Rattlesnakes are the most widely known of the pit vipers (family Viperidae). They are found throughout the United States and parts of Canada and account for most poisonous (venomous) snakebites in North America. They leave one, two, or three puncture marks on the skin, but you won't always see any marks.
Rattlesnakes can be up to 8 ft (2.5 m) long and have:
Rattles at the end of the tail. Young snakes may only have one rattle or "button," which does not make the rattle sound.
Diamond-shaped markings, blotches, or speckles down the back.
Pitlike depressions behind the nostrils.
A triangular head with slit-shaped pupils and fangs.
A single row of plates or scales on the undersurface of the snake, including the tail.
Symptoms of a rattlesnake bite usually appear from minutes to hours after a bite and can include: