Information On Aldabra Tortoise Reproduction

Information On Breeding -The Old And The Young

 

 

   Let's start with the senior citizens, we believe the current oldest giant tortoise is a male Seychelles tortoise named Jonathan who has been in the news recently. He has lived, at Government House, on St Helena in the South Atlantic Ocean, since 1882. Young Jonathan is now a mighty 192 years old! but although he lives with 3 other Aldabras, he is a subspecies of the Aldabra tortoise and may be the only one of his kind left.

 

   The next one is an Aldabran female named Esmeralda who is a spritely 172 years and lives on a small private island, named Bird Island, in the Seychelles. Esmeralda is in the Guinness book of records for weighing in at 296kg, which is a lot heavier than most female Aldabras get but that will be because, despite the name, she is actually a boy. It is not easy to tell the sex of an Aldabra when they are young, so be careful what you name them! 

 

   Ours have a long way to go to catch up- our eldest are only in their early thirties and the biggest female Bonnie is less than half the weight of Esmeralda.

 

   However, these two are only middle aged compared to a male Aldabra tortoise, called Adwaita, who died at Kolkats's Alipore Zoological Gardens in India on the 24^th March 2006. It is thought that Adwaita was an amazing 255 years old and had been born in 1750! He would have lived during the reign of 10 different British Kings and Queens and 19 Popes!

 

   Apparently Adwaita was one of four Aldabra tortoises brought by British seamen from the Seychelles as gifts to Robert Clive of the British East India Company in the 18^th Century. The tortoises went to Calcutta Zoo in 1875.

 

   Although several of the UK Zoos, and private individuals, have Aldabras in their collections and some of them are fully grown adults, none of them are as old as these three. People often ask why this is the case? The answer is simple, the sailors, on the old fashioned sailing ships kept eating them! So none of them made it back to UK shores alive for many many years, despite numerous voyages to retrieve some of these animals for the viewing enjoyment of the population of the time.

 

   150 years plus is not an uncommon age for them to reach, especially in captivity, where they have access to modern Veterinary care. The problem with accurate life span measurement is that the time required for record keeping, spans several human generations, so they outlive the people studying them!

 

Turning to the little guys- How Many Babies Survive To Adulthood?

   In the wild it is probably about 50% success rate, at best. Unfortunately, the hatchlings will often be taken by land crabs or rats. There were also other introduced predators on Aldabra Atoll until recently, when efforts were begun to eradicate them. Eggs were often eaten or destroyed before the babies were even born.

 

   Weighing in at only 87grams, and being 3000 times smaller than its mother, a new, black and shiny shelled, hatching will find it is a big world out there and lots of natural dangers for it to overcome, such as dehydration in the high temperatures, of the equator region, if it cannot find shade.

 

   So if a mother lays a batch of 20 eggs, approximately half of them will be infertile. Half of the remaining 10 could also succumb to predation when they are young, which means in actual fact only a quarter of the batch laid, that is just 5 of them, have a hope of making it to adults.

 

 

 

Have You Bred Any?

   No, and no one in the UK has achieved it either. In fact, it is only very recently that a private collector, in Europe managed to successfully breed the Aldabra Giant Tortoise in captivity. Although, in recent years our animals are showing more interest in mating, they have not yet laid any eggs. The tortoises need to be at least 25 years old before they reach sexual maturity, which is when they reach approximately half their full grown size and that the onset of reproduction is down to the size of the tortoise and not just the age.

 

   Most Aldabras that you can buy in the UK have been bred in the conservation parks on Mauritius and imported to Europe. These are only about 2 or 3 years old, sometimes younger, so you will have a long time to wait before they will breed. It may not even be in your lifetime. They have such a long lifespan that they are not in a particular hurry to pass on their genes, as long as it happens sometime in their lifetime it does not seem to matter to them whether they are 43 or 143.

 

   Aldabra tortoises are Polygynandrus, which means they will mate with more than one partner.  Just like the smaller breeds, the Aldabra male makes a deep trumpeting call when mounting the female and mating, so you would have to have very understanding neighbours! Mating season, in the wild is between February to May and the eggs would be laid between June and September.

 

    Our two largest tortoises are only in their 30’s and so are only just coming into breeding age, but they are beginning to show more interest. However, tortoises are often not particularly gender sensitive!

 

   There is a considerable size difference between most adult male and female Aldabras- the boys are always much bigger than the girls. We have evidence of this with two of our tortoises - Trojan our number two male is 160kg whilst Bekki is 65kg. We know from their import paperwork that they both came into this country at the same time, they were both yearlings and probably siblings but there is nearly 100kg size difference between the sexes.

 

 

Are our Aldabras Related?

   The animals in our collection have come to us, from all over the country, they differ in ages from youngsters to those in their thirties. However, as far as we are aware none have come from the American bloodlines, which means that they were all born in the conservation parks on Mauritius or in the region of the Seychelles. There is a successful captive breeding population of Aldabra Tortoises on Mauritius, so there will probably be some ancestral connection but without DNA testing we cannot be sure.

 

   The tortoises all came to us at different ages and at different times in their lives, so it is hard to know if they are closely related. As I said, although they ended up with different previous owners, we know that Trojan and Bekki were imported together as youngsters and probably came from the same batch of eggs, as they look very much alike. However, as all captive eggs are removed from the nests, dug by the female, by the keepers, and incubated artificially, a batch could consist of offspring from several different parents. So even though they were born at the same time they could be cousins, or totally unrelated, rather than actual siblings.

 

   We are interested in trying to set up a UK breeding program for the Aldabra Giant Tortoise, in the future and would be interested to hear from other Aldabra keepers about their animals. 

 

How To Tell The Difference Between The Sexes?

   As with most tortoises the males have a longer tail and a concave (internally bent) shell underneath them to help when mating. Mother nature has evolved this so that they don’t slide off the back of the females shell and risk rolling over and not being able to right themselves, which would mean death. As mentioned above, Aldabra males will generally be quite a bit bigger than the females, at breeding age, and have a larger head and more muscular neck, so that they can peer over the top of her body and shout down at her to stand still!

 

   However, it is very difficult to know whether Aldabra tortoises are boys or girls until they are about 10-15 years old, (approx 2ft long) without asking the vet to give them an internal examination, like you would with a snake. However, this can be quite stressful for the animal, so we have not had it done. Frankly they know what they are, and their care is not affected by what sex they are, so we don’t urgently need to know. The tortoises will naturally reveal their sex as they get older, well before they are able to actually breed, so all we have to do is wait.

 

   Unfortunately, this means you can put years into looking after them thinking that you have a pair who might breed, only to discover that you actually have two of the same sex! When hormones begin affecting them, both sexes will try mock mounting each other, so this is not a definitive indication of male on female -they could quite easily be two boys or two girls.

 

 

 

 

 

Do Tortoise Have Periods?

   Tortoises have reproductive cycles, which are certain times of the year when they can mate resulting in viable eggs but they are not periods. Males will then only mount the females during the mating cycle, they are able to scent when a female is ready for breeding. For most tortoises, in the wild, this is August to November and then November to April, to lay eggs. In the UK our Herman tortoises usually produce eggs around May/ June time, so in captivity these time scales differ a little.

 

   In the desert species like Sulcata, mating occurs in Autumn, and eggs will be laid in May to July, this is because she is preparing around 25 eggs and it takes a lot longer, whereas smaller species produce usually 4 or 5 but sometimes more.

 

   Experts believe that mating only occurs when the ovaries have fully developed, and both the male and female tortoise experience regulated testosterone cycles. This means they are around 15-20 years old, in the wild, but can be much younger in captivity at approximately 5 years.

 

   For Aldabras it is late thirties to early forties before they come into breeding age but as it has not happened much in Europe and only very recently, successful hatching have occurred, it is difficult to be exact. Many variables could be involved but because they are such long living tortoises, lack of the urge to breed when young could be a factor. Or it could be a physical thing or an environmental thing, more study on the subject is required.

 

   If you do notice blood around your tortoises private parts, whatever the sex, this would indicate an injury or illness of some kind and should be investigated, as it is not normal.

 

Reproduction

   Aldabra tortoises mate between February and May but they do not pair bond with their partner. As mentioned, the female is usually a lot smaller than her partner but they are very strong. The female will stand up during mating to provide access for the male to penetrate her. This means that she has to support her own weight, as well as the males considerable bulk pressing down on her. Adult females usually weighing in at about 100-150kg when fully grown. However, the big males can be over a quarter of a ton (250kg), that is a lot of pressure on her back legs! Neither animal seems to get particular pleasure from the copulation.

 

   Sexual maturity in Aldabras is by size rather than age, most will begin to reproduce when they reach approximately half their full grown size, which is usually when they are around 25 years old. Although this is nearer to 40 here in the UK.  When mating the male thrusts in 4 second intervals, giving a deep accompanying moan or grunt,  up to 44 thrusts are performed before he gives up and goes back to eating.

 

   A female will walk away, or prop herself up on her front arms, to dislodge the male if she's not interested. Successful mating is the females choice.

 

   These tortoise are Oviparous, which means the females lay eggs that she has carried for about 10 weeks. They are usually laid, between June and September, in a dry shallow nest on the ground that she has dug out using her back leg but if the soil is deep enough it can be up to 10 inches deep. Nesting occurs at dusk or in the night allowing the females to avoid overheating, it is hard work for them to dig out a nest using their back legs, especially as they cannot see what they are doing. Next time you go to the beach, give it a go- lie down on your stomach and try digging a neat hole to a foot deep, at the end of your torso, just using your feet and toes- its hard, frustrating, work.

 

   In the wild the female tortoises lay 4-14 eggs, which are rubbery to help with passing, between February and May, they are about the size of a golf ball but in captivity it can be as many as 9 to 25 in a year but usually not all of the, eggs are fertile. Once finished, the female drags herself over the nest to disguise it but after the eggs are safely covered over, that is the limit of her involvement; she does not care for the young, she is not maternal in any way and with luck the babies will hatch about 8 months later, in October to December, when they are on their own in terms of survival.

 

   In the wild, in high density areas, where there are lots of tortoises living, females lays four or five eggs every few years but in low density sectors, on the island, multiple clutches can be produced several times in the year. On Picard there is an average of 19 eggs laid but on Grand Terre, where most of the tortoises live it is only 5 or 6.

 

   The duration of incubation is temperature dependant and can take between 73-160 days depending on temperature but it's usually between 98-148 days, however, it can take as long as 250 days. Eggs incubated at warmer temperatures (30 degrees Celsius and above) – produce females, and hatch more quickley, while those incubated more slowly at lower temperatures (29 degrees Celsius & below) produce males. This temperature is determined by the depth at which the eggs are buried in the ground – a shallow nest, nearer the surface will be warmer, whilst eggs buried deeper will be cooler.

 

  Within the incubation period, sex determination occurs about the beginning of the middle third - somewhere between day 25 and day 75. If temperatures are too high – this may lead to deformities or death.

 

   Babies tend to all emerge during the same 2 week period, which coincides with the rainy season when food will be most abundant. The babies are about 3 inches long and are leathery to touch until the air begins to harden the shell, unfortunately it does make the offspring particularly vulnerable to predators. The baby Aldabra breaks out of its shell with the help of a beak tooth which is present on its mouth at birth and then quickly wears off.

 

   The newborn has a neutrian sac, attached to it’s umbilical, when born, allowing it up to a week before having to forage for food, so it has a chance to gain movement after being cramped up inside the egg. They have all the instincts needed to help them to survive, without being directed by an adult.

 

 

 

 

How Many Giant Tortoises Are On Aldabra?

   There is a self sustaining population living wild on Aldabra Atoll, and now introduced predators are being eliminated, today's population is estimated at around 150,000 animals, which is why they are classed as being a vulnerable species. However, this is 10 times as many as in Galapagos and why the Galapagos Tortoise is an endangered species. Unfortunately, there is some evidence to suggest that the tortoises on Aldabra are not reproducing to the same extent, possibly as natures way of preventing overcrowding because they will have a limited food supply or maybe for other reasons. Due to the fact they all live on an Island about the size of the Isle of Wight, there is also a greater chance of inbreeding developing as the years go on.

 

   The Aldabra Atoll is only a few metres above sea level and with the climate crisis happening causing sea levels to rise, it is just a matter of time before something like a Tsunami strikes and decimates the wild population of the region. It has happened before, in Aldabras past, and it will happen again, it is just a question of when?

 

   We mentioned earlier that the animals can take a long time to decide to breed. Here in the UK we have the added disadvantage that our weather conditions are nothing like those in the Seychelles, so we need to learn how we can artificially mimic what they need to be successful. From the lack of viable eggs being produced, we clearly have not succeeded in this yet.

 

   The unfortunate consequences of such devastation on Aldabra could easily mean that the whole population of the region both wild and captive bred are eradicated and in that case it would be down to animals in collections around the rest of the world to help repopulate.

 

   Yes, there are breeding animals in America but they would also need the UK and European animals to provide gene diversity. So we would like to encourage both UK private owners and zoo and wildlife park collections, to band together and share knowledge of their animals and try to develop a database where we could create as diverse a populations as we can, if it is ever needed. Lets not wait until it is too late, before we start to get organised, instead we should try and do something about it now. We have tried contacting the European Stud book foundation about who holds the Studbook for the Aldabra Tortoise but received no response. It is unlikely that this organisation would be suitable for the majority of Aldabra Keepers in the UK to join because, like ourselves, they are private individuals and not zoos or wildlife collections.

 

 

 

Could Tortoise Eggs Actually Hatch Naturally In The UK?

   Anything is possible, but it is highly unlikely that a batch of eggs laid in the ground in the UK would successfully grow and hatch, especially Aldabra eggs going to full term. One hundred and sixty days is over five months and we do not have consistent enough ground temperatures for that to happen.

 

   A smaller bred tortoise like the Hermann takes a minimum of 53 days, so it they were lucky, and laid in a sheltered spot, at a time in summer when we had a run of warm weather then it is just possible. However, fluctuating temperatures during incubation is much more likely to increase the chances of the babies being born weak or deformed in some way. It is a much safer option to put the eggs into the incubator, if you want to hatch them but there is always a very small chance that you could go outside to your tortoise pen, one day, and find the unexpected miracle of small hatchlings rushing around in there!

 

 

My Tortoise Has Laid An Egg Should I Hatch It?

   It is understandable that you feel the excitement of seeing that your tortoise has laid its first egg or eggs and you want to pop it in an incubator to see if a baby hatches out. However, you need to be aware that it does require quite a bit of monetary investment to hatch babies. You will need an incubator, which will need electricity to run for several months (the length of hatch time does depend on the species, some are much longer than others). You may find that after a number of weeks that there is no sign of your egg being fertile and it has been a waste of time. Or the hatchling may grow but it dies in the egg before its due date and is another waste of time and electricity.

 

   Once the baby is born you will then have to have a separate vivarium type set up, with appropriate heat and lighting, to house it as it begins to grow. It can’t go in with its parents and you wont be able to sell it the moment that it hatches. You have to feed it and keep it warm and again it may die as a newborn. There is also the chance that if, in your inexperience, your incubation temperatures and humidity levels have not been quite right then you may produce a deformed or sickly animal, which you would struggle to sell on. On this note, the first poo is usually a strange colour as it disposes of the contents of its egg sac, so if it is an orangey colour don’t be alarmed and think it is about to die!

 

   When the baby tortoise is happily eating well and the egg sack has all dried up and healed properly, you can turn your thoughts to selling it, if that is your plan. If under 100mm it will require a TSC, which is currently £31, Pet shops may buy the hatchlings off you but they will probably pay around £50 for it . So if you had a successful batch of 6 Herman eggs laid you are looking at £300, which is not bad but once you take off your expenses of £186 for certificates you only have £114 to cover your new incubator, vivarium and heating costs, so it is unlikely you will even make a profit. If you decide to sell the animals privately then you will probably be able to charge a little more as the pet shop will not need to take their cut. However you will then have to have potentially 6 different buyers coming to your house to look and buy, possibly more if not everyone decides to buy one. It could be a long drawn out process and you could have to keep the animal for several months.

 

   During this time the animal is using more electricity and requires feeding, which is chipping into your profit margins. Also when it gets to the 100mm mark you need to apply for its SSC before you would be able to legally sell it. I believe that the upgrade from a valid to TSC to an SSC is £1.50 but you would need to check the CITES website for confirmation on that. You will also need to have the baby microchipped by a suitably trained person, like a vet, which will probably cost £20-£30. So, again you will be able to charge more because it is an older animal but you will have also incurred more expenses, which will keep your profits low. There are people out there who want to buy tortoises and baby animals are always popular but Chelonia are a niche market and you may find you quickly sell 4 of your hatch but are left with one or two that you struggle to sell and as a result you could be running separate adult and baby set up for quite a while. Tortoise breeding is not the instant ‘cash cow’ that some think it is.

 

   Obviously, if you decide to breed another batch of eggs, in the future, then you would be in a better financial position because you already have the incubator and vivarium set up. However, you then have the moral dilemma of should you bring more animals into the system when there are already so many looking for new homes in rescue centres. Just because you can breed them does not necessarily mean that you should, that is something for you to decide.

 

 

Mother and newborn baby Hermann Hatchling, weighing 10g

If You Do Decide To Hatch The Egg

   Firstly, if your tortoise lays an egg above ground, like they have just dumped it in passing, then it is probable that it will be infertile and the female was just getting rid of it. If they have not put the effort into burying it or incubation then they can probably tell that there is something wrong with it. They can reabsorb the egg back into their body, if it is still inside her, after all she has put a lot of calcium into producing this little round ball. However, it is usually better for them to lay them as if they remain inside they can make the female egg bound and cause potentially life threatening health issues.

 

   The next obvious question is, can it be viable- do you have males in with your female. If not then there is no point in incubating, she is not the Virgin Mary! a baby hatchling is not going to result, so, don’t waste the electricity.

 

   The final obvious question is how sure are you that it was laid by your tortoise and not a bird, you don’t want to incubate and find yourself looking after a baby pigeon. Pigeon eggs and Sulcata eggs are about the same size and they are both plain white. The smaller breeds are also white and usually more towards the oval shape, Herman eggs are 30-40mm.

 

   If the female is seen actively digging a nest then they are more likely to be viable. It takes a lot of effort for the female tortoise to dig a hole, using just her back legs. So, if she is prepared to do this, and you have males within your group, then you can seriously consider incubation.

 

   Do not disturb her whilst she is ’in the zone’ she gets into a rhythm of movement and the process is incredible to watch. Once she has dug deep enough, as far down as she can reach with the very tips of her nails, she is ready to deposit the eggs. Number of eggs depends on the size of the tortoise and also if she is a first time mother. We only have recent experience with Hermann’s so newbies will be 3 or 4 eggs, and larger, more experienced, females up to 7 eggs. That is a lot of egg to fit inside a rigid shell, it must be very uncomfortable for them to have their internal organs pressed out of the way whilst the eggs take up a good 3/4 of their body size. At least with pregnant humans their stomachs can swell.

 

   She will carefully but tightly pack the eggs into the hole and then refill it with amazing gentleness once she has finished laying. She does a little dance as she drags to soil back over the nest with her back legs, that looks a little like ‘dad dancing!’ When she is done it is difficult to see where they have dug, so make sure you pay close attention if you are going to dig them out. Wait until she has finished and moved away, you don’t want to upset her. She will usually go off for a well earned drink or somewhere quiet to rest up.

 

   Take a plastic tub or suitable container and gently scrape the soil away, around the egg, they can be difficult to excavate and get your fingers around, so take your time. It is always a marvel to think that in the wild the babies would have to squeeze their way out. I guess that is why the ones at the top hatch quicker, in the warmer temperatures, close to the surface and the ones cooler down come out later. If they all hatched together, the ones at the bottom would never get out alive, their pathway would be blocked by siblings eggs. As it is they just have to get past empty shells.

 

   Once you have got them all out safely, scrape the earth back in and fill the hole up and then you can take the eggs inside for incubation.

 

   With a pencil write on the date that they were laid, before you put them into the incubator. It is a myth that tortoise eggs should be kept in the exact position that they were laid, as you are moving them. Yes, you need to be careful with them but you don’t need to move around as if you are carrying a live grenade. Don’t panic if one accidentally rolls over slightly in the box- you have not killed it! The setting of them only matters once they have begun incubation, then they need to remain still. As long as you don’t stand there and shake them they will be fine, you don’t want scrambled egg!.

 

   With this in mind if you are using a poultry incubator to incubate them then it is important that it does not have an automatic turning facility or if it does that you can disable it. Once the tortoise eggs have begun incubation you do not turn them.

 

   Temperature should be 29/ 30 degrees to get a mixed batch. Above and will be predominantly females and below mostly males. You will need to set the humidity levels according to the species of tortoise you are trying to hatch.

 

   Unlike with poultry eggs, it takes a surprisingly long time before the tortoise actually begins to grow so don’t throw them out too early thinking that they are infertile. About halfway through the incubation periods, if you candle them (thats shine a torch into the egg, through the shell,  so you can see what is happening inside (and not hold a lit candle underneath the egg!) It is best to do this at night or when the room is dark so you can see easier) you should have some signs of activity. it will begin with a dark red or black spot and then veins will begin to sprout out from it around the inside if the egg. as the hatch progresses you will see more of the tortoise begin to develop and gradually fill up the egg.

 

   It is exciting, and curiosity can get the better of you but don’t keep opening and closing the incubator unnecessarily, you will be affecting the temperature each time and it could affect the success of the hatch. Just because the tortoise has progressed this far does not mean that it will hatch successfully, there is still a reasonable chance that it will die in the egg.

 

   Calculate the day you expect it to hatch depending on the species norm and then keep an eye out for the egg beginning to crack. It is not an exact science, so some of them will pop out sooner than the due date and some will take longer. Eggs laid together will usually hatch together, within a day or two.

 

   In the later stages the humidity should be kept high so that it keeps the inner membrane of the egg damp and pliable making it easier for the tortoises to break out. If it is too dry then they wont be able to break through and then it sticks to them and they risk being shrink wrapped in the membrane.

 

   If at any point the egg develops brownish water bubbles on the outside it should be disposed of immediately, as the baby has died and it could contaminate and jeopardise the rest of the clutch. We would not suggest you open it to investigate as it is going to smell BAD.

 

   When it is ready to be born, the hatchling breaks its way out, using its egg tooth, on the front of the beak. It will make a small hole so that it can breath and then it will rest, this can take up to a couple of days, meanwhile it is absorbing the egg sac into its body, so no matter how tempting it might be don’t try to hurry the process along and start chipping the shell away, -it's difficult to resist, we know, but you may end up causing more harm than good.

 

   Once the hatchling is ready to emerge it makes fairly rapid progress out of the egg like opening a tin can and then squeezes and pushes itself free of the restraining shell. Don’t worry if it comes out looking a weird shape it is just how it grew in the egg. Over the next weeks and months it will begin to sort itself out and become a more recognisable tortoise shape. It is amazing how much detail their little bodies have, they are perfect, self sufficient, miniatures of their parents.

 

   You can either leave it in the incubator to rest a while or transfer it to a suitable vivarium where it can be warm in a clean environment. Make sure you take its shell and other contents out of the incubator, so that it does not contaminate anything else. If you do leave it in the incubator, only do so until it begins moving around or it will start dislodging the other eggs and could cause problems.

 

   Make sure that the surface on the floor of the vivarium is one it can grip on, too, the bottom of a plastic box or shiny magazines are not something they can get purchase on and you could inadvertently cause leg and hip displacements as their legs slide from under them. Don’t forget there is still a lot of development for them to do, even now they are out of the egg.

 

   Baby will probably just want somewhere to go and rest so make sure there is a suitable sized hide available to it. It will have the food from its egg sack so don’t worry if it does not immediately begin eating. The day after it was born you can put it in a warm bath. Don’t forget this is a tiny animal, so not too deep and not too hot- it's not a lobster- you aren’t trying to cook it! Don’t leave it unattended either. Do this daily for the next few days so that it is well hydrated and when its systems start to fire up it will poo. It may well be an unexpected colour, don’t worry if it is orangey it is just the colouration from the egg sac and perfectly normal. Don’t panic if it has not eaten in its first week, there is a lot of goodness in the egg sac, as long as it is bright and alert it is normal. Keep up with the fluids so that it can wash its digestive system through. Provide the hatchling with natural leaves like dandelions and clover, they should be readily available at the times of year that they hatch.

 

   As they get older the babies turn into locusts with voracious appetites, as they begin to grow, keep up the natural weed diet and adding the calcium powder to give it strong bones and shell. It is important that they get the right UVB light in their vivarium, to process this calcium though and do not make the humidity too dry. Humidity levels are important, especially with some of the more specialist breeds, such as the Redfoots, who are a jungle tortoise where it is naturally very damp and humid. Be guided by your research on your specific breed and enjoy your new tortoise family addition for many years to come.