Olm Diary 2016

In 2016 the whole world was excited to witness a remarkable event. This is the story of the incredible development of our "baby dragons" from eggs to 8-month-old juveniles.


DAY 01

Cave guide Juan Pablo Maschio noticed the first olm egg and informed Postojna Cave management and scientists who work there. All other olms, which could disturb the egg-laying process or even eat the eggs, were removed from the aquarium, with only the dragon mum and her egg left in it.

Did you know?

The pregnant female olm is fiercely defending her eggs from the other olms.


DAY 05

A new egg was spotted in the aquarium. In the last three days, the female olm relocated its egg-laying territory under a flat rock – one of the two ideal spots.


The olms mark their territory with chemical signals.


DAY 13

During the night, the olm gave us a few more reason to be happy – 24 reasons, to be precise! Today, we saw 24 eggs in total, arranged on both sides of the flat rock.


DAY 21

The female has laid egg number 52. The camera allowed us to watch cave amphipods (the small crustaceans we use to feed the olms) getting nearer to individual eggs. While the female was away, we could see three of them trying to bite through the egg envelope. As soon as the female returned, she immediately noticed them and attacked them.


Olms have an extremely developed sense of smell. They can taste and smell the food, and also assess its quality by smelling. More importantly, they are also able to detect even the weakest electric fields of other animals, which is helpful in complete darkness.


DAY 26

We had a visit by an expert on the biology of olms, Dr Lilijana Bizjak Mali, from the Biotechnical Faculty in Ljubljana, and Dr Stanley Sessions, an expert on integrative biology of amphibians from Hartwick College, New York, USA. They examined the eggs and found that some of them were showing signs of development.

Did you know?

In the USA, Dr Sessions researches, among other, the closest olms’ relative, i.e. a urodele amphibian from the genus Necturus. Necturi live in the surface waters of the Eastern coast of North America. Ancestors and relatives of our olm were also surface-dwelling animals. They died out during the ice age.


DAY 39

Discovery Channel visited Postojna Cave to produce a feature about this one-of-a-kind event taking place in Postojna Cave.
The precious eggs have received extensive coverage by a number of media outlets across the globe. But no other camera is allowed near the eggs, except the infrared cameras recording their development in complete darkness. 


DAY 46

We regularly check the water levels of the subterranean River Pivka, the olms' natural habitat. The river has risen. High water levels put olms in danger as the water may flush them onto the surface, where most of them die.

Did You know?

In Slovenia, olms are a protected species under the animal protection act. Since 1982, olms have also been listed as a rare and endangered species.


DAY 59

The female suddenly left the eggs and moved to the other end of the aquarium, where she laid another egg. The biologists are speculating that this might be the olms' natural behaviour: placing eggs in different spots gives them a greater chance of survival.


According to statistics, a mere two baby olms successfully hatch from 500 eggs in nature.


DAY 63

Some of the eggs are unfertilised. They are recognisable by lack of development, which is slowly followed by the first signs of decay. The decaying eggs become muddy and this is when they need to be removed to protect the developing ones.


DAY 72

The olms were seen making S-shaped movements, which made for a proper little dance performance and a source of entertainment for the cave visitors who were watching it on the screen inside the cave.


DAY 89

The day of the big relocation has come. We carefully moved the rock into the special container, so that we could move it to the aquarium away from the main cave tour route. Some of the eggs fell off and we moved them onto the mesh-like metal construction – some sort of an olm 'nursery'. Their development now continues close to the surface, where there is plenty of oxygen.


Olms have a life expectancy of up to 100 years and can survive without food for up to 10 years.


DAY 99

The gills of our embryos are slowly branching. The blood circulation and the first heartbeat are noticeable. Life is becoming more and more tangible. The embryos have become considerably calmer.


Olms breathe with external gills, as well as with rudimentary lungs and the skin. They have an inner ear, which serves both the purposes of balance and hearing.


DAY 109

Our offspring is spontaneously lying on the back. We are about three periods of change away from the eggs hatching. Earlier today, we were happy to see an embryo turning around in the egg envelope rather vigorously for more than an hour. It won’t be long now until we get to see it.


Depending on the water temperature, the olms' embryo development inside an egg may take up to 140 days, which is extremely long compared to other urodeles (i.e. amphibians that have a tail throughout life).


DAY 112

We received another visit by Dr Mali and Dr Sessions. Dr Mali took a photograph of an embryo under the microscope.
She pointed out that a small dimple for the toes is already visible on the limb rudiment, which is a sign that it is not long until the hatching stage. (We have to admit that we were happy like proud expecting parents seeing their baby's ultrasound.)
The embryo seems to be in the development stage 19 according to Briegleb.

The gills are more branched, the eye pigment is visible, the heart is beating and is supplied with blood. The size of the embryo is between 17 and 18 mm.


Olm larvae have eyes, which are covered by a layer of skin in adult olms.


DAY 124

On the 30th of May, 142 days after one of Postojna Cave's guides first spotted the olm egg, the first baby dragon was hatched. He was born into the darkness of the underground world and the light of the world of excited fans who have been waiting for him with baited breath since 30th of January 2016. 


DAY 125

Only one day after the first baby dragon, its younger sibling was caught in the act during hatching. Another moment of new life being born was captured.


DAY 138

Our firstborn is growing, the eyes and the feet are clearly visible. These days she is keeping busy swimming to the surface and back. Not long after, our brave olm was joined by 12 other newly hatched siblings.


DAY 139

Another olm hatchling has made its way out of the egg. If this makes you think ‘so what’s new’, think again. This particular hatchling is obviously being very cautious, knowing that it is not good to be reckless and hasty. Therefore, it started breaking through the egg envelope with its tail, and hatched differently than what happens usually, i.e. with its tail first and only then – after it had made sure everything was fine – the head followed as well. 


DAY 140

The fast growing hatchlings will soon need to be moved into aquariums, each of them into its own, which is quite a delicate process. However, all of this makes for some 'pleasant problems ' for our biologists, who are busy preparing the first batch of food supplies for our baby dragons to feed on when they are ready to show the first teeth.


DAY 142

What do you call someone who survived even though most of the people had believed (s)he would not make it? Someone who, statistically speaking, was least likely to make it because his/her living conditions were simply too harsh. Someone who surprised and impressed all others with his/her birth, perseverance and persistence. The perfect name seems to be... Boris!

Boris hatched from an egg that was closest to the infected – mouldy – eggs, so we had to move him to a special container, which had no special filtration and the water was filtered in a ‘natural’ way. In the meantime, we waited and waited. And on day 142, Boris finally made it and posed in front of the camera somewhat cheekily. Welcome, Boris, you wild little thing, we wish you good luck. 


DAY 146

Up and down, up and down, the hatchlings are romping around their containers. They love swimming to the surface and back to the bottom of the container. It seems they get more than enough energy from egg yolk. With their heads, which are already trapezoid-like in shape, they increasingly resemble adults. But they are not yet white, they are still nicely pigmented. On the largest of hatchlings, hind legs are already visible as well.


DAY 149

As with any child, there comes a time for some measurements and numbers. When it comes to olm hatchlings, this needs to be done without touching, so a grid sized 1 x 1 cm has been placed at the bottom of the aquarium. The largest ‘dragons’, which hatched first, are now between 2 and 2.5 centimetres long. In some of the hatchlings, yolk is still visible in the abdominal area and some already have all three digits on their front feet.


DAY 153

While the hatchlings are still feeding on yolk, we are busy preparing food. Five embryos are still waiting in the egg envelopes. It has been more than a month since the first hatching and we expect the mouths of the oldest hatchlings to start developing soon, which means they will have to start eating. This is one of the most uncertain moments, which is making us increasingly nervous. 


DAY 161

Our two biologists once again rolled up their sleeves and made their way to one of the few perfectly clean parts of the River Pivka to get some mud, which they then put into a special Petri dish and placed it in the container with one of the olm hatchlings. We wanted to check how the hatchling would react to elements from the natural environment. The baby dragon was happy to plunge into the mud and also made good use of the Petri dish itself, hiding under it. As olms like being right next to stones because this makes them feel safe, we set up some hiding places made of glass for others as well, where they are now resting happily. 


DAY 168

Yoyo has hatched! The last baby dragon. We named it Yoyo, as it was – while still inside the egg – literally hanging from the stone on a string, moving back and forth. A day before, the so-called Laggard had finally hatched too. This hatchling had wanted to really make sure it was worth coming out of the egg envelope. We noticed that in terms of their size and development the last two hatchlings were very similar to others who had hatched well before them. It looks like they were overdue, having developed in the egg envelope in the same way they would have outside of it.


DAY 174

The baby dragons are hungry. Five days ago, we treated the four oldest and largest ones to a proper feast – some delicious worms. Two of the hatchlings were happy to eat them. Although almost all olm hatchlings still have some yolk reserves left, the fact that they are already eating means they are developing just the way they are supposed to. In the days after, we fed the worms to the other hatchlings as well and we are happy to report that some of them munched their way through the prey like fearsome dragons. 


DAY 182

Little toes, limbs and mysterious lines. Some of our baby dragons already have three toes on their forelimbs and their hind limbs are growing and developing quite nicely too. One of the baby dragons lifted its head for the first time earlier today, which is another good developmental sign. They are developing their predatory instinct. They are now able to sense worms (i.e. their lunch) from quite a distance; they slowly approach the worms and eat them quickly. Therefore, you'd better be careful. The baby dragons may be cute, but they can grab hold of you before you know it.


DAY 201

The baby dragons are losing weight – as far as development goes, this is perfectly normal, as our hatchlings are growing in length; in fact, some of them are now even more than three centimetres long. The legs of the most developed ones are already functional, i.e. the baby olms have ten digits, four legs and are busy exploring their surroundings as we speak. When hunting for worms they are making use of their rear legs – they are using them to move around. The most advanced baby olm explorers resemble the dragon momma more and more every day and are growing very fast. Dear baby dragons, you’re welcome to overtake in the left-hand lane, but do it with caution and with best of luck. 


DAY 223

It’s been 110 days since the very first baby dragon hatched. According to a developmental stage table that was published by researcher Durand in 1963,  this period (110-120 days) completes the olms' larval stage and a juvenile or adolescent period starts. The baby olms are between 3.5 and 4 cm in size, their bodies are getting longer and the ratio between the thickness and the length is 1 to 12. Their legs are functional, the head is trapezoid in shape and flattened.  During the larval stage, the baby olms' growth was fast, while during the juvenile stage it slows down.


DAY 256

This is the sound of our baby dragons carefully and slowly moving towards prey. Their hunting instinct is very much alive and kicking. Their eyes are clearly visible, the pigment is still present, but the yolk is all gone, as they now make sure they are not hungry themselves. The biggest baby dragons are between 4.5 and 5 cm long. As far as their looks are concerned, they are now already very much alike adult olms. 


DAY 298

During the past few months, it may have seemed that everything revolves around our baby dragons, but we haven’t forgotten about our adult "dragons". But as far as they are concerned, everything runs smoothly and they are also much less demanding than the little "monsters". Their aquariums need to be cleaned and they have to be fed on a regular basis, and we need to have a bit of a talk with them from time to time when nobody is listening :). To make sure our adult olms get to enjoy a delicious feast, i.e. some amphipods, our two resident biologists need to get down to work, put on some boots, get into the water and catch some amphipods in the stream. Since no dangerous foreign bodies are allowed in the aquariums, the two biologists need to carefully pick the amphipods using a straw. It’s a hard job, but a fun one too. And in the late autumn, also a slightly cold one. 


DAY 307

While our adult olms are feasting on fresh amphipods, the baby dragons enjoy spending time in their hidden kingdom. We are still seeing to their food, and making sure they have their favourite "furniture" at hand – rocks, which they can hide behind. All of the baby dragons are now 5 cm or more in length. May they be growing just as fast as they have so far.


DAY 337

A big dinner, some dancing, some fun and games until midnight and then the fireworks. This may sound like your New Year's Eve, but the baby dragons had an evening just like this. After seven months since the (first) hatching, our baby dragons are now up to six cm long, which means that – on average – they are three times bigger than when they hatched. They started the new year with luck on their side, and we hope it stays there. Happy New Year from the dragon's underground nest.


DAY 350

Two olm babies made sure there was a bit of a panic. We noticed the two oldest olm hatchlings had white spots on their heads. Without having a closer look at it, we were not sure what it was, so naturally we got worried something was wrong. Therefore, the whole team got together and made their way into the cave with a lump in their throat instead of going home to do some Friday afternoon 'couch potatoing’. Dr Mali and Dr Sessions made it from Ljubljana during a blizzard as well. "They are growing up," was our team's official diagnosis. The white dots obviously signify a loss of pigment, which we had said would happen. In about a year, "white spots" will cover their entire bodies and the hatchlings will change "colour" and thus become even more similar to their parents; in fact, during adolescence, pigmentation gradually decreases, until it has completely disappeared. Beautiful, but somewhat painful at the same time. They will grow into proper big dragons almost too quickly.


DAY 367

The baby dragons are celebrating! It's been exactly one year since the first olm egg was found on the glass of the large exhibition aquarium. Our 21 baby dragons are now six centimetres in length. When they hatched, their front legs were fairly well developed with digit gaps, while their rear legs were underdeveloped with digit rudiments. Now, all of their four legs are developed with a total of ten digits. Their head, which was short at the time of hatching, now already resembles a duck's beak, their pigmentation is gradually disappearing, their eyes are still visible. When olms hatched, their mouths had no opening, but had teeth rudiments and yolk reserves. Now, the yolk is all gone, their predatory instinct is well developed and the baby dragons finish off their prey in no time without hesitating, which you see on the following link: https://www.youtube.com/watch?v=GP0xltqovrA


DAY 378

Over a year ago, on 30 January 2016, the daily work of the three-member Postojna Cave laboratory team changed completely and ever since then their workdays kick off in a totally different way. For more than a year now, the team leader and head of the underground laboratory, Katja Dolenc Batagelj, has been starting off her working day by observing the baby dragons in the laboratory, while our two resident biologists make sure the young olms get all the living food they need. Even now, more than a year later, the team members visit the laboratory every single day, keeping an eye on the development of 21 olm juveniles, providing them with the food (every three days), changing the water and making sure the olms have the optimum living conditions. According to experts, the Postojna Cave laboratory is a remarkable success that is setting new paradigms; in fact, owing to a high number of olm survivors it is currently considered the most successful cave laboratory in the world. Here's to a lot of success and luck in taking care of the baby dragons in the future!


DAY 487

Happy birthday, baby dragons! The first birthday cake is being baked at Postojna Cave as we speak. One year ago to the day, on 30 May 2016, the first of our baby dragons hatched. It was joined by other olm hatchlings in the subsequent eight weeks, with the last one hatching on 14 July. Today, there are 21 baby dragons developing successfully at the cave laboratory, which has won the praise of experts for the work it does. All of our baby dragons are all just over 7 centimetres in length, their body and head are elongated, they have three and two digits on their front and rear legs respectively. What makes them different from adult olms are their tiny eyes, the pigment, which is slowly disappearing, and their size. In the next few years, their eyes will get covered with skin, the pigment will disappear completely, and their body will get elongated further. They will reach sexual maturity in the next 14 years and will live to be at least 100 – well, at least that’s what we’re hoping for. All the best, baby dragons! 


DAY 552

Measuring, observing and taking photos... The year-old baby dragons have been visited by a complete team of experts in order to assess how well they were doing: they are healthy, they have a healthy appetite and they are making good progress. At the moment, they are between 7.5 and 8 centimetres in length, which means they have grown 5-6 centimetres in a year. Their skin is still slightly pigmented, but their tiny pigmented eyes, which is the visual feature that distinguishes them from adult olms most, will slowly "disappear". Their eye diameter currently measures 0.5 millimetres, but since the cornea is already slightly thickened, it is no longer so translucent. As soon as their eyes are completely covered with skin, our baby dragons will become real adult dragons. :)


DAY 661

Following the record-breaking numbers of Postojna Cave visitors, new records are now coming from our cave laboratory, where the giant-sized baby dragons are living. At the age between 16 and 18 months, the largest baby dragons are currently up to 10 centimetres in length. You don't think this sounds like much? This is actually far from not much, it is actually a very large size, as the olms are supposed to reach the length of ten centimetres when they are six years old. The last time the baby dragons were fed, two of them got into a bit of a tussle – you can see it here.


DAY 793

We have witnessed how wild young olms can be. They are often territorial and get into fights, which is perfectly normal behaviour at this age. We noticed that after a tussle between two juvenile olms in one of the aquariums, one of our ‘baby dragons’ ended up without his left hind leg! His brother, with whom he had been sharing the aquarium until this unfortunate event, injured him badly by biting his leg. We took care of the olm and then let nature run its course, which showed how amazing mother nature really is when it comes to our baby olms. The injured olm's leg first fell off, however, a new one started growing soon after. We named the injured olm Victor.


Olms have this extraordinary power of regeneration – they can regenerate lost limbs, nerves and even organs, such as the heart or the brain. We now have a unique opportunity to watch the recovery after losing a leg after what happened to Victor – one of the juvenile olms from our laboratory.


DAY 1262


Lately, we've been getting this question a lot. Exactly three years ago, the world was delighted to learn about the hatching of our ‘baby dragons’, the twenty-one olm hatchlings from Postojna Cave. During the first few months, we often reported on their progress because the changes were very obvious and took place on a regular basis. Lately, however, changes in our olms’ development have become less noticeable and slower (in caves, time goes by at a different pace) and many people have been getting a bit worried if the ‘baby dragons’ were ok. No worries, there is no reason to be concerned. Our twenty-one juvenile olms are making good progress and even providing us with new scientific findings. While our biologist is showing visitors new olm aquariums, one of the baby olms is showing off his new leg.


DAY 1322

Victor is proudly showing off his new leg! A mere year and a half after a violent tussle between two young olms, the wounded ‘baby dragon’, Victor, has grown a new leg. We have kept a close eye on the olm’s remarkable ability to regrow limbs and have documented it all on a regular basis. The development of a new leg from a set of cells to a fully functional two-digit leg can be seen here.


DAY 1496


The baby dragons are leaving their ‘nest.’ With a calm hand and a bit of excitement, our biologist and the head of the cave laboratory moved the first baby olm from the Postojna Cave laboratory. His new home is a new exhibition aquarium at the entrance to the Tartarus (the part of Postojna Cave where the subterranean river Pivka flows and is closed for regular cave tours). He will soon be joined by two more baby olms and you'll have the opportunity to get to know all three of them.


DAY 1595


We are proudly presenting our ‘baby dragons’. From today, Postojna Cave visitors can meet our baby dragons face to face. The only baby olms in history that we have been following since they were still eggs are now finally on view. You can visit them in the company of our biologists and learn all about these animals that can regrow the injured parts of their body, go without food for at least eight years, and live to be 100. You may even find out the secret of their eternal youth.


Two Postojna Cave Olms Now Have Godparents

Our olms are growing up! And so are we as we focus on research and on raising awareness of subterranean life and environmental conservation. Our efforts have been recognised by the company Generali Investments Slovenia, who was the first to take on the role of olm godparents, helping us set up a new aquarium, which is now home to two of the olms hatched back in 2016. 


Protect Proteus Project

After Postojna Cave was nicknamed the House of Dragons by a National Geographic journalist, it was time for the Protect Proteus Project – a sustainable project focused on raising funds to ensure optimal living conditions for our baby dragons (olms) and a long-term preservation of clean drinking water.

Olms are known to have some super powers. But anyone can be a superhero by purchasing a Protect Proteus lucky charm bracelet and supporting the project.