the thick forest areas of central and southeastern Iowa, mostly within the Mississippi, Skunk, Iowa, and Des Moines River valleys, in several places in these areas; bites from timber rattlesnakes have been widespread, especially in a localized area of Geode State Park, in southeastern Henry County, along Credit Island Park, in southern Scott County, and in the forested areas of southern Clinton County.

In Pennsylvania, it is not found west of Chestnut Ridge, which is in the Laurel Highlands, nor is it found in the southeastern corner of the state. Thus, its range does not include the areas of Philadelphia and Pittsburgh, the two largest cities in Pennsylvania. C. horridus is extinct in Maine and Rhode Island and is almost extinct in New Hampshire.


Generally, this species is found in deciduous forests in rugged terrain. During the summer, gravid (pregnant) females seem to prefer open, rocky ledges where the temperatures are higher, while males and nongravid females tend to spend more time in cooler, denser woodland with more closed forest canopy.

Female timber rattlers often bask in the sun before giving birth, in open rocky areas known as "basking knolls".

During the winter, timber rattlesnakes hibernate in dens, in limestone crevices, often together with copperheads and black rat snakes.


Their prey are mainly small mammals, but may include small birds, frogs, mice, other small animals, or other snakes. Although capable of consuming other rattlesnakes, the most common snakes they eat are garter snakes. Like most rattlesnakes, timber rattlesnakes are known to utilize chemical cues to find sites to ambush their prey and will often strike their prey and track them until they can be consumed. The primary foods by genera of timber rattlesnakes were as follows: Peromyscus (33.3%), Microtus (10.9%), Tamias (qv) (10.6%), Sylvilagus (10.4%), Sigmodon (5.3%) and Sciurus (4.2%). Based on examination of the snout-to-vent length, it was found that juvenile timber rattlesnakes differed slightly in dietary preferences from adult rattlesnakes, being more likely to consume smaller prey such as shrews (averaging 8 g (0.28 oz) and unable to attack subadult eastern cottontail rabbits (averaging 500â€"1,000 g (1.1â€"2.2 lb) but Peromyscus was the number one prey item for both young and adult rattlesnakes.


Crotalus horridus

Potentially, this is one of North America's most dangerous snakes, due to its long fangs, impressive size, and high venom yield. This is to some degree offset by its relatively mild disposition and long hibernation period. Before striking, they often perform a good deal of preliminary rattling and feinting. Cist (1845) described how he lived in western Pennsylvania for many years, and the species was quite common there, but in all that time, he heard of only a single death resulting from its bite.

Considerable geographic and ontogenetic variation occurs regarding the toxicity of the venom, which can be said for many rattlesnake species. Four venom patterns have been described for this species: Type A is largely neurotoxic, and is found in various parts of the southern range. One effect of the toxin can be generalized myokymia. Type B is hemorrhagic and proteolytic, and is found consistently in the north and in parts of the southeast. Type A + B is found in areas where the aforementioned types apparently intergrade in southwestern Arkansas and northern Louisiana. Type C venom has none of the above components and is relatively weak.

The neurotoxic component of the type A venom is referred to as canebrake toxin, and is a phospholipase A2. It is analogous to the neurotoxins found in the venoms of several other rattlesnake species, and when present, contributes significantly to the overall toxicity. Other components found in the venom include a small basic peptide that works as a myotoxin, a fibrinogen-clotting enzyme that can produce defibrination syndrome, and a bradykinin-releasing enzyme.

CroFab antivenom, while not specific for C. horridus, is used to treat envenomations from this species.


Crotalus horridus


Crotalus horridus

The timber rattlesnake was designated the state reptile of West Virginia in 2008. That state's legislature praised "...a proud contribution by the eighth grade class at Romney Middle School, from West Virginia's oldest county, in West Virginia's oldest town, to have been instrumental in making the timber rattlesnake the state reptile..."

This snake became a prominent symbol during the American Revolution in part because it had a fearsome reputation. The use of the timber rattlesnake as a symbol of American anger and resolve to defend itself was no idle threat. During the period of 1763â€"1787, medical knowledge was not up to the challenge of treating a timber rattlesnake's bite. First, at the time, European standards of medical practice were based on the ideas and concepts of Galen, in which disease was caused by imbalances in the body; this was the standard to which all doctors practicing medicine in the colonies were trained. Because of the then poorly understood effects on the nervous or hematological system of this species' venom, a physician would prescribe a course of action that wound up killing the patient faster (bleeding with leeches) or prescribing herbs without testing of their efficacy as a cure beyond imitation of Native American practices Secondly, Linnaeus only described and identified this snake in 1758; firsthand experience with timber rattlesnakes among London scientists would have been poor, the flora and fauna of the colonies would have been disdained as savage by thinking circles, and published information on its habits would have been thin, allowing for hearsay and superstition to grow on both sides of the Atlantic.

The motto Nemo me impune lacesset (with the verb in the future tense) appears above a Crotalus horridus on a 1778 $20 bill from Georgia as an early example of the colonial use of the coiled rattlesnake symbol, which later became famous on the Gadsden flag.


Crotalus horridus

The subspecies C. h. atricaudatus (Latreille in Sonnini and Latreille, 1802), often referred to as the canebrake rattlesnake, is currently considered invalid. Previously, it was recognized by Gloyd (1936) and Klauber (1936). Based on an analysis of geographic variation, Pisani et al. (1972) concluded no subspecies should be recognized. This was rejected by Conant (1975), but followed by Collins and Knight (1980). Brown and Ernst (1986) found evidence for retaining the two subspecies, but state it is not possible to tell them apart without having more information than usual, including adult size, color pattern, the number of dorsal scale rows and the number of ventral scales. Dundee and Rossman (1989) recognized C. h. atricaudatus, but others take a more neutral point of view.

Conservation status

This species is classified as least concern on the IUCN Red List (assessed in 2007). Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category.

The timber rattlesnake is listed as endangered in New Jersey, Vermont, Massachusetts (along with the copperhead viper), Virginia, New Hampshire, Indiana, and Ohio, and it is threatened in New York, Connecticut, Illinois, Minnesota, and Texas.

See also

Crotalus horridus
  • List of crotaline species and subspecies
  • Crotalus by common name
  • Crotalus by taxonomic synonyms
  • Crotalinae by common name
  • Crotalinae by taxonomic synonyms
  • Snakebite


Further reading

External links

  • Crotalus horridus at the Reptarium.cz Reptile Database. Accessed 12 December 2007.
  • Timber Rattlesnake (Crotalus horridus) at Center for Reptile and Amphibian Conservation and Management. Accessed 8 February 2007.
  • Timber Rattlesnake Crotalus horridus at Center for Reptile and Amphibian Conservation and Management. Accessed 8 February 2007.
  • Timber Rattlesnake â€" Crotalus horridus at Herpnet.net, Reptiles and Amphibians of Iowa. Accessed 15 June 2007.
  • Account of severe C. horridus envenomation at venomousreptiles.org. Accessed 12 December 2007.
  • Canebrake rattlesnake (Crotalus horridus) at Virginia Department of Game and Inland Fisheries. Accessed 7 August 2007.
  • Snakes of Louisiana at Kingsnake.com. Accessed 7 August 2007.
  • Timber Rattlesnakes Facts and Pictures.
  • Timber Rattlesnake Fact Sheet at New York State Dept. of Environmental Conservation. Accessed 14 December 2008.
  • Timber Rattlesnake, Natural Resources Canada

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