Which Snakes Lay Eggs, and Which Give Birth to Live Young?

© 2019, Brandon Cornett | All rights reserved

Did you know that some snakes give birth to live young, while others lay eggs? It's true. And here's something even more interesting. Certain types of female snakes develop eggs inside of their bodies, but end up giving birth to live young. How is this possible? Read on to find out!

How They Reproduce: Oviparous, Viviparous and Ovoviviparous

How do snakes reproduce? It depends on the species. Some species give birth to live young, while others lay eggs. In fact, there are three distinct methods of reproduction, as described below:

Oviparous: Most snakes (about 70% of them) are oviparous, which means they lay eggs. The eggs must then be incubated, or kept warm, until the hatchlings are ready to emerge from the shell. Nearly all members of the Colubridae family lay eggs. This includes rat snakes, grass snakes, kingsnakes and other "common" species. Cobras, mambas, adders, and most other members of the Elapidae family fall into this category as well.

Viviparous: This is when there is no egg at all. Snakes that are viviparous nourish their developing young through a placenta and yolk sac, something that is highly unusual among reptiles. Boa constrictors and green anacondas are two examples of viviparous snakes, meaning they give birth to live young with no eggs involved at any stage of development.

Ovoviviparous: You can think of this as a "cross" between an egg layer and a snake that gives birth to live young. Female snakes that are ovoviviparous develop eggs inside their body. But when the babies are born, the female retains the eggs inside of her. So the hatchlings are born live, outside of an egg. Basically, the eggs hatch inside of the female, and the baby snakes emerge fully active with no shell at all. Rattlesnakes are ovoviviparous. This means they give birth to live young after developing and retaining the eggs inside their bodies. Amazing!

The reproduction terminology can be confusing. So think of it this way:

Oviparous means egg-laying.

Viviparous means live birth, with no egg hatching at all.

The word "ovoviviparous" is a combination of the two -- there's an egg that develops inside of the female snake, but those eggs are retained inside the female's body at birth to produce live young. ( Ovo viparous + vi viparous = ovovi viparous)

Which Snakes Give Birth to Live Young?

So, which snakes give birth to live young? As mentioned above, both viviparous species (no eggs) and ovoviviparous species (egg retained inside the body) produce live and fully functional baby snakes. Most vipers, and all of the rattlesnakes, fall into this category. Members of the Boidae family, which includes boa constrictors and anacondas, also give birth to live young.

Interesting fact: When baby snakes are born live, as is the case with viviparous and ovoviviparous species, they are completely on their own from day one! There is no parental protection in the snake world. The babies go off on their own shortly after birth, and must fend for themselves. That is why baby rattlesnakes are born "fully loaded" with fangs and venom.

Sea snakes are a mixed lot. They are members of Hydrophiinae, a subfamily of the Elapidae family that also includes the venomous cobras, adders and mambas. Most of the sea snake species give birth to live young, which means the babies are born alive in the water. But there is one genus, Laticauda, which is oviparous. The female members of this particular genus lay eggs on land, as opposed to giving live birth like the other sea snakes.

Which Ones Lay Eggs?

As mentioned earlier, approximately 70% of the world's snakes lay eggs. This includes members of the Elapidae family (cobras, adders, mambas, taipans, etc.), as well as the much larger Colubridae family that accounts for two-thirds of all snake species.

In most cases, the female will abandon the eggs shortly after laying them. But a few species will actually coil around the eggs to incubate them, keeping them warm until they are ready to hatch. The parenting award goes to the female king cobra (Ophiophagus hannah). The highly venomous king cobra builds a nest for her eggs, and even stays with the hatchlings for a while after they have hatched.

Conclusion: Most of the world's snake species (about 70%) reproduce by laying eggs. But vipers, rattlesnakes, boas, and most of the sea snakes give birth to live young.