These passages are reproduced in the Info Page on Reptile Physiology. Mating may occur before the winter cool-down in the fall. Females have been found able to store sperm for later use. It may be that a female bred in the fall does not allow the sperm to the eggs till spring warm-up. Or, the snakes may breed in the spring before dispersal from the den.
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.