Some of us are homebodies, but olms take it to a new level. These cave-dwelling salamanders may stay within the same little patch of ground for years on end.
“They are hanging around, doing almost nothing,” says Gergely Balázs at Eötvös Loránd University in Budapest, Hungary.
Olms are salamanders that live in European caves. They have adapted to life in total darkness: their skin is pale and their eyes don’t develop, leaving them blind. They can live for decades, and possibly even a century.
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Their peculiar lifestyle makes them difficult to study in the wild, says Balázs, so most observations are made on captive specimens. His team has performed one of the first long-term studies of wild olms.
They monitored olms living in the Vruljak 1 cave in Bosnia and Herzegovina. Between 2010 and 2018, the team repeatedly entered the cave and tagged olms by injecting their tail fins with a black pigment in a unique shape. When they returned, they looked to see where the tagged olms were. In total, they tracked 19 olms.
Most of the olms moved less than 10 metres, even if they were recaptured years after being tagged. About 5 metres per year was typical. The most active olm moved 38 metres in 230 days. In contrast, another was found at the exact same spot after 2569 days – more than seven years.
It is possible that the olms are more active than the data suggests, says Balázs’s colleague Gábor Herczeg. “We do not know the daily activity,” he says, emphasising that visits to the cave were often months apart. The olms may move around within a confined patch, he says.
Nevertheless, an inactive lifestyle would make sense for them. They are predators that use a “sit-and-wait strategy”, says Balázs. Their prey are small crustaceans, which aren’t common. The olm may do best to save energy by sitting still and slowing their metabolism until one comes close. “They can survive without food for years,” he says.
Although the olms’ slow lifestyle suits their underground habitat, it does also make them vulnerable to dramatic changes in their environment. If conditions in their cave become inhospitable, perhaps because of increased flooding due to climate change, they may struggle to move to a new habitat.
Journal of Zoology
