Rattlesnake

The rattlesnake is a kind of snake, a reptile. About 50 species of rattlesnakes are known: they are a kind of pit viper. 
There are two groups of rattlesnakes: the genera "Crotalus" and "Sistrurus". All have a venomous bite, and some are much more dangerous than others. Pit vipers have a set of heat-sensing "pits" on their heads which help them find prey and move towards it, even in the dark.
The name "rattlesnake" is used because they have a special tail with several parts on the end that can make a loud "bzzzz" sound, or rattle. This defends them against predators and large animals. It acts as a warning signal. 
Rattlesnakes are native to the Americas from southwest Canada to central Argentina. They usually live in dry areas. They eat small animals such as birds and rodents.
When they are young, many are eaten by birds. When they are adult, they have a particular enemy: the common kingsnake, "Lampropeltis getula", a colubrid snake.