It is the only venomous snake found above the snow line, and may be active in weather generally considered too cold for snakes. It hunts during the day, except on hot days, when it is active at night. Copperheads are attracted to swamps, rivers and creeks, where they hunt for frogs, reptiles and small mammals. They also eat other snakes, including their own young. The copperhead is solidly built, with a small head.
Coloration is variable, from dark brown to light copper.
The lip may be striped in white and brown. Average length is 1.2m, maximum 1.83m. The litter of 18-20 is born alive, and are lighter in colour than adults. Bites to man are rare, as copperheads are generally slow to strike and may be inaccurate. The venom has neurotoxic, procoagulant and myolytic activity, but rarely causes fatalities.