How many eggs do Ball Pythons lay? This might sound like a simple question – and it is. Why they lay this many and whether they all hatch, on the other hand, is a little more complicated!
Ball Pythons usually lay around 7 eggs
Ball pythons are a pretty reliable species when it comes to clutch size, both in the wild and captivity. The majority of their clutches have 4 to 10 eggs, and an average of roughly 7. Occasionally, clutches of only one or two eggs, or as many as 16 do occur, but this is rare (especially 16!).
This may sound like a low number compared to some animals, but it’s quite normal for an iteroparous reptile. Iteroparity is a breeding mechanism whereby an animal has a small to medium number of offspring more than once. This can be every year or once each season. The advantage of this is that an iteroparous species can ride out a few bad years and still repopulate the area, even if most of their recent offspring haven’t survived. They also don’t need to sacrifice all their resources to produce thousands of offspring, as they can always breed again in the future.
The opposite of this is semelparity. Semelparous animals only reproduce once but invest all their energy in either a mega-clutch or a very well provisioned clutch. The advantage of a mega-clutch is strength in numbers: a few babies will survive no matter what. Differing slightly, a well provisioned clutch means babies that are bigger and stronger, making them more likely to survive – but also able to reproduce sooner. The disadvantage in either case is that most of these animals literally kill themselves to produce their offspring!
Examples of semelparous animals would be salmon and octopuses, whereas examples of iteroparous animals would be you’re popular pet reptile species such as Bearded Dragons and our subject, the Ball Python.
Check out the video below from Olympus Reptiles, it shows a couple of typically sized clutches.
Are all Ball Python eggs fertile?
Ball Python eggs are not always fertile. In fact, a great deal of Ball Python clutches contain at least one or two infertile eggs. Hobbyist breeders call these “slugs”, and believe me, they don’t make for a nice surprise! Fortunately, they are easy to recognise and remove. Slugs are small, yellow-ish and waxy. They look nothing like plump, healthy, white, fertile eggs do. What’s more, they lack the networks of healthy veins that can be seen in fertile eggs when you candle them.
If you aren’t familiar with candling, this is what the breeder is doing with a flashlight in the video above. I don’t recommend doing this too often – but it’s a good tool for checking the fertility of freshly laid eggs. If you ever need to candle eggs, remember to never turn them upside down! Keep them orientated the way they were laid to reduce disruption to the embryo.
This is a typical “slug”. There’s no point even trying to incubate these – they’re completely infertile!
What causes Ball Python slug eggs?
Slugs probably occur for different reasons in different cases, and every breeder has their theory as to the main reason. Personally, I think the most common reasons behind infertile eggs are poor sperm quality, poor female body condition and poor environmental conditions. My reasoning for the for each point is the following:
- Poor sperm quality occurs in certain males of all species. It can be due to genetic defects, disease, or general poor health. Whatever the case, it seems to be one of mother nature’s favourite methods for making sure lower quality males reproduce less.
- Poor female body condition can occur when a female has suffered stress or another issue that has caused it to fast for an extended period or burn more calories than you’d expect. How does this result in less fertile eggs rather than less eggs overall? I’m not entirely sure, but feedback from other breeders does seem to support the idea. It could be that a certain number of eggs are “discontinued”, so to speak, when it becomes apparent there aren’t enough resources for full development.
- By poor environmental conditions I really mean temperature. High temperatures kill sperm. In a species that stores sperm for months, high temperatures or a tub that is too small for thermoregulation will cause slugs.
This is only my opinion, however, sodon’t take it as scientific fact!
Why do Ball Pythons only lay this many eggs?
Iteroparity, as I mentioned above, is only one determining factor in brood size – and has a very broad effect. Some iteroparous animals lay one egg, for example, whereas others (like some sea turtles) can lay over a hundred. The factor that has a much more specific effect on clutch size in the Ball Python is whether the female can wrap herself around them all!
In fact, a common occurrence for a Ball Python breeder is opening the tub of a big, healthy female to find her wrapped 8 or more eggs – but also 1 or two tossed to the side. Breeders call these eggs “roll outs”. Even more puzzling, the vast majority of “roll outs” are completely healthy and incubate without any issues. It seems some females will simply reject an egg or two if they can’t wrap around them all perfectly.
After I encountered this, I started to investigate because frankly it didn’t make any sense to me. Thankfully, I stumbled onto an excellent study in The Biological Journal of the Linnean Society called Clutch size manipulation, hatching success and offspring phenotype in the ball python (Python regius).
As you probably know, female ball pythons are unable to generate heat like some species but do wrap around their eggs to protect them. This study found that this protection isn’t just against predators, it’s also against the elements. By removing eggs from females and decreasing the clutch size the authors generated no negative effects on the eggs, but by adding eggs they lowered the hatch rate for the whole clutch! Through their investigation, they found that in big clutches some eggs were drying out and dying because of exposure to the air, and that the eggs took longer to hatch (a classic sign of not being warm enough).
How many eggs do Ball Pythons lay? As many as they can successfully brood
This study seems to indicate that, as in birds, brooding reptiles have an ideal clutch size for optimal parental care (I’m oversimplifying a tad, but this is the gist of it!). In this case, the ideal clutch size corresponds to how many the female can successfully wrap around to protect from the elements. This varies in accordance with the size of the female but makes the average clutch size roughly 7 eggs.
Admittedly, I’m not one to take a single study as much proof of anything, but this article makes perfect sense. In fact, its results fit perfectly with what fellow hobbyists have observed when letting female ball pythons brood clutches themselves. Warmth and hydration do impact hatch rates in this species, so why would they produce 20 eggs when they can only protect 7 or 8 from dessication and temperature fluctuations? One or two too many can happen (hence the roll outs), but more than that is highly unlikely!
In this photo you can see a female wrapped around a 10 egg clutch. You can see a little slug egg in middle, but also a roll out behind her.
Why don’t Ball Pythons just lay more eggs, but smaller ones?
This is of course the next logical question. Couldn’t these snakes just have evolved to produce 100 little eggs rather than 7 big ones? One reason why this wouldn’t work is the question of prey. Ball Pythons are rodent predators that ambush them either in their burrows or at the entrance to a hideout.
They are, it seems, very specialised towards this prey type, having thermoreceptive pits in their labial scales to see their body heat, and nice, medium sized teeth to grip them with. They also tend to only constrict prey using the first third of their body, which is likely an adaption to hunting in rodent burrows. This contrasts sharply with larger, more free-roaming pythons, who will wrap a big prey item up with their whole body as if they intend to roll away with it.
Other than rodents they also take nestling birds when available. This is probably due to opportunism rather than true preference, as baby birds are easier and less dangerous to subdue. Animals love energy-saving shortcuts like this, a factor conveniently ignored by those that try to sell us the semi-arboreal ball python idea!
Anyway, I better to get to the point… The evolutionary processes that have led to Ball Pythons being rodent specialists have also selected them for offspring that are big enough to eat rodents. Big babies mean big eggs!
Rodents (and birds) are fairly big at any age, and tiny snakes simply can’t swallow them. If Ball Pythons ate invertebrates, then they could indeed produce lots of tiny babies who would be able to survive by eating small bugs. As rodent specialists, however, tiny babies = starving babies.
Typical Ball Python constriction using only the first third of the body.
Could another reason be that Ball Pythons are (kind of) a giant snake?
The Ball Python (Python regius) is what is called a “True Python”. This means it belongs to the genus Python, whose species include some of the largest in the world. The problem is that the Ball Python is the smallest in the genus, only growing to a fraction of the size of some of its giant cousins like the Indian Python (Python molurus), for example. Even pythons outside of this genus tend to be big, with the great Reticulated Python (Malayopython reticulatus) being the longest snake in the world (and perhaps the one that tends to grow largest in captivity).
So, the Ball Python’s closest relatives and even their slightly more distant cousins tend to be large animals. Do animals from families of giants have big babies – even if they have evolved to be much smaller than their relatives?
Do animals from giant families have to have big babies – even if they’re smaller than their relatives?
This is a possibility that is still being debated by the scientific community, particularly when it comes to the Kiwi. The Kiwi is a flightless bird belonging to the ratite group, standing about 16 inches (40cm) tall. Ratites include the largest flightless birds in the world, including the Emu and the Cassowary. Like the Ball Python, the Kiwi is the smallest of its family – but still lays big eggs. Sorry, I meant to say massive eggs! These birds lay a single egg that is up to a quarter of the female’s mass.
The Kiwi is obviously an extreme case of a small bird that is from a big family. Did it evolve to become smaller over time, without managing to shrink down the size of its eggs? Or did the Kiwi evolve to have larger eggs to confer a benefit to the offspring? Did a similar process occur with Ball Pythons? Or do they mainly have big eggs because they’re rodent eaters, as I mention earlier? It may be a mix of the two, but we probably won’t know for sure for quite some time. Whatever the case, it’s an interesting thought!
This male Pewter Ball Python went crazy for adult mice from a young age, but refused rats and chicks. There’s no way small prey would have interested him.
Ball Pythons lay an average of 7 eggs, for good reason!
So, there you have it, a complicated answer to a very simple question. Across both wild and captive female Ball Pythons the average clutch size is roughly 7 eggs. Though a variety of factors influence this, the broad characteristics of the species and their environment make this number the optimum for a decent hatch rate.
If I breed Ball Pythons for the rest of my life, I will almost certainly never see a 20-egg clutch. But this isn’t a bad thing – nature knows best! The goal should always be to produce big, chunky, healthy babies like the ones below, both of which hatched from the eggs pictured in this post.
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