How To Sex A Baby Boa Constrictor

Do you wonder if your new boa constrictor is a male or female?

Are you considering breeding your baby boa when it gets old enough?

If you want to breed your snake, knowing the sex of your boa constrictor will tell you who their partner needs to be. 

Plus, learning how to sex a baby boa constrictor is just another way to be a good owner and learn more about your pet.

There are several ways to sex boa constrictors: visual identification, probing, popping, and palpation (also known as the “bump test”). All of these are appropriate tests for baby boas, but all are not equally safe or reliable.

Let’s learn more about sexing boa constrictors.

how to sex a baby boa constrictor

Boa Constrictor Anatomy

Every snake has a cloaca or a vent. 

This is a pocket at the base of the tail, housing the snake’s different sex organs.

Males have a forked penis, known as hemipenes. 

There is one shaft for each testicle, and they run along both sides between its vent and tip of its tail.

Females have glands, ovaries, and an oviduct, where eggs develop.

Ways To Sex A Boa Constrictor

There are four different ways to determine the sex of your boa constrictor.

  • Appearance: safe, but not necessarily reliable or accurate.
  • Probing: moderately safe and the most reliable method.
  • Popping: generally unsafe and potentially unreliable.
  • Palpation: safe and relatively accurate.

How To Sex A Baby Boa Constrictor By Appearance

Female boa constrictors are larger than males, but this only applies when the snakes are fully grown. 

However, sometimes we can tell the sex of a baby boa by its tail appearance.

This is an unreliable way to identify a snake’s sex if you’re not used to looking at both males and females.

Female tails taper evenly to the tip.

Males have longer tails than females, thicker at its base and in the middle. 

Then they drastically thin out at the tip.

How To Sex A Boa Constrictor By Probing

Probing is the most accurate way to sex a boa constrictor.

Only attempt probing if you’ve been trained by someone who has experience doing it. 

Probes could bruise or more seriously injure the snake when misused.

To probe a snake:

  • Someone else must hold the snake entirely still.
  • The snake must be awake.
  • You must use the appropriate probe size.
  • Make sure everything is sanitary.
  • You must lubricate the probe.
  • You must be confident you know what you’re doing.

Gently insert the probe into the cloaca, pointing it toward the tail.

Snake sexing probe kits like this one are available on Amazon.

Results Of Probing

If the snake is male, the probe will insert into one of the two hemipenes, going deeper into the snake than it would with a female.

Females will measure on average 1 to 3 scales on the probe.

Males will measure on average 9 to 15 scales on the probe.

How To Sex A Baby Boa Constrictor By Popping

Popping will expose the hemipenes, if the snake is male, temporarily turning the genitals inside out.

Generally, popping should only be done by a professional breeder or vet or by an owner who is trained and experienced.

This is only safe to do when boa constrictors are very small. 

As the snake gets older, the muscles holding the hemipenes in place will strengthen. 

Popping will damage these muscles in larger snakes.

To pop a snake:

  1. Put your thumb on the tail, pointing toward the head of your boa.
  2. With the same hand, place a forefinger under the boa
  3. Roll your thumb tip toward the cloaca, applying a little pressure.

If your boa constrictor is male, its hemipenes will pop out.

Why Is Popping Unreliable?

Popping is not a preferred nor reliable method of sexing. It’s hard to do correctly.

Applying too much pressure could hurt the snake and traumatize it.

Not applying enough pressure will not give you accurate results. 

Either you didn’t perform the procedure correctly, or your snake is female. 

You won’t know for sure!

How To Sex A Boa Constrictor By Palpation

Also known as the “bump test,” palpation is an excellent method to sex snakes for people who have no experience doing so.

The bump test is 98% accurate for boas younger than 2 to 3 years of age.

To perform palpation on your boa:

  1. Hold the snake in one hand.
  2. With the other hand, lightly grip the snake at its vent. Put your thumb on its spine and a fingertip on its vent.
  3. Slide your fingers down toward the snake’s tail. Hemipenes can be surprisingly close to the tail’s tip. Slide your fingers farther down than you may think you need to.
  4. Repeat this process several times.

Results Of The Bump Test

If your boa constrictor is male, you’ll feel two little bumps under the skin. 

Those are his hemipenes.

If your boa constrictor is female, you will not feel any bumps.

Some males tighten their hemipenes more than others, and it may be harder to feel the bumps in these snakes. 

Repeating the bump test several times will ensure you don’t mistakenly identify your snake as female.

When Do Boa Constrictors Reach Sexual Maturity?

Boa constrictors become sexually mature when they are around 2 or 3 years old or reach a length of approximately 5′ feet (1.5 m).

Differences Between Owning Male And Female Boa Constrictors

Female boas are bigger than males, so you’ll need a larger enclosure if your snake is female.

Females also tend to be more expensive and are more valuable since they can birth offspring.


Sexing your baby boa constrictor has its advantages, especially if you plan to breed or sell your snake.

Of the four sexing methods, the bump test is the best combination of safety and reliability.

Whichever method you choose, make sure you keep the health and safety of your snake in mind.

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