Cave Climates of Great Basin National Park

This article was originally published in The Midden – Great Basin National Park: Vol. 25, No. 1, Summer 2025.

The author in a wild cave in Great Basin National Park.

NPS

By Clara Morrison, Scientists in Parks Cave and Karst Intern

This last winter, I was a Scientists in Parks Cave and Karst Intern at Great Basin National Park. In addition to learning how to go caving, organizing and participating in this year’s Lint Camps, and taking part in a bunch of super fun bird and snow surveys, I was tasked with analyzing all of our existing temperature and humidity data for the park’s 40 caves.

The data was collected by dataloggers: the small tubes that can be easily spotted along the trail in Lehman Caves. Depending on how old the data was, different types of dataloggers were used, but the current dataloggers in use are the white HOBO Pro v2s, which measure temperature and relative humidity, and the black HOBO Onset U20Ls, which measure temperature and barometric pressure (that is then used to calculate water depth). These usually measure data every hour and can last up to 5 years without being switched out! We try to download data from the dataloggers in the caves about once a year using a shuttle, which can then be uploaded to our computers and exported into Excel files, where I worked my magic.

A HOBO Pro v2 datalogger in a Park cave.

Clara Morrison

In total, we ended up with data from 23 caves, most of which had multiple dataloggers. Some of the data dated back all the way to 2005! For both temperature and humidity, I calculated hourly, monthly, yearly, and total averages, maximums, minimums, and standard deviations, as well as creating multiple graphs for each cave to visualize long-term and yearly trends and compare locations within caves, between caves, and outside.

So what did all of this data crunching tell us? And why do we care if it's warm, cold, or humid inside a cave? One huge reason is to protect our bats from white-nose syndrome. From research done by Verant et al. in 2012, we know that the ideal temperature for the growth of Geomyces destructans, the fungus that causes white-nose syndrome, is between 12.5 and 15.8°C. Looking at our caves, this means that if white-nose syndrome ever made it to Great Basin NP, bats in lower-elevation caves would be the most at risk, which includes Lehman Caves.

Knowing the climate of a cave also allows us to predict the biota that we can find in each cave, informing future discoveries. And as the climate continues to shift, long-term monitoring will allow us to understand its impact on caves and their inhabitants as well as what we can expect in the future.

In addition to getting a better understanding of each of the caves' yearly cycles and average temperatures, we found that a couple of the caves behaved completely differently than we expected! For background, caves are usually a very stable representation of the average temperature outside over the entire year. If the cave experiences fluctuations in temperature, it usually corresponds to the temperatures outside– a cave will get slightly colder in the winter and slightly warmer in the summer. The following three caves were unlike any others.

Figure 1. Temperature data for Fox Skull Cave compared to outside temperatures, October 2022-October 2024. Note that the cave temperatures (Hourly in orange and Monthly in red) are higher than outside projected temperatures (Prism in grey).

Fox Skull Cave, in the Snake Creek area, was one of the most fascinating. It had completely inverse temperatures compared to what was being experienced outside (Figure 1), which we still don’t understand. The geometry of the cave has a raised area in the middle, which could limit airflow but does not fully explain the behavior, unless maybe another entrance is present. A second datalogger was installed at this raised area in March so that it can be determined which way temperature is flowing in the cave. It’ll be incredibly exciting to look at the results!

Figure 2. Temperature data for Root Cave compared to the outside temperatures, May 2019-November 2021. Note that the temperatures in the cave (Root in red) are delayed from the outside measured temperatures (BKRN2 in blue) and projected temperatures (PRISM in dark blue).

In Root Cave, which is not far from Lehman Caves, the temperatures recorded in the cave are delayed by a couple of months compared to those outside (Figure 2). This could be due to limited airflow into the cave since the entrance is pretty tight, but it’s not certain yet!

Little Muddy Cave temperature data for two locations, Flatrock near the back of the cave (dark blue) and Photo Junction (light blue), near the front of the cave, compared to outside temperatures (grey), February 2024-February 2025.

And last but not least is Little Muddy, which we already know has high CO2 in the summers, but which, temperature-wise, is completely surprising. The back of the cave (Flatrock) is warmer than the entrance, which is unusual, and the temperature at this location is inversely related to the outside temperature (Figure 3). Closer to the entrance (the Photo Junction), the temperature seems to act differently based on the season, with the temperature experiencing a steady increase in the summer and a lot more variation in the winter. There’s still much to understand here.

Overall, this preliminary look at Great Basin caves’ climates has informed where to focus our efforts next, and I can’t wait to see all the new things that’ll be found out as we continue to study the park’s caves!