timber rattlesnake

timber rattlesnake, (Crotalus horridus), species of venomous North American snakes classified in the family Viperidae that inhabit low mountain ridges and upland woods in the eastern United States. Its range extends from New Hampshire along the Appalachian Mountains to northern Florida and, on its western edge, from southeastern Minnesota to southeastern Texas; the snake’s range once extended into southern Ontario, Canada, but was last observed there in 1941. Bites from a timber rattlesnake result in envenomation of the victim about 50 percent of the time; however, they are rarely fatal.

Natural history

The average adult length ranges from about 0.8 to 1.5 meters (about 2.6 to 5 feet), though the largest males can grow as long as 1.9 meters (6.2 feet). The head is broadly triangular due to the presence of large venom glands and their associated muscles. The neck is narrow, the body stout, and the tail blunt, ending in a rattle. Small scales cover the head, and the eyes have vertically slit pupils. Body coloration may be golden yellow, grayish olive, or brown; some snakes are entirely black. The head usually has no markings; however, the heads of some individuals may be accented by a dark diagonal line. The snake has markings across the body, with brown or black wavy bands or chevrons, some of which may be edged in pale yellow. The tail is black. A southern variant called the canebrake rattlesnake, which is classified by a handful of taxonomies as the subspecies C. horridus atricaudatus, has the same body pattern with the addition of an orange, yellow, pinkish, brownish, or reddish stripe along the back and a dark diagonal stripe on the sides of the head.

The timber rattlesnake is a forest snake. In spring and fall it may be found basking on south-facing rocky slopes. It preys on small mammals and ground birds, foraging in fields, pastures, and farms and along old stone fences. It perceives scents with its forked tongue and stations itself with its head resting on its coils or on logs that serve as mammal runways, ready to ambush passing animals. In the heat of summer it hunts at night, locating prey with the aid of its pit organs, a pair of sensory receptors at the sides of its head that can detect infrared radiation given off by the body heat of its victims.

In late summer and fall, large numbers of timber rattlers gather on mountain slopes to hibernate in rock crevices. Most mating occurs during this time, but some may occur when the snakes emerge in spring. The timber rattlesnake is ovoviviparous, meaning that fertilized eggs are retained within the female’s body and young are born alive. Females become sexually mature between ages 7 and 13—which is significantly later than males, which become sexually mature between ages 4 and 6—and bear up to 20 live young every 2 to 6 years. Young timber rattlesnakes, which are generally 19.5–32 cm (7.7 to 12.6 inches) long, are born between July and October, and they remain with their mother for about one week before dispersing. Timber rattlesnakes can live as long as 30 years in the wild and as long as 37 years in captivity.

Snakebites

Although the snake is considered dangerous, it is not aggressive. It rarely bites, unless startled or stepped on, preferring to give prolonged warning rattles instead. Defensive bites delivered to human beings can introduce a mix of toxins that can result in death in up to 10 percent of untreated victims. So tenacious is the snake’s bite that the snake became a national symbol in the United States. Flags of the American Revolution and later the Gadsden flag portrayed a coiled timber rattlesnake with 13 segments on its rattle and the motto “Don’t tread on me.”

Conservation status

The International Union for Conservation of Nature and Natural Resources (IUCN) considers the timber rattlesnake to be a species of least concern. Although ecologists estimate that the entire timber rattlesnake population numbers more than 100,000 adults and that its range is very large, studies have shown that local populations throughout its geographic range are declining because of hunting and collecting, habitat loss, and vehicle strikes. Since the 1990s the timber rattlesnake is becoming more scarce in the northeastern United States; populations in New York, for example, fell by 80 to 85 percent between the 1940s and 1980s. Although the snake was listed as a threatened species in New York in the early 1980s, the population’s recovery since then has been slow or nonexistent, with some studies noting that populations continue to fall, albeit slowly, in many areas of the state. The southern parts of the snake’s range are characterized by populations of mixed success, with subpopulations in some areas thriving and those near agricultural, residential, and urban areas declining from habitat loss and human persecution.