The Timber rattlesnake is a large venomous pit viper native to eastern North America. Dorsally, these snakes 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.
Timber rattlesnakes are found in the eastern United States from southern Minnesota and southern New Hampshire, south to east Texas and north Florida. They inhabit 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 the more closed forest canopy. These snakes can also be found in swampy areas and floodplains, wet pine flatwoods, river bottoms, hydric hammocks, lowland cane thickets, and hardwood forests.
Timber rattlesnakes are almost entirely terrestrial rather than arboreal, however, they are excellent climbers. 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. Timber rattlesnakes are known to use fallen logs as a waiting site for prey to pass by, giving them an elevated perch from which to effectively strike their prey. These snakes can be active both during the day and night. Females often bask in the sun before giving birth, in open rocky areas known as "basking knolls". Timber rattlesnakes are generally solitary creatures. They prefer to hunt alone but during the winter, they often brumate (hibernate) in dens, in limestone crevices, often together with copperheads and Black rat snakes. Potentially, the Timber rattlesnake 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 brumation period. Before striking, Timber rattlesnakes often perform a good deal of preliminary rattling and feinting.
Timber rattlesnakes have a polygynous mating system in which one male mates with more than one female. Their breeding season takes place from July to October and females reproduce every two to three years. During the mating season males compete for females and perform a courtship "dance." In this display, the male slides next to the female and rubs his head and body against her. Timber rattlesnakes are viviparous; they give birth to live young. Females give birth to 1-20 young after the gestation period that lasts around 135 days. Snakelets are born fully developed but will stay with their mother first 7-10 days of their life. After that, they disperse and become independent. Males become reproductively mature at 4-6 years of age while females attain maturity when they are 7-13 years old.
Main threats to Timber rattlesnakes include habitat destruction, logging, snake hunting, commercial collection for the pet trade and roadkill.
According to IUCN, the Timber rattlesnake is locally common and widespread throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List but its numbers today are decreasing.