Reptiles
Timber Rattlesnake
Crotalus horridus · also called canebrake rattlesnake, American viper
The timber rattlesnake is the snake on the “Don’t Tread on Me” flag — chosen by the Revolutionary generation for giving fair warning and never starting a fight. It is also, in much of the northeastern United States, a snake in serious trouble.
Overview
Crotalus horridus lives across the eastern United States, in deciduous forest and rocky ridges in the north and in lowland cane and hardwood thickets in the south, where it is called the canebrake rattlesnake. It is a large, heavy-bodied pit viper, patterned with dark crossbands, and it hunts rodents from ambush, often beside a fallen log.
Calm, but potent
It is one of the mildest-tempered large rattlesnakes, usually staying still and silent. But its venom is strongly tissue-destroying, and some southern populations add a neurotoxin, so a bite is a real emergency — even though the snake rarely delivers one.
One den, one population
In the north, rattlesnakes from a wide area overwinter together in an ancestral rock den used for generations. Destroy the den — as bounty hunters and collectors did — and the whole regional population is gone, with no way back. Females also breed only after 7–11 years and only every few years.
Status
Least Concern overall but declining, extirpated from Canada, Maine, and Rhode Island, and endangered or threatened across many northern states.
Timber Rattlesnake: common questions
How dangerous is a timber rattlesnake?
The venom is dangerous, but the snake is not aggressive. Timber rattlesnakes have a well-earned reputation for a placid temperament; the usual response to a person is to freeze and rely on camouflage, and a snake often will not even rattle. Most bites happen when someone tries to catch, kill, or handle one, or steps directly on a hidden snake barefoot. When a bite does occur it is serious, causing severe pain, swelling, tissue damage, and in the populations with neurotoxic venom, effects on the nerves and muscles, and it needs prompt hospital treatment with antivenom. Deaths are rare with treatment. Given space, the snake simply wants to be left alone.
Why is the timber rattlesnake disappearing in the northern states?
Its life history makes it fragile, and one behaviour makes it worse. Females breed for the first time only after about a decade and then only every few years, so a population cannot absorb heavy adult losses. And in the north, rattlesnakes from a large surrounding area all return to the same ancestral rock den each autumn to survive the winter. If that den is dynamited, dug out, or its snakes are collected, as happened widely during bounty and roundup eras, an entire regional population can be wiped out in a single season with no way to recolonise. Add road mortality and casual killing, and the species has been pushed out of the northeastern edge of its range entirely.
What is a canebrake rattlesnake?
It is the same species. In the southeastern lowlands, timber rattlesnakes tend to be pinkish or tan with a rusty stripe down the back, and they live in dense stands of native cane and bottomland hardwood, and there they are traditionally called canebrake rattlesnakes. Snakes in the northern uplands are often darker, sometimes almost black, and are called timber rattlesnakes. For a time the canebrake was treated as a separate subspecies, but that is no longer generally recognised, and both are Crotalus horridus.
Are timber rattlesnakes good for anything?
Ecologically, yes. They are significant predators of forest rodents, and because rodents are the primary hosts for the larval and nymph stages of black-legged ticks, the ones that transmit Lyme disease, studies have estimated that each timber rattlesnake indirectly removes thousands of ticks from the environment per year by eating their hosts. Rattlesnake venom is also a source of compounds studied for medical use, including drugs affecting blood clotting. And the species has deep cultural weight in American history as the emblem of the early republic.