By Connor McCarthy<\/p>\n\n\n\n
It\u2019s completely dark. The eastern-European cave you find yourself in is silent, save the whirring of a passing aquatic invertebrate. Your undeveloped eyes can\u2019t see it, but the vibrations on your slimy pink skin let you know as it passes, just out of reach. You know more food will come if you are patient, so you cling to your submerged rock and wait. And wait. And wait. And wait some more until seven long years have passed by your mysterious, unblinking eyes. <\/p>\n\n\n\n
No, this is not a study-abroad-psychedelic-experience gone\nhaywire or the opening to a B-list horror movie\nstarring a Bosnian cave monster. This is the reality of the Olm salamander (Proteus anguinus<\/em>), a slender pink cave-dweller from eastern Europe that\nspends its entire life cycle in the underground rivers that flow from the region\u2019s karst\nlimestone bedrock. The species is 20cm long when full grown, lives its entire\nlife underwater, and keeps its external gills into adulthood. Like most other\nsalamanders, the Olm eats a mix of snails and other aquatic invertebrates. What\nsets the Olm apart from other salamanders and other animals in general is its\nability to remain effectively motionless for years at a time.<\/p>\n\n\n\n This behavior (or\nlack thereof), was first studied by Gergely Bal\u00e1zs, an\naccomplished cave diver and researcher at the Department of Systematic Zoology\nand Ecology at E\u00f6tv\u00f6s Lor\u00e1nd University in Budapest, Hungary. Bal\u00e1zs and a team\nof other divers conducted a mark-recapture study on Olm in the eastern part of\nBosnia and Herzegovina, a small country in\nsoutheastern Europe. Mark-recapture studies are one of the herpetology field\u2019s\nmost commonly used tools for estimating population, the idea behind them being\nif you capture a group of amphibians, mark them, release them into the wild,\nthen come back later and capture roughly the same number as before, the\nproportion of marked individuals captured in the second survey is equal to the\nproportion of the total population captured in the first survey, which gives\nyou a rough estimate of total abundance. <\/p>\n\n\n\n Due to their inaccessibly Olm are a\nfairly large question mark on the map of herpetology. Very few studies have\nbeen conducted on their life cycle and natural history, and most of what is\nknown about the species has come from captive populations in zoos and\naquariums. As a result, the species is shrouded in mystery. In medieval times, Olm\nwere thought to be the offspring of cave dwelling dragons, as they would\noccasionally wash out of the caves during flood events. Though they cannot\nbreathe fire, reproduce with donkeys, or do any of the other things dragons\nfrom our pop culture do, a wormlike creature with gills understandably must\nhave seemed to be the spawn of something much more sinister.<\/p>\n\n\n\n According to Bal\u00e1zs, the species\nsedentary lifestyle makes them somewhat easy to catch. Researchers would use a\nflashlight to locate the Olms from a few meters away, then shut the light off (Olm\nare blind but can still see light and dark) as they slowly swam up to the\nsalamanders. Once they were close, they would turn the light back on, grab the Olm,\nmark it with a visible implant elastomer (a liquid polymer injected under the\nsalamanders\u2019 skin that solidifies, allowing for re-identification later on).\nThe Olm would then be set free, returning to the subterranean riverbed in a\nsingle burst of writhing speed.<\/p>\n\n\n\n The study itself had several layers and\nincluded data from previous expeditions into the caves. Bal\u00e1zs and his team\nconducted their first study in these caves in 2010, where they tagged 7 Olm,\nfive of which were recaptured in the 2020 study. 19 additional individuals were\ntagged in 2016, 13 of which were observed in the subsequent 28-month monitoring\nperiod. <\/p>\n\n\n\n By comparing the locations of individual\nOlm during each of fifteen recapture expeditions, Bal\u00e1zs and his team attempted\nto discern exactly how much moving these salamanders were doing in the\ndarkness. Like people, some Olm seemed to be travels whereas others were not.\nOne salamander moved an impressive 38 meters over the course of 230 days, while\nanother was found in the exact same spot after 2569 days (just over 7 years).\nIt is unclear if this sedentary individual (along with the rest of the Olm in\nthe cave studied) was feeding during this time or exercising its starvation\nresistance. <\/p>\n\n\n\n Over the entire study, no Olm traveled\nmore than 80 meters from the site it was first captured at and on average they only\nmoved about 5 meters a year. In the 37 total recaptures in the study, only ten animals\nhad moved more than 10m away from their original location. <\/p>\n\n\n\n Interestingly, all the Olm captured in the\nstudy were quite out in the open and very visible to the divers. This is in\nstark contrast to Olm behavior of captive Olm, which hide in cracks and\ncrevasses of rocks. Furthermore, individuals could be found within a few meters\nof each other, but displayed no sign of grouping or avoidance behaviors.\nEssentially, Bal\u00e1zs and his team couldn\u2019t make any conclusions as to why <\/em>Olm\nspend so little time moving especially considering they have no natural\npredators or other competitors.<\/p>\n\n\n\n But are these individuals really not\nmoving, or do they just move back and forth between the same places like\nretired old men and therefore create the illusion of a sedentary lifestyle?\nBal\u00e1zs\u2019 current theory is that the Olm are trying to minimize the amount of\nenergy expended. Female Olm only reproduce about once every twelve years and it\nis predicted the species can live to be over 100 years old. Furthermore, they\nare extremely resistant to starvation and some studies have shown individuals\ncan go ten years without eating. They do this by eating large quantities of\nfood at once, then storing excess nutrients, glycogen, and lipids in the liver.\nWhen food is scarce, they can reduce their metabolism and in extreme cases\nreabsorb their own tissue until more food becomes available. They also have a\nhigh tolerance for hypoxic water, meaning their oxygen demand is quite low\nwhich allows them to survive in cave environments. Essentially, everything about\nthe Olm, from there anatomy to their reproductive cycle, is perfectly designed\nfor to survive in the some of the most abysmal reaches of the earth\u2019s surface. \n\nSo,\nwill we ever really know what goes on in the caves of eastern Europe while\nBal\u00e1zs and his expert team of divers are not there to document it? For the time\nbeing, it\u2019s unlikely. Setting up a motion trap for a species that hardly moves\nis a task in itself especially when these cameras would need to be placed in\nsubterranean rivers. What we do know is these slender, pale, blind salamanders\nmight have the most stoic lives of any vertebrate. While it\u2019s difficult to envy\na creature that spends in entire life in darkness, hardly eating, rarely\nmoving, and reproducing once every decade, it\u2019s also hard to argue the\nevolution and lifecycle of the Olm is anything but fascinating. Hopefully\nfuture studies will give us more insight on their mysterious lives as their\ndelicate karst environments may be at risk due to stormwater runoff, pollution,\nand climate change.\n\n\n\n<\/p>\n","protected":false},"excerpt":{"rendered":" By Connor McCarthy It\u2019s completely dark. The eastern-European cave you find yourself in is silent, save the whirring of a passing aquatic invertebrate. Your undeveloped eyes can\u2019t see it, but the vibrations on your slimy pink skin let you know … Continue reading