YELLOWSTONE NATIONAL PARK — Ever wonder how Yellowstone National Park (YNP) wildlife interacts with thermal areas? This week’s Yellowstone Volcano Observatory’s (YVO) Caldera Chronicles, written by U.S. Geological Survey Geologist Stanley Mordensky, explores species adaptations to the unique landscape.
When considering life in Yellowstone’s thermal basins, extremophiles, or organisms that thrive in and even require extreme temperature or acidic conditions, might come to mind. These are the species that can give YNP its vibrant display of colorful bacterial mats that are characteristic of some thermal features, like the Grand Prismatic.
However, there are a myriad of other species that evolved to coexist with the geothermal activity, according to Mordensky. He notes a small fly known as an ephydrid remains active year-round due to the heat provided at YNP thermal features. Adult ephydrids can survive direct exposure to 109 degrees Fahrenheit fluids, Mordensky writes, but can withstand even higher temperatures by using air bubbles as additional insulation.
These flies then serve as a food source for other organisms like spiders, which run quickly across the surfaces of the hot water to avoid being burnt, and a species of tiger beetle that has an abdominal belly that reflects infrared radiation.
Mordensky also writes that garter snakes evolved to require temperatures greater than 90 degrees Fahrenheit for digestion of their food, and have been observed thermoregulating in thermal waters when air temperatures are near freezing.
But some of the megafauna iconic to the Park don’t have quite as strong adaptations to the landscape. While thermal features along the Firehole River provide enough heat to expose vegetation for elk to graze there year-round, making elk in this part of YNP the only elk herd to spend both summer and winter inside Park boundaries, the hydrothermal fluids and gasses enrich this vegetation with higher concentrations of fluoride and silica. Mordensky writes that this can cause too much flouride exposure, which can wear down elk teeth.
“Unhealthy teeth in ungulates, like elk, contribute to poor nutrition and shorter lifespans,” Mordensky writes. “Consequently, the elk along the Firehole River have lifespans of generally 13 to 15 years, roughly five years shorter than elk elsewhere in YNP.”
Overall, the adaptability of a species often corresponds to its reproduction rate. Mordensky writes that this is why microorganisms, who reproduce quickly relative to megafauna, have already evolved to survive the extreme geochemistry and thermal conditions that would cook and kill larger creatures.
