artificial incubation of reptile eggs

MONITOR - JOURNAL OF THE VICTORIAN HERPETOLOGICAL SOCIETY 9 (2) 1998

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MONITOR - JOURNAL OF THE VICTORIAN HERPETOLOGICAL SOCIETY9 (2) 1998:4-8, 31 Copyright Victorian Herpetological Society

ARTIFICIAL INCUBATION OF REPTILE EGGS

BRIAN BARNETT16 Suspension Street, Ardeer, Victoria, 3022, Australia.

Phone: +61 3 9363-6841 Fax: +61 3 9360-5704 E-mail: [email protected]

been successfully incubated in ‘old faithful’ with aminimum of effort and an extremely high success rate.

INTRODUCTION

Over the early years (1960’s - 70’s) I had tried manymethods of artificial incubation of reptile eggs andalthough many of these did work to some degree, Iwas looking for perfection. In the past I had incubatedeggs in a wide range of incubators, hatching containers,substrates etc.

Eggs having been incubated in heated rooms, in snakecages, on top of cages (floor heat to eggs) and underlight bulbs.

Egg containers varied from margarine and plastic ice-cream containers to plastic bags and glass jars.Substrates ranged from sand, peatmoss, sphagnummoss and paper towels. In some cases eggs werecompletely buried in the substrate and at other timesonly half-buried or even placed on top of the substrate.

Although a combination of many of the above materialsand methods are still used by others, and often quitesuccessfully, my article will not include alternativemethods but simply relate the system that I have usedfor several decades now, with complete satisfaction.

I sometimes laugh to myself when told of bettermethods, better incubators etc. Quotes like “ we havethis super dooper double insulated, triple thermostated,high tech humidity controlled incubator.” Sure some ofthese will work but are generally unnecessary.

Eggs are created to successfully hatch, in most cases,and I have found it is generally the ‘human element’that develops the failure rate.

INCUBATOR CONSTRUCTION

The incubator was constructed from 19mm particleboard and measures 1.2m in length x 56cm high x51cm in width. The size was calculated toaccommodate the number of a particular size ofcontainer that was to be used. As the incubator wasfixed to a wall, the door was hinged to the front (fromthe top) for easy access. The box was not ventilated inany way. As my incubator has always been kept in aroom that did not suffer from extreme variations intemperature, it has not been necessary to insulate it.However, as others circumstances may change fromtime to time, it would not hurt to insulate the entire box,either inside or outside with styrofoam sheets.

HEATING

Incandescent light globes are used for heating and arefitted to the ceiling of the incubator. Originally one globewas above each container to apply an even spread ofheat. The incubator holds 11 containers. In recent yearsI have reduced this to one globe over every secondcontainer, using only 5 globes. One end not having anyglobe directly over, has containers that I may wish tohave 1-2 degrees C. lower in temperature. 15watt,normal size, incandescent globes are used and thedistance between the globe and top of the egg containeris approx. 30cm.

The low wattage and distance are to ensure that thereis no sudden or intense application of heat. Choosethe lowest wattage possible that will work up to thetemperature you require in your own circumstances,but make sure that it can reach this temperature underadverse conditions. I can get away with the lowerwattage because the room in which the incubator is

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FOREWORD

An earlier paper was published as ‘ArtificialIncubation of Snake Eggs’ in Monitor in1981 (Vol.1 No.2 31-39). Several requestshave been made for a rerun or better still,an updated version. The same incubatorreferred to in that article is being used,which was constructed and first used in1976.

Twenty three years on has seen only veryminor changes in my technique and mypolicy is to keep it simple, follow provenmethods exactly and don’t interfere.

As well as incubating my own eggs, in thepast, other peoples were also incubated inmy incubator. It would be impossible toestimate the thousands of eggs that have


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kept never goes under 20 deg. C.

The lower wattage choice is also a safety measureto avoid any quick rise in temperature, pass thesafety margin, should a thermostat becomejammed, etc.

The globes are controlled by a room thermostat,IMIT TA2, which is mounted on one of the insidewalls. It is placed in a position where it is not directlyaffected by the heat of the globes when they switchon and in a position at container height is suitablebut as detailed later on is not crucial.

A pilot light is fitted to the outside wall of the incubatorand connected through the thermostat to indicatewhen the heating is on or off. This is simply a safetycheck without having to regularly open the incubator.

SITE FOR INCUBATOR

The incubator should be kept in an area where it willnot be unduly affected by extremes of naturalweather conditions. A cooler area where the lightsare required to work more often is preferred to awarmer area where temperature control may bedifficult to maintain during our warmer seasons. Avoidplacing the incubator on top of other heated reptilecages, if they are heated from the roof of the cagewith high wattage globes etc, as the temperatureemitted from the lower cage may be higher than thesafety margin required for incubation.

EGG CONTAINERS.

The containers that I use are known as breadcontainers, originally made to hold a loaf of bread.This will give you some indication of their size andshape. The bases are coloured plastic and theremovable tops are clear plastic which makesobservation quite simple without having to remove thelid and regularly spray the eggs from loss of humidity.The containers are sealed and not ventilated in anyway. I believe these containers are no longer availablebut there are many similar choices available these days.

SUBSTRATE.

The only substrate I use is Vermiculite which is a sterileabsorbent mineral. There are generally three gradesavailable; fine, medium, large. For what reason I amstill not aware of, the fine grade has resulted in somebad hatch rates. The medium I used for several yearswithout problems apart from purchasing batches that Ibelieve had some fine grade mixed in with it. For qualityreasons mainly, I use only large grade Vermiculite.

TEMPERATURE PRE-SET AND CHECK.

It is advisable to pre-set the desired temperature in theincubator before the eggs are placed in the containers.The temperature shown on the thermostat may vary tothat in the actual egg containers. I select one of thecentral egg containers as a permanent temperatureguide for accuracy. In this container I used to fix amaximum/minimum thermometer to provide me withaccurate daily readings. With the modern digitalthermometers available these days I have the probe of

the thermometer in the container and the body of thethermometer placed on the outside wall of the incubatorfor easy checking of current as well as maximum andminimum readings.

The thermostat is adjusted above the desiredtemperature and when the temperature in the container,as indicated on the digital reading of the thermometer,reaches the desired level the thermostat is turned downuntil it just clicks off and the lights cut out. The readingof the thermostat is of no interest, the reading in thecontainer is all that counts. Check this over the next 24hours and adjust if necessary.

HUMIDITY.

Relative humidity is kept high during incubation and Iuse a quantity of Vermiculite which would amount to adepth of approx. 25mm in the egg container. Water isadded to the dry Vermiculite in a measured ratio of 1:1,150gm Vermiculite to 150gm or 150ml water. This willresult in almost 100% humidity. If the container lid isnot regularly removed, very little additional water, if any,needs to be added during the period of incubation. If

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any eggs do start to ‘cave in’ during the early stages ofincubation, a fine spray of water over the eggs andmedium should be applied. Repeat this every coupleof days, in moderation until the eggs return to theirnormal full shape. During the last weeks of incubation,if the eggs have not swollen considerably, they willnaturally ‘cave in’ to a certain degree before hatching- I do not apply any additional moisture when thisoccurs. Condensation may appear on the inside of theegg containers, this is not a worry and the amount willbe influenced by the outside temperature. The warmerthe outside temperature, the less condensation visible.With my incubator, the coolest part of the egg containeris that at the front. The condensation tends to flow inthis direction and makes the Vermiculite at this endmore moist than at the other which can result in largerswollen eggs at the front and drier smaller eggs at therear. I simply rotate my containers around, front to backand back to front, once per week which evens out thisflow of condensation.

INCUBATION TEMPERATURE.

My incubator, or more precisely these days, my controlcontainer (the one with the probe thermometer) is setat a maximum temperature of 32 deg. C. When thistemperature is reached, the thermostat cuts out andbrings the power back in again when the temperaturefalls to 29.5 deg. C. I can maintain 3 or 4 containers ata slightly cooler temperature i.e. those at one endwithout the globes directly above them. This has beena very successful range for me in incubating a widerange of reptile eggs.

I have never incubated above this temperature (32 deg.C.) but on occasions, such as power supply strikes,the temperature has fallen below the desired minimum(as low as 24 deg. C.) for short periods of time withoutany damage to the eggs.

One point of interest in regards to incubationtemperatures was an experience with a clutch of SandGoanna Varanus gouldii eggs (Barnett 1979). The eggswere laid by a monitor in the care of a friend of mine.We decided to incubate half of the eggs each and theones incubated by myself using the aforementionedmethod and temperatures hatched in 169 - 172 days.The other eggs were being incubated at a lowertemperature, unfortunately not recorded, but estimatedat 24 - 25 deg. C. Only one of the three eggs survivedand were not necessarily lost through lack of heating.After 10 weeks of incubation at this lower temperature,the remaining egg was given to me to place in myincubator. This egg hatched in 208 days which was 39days longer than the ones that I incubated for the fullperiod at 29.5 - 32 deg. C.

REMOVAL OF EGGS FROM CAGE:

I remove the eggs from the cage where they are beinglaid as soon as possible. Normally the eggs adhere toeach other and form a clutch. Fortunately I have beenpresent whilst most of my eggs were being laid andthis has made the task much easier. In the case wherethe eggs have already adhered to each other it is not

essential to separate them unless you need to weighand measure them, need to fit them in a specificcontainer or it is just your choice for incubation.

Within the first 12 hours or so it is not too difficult toseparate the eggs. Select the eggs that are easiest toseparate, that is, those on the outside of the clutchand those with the least amount of surface areaadhered to the other eggs. The key word is ‘gently’. If itlooks like any of the eggs may be broken, maybe splitthe clump into several smaller clumps and incubate inthis manner.

The majority of eggs are quite soft as they are laid bythe female and I prefer to leave them to dry out and‘harden’ for approx. 30 minutes before placing them inthe hatching containers. This is done in a reasonablywarm area. In most cases, if you are going to weighand measure the eggs, it would take you this amountof time anyway.

I then discard any obviously infertile eggs. Size is reallyno good indication of this as fertile eggs from the sameclutch may vary greatly in size and/or weight. Any thatare extremely soft, do not ‘harden up’ or have the ‘non-white’ appearance (normally yellow/brown) arediscarded. These days I have a candler lamp whichilluminates the interior of the egg but generally onlyconfirms what I already know.

It is advisable to keep records (not memory records -they don’t work) of clutch sizes, egg measurements,weights, incubation periods etc.

EGGS TO HATCHING CONTAINERS

With the hatching containers prepared with thesubstrate and moisture, the eggs are now ready to beplaced in the containers. I make a shallow seat in thesubstrate by pressing down with a finger or removinga small amount of substrate from where the individualegg is to be placed. This is to ensure that the eggsremain stable and retain their position throughincubation. Eggs, if handled or removed, should notbe turned but kept in the same position throughoutincubation. The embryo develops very close to the topof the egg in the early stages and movement of thisposition may result in the loss of the developing animal.The incubator containers are not overcrowded and theeggs are placed so that they are not touching eachother although I do not have any specific reason fordoing this, it is more out of habit.

The same amount of medium and water is placed ineach hatching container whether it be for a clutch ofChildren’s Pythons eggs weighing a total of 200gms orfor 3 Black-headed Python eggs weighing a total of500gms.

RUPTURED EGGS

I have rarely experienced this and all occasions werein the early days when experimentation was part of thechore. This always occurred from over watering orinitially a bad incubation media ratio. No doubt someeggs would have been lost from this but some survivedlooking maybe 50 - 60% larger when they were laid.


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There comes a point when thepressure becomes too greatand the egg simply dies or aweak point in the shell,possibly created when pullingeggs apart, allows some of thecontent to weep out. In thiscase I have removed problemeggs into a dry substrate untilthe massive expansion hassubsided. With modernknowledge this should notdeteriorate this far. I prefer tohave my eggs looking as theywere laid or possibly only veryslightly larger. If you can seethis problem occurring shakeany excess moisture from thecontainer lid. Weigh one of theeggs to give an accurateaccount of whether it issubsiding.

My most notable ruptured eggwas that of a Childrens Pythonegg that split right open anddeflated 31 days intoincubation with an estimated24 days to go. Looking at thelittle pink occupant one wouldnot give it much of a chanceof survival. I decided to try andsave this egg andexperimented with a‘humidicrib’ (Barnett 1980).The egg was tied at eachcorner and suspended in anelevated position in acontainer in the hatchingcontainer. It was treated moreor less as a normal egg fromthat time on and ‘hatched’ 24days later. Its whole progresscould be witnessed andphotographed in the fullyopened egg.

HATCHINGWhen the time for hatching arrives, the young reptilesmake cuts in the egg shell with their egg tooth. Theymay not emerge from the egg immediately and in somecases remain with their head out, or emerging in andout, for several days. The snake will emerge when allor most of its egg food has been absorbed. Do notmake a practice of removing reptiles from eggs simplybecause of impatience. On the odd occasion where itseemed that a problem was existent a reptile has beenremoved from an egg its umbilical cord tied and cut,antiseptic to the cut area and placed in a sterilecontainer for several days. Some of these died as therewas obviously other complications but also somesurvived.

Once the first of the clutch has broken through its egg,

I sometimes make a slit in each of the other eggs inthe clutch. This is generally done for some of the moreuncommon or valuable species. Usually I attempt toleave most of them alone. If I slit an egg I rip it ratherthan cut it. By grabbing the top between the thumb andindex finger of both hands I find it pretty simple to createa small rip that exposes the contents without doing anydamage to the blood vessels etc.

GENERAL

Incubation periods vary from species to species andthose I have incubated ranged from around 8 weeksup to 30 weeks. Periods within a certain species mayvary and minor variance in incubation temperatures canproduce some interesting ranges. When working witha certain species consult a known authority and discuss

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techniques with them, it makes sense toget it right this year and not have to waitanother twelve months. You will no doubtmeet or hear about some local expertson incubation. A second opinion neverhurts as many of the so-called expertsmay have not much more knowledgethan yourself. Everyone knows how to doit better and some how come up withthese new techniques, devices andequipment that are going to change theherpetological world. They, and theirequipment, are usually short lived.

After sharing my experiences with you,on incubation, I hasten to add that whenmy incubator is full, I put any additionaleggs in the hatching containers in asnake cage, after the snake has beenremoved. They’ll hatch there anyway.

ACKNOWLEDGMENTS

Raymond Hoser and Peter Comberdiscussed parts of earlier materialpublished by myself and offered valuablesuggestions on the updating of it.

REFERENCES

Barnett, B.F. 1979. Incubation of SandGoanna Varanus gouldii eggs.Herpetofauna 11 (1): 21-22.

Barnett, B.F. 1980. Captive breeding anda novel egg incubation technique of theChildrens Python Liasis childreni.Herpetofauna 11(2):15-18.

Barnett, B.F. 1981. Artificial incubation ofsnake eggs. Monitor 1(2):31-39.

BRIAN BARNETT has been involved inherpetology for nearly 50 years. Arecognised authority, he’s successfullybred many reptiles including somespecies for the first time recorded inherpetology.

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artificial incubation of reptile eggs

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