Snakes are fascinating creatures, always with a new surprise in store! Lots of people think snakes are all egg-layers. But in fact, many snake species give birth to live young. There are also snakes who do lay eggs, but hatch the eggs inside their oviduct before giving birth to them.
Not all snakes lay eggs. Most do, but not all. There are three types of snake – oviparous, viviparous and ovoviviparous. Only oviparous snakes lay eggs. These account for 70% of snake species, so there’s a good reason why most people assume all snakes lay eggs.
The other two types of snakes – viviparous and ovoviviparous snakes do things a little differently. Viviparous snakes, such as garter snakes and boa constrictors, give birth to live young fed nourishment by a placenta. Rattlesnakes, on the other hand, are ovoviviparous. This means they keep their eggs inside their bodies until they hatch. Then they deposit the pre-hatched snakes into the real world. Fascinating stuff!
So, lets look at more details of these 3 types of snake:
- Oviparous snakes: these account for roughly 70% of snake species. Examples include pythons, corn snakes and milk snakes. Many of these are popular pet snakes, and are found in a great many homes in the United States.
- Viviparous snakes: these are a little less common. Garter snakes (popular pet snakes) and boa constrictors (not so popular) are viviparous. They give birth to live babies.
- Ovoviviparous snakes: again, these account for a smaller proportion of snake species. Examples include rattlesnakes, which definitely aren’t common pet snakes. Ovoviviparous snakes keep their eggs inside their bodies until they hatch.
Viviparous snakes leave their offspring to fend for themselves as soon as they are born. How do they survive? And how many eggs do oviparous snakes lay at once? Where do they go to lay their eggs, and how long does it take before they hatch? You’re in the right place to find out the answers to these questions, and more.
Which snakes lay eggs?
Egg-laying snakes are called ‘oviparous’ snakes. These make up the greatest proportion of all living snakes.
In oviparous snakes, the female produces undeveloped egg cells in her ovaries. After mating, some of these eggs become fertilized. The fertilized eggs begin the process of development and growth in the oviduct. A protective shell forms around the eggs, making them look like what we think of when we think of eggs.
The shell is not hard and brittle like a chicken egg though. It is soft, and feels a bit like leather. Slowly, a yolk develops inside the egg. This yolk, like in a chicken egg, nourishes the baby snake while it’s growing.
A female snake is usually pregnant, or ‘gravid’, for 4-6 weeks. When her time is up, she will find a safe and secure place in which to deposit her eggs. It is important for her to find somewhere secluded, hidden from potential predators. This is because, for most snake species, once the eggs are laid, the female does not return to them.
Baby snake are ‘precocial’, which means they can survive independently as soon as they enter the world. They usually hatch after approximately 2 months. They break free of their eggs by cutting a small hole in the shell using a specialized ‘egg tooth’.
The list of egg-laying, or ‘oviparous’ snakes includes almost all of the Colubridae family. For example…
Milk snakes and kingsnakes
Members of the genus Lampropeltis, kingsnakes and milk snakes form part of a large family of oviparous snakes. Native to North, Central and South America, these two species are distinctive for their vivid colored bands.
These snakes brumate over winter – this is a process many reptiles undergo that is similar to hibernation, only it involves shutting off fewer metabolic processes. Then they become active again in the spring. They usually mate when the weather warms up a little, in late April or May.
Most milk snake species lay 5-20 eggs per clutch, typically 6 weeks after mating. The eggs sit for around 2 months before hatching.
Rat snakes
Like milk snakes and kingsnakes, rat snakes are common in the United States, and are oviparous. There are many different species of rat snake, including corn snakes and black (rat) snakes. They all have much in common.
Rat snakes also mate in the spring, after a period of brumation. Female rat snakes are gravid for a month, and lay 10-20 eggs in a clutch. After 2 months, they eggs hatch and must fend for themselves immediately.
Hognose snakes
These cute, blunt-faced snakes are easily recognizable, and common in many parts of the United States and Mexico. Hognose snakes are egg-layers. Like the aforementioned species, hognose snakes brumate over winter and mate in spring.
Again, like rat snakes, hognose females are pregnant for about a month, and lay on average 15-20 eggs per clutch. Hognose hatchlings break free from their shells after 6-8 weeks.
Pythons
Pythons are found all over the world: Australia, Asia, Africa, and in many homes in the United States. Among the most recognizable are ball pythons, reticulated pythons, Burmese pythons and carpet pythons
What sets them apart from the others in this list is that pythons do not brumate over winter. This is because they live in warmer climates. Brumation is triggered by a seasonal reduction in temperature. In tropical rainforest, for example, there is no such seasonal change. For this reason, pythons tend to lay their eggs earlier in the year: between February and April.
Ball pythons lay up to a dozen eggs; reticulated pythons can lay up to 80. With such a broad range of snakes, there is bound to be variation in clutch size!
Gopher snakes
Last but not least, the common gopher snake. This broad set includes bull snakes and pine snakes. Despite resembling rattlesnakes, gopher snakes are non-venomous and mostly harmless.
Gophers follow the pattern: they brumate over winter, mate in spring, lay up to two dozen eggs in a clutch, and leave their eggs after laying. 7-10 weeks later, in the height of summer, the hatchlings emerge into the world.
Other examples include
- Grass snakes
- Bull snakes
- And many others. Colubrids make up around two thirds of all snakes.
Many members of the Elapidae family of snakes are also oviparous, such as…
- Mambas
- Cobras
- Adders
How many eggs do snakes lay at once?
There’s no cover-all answer for this. Different species lay different numbers of eggs. Even within a species there can be variation. Some snakes lay lots and lots of eggs, while others lay just half a dozen in one go. Here’s an example…
Burmese pythons, native to Southeast Asia, reportedly lay up to 80 eggs in a singular birthing period. Ball pythons, on the other hand, lay much fewer. Recognizable for their distinctive and variable color morphs, ball pythons often lay just 5-7 eggs at a time. There are many factors that play into this contrast.
Here are some things that may play into how many eggs a snake needs to lay.
- If a snake lives in a dangerous habitat, with many natural predators, it has to lay more eggs, because they are more likely to get eaten. This could also be the case if a snake is small, and cannot guard its eggs effectively.
- Snakes that are less threatened by predators need to lay fewer eggs.
- Snakes that have access to particularly good hiding places – in trees, caves or crevices, for example – may need to produce fewer eggs.
Where do snakes go to lay their eggs?
This depends hugely on the snake species, and the hide spots its habitat has to offer. For example, the kingsnake lives in a huge range of habitats. Kingsnakes are all oviparous, but different subspecies have access to different habitat advantages. Here are a few examples…
- Desert kingsnakes, as you can guess, occupy areas of semi-arid grassland, dry shrub-land and open desert with rocky outcroppings. In conditions such as these, their best hide spots to safely deposit eggs are in nooks, stony crevices and under rocks. They may also bury their eggs in the sand, where they will go unseen until they hatch.
- Californian kingsnakes live in forest and field habitats. These snakes can take advantage of the flora available to them. They lay their eggs under fallen trees, buried in shrubbery and or concealed amid clumps of moss.
- In the eastern parts of the United States, eastern kingsnakes live in wetter climes, such as rainforests, swamps and riverbanks. In these habitats, different hide spots are available to female snakes.
Do snakes bury their eggs?
Most snakes will bury their eggs underground in loose soil or sand, if possible. Such conditions act as a natural incubator. The eggshells are soft, and cannot withstand much pressure. Moss, grass, loose soil or sand all provide a buffer zone and protect the eggs from the outside world.
Can snakes lay eggs without mating first?
Yes, this is technically possible, but it is quite rare. Some species of snake can store sperm inside their bodies. Rattlesnakes, for example, can reportedly store sperm for up to 5 years. In effect, this allows female rattlesnakes to fertilize their own eggs, without having mated in a very long time.
Other snake species can actually produce viable eggs without mating at all. In these cases, an unfertilized egg, containing only the mother’s DNA, develops into a healthy hatchling. This is called parthenogenesis, and is only done by a few snake species. One example is the tiny Brahminy blind snake. In this species, every member is female, and babies are genetic clones of their mothers.
If the female isn’t able to fertilize the eggs herself, they will be infertile. They will not develop into baby snakes. These unfertilized, infertile eggs are called slugs. Even after mating with a virile male, a female’s clutch of eggs can contain a few of these ‘bad’, infertile eggs among the viable ones.
How do snakes lay eggs?
Up until now we’ve only been talking about oviparous, or egg-laying, snakes. Now, this question applies to two of our snake types. Oviparous lay eggs through their cloaca – more detail on this below.
Ovoviviparous snakes, on the other hand, are sort of a cross between oviparous snakes and viviparous eggs. You can tell this because the word ‘OVO-VIVI-parous’ is a combination of OVI-parous and VIVI-parous. Ovoviviparous snakes hatch their eggs inside themselves right before giving birth. So, in effect, they give birth to live young.
Oviparous snakes lay their eggs in the following steps:
- As you learned earlier, the ovary releases an ovulated egg into the oviduct – specifically to a place called the infundibulum. Secretions from the oviduct coat the egg. It gestates.
- When the female is ready to lay her eggs, the gestated eggs move from the uterus and out through the snake’s cloacal opening. The cloaca is, in many ways, a one-size-fits-all opening about two thirds of the way down a snake’s length. The cloaca serves many purposes, one of which is egg laying.
- For this to happen, the female snake has to make rhythmic muscle contractions. Some pregnant snakes bask with their bellies up before they lay eggs, probably to warm their reproductive tracts.
- The mother lays the eggs in a cluster, all in quick succession. They should clump together, because of the adhesive fluid that binds them. Accidental displacement threatens the survival of the hatchlings, so this adhesive goo is essential.
- Most oviparous snakes will at this point abandon the eggs. Some snakes, such as pythons, coil themselves around their eggs to protect them and keep them warm.
Which snakes give birth to live babies?
Approximately 30% of snakes give birth to live young. This includes viviparous snakes and ovoviviparous snakes. Viviparous snakes grow their offspring internally without the use of eggs, nourishing them directly from a placenta. Ovoviviparous snakes hatch their eggs inside them and immediately give birth.
So, what are some examples? First, here are some ovoviviparous snakes.
Rattlesnakes
The not-so-humble rattlesnake is a great example of an ovoviviparous snake. They produce eggs, but they do not lay their eggs. Instead, once their ova are fertilized, they remain in the oviduct until after they have hatched.
Rattlesnakes are typically pregnant for 3-5 months, giving birth in late summer. Keeping their eggs inside them during the incubation period ensures they are safe from predators, and the elements.
The number of snakes born during one birthing period depends on the species. It is often between 10 and 20. Baby rattlesnakes stay with their mother in her den for 7-10 days, then head out into the world.
Cottonmouths and copperhead snakes
Also not on many people’s pet list are cottonmouths (or water moccasins) and copperheads. These pit vipers are closely related to rattlesnakes, and are found in the southeastern states.
Their similarities run deep – right down to their reproductive processes. One difference between these two snakes and rattlesnakes is the number of babies born in a single birthing period. Cottonmouths usually only give birth to 6-8 young per litter; copperheads bear between 4 and 10.
Like the Brahminy blind snake mentioned above, copperheads and cottonmouths can reproduce asexually. This means they do not have to mate before giving birth. The process is called parthenogenesis, and results in genetically identical offspring to the mother.
Now, let’s move into the category of viviparous. These are different from ovoviviparous snakes, because they do not produce eggs at all.
Boa constrictors
During a 4-month pregnancy, a boa constrictor’s young grow inside its oviducts. While an average litter numbers between 12 and 20, boa constrictors have been known to lay as many as 50 babies in one litter.
They may not develop inside eggs, but baby boa constrictors are each born inside soft, transparent membranes. These prevent any issues during cell development. Once they are born, the babies usually stay together for a while before heading out into the world.
Garter snakes
Like boa constrictors, garter snakes are viviparous. Very common in the wild, garter snakes are harmless, small-to-medium sized snakes belonging to the genus Thamnophis.
Similar to boa constrictors, female garter snakes grow their babies encased within thin, cellular membranes – as opposed to a calcified shell. There is still a yolk within the membrane, but developing babies get most of their nutrition from a placenta, which is connected directly to the mother.
Garter snakes can give birth to anywhere between 3 and 80 babies at a time. Garter snakes are precocial, which means they are sufficiently developed to hunt for themselves as soon as they are born.
How do snakes give birth?
Snake birth is an astonishing spectacle. As it can take up to a few hours, female snakes retreat to a safe and secluded space before giving birth. They are stationery and vulnerable during the birthing process, so it is important to be somewhere quiet and comfortable!
When the mother is ready, she will begin to birth her baby snakes. They will emerge from her cloaca – a passage which exits the body on her underside, about two thirds of the way down her body.
Depending on the species, she may deliver one snake, as many as 40 (as with diamondback water snakes), or even up to 100! The largest documented live litter was 156 baby snakes, birthed by a puff adder. However, most litters are somewhere between 10 and 30.
When do snakes lay eggs or give birth?
Unlike humans, most animals tend to reproduce according to a particular rhythm. Oviparous snakes, for example, brumate over winter and mate in the spring. Many other animals follow a similar pattern: hibernation is common among mammals, brumation among reptiles.
Some snakes give birth twice a year. Oviparous snake species usually deposit one clutch per year. Some produce two, and a smattering even produces three in a year! An example is the African house snake.
Mating season and frequency
The most common mating months for snakes of all types are February, March, April and May. Snakes that brumate tend to mate later, and give birth later in the summer. Non-brumating snakes mate earlier, and give birth either in late spring (May-June) or early summer (June-July).
How many times can a snake reproduce in its lifetime?
Snakes become sexually mature at an age that depends on a host of factors. There are approximately 3,000 snake species inhabiting divergent habitats across the world. There is bound to be variance.
On average, snakes reach sexual maturity after 2-3 years, as long as they are healthy. Burmese pythons take a little longer, often 4-5 years. Black rat snakes take even longer, sometimes requiring 7 years to reach maturity, or even 10 years in the case of females.
Once they are active, snakes can reproduce until they expire. For some snakes, that means 10 years of reproduction; for others, it means 30 years.
Conclusion
To conclude, most snakes lay eggs – a few don’t. There are three types of snakes: oviparous, viviparous, and the halfway house, ovoviviparous.
Have you still got any questions? Ask them in the comments below! Have you got any fun facts about snake reproduction? Share them in the comments below! We always love hearing your side of the story.
Share this with anyone who might find it useful. And good luck in all things herpetological!
