The eastern garter snake breeds during both the spring and fall. After mating the female garter snake is able to keep the males sperm alive in her body for a several weeks. This allows the sperm to fertilize her eggs when the eggs are developmentally ready.
Fertilization can thus take place several weeks after mating with the male.
The female does not lay eggs as do most reptiles. Females give birth to 10 - 40 young. The newly born snakes are about twelve cm in length. The young snakes receive no parental care and many become food for other animals. Once born, the young eastern garter snake grows quickly .