Not all species of snakes have the same reproductive pattern. While 70% of snakes lay eggs, other species retain the eggs inside their bodies. They give birth to live young or produce no eggs at all.
Boa constrictors are viviparous, so they don’t lay any eggs. On average, one female boa may give birth to 30 to 60 live babies at a time.
Boas nourish their young via a placenta and yolk sac, where they’re enveloped in clear tenuous membranes. This is unusual among reptiles. The babies develop inside their mother for a few months and before birth, the clear membrane ruptures, allowing the female boa to give birth to live, fully-active baby boas.
How do Boa Constrictors Give Birth?
When a snake or reptile is viviparous, it means there is no egg involved in its reproductive process. Neonate boa constrictors are already alive and active when they come into the world.
The embryo develops inside the mother boa and is nourished through a placenta, just like with mammals. Because the boa offspring enter the world fully formed, they are generally quick to grow and become self-sufficient.
Fertilization takes place internally among boas. The developing boa is directly connected to a yolk sac and is cocooned in a clear, tenuous sac inside. The embryos continue in this state for a few months, growing steadily inside the mother boa.
When the offspring are ready to be birthed, the protective membranes quickly break, facilitating the babies’ exit out of the body.
However, this process is rare among snakes, as most species are either oviparous, and some are ovoviviparous.
Reproduction Methods in Snakes
|Reproduction Method||Facts and Information|
|Oviparous:||About 70% of snakes reproduce by laying eggs. The eggs have to be kept warm or incubated until the boa offspring are ready to come out of their shells. Rat snakes, king snakes, grass snakes, cobras, adders and mambas are all egg-laying species.|
|Viviparous:||Reptiles produce offspring without laying any eggs. The offspring develop inside the female reptile and are nourished through a placenta. This is similar to that of mammals and is extremely rare among reptiles.|
|Ovoviviparous:||Ovoviviparous reptiles produce eggs that hatch inside their bodies. This is a cross between egg-laying snakes and snakes that give birth to live young. Snakes that are ovoviviparous, such as rattlesnakes, develop eggs inside their bodies. As the babies are born, the mother boa continues to retain the eggs inside her, causing the hatchlings to come out of their mother alive and outside of an egg.|
When do Boa Constrictors Breed?
The boa constrictor breeding season usually starts between April and August, according to the University of Michigan. This is when the weather is dry and ideal for boa breeding.
Boa constrictors are polygynous. This means that both female and male boa constrictors often have multiple mates within one reproductive season.
During their breeding season, a female boa will emit pheromones from her cloaca, which helps attract males. The male boas wrestle in order to select one suitable mate that can breed with her.
Following breeding, ovulation may not occur rapidly. However, the female boa can hold the sperm inside her body for approximately one year.
During ovulation, you may notice a swelling in the female boa’s mid-body – similar to when a snake has consumed a large meal. Two to three weeks after ovulation, the female starts shedding – a process called post-ovulation shed, which can last for up to 2 to 3 weeks.
The gestation period of a boa mother lasts for about 100 to 150 days. Once the offspring are physically formed and birth is impending, it leaves the mother boa’s body through her cloaca cavity.
Baby boa constrictors instinctually gain the ability to stay alive from the day of their birth. The young are independent right from the start and can begin feeding. This allows them to grow rapidly in the first few years, shedding continuously every 1 to 2 months.
After 3 to 4 years, boa constrictors reach full maturity, physically and sexually, and grow up to the average adult length of 6 to 10 feet.
After the birth of their offspring, it’s critical that mother boa constrictors have time to rest and heal. The internal embryonic development of baby boas involves high energy expenditure from the mother and takes a physical toll on her body.
Without proper healing, a boa may not be able to replenish her fat supplies sufficiently.
How Many Babies do Boa Constrictors Have?
There are approximately 25 baby boa snakes in one litter. However, they have been known to range anywhere from 10 to 60 snakes.
Some of the young may be stillborn, or unfertilized eggs called “Slugs.”
Why Are Boa Constrictors Viviparous Reptiles?
Most scientists agree that some species of snakes have a survival advantage of giving birth to live offspring rather than laying eggs.
Most egg-laying species of snakes (except for the King Cobra) do not build their nests. They place their eggs in alligator nests, piles of rotting vegetation or any other suitable spot that’s warm and has the ideal humidity levels that will incubate the eggs and prevent them from drying out.
Most snake eggs can take 50 to 60 days to hatch, so a proper location with the right temperature and moisture levels is imperative.
However, snakes that reside in cooler climate areas may face problems finding ideal nesting grounds for their eggs. This gives viviparous and oviparous an evolutionary advantage.
Since these snakes can continue developing their young inside their bodies, they can do what a mother snake with a clutch of eggs cannot – they can move to a warmer location.
Snakes that can look for proper incubation conditions have a selective advantage over snakes that have to drop or abandon their eggs in search of a good spot.
This shows that egg-laying snakes may not do so well in cooler parts of the world, hence the reason why they’re more densely found in warmer, tropical conditions.
Does this mean that all live-bearing snakes reside in cooler climates? No, you can find snakes (including boa constrictors) that give birth to live young in every climate. However, egg-laying species have a slimmer survival advantage the further north you go.
How to Care for Newborn Boas
In the wild, newborn boa constrictors have to be independent as early as within a few hours after birth. Healthy boas will shed their skin within 14 days after their birth and will begin feeding on their own. Theoretically, there are no further steps, other than cleanup and providing a suitable enclosure.
However, providing newborn boas first care following their birth can be advantageous for your relationship with them and their overall health. Primary care for neonate boas includes:
- Drying the newborn boa with a paper towel
- Tying the umbilical cord with a dental string or thick thread, two fingers width away from the stomach and cutting it below the tied area with sterilized scissors
- Quick bathing of the newborn in lukewarm water to remove off any sticky residue and drying the baby with a paper towel afterward
- Powdering the umbilical cord using a wound powder and repeating this process the next day
- Placing the baby boa inside a clean enclosure along with kitchen paper as a substrate.
First care following birth helps the newborn get used to you, allowing it to become more docile. Furthermore, taking care of the umbilical cord will also prevent infection.
If one of the newborns is still attached to a decent-sized yolk sac, avoid cutting the umbilical cord as described earlier. Instead, place the baby boa with the yolk sac inside a plastic container that has been lined with a paper towel.
Next, place the plastic container inside a warm enclosure. This will cause the newborn to absorb some of the remaining yolks, allowing it to become just as healthy as its fully-developed siblings.
How often do boa constrictors reproduce? Boa constrictors produce live offspring only once a year. However, only about half of the female boa constrictor population is reproductive each year. Also, female boa constrictors can only be reproductive when they are in good physical condition. Boa constrictors typically have 25 offspring in one litter, but this number can go up to 60 in some cases. On average, female boa constrictors have three to five litters during their entire lifespan.
Can boas reproduce without mating? In boa constrictors, reproduction is almost always sexual. However, one boa constrictor was found to reproduce asexually via a process called parthenogenesis. According to Science Direct, this is the growth and development of an embryo occur without fertilization.