Watersnakes (subfamily Natricinae: Genus Nerodia) are medium-sized colubrid snakes that, like other members of the Natricinae, give birth to live young. Live birth (viviparity) allows mothers to hold their offspring to term (or near it), likely reducing offspring risk of death due to environmental fluctuations or predation. Watersnakes, gartersnakes, boas, most vipers, and some sea snakes are all viviparous.

Here are a series of pictures (taken by Glenn Manning) illustrating the amazing number of offspring that some viviparous snakes are capable of carrying. A large, gravid Nerodia fasciata pictiventris (Florida watersnake) was found dead on road (DOR) in Levy county, Florida. Neither of us had ever seen a watersnake so large, and it was obvious that she was full of babies. We decided to open her up to both count, and possibly rescue, the offspring. Unfortunately, all were dead. During the process, it became obvious that this large female was within days of giving birth. All offspring were fully formed, and at least one popped out of the cloaca during the procedure.