| Crotalus horridus | |
|---|---|
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Vertebrata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Viperidae |
| Subfamily: | Crotalinae |
| Genus: | Crotalus |
| Species: | C. horridus |
| Binomial name | |
| Crotalus horridus Linnaeus, 1758 |
|
| Synonyms | |
|
|
Crotalus horridus, the timber rattlesnake, is a species of venomous pitviper found in the eastern United States. This is the only rattlesnake species in most of the populous northeastern United States.[4] No subspecies are currently recognized.[5]
Contents |
Adults usually grow to an average length of 91–152 cm (35.8-59.8 in).[4] The maximum reported length is 189.2 cm (74.5 in)(Klauber, 1956). Holt (1924) mentions a large specimen caught in Montgomery County, Alabama, that had a total length of 159 cm (62.6 in) and weighed 2.5 kg (5.5 lb).[6]
The dorsal scales are keeled[7] and arranged in 21-26 scale rows at mid-body (usually 25 in the south and 23 in the north). The ventral scales number 158-177 in males and 163-183 in females. Males have 20-30 subcaudal scales while females have 15-26. The rostral scale is normally a little higher than it is wide. In the internasal-prefrontal area there are 4-22 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 5-7 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.[6]
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.[8] Melanism is common, and some individuals are very dark, almost solid black.[9]
Found in the eastern United States from southern Minnesota and southern New Hampshire, south to east Texas and north Florida[10] The type locality given is "America", although Schmidt (1953) proposed that this be restricted to "vicinity of New York City" (USA).[1]
McDiarmid et al. (1999) also states that its range includes southern Ontario in Canada,[1] but in May 2001, the Canadian Species at Risk Act listed it as extirpated there.[11]
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.[12]
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 non-gravid females tend to spend more time in cooler, denser woodland with a more closed forest canopy.[13]
Female timber rattlers often bask in the sun before giving birth, in open rocky areas known as "basking knolls".[14]
During the winter, Timber Rattlesnakes hibernate in dens, in limestone crevices, often together with Copperheads (Agkistrodon contortrix) and Black Rat Snakes (Elaphe obsoleta).[15]
Their prey is mainly small mammals, but may include small birds, frogs, or other snakes. Although capable of consuming other rattlesnakes, the most common snakes they eat are garter snakes.[13]
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.[16] Before striking, they often do a good deal of preliminary rattling and feinting.[17] Cist (1845) described how he lived in western Pennsylvania for many years and that the species was quite common there, but that in all that time he heard of only a single death resulting from its bite.[2]
There is considerable geographic and ontogenetic variation regarding the toxicity of the venom; something that 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 [1]. 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.[16]
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.[16]
CroFab antivenom, while not specific for C. horridus, is used to treat envenomations from this species.[18]
The timber rattlesnake was designated the state reptile of West Virginia in 2008.[19] 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, [see "Romney, West Virginia"] to have been instrumental in making the timber rattlesnake the state reptile..."[20]
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 1763-1787, medical knowledge was not up to the challenge of treating a timber rattlesnake's bite. First of all, at the time, European standards of medical practice were based on the ideas and concepts of Galen, where disease was caused by imbalances in the body; this was the standard to which all doctors practicing medicine in the colonies were trained.[21] 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[22] (This was further complicated by the venom's ability to kill within the space of one day in a world where doctors were fewer.) 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[23] and so published information on its habits would have been thin, allowing for hearsay and superstition to grow on both sides of the Atlantic.
The subspecies C. h. atricaudatus (Latreille in Sonnini and Latreille, 1802), often referred to as the canebrake rattlesnake,[2] is currently considered invalid.[24] Previously, it was recognized by Gloyd (1936) and Klauber (1936). Based on an analysis of geographic variation, Pisani et al. (1972) concluded that 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 that 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 atricaudatus, but others take a more neutral point of view.[6]
This species is classified as "least concern" on the IUCN Red List of Threatened Species.[25] Species are listed as such due to their wide distribution, presumed large population, or because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend is down. Year assessed: 2007.[26]
The timber rattlesnake is listed as endangered in New Jersey, Vermont, Massachusetts, New Hampshire, Indiana and Ohio, and it is threatened in New York, Connecticut, Illinois, Minnesota and Texas.