General Information about Breeder Animals

In order to produce offspring, you need at least one female and one male specimen. We point this obvious fact out, because some proud boid keepers realized in their first attempt at breeding that they had unknowingly acquired two specimens of the same sex when they purchased their animals a few years ago.

It is therefore an important fact that a successful breeding starts with an appropriate selection of specimens at the point of purchase. As we already established, the best source for this is an experienced keeper. If you acquire your animals from somewhere else, and you lack the necessary experience in properly sexing the animals, an experienced keeper should accompany you when choosing your animals.

The best breeder animals will always be those that you purchased as neonates or hatchlings, and then raised yourself. The least ideal ones are wild-caught specimens. This is especially valid for fresh imports.

Male or Female?

Sexing boas is one of the first skills that an aspiring breeder should acquire. It is useful to not having to rely on the skills (and honesty) of the seller when picking out offspring for future breeding projects.

Imagine that your efforts of many years are finally rewarded with a litter of newborn boids. However, when your potential customers show up, you can’t even tell the boys apart from the girls (among the snakes, not the customers).

In order to avoid this, we want to demonstrate the most common methods of gender determination in boas,  as much as this is possible to do in theory:

The only method to determine the gender of young animals accurately is probing, which is done by use of a metal probe, which is available in the trade in various sizes.

When sexing the snake, a lubricated probe of adequate size is inserted into the right or left side of the cloaca, and then
gently (!) pushed towards the tip of the tail.

The probe hereby enters the hemipenial pocket of the male or the musk gland of the female. Depending on the species of boa,  the probe can be inserted 2 to 5 scales deep in females, and 6 to 15 subcaudal scales (the ventral scales between the cloacae and the tip of the tail) deep in males. In order to “measure” this, place your index finger at the spot where the probe entered the cloaca, after the same has been inserted as far as possible. Afterwards, you pull out the probe and hold it on the outside of its body, right at the ventral side of the tail and count the subcaudal scales.

The previously mentioned work by Ross and Marzek contains a detailed listing of probing depths in the various species of boas on page 39 (German edition).

Another method of determining the gender in young snakes is by probing the surface of tail with your fingers. This is done by sweeping with gentle pressure from the cloaca towards the tip of the tail, using the index finger. On the upside of the tail, the thumb exercises slight counter-pressure. If the animal is a male specimen, you can feel a slight, double “crunching” when sweeping across it. This is due to the hemipenis, which is slightly moved from the pressure exerted by the index finger.

This type of sexing works with most boas. However, it is not entirely reliable. If a male specimen flexes its muscles in the tail area, the “crunching” may be absent, and the animal is then erroneously considered to be a female specimen.

Due to the increased amount of fat and muscle tissue in the tail area, it is not possible to use this method to successfully sex adult snakes. In that case, the spurs give an important hint regarding the gender of the animal, as they are much more prevalent in males.



Sexual Maturity

The point of reaching sexual maturity depends mainly on the age and weight of the boas. With regular feeding, it is usually reached in approximately 4 years. Some boids can reach sexual maturity even within a year and a half through so-called “power-feeding” (meaning you feed it as much as possible). Although practiced by some breeders, it places a significant burden on the shape and condition of the animals.

Males generally reach sexual maturity about one year earlier than females. It does not matter if the male is still a bit small when first reaching sexual maturity, as long as he produces fertile sperm. If that is the case, then his size is irrelevant. We have scratched our heads over many small Boa constrictor males, who enthusiastically mated females with 5 times the body mass of their own.

On the contrary, we do not recommend using “border line” females for breeding. The result – if the animal will even become gravid – will be quite meager with a handful of young or so. In addition, due to the frequent refusal to feed during gravidity, the snake will barely grow during this time, which means that next year’s litter won’t be much better. Besides, there also is the risk of young females to have difficulty giving birth or laying eggs, and thereby either die or require surgery.

The aspiring breeder should therefore be patient and rather wait another year. He or she will be rewarded with significantly better results and a healthy mother female.



Sex Ratio in the Breeding Group

You take one male and two, or even better, three females. The male will do his job, mate them all, and a good half a year later, the breeder will have babies popping out left and right. Since these will all be pure locality Boa constrictor, he or she will have no trouble finding buyers and get filthy rich.

So much for the theory. Unfortunately, reality is quite different. Not regarding to the pure locality Boa constrictor, but rather in regard to the tale of the “stud that knocks up three females" (to say it in breeder-slang).

We have never experienced or heard about a single male mating with two females AND receiving acceptable litter sizes. Although it does happen that a single male successfully mates two females, the result of that is similar to what a friend of ours experienced. He had two female Boa c. imperator, distribution area Colombia. Both were sexually mature, very strong animals, almost 2 m (6.5ft) in length. During the breeding season, they were put together with one male, and were both mated. One of the females had 11 young and 12 slugs; the other one had 4 young and 8 slugs.

We are certain that the result would have been significantly better if he had placed just one female (the larger one) to the male. Similar results have been reported from other breeders. We had to learn this the hard way several times ourselves. During the breeding season 1999/2000 we placed our Boa c. longicauda male together with two appropriate females. Our hard-working male mated both females intensively. While these efforts were rewarded in the larger female (she had 17 young), the second female ended up with all infertile eggs, and died from the anesthesia during the surgery resulting from the animal being egg bound. It should be mentioned that it is much more difficult for a female boa to drop so-called “slugs” than to give birth to live young, since the young simply “slide” better, and are thereby easier to pass. It appears that an intensive mating over the duration of the entire mating season is necessary, in order to fertilize all eggs.

Therefore, if you have the option to either place two males with a female or to place two females with a male, we recommend that you choose the former option. This is especially valid for species that are difficult to breed, as for instance Boa c. constrictor. The males of that species often show little inclination for breeding, and a second male can help solving that problem, as the rivalry between the two males often increases their motivation to mate.

In our experience, success in breeding is mostly dependent on the male’s willingness to mate. Unfortunately, the males in some species of boas tend to display little motivation to mate. You may have the most beautiful and massive female, and it won’t do you any good, unless the male copulates with her. Therefore our advice for beginning breeders: Every breeding group should contain at least two or even three males.



"Brumation"

This has long been a very debated topic, and opinions vary among breeders. The convinced breeder gradually reduces the lighting period and temperature in the enclosures before the mating season begins. During this so-called “cooling period”, the snakes are not to be fed, since the metabolism of the animals is reduced to such a degree that appropriate digestion may no longer be possible. Reducing the lighting period and lowering the temperature is done in various ways. Some boid keepers reduce the temperature by just 2° Centigrade (3.6 degrees Fahrenheit) and the lighting period by 2 hours, others implement a nighttime drop to 15° Centigrade (59 degrees Fahrenheit) and turn the lights off entirely. This is often done without detailed knowledge of the climatic conditions that are apparent in the distribution areas of the animals. The record holder in temperature reduction is a boid keeper in Bavaria, who bromated his ball python together with his colubrids at about 8° Centigrade (46 degrees Fahrenheit). Needless to say, the ball python did not survive.

After a certain period of time, which lies between four and ten weeks, depending on the breeder, the normal temperature is gradually reestablished, and … the antibiotic injections are prepared.

This brings us to an important aspect. Most of the boas that are used for breeding in this country are bred and raised in captivity or long-term captive wild-caught specimens. These animals no longer have the same tolerance towards variations in temperature that specimens in the wild have. This results in captive animals often getting a respiratory infection from the so-called “cooling period”. In that case, breeding season is obviously over for the animal.

To our knowledge, almost all of the species of boids kept in this country have been successfully bred without a “cooling period” by now. This includes species that come from distribution areas, where it can get pretty chilly. An example for this is Boa c. occidentalis, the Argentine boa. This species has been regularly reproduced by an acquaintance of ours without any change in lighting period or temperature, which was actually rather high (30° C [86 F] daytime, 26° C [79 F] nighttime).

We wish to point out an aspect that is rarely ever paid much attention to: Due to the increased ambient temperature in the room, the nighttime drop occurs significantly slower in the summer months than it does in the winter.

One example: The daytime temperature is 29° C (84 F) with a nighttime drop by 6° C (10.8 F). Due to the relatively high room temperature (which in turn is caused by the higher ambient temperature outside), the nighttime low temperature in the summer months is not reached until the early morning hours, while it only takes about an hour or so to reach nighttime lows in the wintertime, when outside temperatures are as low as
-10° Centigrade (14 degrees Fahrenheit) in some regions.

The number of daytime hours is thereby changed without any additional modifications. It is therefore valid that if a cooling period is necessary for the reproduction of boas, then such is automatically established through faster cooling at nighttime in the winter months. The same also applies for the reduction of daylight hours. This type of automatic “cooling” does not cause any harm to the animals and is more likely to lead to a successful reproduction than any kind of forced brumation.


Introducing the Animals

Surinam redtail boas (Boa c. constrictor) are among the most difficult species of boas to successfully reproduce. One of the most successful breeders of these animals kept his breeder animals together for 12 months of the year. The male was in the cage even when the female was giving birth to the young.

We are aware of several successful breedings of other species of boas by other breeders that utilized a similar approach. In addition, we are also currently experimenting with a similar and very promising approach ourselves, and are therefore no longer certain that the male and female must be separated outside of the breeding season.

The permanent co-housing has one great advantage: The perfect point in time to introduce both sexes can no longer be missed. This results in neonates and hatchlings that are born at a time of the year, at which they are usually not born at all. This demonstrates that species that are regarded as seasonal (=mating and birth of the young occurs around the same time each year) may become unseasonal in captivity or have always been unseasonal. The belief in seasonality may even be the cause of a lack of successful breedings at times. If the animals are separated during the fertile months in the summer, because the breeder is convinced that fertility is given between October and March only, successful reproduction becomes unlikely.

People who prefer to house the animals separately outside of the mating season (like ourselves until recently) should be aware that it is better to place the female to the male rather than the other way around. As mentioned in an earlier section, the male’s willingness to breed is the bread and butter of successful reproduction. If the male is not motivated, then that’s it. It is therefore recommended to disturb or confuse him as little as possible. The transfer to another enclosure may already eliminate any motivation to mate with a female.

We believe that both separation and permanent co-housing of the two sexes has their own advantages and disadvantages in regard to propagation. Every keeper has to determine his/her own strategy to succeed.


Courtship Behavior

When the male feels inclined to breed, he begins to crawl over the female and flicks his tongue at the body of his object of desire. The female usually tries to escape the intentions of the male by crawling away. This leads to a situation, in which the male chases the female through the enclosure until she no longer escapes. Once she finally holds still, the male coils his tail around hers and attempts to force the female to open her cloaca by scratching with his spurs, in order for him to introduce his hemipenis.

The sex organ of the male, the so-called hemipenis is y-shaped. One of the two ends is introduced into the cloaca of the female during copulation.

The female is usually not immediately ready for this. The male therefore attempts to get it anyways, by coiling the tail of the female with his tail and pressing both together in short intervals. Another medium to induce temptation is the scratching of the sides of the female’s body with the spurs. These very small nail-like structures can be found to the left and right of the male’s cloaca. They are the remainders of the rear extremities, which the snakes lost in the course of evolution. The spurs are much more developed in males than they are in females. Experienced boid keepers utilize this fact to determine the sex of adult specimens.

But back to the mating attempts of the male.

These can last for many hours and often end without success. Boid keepers will occasionally develop severe antipathies towards a female that refuses copulation for weeks or even months at a time.

We experienced the same in the beginning ourselves, until we realized that this behavior leads to the production of fertilizable eggs in the body of the female. Once the right point in time arrives, the female opens her cloaca and lets the male insert his hemipenis into it. As mentioned earlier, only one of the two ends of the hemipenis is inserted, the other one remains in the so-called hemipenial pocket.

Duration of the Co-housing

Potential breeders have unknowingly kept themselves from being successful by separating their snakes too early. Ovulation in the female is often associated with an enormous gain in body girth. To simply assume gravidity and to miss out on further copulations by separating the animals is the easiest way to receive a bunch of slugs from the female. This also raises the possibility of egg binding (more about this topic later).

As we mentioned earlier, we know several successful breeders who keep both sexes together during the entire year, even while the female is gravid or giving birth. The risk of unknowingly keeping the animals from mating successfully by separating them too early is thereby eliminated entirely. If a separation of the breeder animals is desired, we recommend waiting at least three weeks after the last copulation was observed.



Signs of Gravidity

Gravid or not gravid, that is the question. Or how did it go in Shakespeare’s “Macbeth”?

Jokes aside. Every boid keeper who has observed mating of his/her animals will constantly observe the female and wonder whether she is gravid or not. We therefore want to take a look at the potential signs of gravidity:

Increase in girth:
This increase in the girth of a gravid female snake is notable in the area shortly after the mid-body. While the increase in girth during ovulation only lasts a few days and then disappears again, it remains a constant condition during gravidity. However, even then the female sometimes appears to be a bit thinner, depending on how the eggs are positioned.

Refusal to feed
Gravid females often – though not always – refuse to feed. A reduced appetite is almost always notable. By the way, gravid females should also regularly be offered prey, even if they reject it for months at a time. At some point, they may want to have a snack in between. However, it is recommended to use fresh pre-killed or thawed rodents, in order to avoid unnecessary battles between the expecting mom and her prey. Rabbits and guinea pigs should be avoided altogether during this time, since the “abdominal area” of the gravid snake is already very occupied as far as space is concerned.

Reduced Activity
This is a sign that is almost always apparent. Once the boa or python is gravid, she usually becomes passive. Even our female Bahia Island boa (Boa c. imperator), who always used to disassemble her enclosure at night (4 “Repti-glo” fluorescent tubes are on her record) turned into a lazy snake and finally settled down, much to our joy. As punishment for destroying those fluorescent tubes, we sold her young.

We don’t want to omit the fact that there are some females who actually become more active when they are gravid. However, this is rather rare.

Seeking Hot Spots
A gravid boa or python has a greater desire for warmth, which the snake satisfies by frequently seeking the warmest spot in the enclosure for prolonged periods of time. An observant keeper will not miss such a change in behavior.

Darkening in Coloration
This is related to the increased desire for warmth as well. Gravid females almost always take on a darker coloration, which enables them to thermo-regulate more effectively.

Birth of Boas

In boas, birth occurs according to the motto, “what you see is what you get”. There is no guessing of whether the egg is still good, fertile, or if the young inside is still alive, as is the case with the egg-laying pythons.

Neonate boas are born in an elastic, transparent egg sheath, which they need to penetrate. At that point, nature already makes its first choice: Weak animals do not make it and die.

However, we have observed numerous times how mother boas use their mouth after birth to stimulate their young to become active, and even tear the egg sheath to help the young. Should you be lucky enough to observe the process of giving birth, you may do this for the boa mother, if she fails to do so. Of course, you may also decide to be tough and let only the strong ones live.

Caution is necessary, should you do it yourself, as the boa mother is not exactly friendly during and immediately after birth.

Infertile eggs, so-called slugs, are also passed during birth. In the worst case, none of the eggs was fertile and you receive a delivery of 100% slugs (every breeder’s nightmare).

First Care for Newborn Boas

In the wild, newborn boas are entirely dependent on themselves from the start, leaving the protective care of the mother within a few hours. Healthy and strong animals shed their skin within 14 days following birth, and start feeding on their own after doing so.

Besides the necessary cleanup in the enclosure, no further measures are theoretically required. However, providing the neonate boas with a first care has a number of advantages. The first care consists of the following:
 

• Drying the boa baby with a paper towel from the residues of birth
   
• Tying of the umbilical cord with a thick threat or dental string two fingers in width from the stomach
   
• Cutting the umbilical cord below the tied part with a sterilized pair of scissors
   
• Quick bathing of the animal in lukewarm water to wash off sticky remains of the birth process
   
• Drying the boa baby with a paper towel
   
• Powdering the umbilical cord with a wound powder available at pharmacies
   
• Placing the animal inside a freshly cleaned enclosure with kitchen paper as substrate 
   
• Repeat powdering of the umbilical cord again the following day

This handling immediately following birth gets the animal used to the person, which will thereby lose most of its aggressiveness. In addition, taking care of the umbilical cord prevents any potential infections.

The yolk sac, to which the neonate boas are connected through the umbilical cord, is completely exhausted in normally developed young at the time of birth. However, often times there are also some neonates in a given litter that “would have needed a few more days”. These animals are still attached to a more or less large-sized yolk sac.

At this point, it would be wrong to cut the umbilical cord the way it was described earlier. Instead, try to place the animal with the yolk sac inside of a plastic container that is lined with moist kitchen paper. Then place the plastic container inside of a warm enclosure. With a little bit of luck, the early bird will absorb a good bit of the remaining yolk, and thereby become just as strong and healthy as its well-developed siblings.

One more tip for people acquiring neonate boas: The approximately 1.5 cm (~0.6 inches) long lengthwise cut on the stomach of the animals is normal. This is from the umbilical cord that was positioned at that spot, and disappears in time.