A new study shows salamanders — also called olms — subsisting in caverns with almost no food share one advantageous trait: salamanders hold very still, which conserves a great deal of energy. One olm in the study even seemed to live in exactly the same position for seven years, without leaving a limestone cave in Eastern Bosnia-Herzegovina, according to an online report in the Journal of Zoology.
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The sloth-like lifestyle of cave-dwelling salamanders
Long ago, salamanders lived above water. They knew the glimmer of the sun and the rejuvenating experience of resting under rain showers. However — millions of years ago — the salamanders moved underwater to live in caves beneath southeastern Europe's Dinaric Alps, and later evolved into pale, blind, 0.3-meter-(1-foot)-long creatures we know today.
The pitch-black cave was filled with creatures when zoologist Gergely Balázs of Eötvös Loránd University in Budapest and his colleagues began their search for olms nearly 10 years ago. After several dives into the cave, the researchers wondered why they observed the same olms in almost exactly the same location, every time.
This is why — from 2010 onward — the team used injectable liquid markers to tag 26 olms suspected of sloth-like behavior. They used a unique marking pattern for each olm, which allowed the researchers to identify distinct salamanders at first glance, and record the motion between observations spaced eight years apart. To their surprise, most of the salamanders didn't move more than 10 meters (33 feet) from their original positions.
In other words, salamanders are "out-slothing" the sloths.
The virtue in aquatic cave-dwelling vice
But this isn't necessarily bad because, not counting the energy expended every 12 years for procreation, this profound lack of movement may help explain salamanders' incredible 100-year life-span, according to the researchers. This could also help explain why salamanders can subsist in environments so scarce of their main diet: snails and crustaceans, from which olms can abstain from eating for 10 years.
However, it's also possible that the salamanders in the study actually wandered around the cave, and later conveniently returned to their original positions upon the researchers' subsequent visit — although Balázs thinks this improbable.
"They are really good swimmers," said Balázs, in a Science News report. This means the salamanders might "move around and try different spots to see if the neighbor is nicer, or there's more prey ... or whatever. And they just don't do it."
Other amphibious creatures with sloth-like behavior usually rely on wildly unique micro-habitats — like the water-filled leaves of a singular bromeliad plant, or under stones. Olms' habitat exists amid long, serpentine systems of caves, where prey density is a near-constant.
This provides further incentive for salamanders to hold their ground, because the chances of nearby food at any given time are slim-to-none.
Whether one envies the salamanders or recoils in horror at such a low-key lifestyle, it's still interesting to know that nature adapts to suit any environment — even where one almost hesitates to call it a habitat.