Female rattlers are ovoviviparous. The eggs are retained until they are ready to hatch. The young, encased in a thin membrane, are born live, wriggling free. A four-foot female may have some twenty young, each about 10 inches long. The normal brood size is five to ten.
Maturity is reached in about three years.
Young snakes grow rapidly, feeding very frequently. They may molt 5 to 7 times in their first year. Growth is based, not on age, but on food intake and health. It behooves hikers to watch where they put their hands and feet.