The western diamondback rattlesnake is, like all rattlesnakes, viviparous. A female is pregnant for around six to seven mouths before giving birth to her young. The young only stay with their mother for a few hours before leaving on their own to go and hunt. They mate in spring and the female gives birth to around 12 to 25 young at a time. When they are born they are around 30 cm (12 in) long. Young western diamondback rattlesnakes have a venomous bite from the moment they are born. Western diamondback rattlesnakes live for around 20 years.