Olm Eggs Finally Hatch in Rare 'Dragon' Birth

Olms are amphibians, but their odd appearance led a 17th-century naturalist to mistake them for baby dragons. (Photo: SanShoot/Flickr)

The olm is almost too bizarre to believe. Nicknamed "baby dragon" and "human fish," the cave dweller owes its odd looks to subterranean adaptations like external gills, skin-covered eyes and a long, pale body. If that's not alien enough, it can also live for 100 years, go a decade without food and use electricity to "see" in total darkness.

Olms have lurked deep within parts of Europe for 200 million years, or about 1,000 times longer than our species has been around so far. The spectral cave salamanders were first reported in 1689, when the Slovenian naturalist Janez Vajkard Valvasor understandably mistook them for the offspring of dragons.

Science has since cleared that up, yet olms remain shrouded in mystery centuries later. And despite their long history of evading and confusing us, we now represent one of the species' greatest threats — and possibly one of its best allies.

Given their lengthy life spans, olms take an unhurried approach to romance. They only breed once or twice a decade, making olm eggs an extremely rare sight. That's why scientists were so excited about a clutch of 64 eggs laid at a cave in Slovenia earlier this year. And now, four months after those eggs were discovered by a tour guide, the baby dragons have finally started to hatch:

olm hatchling
This baby olm hatched May 30, followed by another of its siblings a day later. (Photo: Postojna Cave)

"Our first dragon literally shot itself out of the egg in a single attempt," according to a press release from Postojna Cave, where the eggs are located. The first egg hatched May 30, followed by a second on June 1, the BBC reports.

A female olm laid 64 eggs over several weeks in January and February, 23 of which were deemed viable by scientists. Even those eggs faced steep odds, points out the Slovenian Press Agency, citing an estimate that, under natural conditions, only about one in 250 olm eggs ever hatches. But since these eggs are being protected from predators, cave operators say they hope all 23 will hatch.

Postojna Cave dives at least 24 kilometers (15 miles) under Slovenia, carved from limestone over millions of years by the Pivka River. It's a popular tourist destination, thanks to dramatic scenery, native olms and an aquarium built inside the cave, which also contains olms for easier public viewing. That aquarium is where the new olm eggs are located, offering an unusual level of visibility for the shy salamanders. Until now, they've only been seen emerging from eggs in a laboratory setting.

olm egg
This photo shows one of the 2016 olm eggs shortly after it was laid. (Photo: Iztok Medja/Postojnska Jama)

Olms are entirely aquatic, unlike most amphibians, and their subterranean lifestyle has allowed their skin to abandon pigment and grow over their eyes. They can still sense some light, but that's nothing compared with their other, weirder senses.

"In place of sight, the olm has developed an acute sensory system for hunting in the dark," explains the Zoological Society of London. "The front part of the olm's head carries sensitive chemo-, mechano- and electroreceptors. Olms have one of the best senses of smell of any amphibian, and are capable of sensing very low concentrations of organic compounds in the water through both smell and taste."

Along with ears specialized to hear underwater, olms' ability to sense electrical and magnetic fields — and to detect subtle chemical cues in water — more than makes up for their undeveloped eyes. And even if all those skills fail to help them find food, they can survive 10 years without a meal. Yet despite such impressive adaptations, 200 million years of evolution may still not have prepared olms for us.

olm at Postojna Cave in Slovenia
Olms are Europe's only true cave vertebrates, and the only species in the genus Proteus. (Photo: Jure Makovec/Getty Images)

Scientists don't have enough data to estimate the overall abundance of olms, but due to population declines observed in recent decades, the salamanders are listed as Vulnerable on the IUCN Red List of Endangered Species.

The main threat for olms is transformation of the forests and fields above their caves, according to the IUCN, "largely through tourism, economic changes and increasing water pollution." Such upheaval has a direct effect on the quality of habitat available to olms, which rely on clean water and are susceptible to pollution seeping from the surface. Poaching for the pet trade has also been a persistent danger, even after Slovenia legally protected olms in 1922, but the country's protection mechanisms have reportedly improved since it joined the European Union in 2004.

Postojna Cave in Slovenia
Postojna is known as 'the queen of Slovenian caves' — high praise in a country with 11,000 caves. (Photo: Shutterstock)

As rare as olm eggs are, Postojna does have some recent experience. Another female olm graced the cave with eggs in 2013, but some were eaten by predators (including other olms) and the rest failed to hatch. Scientists learned from that failure, however, and are taking extra precautions with the 2016 crop. All olms except the mother were removed from the tank, while cave staff added extra oxygen to the water and used shades to protect the eggs from light. Each newborn is being placed in its own tank for safety, where it receives food and daily water changes to fight infection.

"We took care of the eggs nonstop, observing them, connecting scientific findings with our own experience," the cave management explains in the press release. "We had to take decisions nobody had taken before. Everything was new."