Scientists have discovered that blind cave salamanders in northern Italy leave their underground homes to go on expeditions to the surface.
Eyeless and ghostly pale from millions of years spent below ground, the salamanders appear to commute back and forth to the sunny surface using springs where water bubbles up from hundreds of feet deep. Raoul Manenti, a zoology professor at the University of Milan, and colleagues described the unexpected discovery in a study published last month in the journal Ecology.
The salamanders, a species called olms, were once believed to be baby dragons. While we now know they won’t sprout wings, olms still seem like mythical creatures.
About the length of a banana, olms have eel-like bodies and spindly legs. Their faces are featureless except for a crown of frilly pink gills. When olms hatch, their eyes are quickly covered with skin, leaving them blind. They navigate their dark world by sensing vibrations, chemicals in the water and magnetic fields. Olms can live for more than a century and are famously thrifty with their energy (one olm in the Balkans didn’t move for seven years).
Over the centuries, a handful of olms had been spotted aboveground, but scientists assumed that they were the victims of flooding. Cave salamanders are so specialized for life underground, the thinking went, they couldn’t possibly survive outside their native caves.
To find an olm, Dr. Manenti and his team usually have to rappel down well-like openings to reach caves including the Trebiciano abyss, about as deep as the Eiffel Tower is tall. But in 2020, a group of spelunkers and ecologists, including Dr. Manenti, spotted an olm swimming in an aboveground spring. They were floored.
Veronica Zampieri, then a graduate student at the University of Milan, began monitoring 69 aboveground springs in the area. She was surprised to find olm visitors at 15 of the springs, even when no recent floods had occurred. Some of the springs saw high traffic, with multiple olms visiting consistently.
To her shock, Ms. Zampieri found olms on aboveground jaunts not just in the nighttime but also in broad daylight. Underground, the “mighty olm” is the apex predator, Ms. Zampieri said, but on the surface the animals’ stark-white bodies and blindness should make them easy pickings for predators.
So what were the olms doing up there? Dr. Manenti used some unconventional forensics deep in the caves to find a clue.
During population surveys, scientists briefly scoop olms out of cave waters to collect data. Occasionally, Dr. Manenti said, an olm will accidentally gulp down some air while being handled. Once it’s returned to the water, an olm that has swallowed air floats on the surface like a pool noodle and can’t swim properly.
To right them, “you have to make them burp,” Dr. Manenti said. By gently “massaging” their long tummies, researchers encouraged floaty olms to belch up the offending air — but sometimes that wasn’t all that came up. Burping olms sometimes spat up parts of earthworm species that aren’t found underground, suggesting that the olms hunt during their forays topside.
It would be a huge investment of energy for a little olm to wriggle up and down a spring, but the payoff seems significant, Dr. Manenti said. While olms are generally very slender, verging on skinny, some of the olms he and his team caught on surface errands were downright plump.
Danté Fenolio, an ecologist at the San Antonio Zoo who has studied North America’s cave-dwelling salamanders for more than three decades, said that the Italian team’s discovery “challenges our assumptions of what we ‘know’ here in North America,” adding that it could inspire further research on cave salamanders in the United States.
Ms. Zampieri said that the discovery about olms highlighted the ecological importance of places like the springs, which unite two different worlds.
For Dr. Manenti, that connection was clearest on an afternoon in 2022. Using an empty can of mackerel from his lunch, Mr. Manenti gingerly scooped up a larval olm from a spring near a highway. Barely the length of a safety pin, it was the smallest olm ever discovered in the field. Based on estimates from captive-raised olms, it was probably just three months into its hundred-year life span, suggesting olms may not just commute up to the springs — they may also breed there.
“The border itself between underground and surface is something that we humans place,” Dr. Manenti said. Clearly, we forgot to inform the olms.
