Underground ‘baby dragons’ are revealed to sneak to the surface
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 spending millions of years underground, the salamanders appear to shuttle back and forth to the sunny surface using springs where water bubbles up from hundreds of feet deep. Raoul Manenti, professor of zoology 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 elms, were once thought to be baby dragons. Even though we now know they won’t grow wings, elms still seem like mythical creatures.
Elms are about the length of a banana and have an eel-like body and spindly legs. Their faces are featureless except for a crown of pink, frilly gills. When elms 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 known for being economical with their energy (an olm in the Balkans not moved for seven years).
Over the centuries, a handful of elms had been spotted above ground, but scientists assumed they were victims of flooding. Cave salamanders are so specialized in living underground, the thinking went, that they would be unable to survive outside their original caves.
To find an olm, Dr. Manenti and his team usually climb down good-looking openings to reach caves, including the Trebiciano Abyss, about as deep as the Eiffel Tower is high. But in 2020, a group of cavers and ecologists, including Dr. Manenti, spotted an elm swimming in an above-ground spring. They were floored.
Veronica Zampieri, then a graduate of the University of Milan, began monitoring 69 above-ground wells in the area. She was surprised to find old visitors at 15 of the springs, even though there had been no recent flooding. Some springs experienced heavy traffic, with several elms consistently visiting.
To her horror, Ms. Zampieri found elms on above-ground excursions, not only at night 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 to pick off for predators.
What were the elms doing up there? Dr. Manenti used unconventional forensics deep in the caves to find a clue.
During population surveys, scientists briefly remove elms from the cave water to collect data. Occasionally, said Dr. Manenti, an elm will accidentally gulp in some air while being handled. Once placed back in the water, an olm that has swallowed air floats on the surface like a pool noodle and cannot swim well.
To straighten them out, “you have to burp them,” said Dr. Manenti. By gently ‘massaging’ their long bellies, researchers encouraged floating elms to belch the offending air – but sometimes that wasn’t the only thing that emerged. Burping elms sometimes spit out parts of earthworm species that do not occur underground, indicating that the elms hunt above water during their forays.
It would be a huge energy investment for a small olm to move a spring up and down, but the reward appears significant, Dr. Manenti said. Although olms are generally very slender, almost skinny, some of the olms he and his team caught doing casual shopping were downright plump.
Danté Fenolio, an ecologist at the San Antonio Zoo who has been studying North America’s cave-dwelling salamanders for more than 30 years, said the Italian team’s discovery “challenges our assumptions about what we ‘know’ here in North America into question,” and added that it could inspire further research on cave salamanders in the United States.
Ms Zampieri said the discovery about elms highlights the ecological importance of places like the springs, which unite two different worlds.
For Dr. Manenti, that connection was most apparent one 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 as long as a safety pin, it was the smallest elm ever discovered in the field. Based on estimates of olms raised in captivity, it was probably only three months into its hundred-year lifespan, indicating that olms not only commute to the springs but can also reproduce there.
“The boundary itself between underground and above ground is something that we humans place,” said Dr. Manenti. Obviously we forgot to inform the olms.