Birthing live young, as opposed to laying eggs, seems to fall almost completely in the domain of mammals. With only two exceptions, the echidna and the platypus, all mammals deliver live births. Reptiles, on the other hand, almost exclusively lay eggs to hatch their young. Like the two rare mammals that lay eggs, this trend is broken for reptiles by a few species that give live birth to their young.
Every species of boa gives birth to live young. Boas are one of the largest snake species in the world and can be found all along the equator and the southern hemisphere. They can also be found in western North America. Boas are not poisonous. They hunt and kill by first ambushing and then squeezing their prey to death.
Vipers are heavy bodied poisonous snakes with fangs that fold back into the mouth until ready to strike. They can be found throughout Africa and Eurasia. The asp and the adder are two well-known kinds of viper. All vipers give birth to live young.
Garter snakes encompass a wide variety of snakes that can be found throughout North America. Garter snakes are considered technically non-poisonous, as they do have a neurotoxin, but it is too weak to cause any damage to humans. In addition, the garter snake has no effective way of delivering its poison. All garter snakes are ovoviviparous, which means the embryos still develop inside eggs but are retained within the mother's body until ready to hatch, thus giving birth to live young.
A skink is a type of lizard that can be found all over the world. There are hundreds of different species of these lizards. Three species of skinks give birth to live young: Solomon Island skinks, blue-tongue skinks and shingleback skinks. Solomon island skinks, which have a prehensile tail, are found in Papua New Guinea and the Solomon Islands. Blue-tongue skinks are found in Australia, Tasmania and New Guinea and are named for their dark blue tongue. The shingleback skink, which is found in southern and western Australia, is the only other species of skink that has live births.
The Jackson’s chameleon is a true chameleon that is native to Kenya. It is noted for the three prehistoric looking horns on its forehead. The Jackson’s chameleon has the unusual ability to focus its eyes in two different directions at the same time. Its brain is designed to process the two visual signals separately. The Jackson’s Chameleon is the only other type of reptile that has live birth instead of laying eggs.