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.
Description Adults usually grow to total length of 91–152 cm.
The maximum reported total length is 189.2 cm. Holt mentions a large specimen caught in Montgomery
County, Alabama, which had a total length of 159 cm and weighed 2.5 kg. Large specimens
can reportedly weigh as much as 4.5 kg. Most timber rattlesnakes found measure less than
100 cm in total length and weigh 580–900 g. The dorsal scales are keeled and arranged
in 21–26 scale rows at midbody. 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 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.
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 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. Habitat
Generally, this species is found in deciduous forests in rugged terrain. During the summer,
gravid 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. Feeding
Their prey are 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. Venom
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 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.
Gallery
Symbol 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 1763–1787, 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 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 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. Taxonomy
The subspecies C. h. atricaudatus, often referred to as the canebrake rattlesnake, is currently
considered invalid. Previously, it was recognized by Gloyd and Klauber. Based on an analysis
of geographic variation, Pisani et al. concluded no subspecies should be recognized. This was
rejected by Conant, but followed by Collins and Knight. Brown and Ernst 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 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. 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, New
Hampshire, Indiana, and Ohio, and it is threatened in New York, Connecticut, Illinois, Minnesota,
and Texas. See also
List of crotaline species and subspecies Crotalus by common name
Crotalus by taxonomic synonyms Crotalinae by common name
Crotalinae by taxonomic synonyms Snakebite
References
Further reading
External links Crotalus horridus at the Reptarium.cz Reptile
Database. Accessed 12 December 2007. Timber Rattlesnake 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 – 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 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