Olms go on display for the first time in Slovenia in juvenile form

June 3, 2020

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World’s first public exhibit of juvenile olms, mysterious underground amphibians, will open on 11 June in Slovenia’s famous Postojna Cave.

Local legend had it that the olm was the offspring of cave-dwelling dragons – it’s as good a way as any of explaining the strange, pink wrigglers that were washed out of the caves after heavy rain. The truth is hardly less extraordinary. Olms are neotenous, meaning they retain juvenile characteristics for all of their 100-year lifespans – they never lose the pink external gills that look like sea anemone tentacles.

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At 30cm long, adult olms are the world’s largest subterranean animals; these aquatic salamanders are also blind, sensing light and vibration through their skin and sensory pits on their heads. Their hearts beat just twice a minute, and they can go more than a decade without food.

The creature considered by some to be Slovenia’s national animal had never bred in captivity in the country before, nor had olms ever been seen breeding in the wild. So when, in 2016, a translucent spherical olm egg appeared on the glass of Postojna’s main vivarium, Gnezda and his colleagues couldn’t believe their luck. More eggs appeared. The nation held its breath for an agonising 120 days before 22 babies hatched in the underground laboratory.

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Researchers knew the animals could regrow lost limbs, but when one of the young tore off a sibling’s leg, they were able to study the regeneration process up close. Yet much about the amphibians remains mysterious. We have no idea how many olms live in the wild, nor even how many species there are, says Lilijana Mali, an amphibians expert at Ljubljana University.

Her team think there are probably nine types. They do know, though, that the amphibians are sensitive to pollution as well as light, which makes Postojna’s breeding success all the more vital.