General Breeding Information
Morelia viridis is a challenging and fulfilling species to reproduce in captivity. For an in-depth presentation of how-to breeding info, please order my book, The Complete Chondro. An overview of the fundamentals can be found below.
Few species of snakes being bred in captivity today evoke the passion and excitement as do Green Tree Pythons (Morelia viridis). Their highly variable colors and patterns, great beauty, fascinating offspring, and challenging breeding requirements, add up to make chondros one of the most sought after and addictive species. Most chondro owners find that they simply can't have just one! Actually, having a group of these animals is the rule for a good breeding project. Keeping just a single pair is a low percentage approach to successful breeding, and the odds of getting a fertile clutch go up dramatically when multiple pairs are set up to mate.
Chondro breeding is a major league study in patience. As you may conclude from reading this section, breeding the Green Tree Python is not for everybody. But if you have been infected with "chondro fever", conquering the challenges of breeding will add immeasurably to the satisfaction and enjoyment of keeping these beautiful and mysterious rain forest serpents.
There are several ways to determine the gender of your chondros. Everting the hemipenes of male neonates by applying pressure to the base of the tail is a common practice with many species of snakes. Due to the very fragile vertebrae of baby tree pythons, it is strongly recommended that this technique not be used on them, or in fact on chondros of any age. Probing, done by an experienced person using sexing probes made for this purpose, is a far safer way to sex your animals. Probing to determine the gender of chondros should be done only after the animals are a year old. Again, this will help avoid damage to the fragile vertebrae of young animals.
It may also be possible to determine the gender of yearling and older pythons by observing the body shape and feeding tendencies. Many males will begin to feed less aggressively, and will go off feed at times, beginning at eighteen months or so in age. Males often have more of a lean, slim body shape than the stout, stocky shape of most females, which also tend to grow larger. Of course, observing breeding behaviors is another way to sex chondros.
Mature male chondros will sometimes shed sperm plugs when they slough their skin. These are not shed hemipenes as is often claimed, but a brownish, dry string-like accumulation of dead sperm. The presence or absence (or size) of cloacal spurs is not a reliable indicator of gender, but the presence of sperm plugs is a safe sign of a male animal.
Some people feel frustration with the neonate non-sexing statements above, because they wish to purchase sexual pairs of animals for breeding. The best policy is to purchase a group of animals if the goal is to obtain a breeding colony. Just buying one pair, even a known sexual pair, is a low percentage method for those attempting breeding success. The steadfast avoidance of sexing neonates is something knowledgeable and responsible keepers and breeders accept as a part of working with these pythons.
In reality, getting chondros to copulate is the easiest part of the whole breeding process. GTPs can be bred through out the year provided the necessary environmental stimuli are provided. In a word, "change" seems to be the catalyst to inducing successful mating. For most breeders, this change is provided by dropping the night time temperature by ten to fifteen degrees F, after providing stable temperatures during the period prior to breeding. This temperature drop can be created by using natural temperature cycles where the keeper lives. I drop my cages down from a day time high of around 88 F to as low as 65 F at night. As long as the animals are warmed during the day, and have been properly conditioned prior to cycling, no health problems will be encountered. I cycle my breeders for four to six weeks before introducing them. Maintain this temperature regimen after the pairs begin to mate. I have had equal success regardless of which gender is placed in with the other. However, never place two males (or unsexed animals) together, as males can be territorial and may violently attack each other with serious injury often resulting.
I cycle my animals and leave them more or less together until I am sure that a successful breeding has taken place, or I determine that the pair are not compatible for breeding. Females developing egg follicles usually go off feed about 4-6 weeks prior to ovulation. I remove males once they lose interest in the female, normally about the same time she goes off feed. I restore nighttime heat for females once they ovulate, or if they are seeking heat and no longer being bred by the male.
Females produce follicles in their ovaries, which ripen and grow prior to ovulation and fertilization. Common symptoms associated with follicle development are loss of appetite, color and personality changes, and some swelling. This last symptom may or may not be clearly noticeable, depending on the size of the clutch. Females with ripening follicles tend to roll the coils slightly on the perch, was if exposing the eggs to overhead heat. Once females go off feed, turn pale or blue, and begin to swell, many breeders assume the female is gravid. In fact, females are technically not gravid until they ovulate. This event usually takes place about a month after swelling begins and food is refused.
A good ovulation produces a very noticeable mid-body swelling that appears suddenly, lasts for about 24-48 hours, and then disappears. Egg laying normally follows this swelling by about 40 days, but I have had females lay as long as 45 days after ovulation, and as early as 38 days. Shown below are photographs of females at the height of this 24 hour swelling. It is important to stop temperature cycles and provide the female with around the clock access to basking heat as soon as you observe ovulation, and to remove the male if you have not done so.
Ovulating females showing sudden localized swelling
Females will go through a pre-egg laying shed fourteen to twenty one days before the eggs are laid, with most clutches arriving on day 18 or 19. A nest box should be provided for gravid females once they have shed, and some may enjoy the security of one even sooner. I use wood nest boxes made of white pine, ten inches square, with a hinged lid, Plexiglas front, and a three inch access hole in one side. (See picture below.) The Plexiglas front is covered with dark paper except when viewing. I suspend the nest box in the top of the cage with an ambient temperature of about 82-85 F. Some breeders place the nest box on the floor. The best medium for the inside of the box is dry sphagnum moss, but whatever you use, it must be bone dry. Mist the cage, but not the inside of the nest box, to keep the humidity up until the eggs are laid. Females will normally enter the nest box soon after they shed, although some will not enter until a day or so before egg deposition. Some activity is normal, especially at night, but as egg laying time draws near the female should stay in the box.
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Green Tree Pythons have the ability to thermoregulate their eggs, and if your female will brood her eggs, then most of your incubating concerns are solved. Set up a brooding chamber for the female, which may be the same cage she lays the eggs in, or a special chamber you use just for the purpose. All the female needs to successfully incubate her eggs is an ambient temperature of 82-85 F outside the nest box, and moderate relative humidity. I say "moderate" because chondros don’t need excessive humidity when incubating eggs maternally. In fact, excess moisture will kill the eggs very quickly, and very high humidity will escalate the decaying process of any bad eggs, endangering the rest of the clutch. Water dripping down the cage glass or mold growing in the cage or on the wood nest box indicates too high a humidity level. Make sure you measure the temperature outside the nest box, as temps will be warmer inside due to the female generating heat for the eggs, which she does by muscular contractions.
Maternally incubated eggs take 49-51 to hatch. It is a good practice to carefully check inside her coils a few days after laying to make sure the eggs are fertile. Good eggs are milky white, and full looking, whereas slugs appear yellow or brown. As long as they stay dry and don’t begin to smell foul, a slug or two will not hurt the rest of the egg mass. If they start to rot and turn wet, with a distinct bad smell, they must be removed or the female pulled off and the rest of the clutch incubated artificially. For this reason, an incubator should always be set up and ready. Also, the eggs must be artificially incubated if the female will not form up a good "beehive coil" and incubate them herself. A proper coil completely envelops the eggs, with the female's head covering the center (see photo below.) Females properly brooding healthy clutches do not leave the eggs to drink or bask.
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I set up hatching eggs in a clear shoe box with slightly damp paper towels on the bottom, in an incubator set to around 84 F. I manually pip unopened eggs on day 49, and any eggs that have not done so on their own within 24 hours of the first ones. If any babies have part of the umbilical cord attached to their belly, do not try to remove it, it will drop off in a few days, and the first shed will heal the spot.
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At a point in time not all that long ago, hatching chondro eggs artificially was considered a very difficult proposition, with first-time success being a rarity.
For years the "jar" method, pioneered by Trooper Walsh and Gene Bessette, was the typical artificial setup. While this setup has been used successfully by both Walsh and Bessette and has worked for me, I have found it to be very intolerant of errors, and it is not easily duplicated by inexperienced breeders.
The Jar type incubation setup
Vermiculite
Recently, several breeders have described the use of damp vermiculite for incubating chondro eggs, and I have used this method with success. Mix a medium grade of vermiculite with clean water, and squeeze out the excess until the stuff clumps in your hand like a snowball. The eggs are buried slightly in the vermiculite and set up in the incubator at the temperature discussed below.
Moisture may need to be added occasionally during the incubation process, and if the eggs dent in during the early or middle period of incubation, conditions are too dry. It is normal for the eggs to dent in slightly during the final two weeks of incubation. I find it best to make up a batch of new vermiculite when the eggs need more moisture, rather than trying to add water to the tub holding the eggs. Be sure to inspect the undersides of the eggs to make sure they aren't desiccating, and decrease moisture if clear spots develop. Chondro eggs should look full and white, but not tight or stretched.
The vermiculite setup, showing lid opened and thermometer probe.
It is important to switch the eggs over to damp paper towels at hatch time, to prevent the hatchlings from getting covered in damp sticky vermiculite. This can kill them, especially if they ingest it. I place pipped eggs in a clear plastic shoe box lined with damp paper towels, and set the temperature at about 85 degrees.
For details about my use of vermiculite to hatch the 2001 calico eggs, click here.
Water Substrate
Most recently, an even easier method adapted by Trooper Walsh has been used with success by first-time breeders and experienced persons alike. Referred to as the "no-substrate" method because the eggs are not in contact with anything, this setup uses standing water to provide humidity. The eggs are placed embryo up in small plastic deli cups, about 6 eggs per cup. The egg cups are then placed on a plastic grid that is suspended above clean water in the bottom of a clear plastic box. Small pieces of PVC pipe are used to suspend the grid. The lid is placed on the clear box, and no ventilation holes are used, other than a small hole in the lid to allow insertion of the thermostat and thermometer probes.
Water substrate setup, showing egg cups, plastic grid, water, pvc pipe holding up the grid above water, and the thermostat and thermometer probes in contact with the eggs. The mercury lab grade thermometer in the foreground is used by the author to calibrate all his other devices.
During the final week, the eggs begin emitting moisture, and must not be allowed to set in the water that will collect in the bottom of the deli cups. Increase the ventilation to deal with this. Remove the eggs and set them up in a hatch tub as described in the vermiculite section. The eggs in the photo above were manually pipped on day 49 and the young emerged over the next few days. They averaged 12 grams in weight.
I like this method very much because it eliminates an important variable, namely how much moisture is present. There is no measuring or guesswork, as is needed when using vermiculite. Also, this method is very low maintenance in nature...there is no need to add water, and experimentation has shown there is no need to open the egg box for ventilation. This setup can therefore be left as is for days, except for making the recommended temperature changes outlined below.
Incubation Temperatures
Some breeders use one steady temperature throughout incubation, but I prefer to use the regimen developed years ago by Ophiological Services and based on the careful monitoring of multiple brooding females. I use Celcius to calculate temps, but I have given the Fahrenheit equivalents here too. The regimen is:
30.5 (86.9) for the first week
31.5 (88.7) for the middle five weeks
29.5 (85) for the final week
Make changes gradually. It is important to note that these are egg surface temps, not air temps. Also, properly calibrated and consistent equipment must be used to monitor eggs. I use an Atkins thermocouple probe thermometer that has been calibrated to within 0.01 of a degree C using an ice water slurry. I regularly experience 49 day hatches using this regimen and the Atkins thermometer.
One of the most common questions asked of me, and a cause for concern among many new breeders, is which incubator to buy or use. Let me state up front: There is no magic brand of incubator! There seems to be a common mindset that if the "right" incubator is used, then chondro egg incubation will be greatly simplified. This is just not so...GTP eggs will die inside a $6000 Forma Scientific incubator as quickly as they will in a Styrofoam Hovabator if the parameters for successful incubation are violated. However, there is now an excellent reptile egg incubator available, and at a very reasonable price for the performance. These are the precision Avey Inc. incubators, available in two sizes.
The most important characteristic of any incubator and its electrical components is consistency. Consistency is the term used to describe how much temperature fluctuation a given incubator will allow, and is largely determined by several factors, including the design and materials used in making it, the environment it is operating in, and the quality of the thermostat and other electronics. This is definitely not to be confused with accuracy, which is the term used to describe how close to a calibrated standard any thermostat or thermometer is. The most accurate thermometer in the world isn't much good if the incubator it is monitoring allows too much temperature fluctuation. When people ask which incubator is most accurate, what they really should be asking is which one is most consistent. The Avey units are stable to within one tenth of a degree Celcius, making them well-suited for incubating GTP eggs.
Consistency is the most important factor when building or buying an incubator. I would consider any fluctuation in temperature greater than 0.3 of a degree to be a problem. What this means in practical application is that if I want to have a clutch of eggs incubating at 31.5 C, I want my incubator to hold the egg temps between 31.2 and 31.5 all the time. Any brand or design of incubator will be more consistent if it is placed in a thermally stable environment. The more the ambient temperature changes around the incubator, the harder the incubator must work to hold a steady temperature itself. Also, the ambient temp should be at least 10 degrees F. cooler than the desired incubator setting. This will ensure the incubator will always be "working", rather than cycling on and off, which can introduce fluctuation.
The thermostat used to control the incubator temperature must be consistent as well. Make sure to use a proportional type thermostat, one that "trickles" electrical current to the heater, rather than the kind that merely cycle on and off. Helix Basic System thermostats work well. Don't use the Helix DBS-1000 as these can't be programmed with enough accuracy for chondro eggs. Wafer type thermostats, such as are commonly supplied with cheap incubators, should be avoided. The Avey incubators have dual heating elements and digital microprocessor controls for accuracy and reliability.
I use a high quality, lab grade mercury thermometer to calibrate all my other instruments and thermostats. You should know that most thermostats and thermometers are not accurate enough for chondro eggs unless calibrated. However, I highly value my thermometers that have been found to be consistent, regardless of how accurate they may or may not be. As long as they are consistent, I can factor out the small margin of error when using them.
The incubators I have used for years are not complicated. They are made of melamine, with wire shelves and a chick brooder heater installed in the bottom. These were designed as colubrid egg incubators, and originally used fans, also in the bottom, to circulate air. Now used exclusively for chondros, I don't run the fans. The incubator on the left is used for artificial incubation, and the larger unit doubles as an artificial incubator or as a brooding incubator for females in nest boxes. Humidity is supplied and controlled by placing tubs of water on shelves not occupied by eggs. The water tubs also act as a heat sink, providing thermal stability and a quick recovery of temperature when the door is opened. These incubators are low tech, but they work well, and hold temps consistently within 0.1 of a degree C. These incubators are housed in a small temperature controlled room.
Once the babies hatch I set them up in shoe box tubs with paper towels on the bottom, a small water dish, and a perch. A heat gradient of 82-86F is maintained by heat tape under the tubs. Plastic coat hangers cut to length and held at right angles with cable ties make good, easy-to-clean perches. Do not disturb the new hatchlings until they shed for the first time, usually 10-12 days after the hatch date. Do keep the paper towels damp and the humidity high, as the little guys are thin skinned and dehydrate easily.
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After they shed you can begin working on getting them to feed, and this is the step that separates a true breeder from someone who dumps poorly started babies on unsuspecting customers, or brokers them off to dealers. Learning to feed baby chondros is a learned art, but it is important to master the techniques involved if you want to be a responsible breeder.
Some of the babies will usually eat the first or second time you try them, although it may take many attempts per session before they will hold and swallow. Thaw out some frozen mice pinkies in hot tap water, and offer them one at a time to the new hatchlings after they shed. You will need to provoke strikes from the babies by pestering them with the pinky held in 12" forceps. After many misses and drops, the baby will bite and hold the pink. Freeze until the baby has committed to swallow. The use of a little scent on the nose of the pink may help with babies who will strike but not hold on. I have the best luck with baby chick down, and I keep one in the freezer for this purpose. Gerbil, hamster, lizard, or other things will work at times. Always make a note on the data cards you are keeping if a baby responds to a scent animal so you will know which one to use the next feeding. Never feed baby chondros whole frogs, lizards, etc as these are often parasitized. Use them for scenting pinkies instead.
I can usually get about 80% of a given clutch to eat on the first or second try. Work with troublesome babies once a week or so, when you are relaxed and have adequate time and patience to commit to the task. Don't pester babies day after day or you will over-stress them. For much more about feeding neonates, order my book The Complete Chondro. No book or web site is a substitute for learning yourself, but the tips and photos in the book will help you get started correctly.
Feeding hatchlings can be the most frustrating aspect of breeding GTPs. So to review:
1/ Tease and/ or irritate the baby into striking at a warm pinky. Poking, prodding, light pinching, blowing in the face of the baby, pressing lightly on the neck, are all techniques that may work. Usually the first meals are eaten from an angry strike response and not from a hunger response.
2/ Hold the pink in long forceps, and present it in such a way as to cause the snake to grasp the head when it bites. If the baby bites and lets go repeatedly keep trying. Often it takes just one lucky moment for all to go right, after many failed attempts.
3/ Allow the baby to eat where it can hang down with it's food item and not hit the bottom of the tub or cage. This can be a big key to success.
4/ The use of scent on the nose of a washed pinky can work. I have the best success with chick down, but lizard, "Lizard Maker", gerbil fur, hamster fur, and bird blood can all work.
5/ If the baby starts to run away or stops striking after repeated attempts to induce it, try later. Overly stressed babies seldom eat during that session.
6/ Try different times of the day or night, and always work in dim lighting.
7/ Assist feed pieces of mouse or rat tail, or very small pinks, to animals that refuse to eat for more than 8 weeks after hatching. It is better to try this than to let a baby starve.
The good news is that after a few feedings the babies usually begin to feed aggressively. Once they do, it's all down hill! It is extremely rewarding to watch the offspring from your own breeding efforts grow and change into beautiful adults.
