Olm Diary 2022

The 2022 Brood of Baby Olms 



"Are there new eggs?" was the perfectly innocent question asked during a school trip by Jaka Kresnik, a 13-year-old pupil from the Loče Primary School, who has thus gone down in the history of Postojna Cave as a "new discoverer". Jaka was the first person to notice tiny olm eggs in one of the cave aquariums, thus surprising even the tour guide and the cave biologists with his question. Of course, this has resulted in immense joy and excitement! And indeed, one of Postojna Cave's female olms has laid some eggs, this time in the Vivarium. We'll soon have a new brood of baby dragons.


In 2016, we witnessed the first ever hatching of olms in Postojna Cave in its 200-year history as a tourist cave.



The cave laboratory team is about to have their hands full again! This time around, the team is slightly different than during the first venture in 2016. In the meantime, the head of the team Katja Dolenc Batagelj and biologist Primož Gnezda have been joined by biologist Katarina Kanduč.


Earlier this year, the baby dragon guardians, i.e. the team taking care of Postojna Cave's baby olms, was named finalists of the prestigious NATURA 2000 competition, organised by an EU expert panel of judges, which sits in Brussels.



The first thing for the team to take care of was make sure our new treasure is safe. Katarina has used dark felt to darken the aquarium and thus secure the area from prying eyes. IR cameras have been turned on and will be used to film the female olm during the egg-laying process and capture the first images of the eggs of our future baby dragons.


Since 2016, we have been carefully recording the interesting life of Postojna Cave's olms with IR cameras. Our archives, which contain thousands and thousands of hours of footage is an invaluable source of information for the world of science and offers valuable insight into the development of one of the least studied animal species. 



We have counted 13 healthy eggs! Once again we have teamed up with the Biotechnical Faculty of the University of Ljubljana and our 2022 brood of olms has been visited for the first time by Prof Lilijana Bizjak-Mali, PHD. According to her estimates, the eggs are now 5–6 days old and in the early stage of embryogenesis, i.e. the zygote and division stage of development.


The olms' egg-laying process can take several weeks, which allows us to observe embryos in different stages of development at the same time.



Our female olm has been hard at work laying eggs. There's now 24 of them and cleavage (the division of cells) is progressing smoothly. One of the eggs in particular stands out from all the rest: we are witnessing a rare thing, i.e. two eggs inside a single egg jelly coat! Fingers crossed for twins!


What we are not witnessing is identical to a drawing by the German scientist Marie von Chauvin from as far back as 1883, when she was researching the reproduction of olms. He drawing is believed to be world's only drawing and record of olm twins, but there is no information about the completion of her research. 



"It's all about TCL," emphasises the head of the cave laboratory, Katja Dolenc Batagelj, using the acronym that is always at the back of the team members' minds, to point out how very important unconditional and tender loving care is for the olms. The eggs are carefully examined every single day. Of the current 27 eggs, 3 have been found to be critical. Katarina has put one of them in quarantine, while the team will keep a close eye on the other two. 



We were staring at the twins full of hope and excitement when there was an unexpected turn of events. After several long attempts, the female olm devoured the egg jelly coat containing the two eggs. For a bit there was nothing but silence and the team's mood swung back and forth between sadness and disappointment. All sorts of new scientific questions have arisen, the main one being WHY.


According to the information known so far, the olm mother is believed to have eaten only the unfertilised or damaged eggs. Which category do the twins fall into?


DAY 20

There is no shortage of action when it comes to our baby olms. Our baby dragon guardians have counted 43 eggs so far! It's almost time to move the eggs from the large aquarium to a controlled environment, which will provide them with optimum conditions for development. We are well aware of how challenging the next step is, but have no doubts about the skills and ingenuity of our team.


Since 2016, Postojna Cave has housed a one-of-a-kind cave laboratory, described by the scientific community as "an important step towards the implementation of optimum living conditions for successful olm breeding in captivity". 


DAY 26

The wetsuit was prepared and the moving team ready for action. The focus was on 43 precious eggs. Biologist Katarina dived into the aquarium and, assisted by a fellow biologist Primož and the head of the cave laboratory, successfully completed the "migration" operation with surgical precision, After a process lasting several hours, the baby-dragons-to-be were moved into two completely new aquariums, carefully planned with our own know-how.


The temperature of the water in the aquarium is consistent with the temperature of the Vivarium throughout the year, approximately 10.5 °C.


DAY 41

Taking care of olm eggs is our top priority. Our team of biologists and the head of the cave laboratory are keeping an eye on their every move, progress and any developmental deviations 24/7. We have removed three more decaying eggs.


DAY 43

Decaying eggs can endanger the rest of the brood. The biologist noticed abnormal development and decay in two more eggs, which were immediately removed.


According to the scientists’ statistical reasoning, out of 500 eggs laid in the wild, only two olms reach adulthood. The size of the brood is impacted by a number of factors, including the fertilisation of the eggs, the possibility of infection, the genetic code and how many eggs are eaten by the olm mother. 


DAY 60

We are keeping an eye on the successful development and progress of our dragons on a daily basis. Now we are already curiously observing the visible rudiments of the front limbs and external gills.


As olms live in water, they have retained the external gills, much like the ones that are found in amphibian larvae. 


DAY 70

The larvae are now already happily dancing inside their egg jelly coats, getting ready to hatch.


DAY 78

Egg embryos are developing remarkably quickly and are nicely pigmented, the black eyes are also clearly visible.


When they hatch, olm hatchlings have eyes. Adult olms on the other hand are generally without the dark protective pigment, their eyes are degenerated and covered with skin.


DAY 100

All the positive and exciting developments have been accompanied by a discovery that gives reason for concern: our biologist has noticed microplastics even in the cave rainwater, which seeps into the cave through soil layers that are several metres in depth.


Italian scientists recently found microplastic particles even in breast milk. 


DAY 115

While twenty-four baby dragons are already out, eight others are still in the safe shelter of their egg jelly coats. One is struggling to get out, our biologist – midwife Katarina – will come to his aid! 😊


DAY 120

During the first few weeks after hatching, the baby olms lie on their side without moving, they start swimming only if something disturbs them. They get food from the yolk, which is clearly visible on the abdominal wall. 


DAY 123

The baby dragons are now already showing how strong they are. They have turned on their bellies, got up on their legs and are already moving with their help. 


DAY 127

We’re counting down the days, checking how many baby olms there are!

Thirty baby dragons have already hatched. We’re waiting for the last two...


DAY 149

This day will go down in history! The very last of the baby olms from the 2022 brood is finally here and the record-breaking 74% reproduction rate has been achieved!

The last baby olm, the 32nd one, has finally made it out. Halfway out of the egg jelly coat, it was unable to hatch for days. Our head of the cave laboratory realised this was an emergency. Giving him step-by-step instructions via phone, she directed the biologist Primož, who used a precise technique to remove the egg jelly coat from the baby olm, helping him come into the world.

26. 1. 2023

DAY 226

The Protect Proteus Project has been launched.

After Postojna Cave was proclaimed the House of Dragons by a National Geographic journalist, it was time for PPP – a sustainability-focused project aimed at collecting the funds that will be used for providing the baby dragons with optimal living conditions and for a long-term preservation of clean drinking water.

The olms – veritable superheroes – have a number of super powers. And anyone who decides to support the project by purchasing a Protect Proteus lucky charm bracelet is a superhero too.