Our directory of things of interest

University Directory

The secret life of olms

The secret life of olms Iztok Media
01 Mar
2016
Deep in a subterranean, underwater cave system, questions are finally being answered about one of the world’s strangest amphibians

It’s been called everything from ‘dragon’s offspring’ to ‘the human fish’. The olm (aka Proteus anguinus) is the world’s largest cave-dwelling animal, and Europe’s only cave adapted vertebrate. It has a pale salamander-like body around 25cm long, and lives entirely within underground aquatic systems beneath the Dinaric Alps, spanning countries such as Slovenia, Croatia, and Bosnia and Herzegovina. Its subterranean existence means it is entirely sightless, instead utilising a powerful sensory system of smell, taste, hearing and electrosensitivity to find small crabs, worms, or snails to eat. Nevertheless, even if a meal is hard to come by, they can live for up to ten years without eating.

New images from the Pivka River flowing within the Postojna Cave, Slovenia, where an estimated 4,000 olms live and are studied, now provide a glimpse into the animal’s unique reproductive process. ‘Because they live most of their lives hidden away in subterranean aquatic habitats, we know very little about the reproductive biology of olms,’ says Liljana Bizjak-Mali, from the Biotechnical Faculty of the University of Ljubljana.

Photographs, such as the one displayed here, show an olm egg, the completion of a breeding cycle which can take as long as six or seven years to reach fruition. ‘Olms lay eggs, and these white, jelly-coated pearls are then fertilised one by one as the female attaches them to the underwater rocks deep in the caves,’ explains Bizjak-Mali. ‘Some had believed that Proteus sometimes deliver their young alive, like mammals, but we now know this is not true.’

They are among the world’s most unusual species, ancient creatures from another world

Olms are extremely popular in Slovenia, where in the past they have even made their way onto a national coin. However, even though it is forbidden to catch one without consent by Slovene authorities, there have been reports of olms being illegally collected and sold as pets.

‘They are among the world’s most unusual species, ancient creatures from another world,’ says Helen Meredith, from the IUCN SSC Amphibian Specialist Group. ‘Olms can survive hundreds of metres below the Earth’s surface in huge cave systems, yet their conservation is intrinsically linked to the management of land and rivers above ground.’

Tragically, even this isolated creature is suffering from population decline, as its fragmented distribution, loss of quality habitat, and increasing water pollution has earned it ‘vulnerable’ status by the IUCN Red List of Threatened Species. ‘Conserving forests and other native vegetation above cave systems, minimising the pollution of waterways, and not dumping refuse in cave entrances would all help protect this fascinating salamander,’ explains Meredith.

This was published in the March 2016 edition of Geographical magazine.

Related items

NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Climate

Katie Burton explores the practicalities and ethics of geoengineering, the…

Energy

Though the pandemic has gripped the world's attention, lying just…

Climate

The IPCC embraced the notion of carbon offset schemes in…

Geophoto

The shortlist for the 2020 Wellcome Photography Prize has been…

Climate

Millions have been displaced due to severe floods in central…

Wildlife

A portable DNA assay could revolutionise the way border officials…

Climate

A handy gathering of facts about carbon emissions with graphs…

Oceans

Researchers have revealed just how many polluting microfibres are released…

Wildlife

Increasing reports of seized jaguar fangs and skin suggest that…

Geophoto

Forced isolation has given many of us the chance to…

Oceans

A fifth of the ocean floor has now been mapped,…

Wildlife

Four ex-circus lions discovered in France are due to be…

Oceans

A roundup of some of the top discussions from the…

Energy

The agave plant, used to make Tequila, has proven itself…

Climate

Concerns about the ozone hole have diminished as levels of…

Wildlife

In the Eastern Cape of South Africa, Munu – a…

Geophoto

Photography competition, Earth Photo, returns for the third year with…