Appearance
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.
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.
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.
Food
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.
Defense
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.
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