Lyman Dudley - May 2018

As average temperatures rise in the Rocky Mountains, ecosystems are undergoing changes as they have to cope with hotter temperatures, and in many regions, more arid (dry) conditions. The American pika, a small mammal in the ground squirrel family that lives in talus patches at high elevations, is one of the animals that is being most affected by these changes. Pikas are extremely thermally sensitive, that is to say, they need a very specific range of temperatures to survive and even moderately hotter conditions than what they are used to can kill them. This summer, I will be working along side a team of researchers including Dr. Dave McWethy, my faculty sponsor for this project, Peter Billman, a graduate student here at Montana State University that is studying the effects of climate change on pikas for his master’s thesis, and Aimee Heffernan, another undergraduate who is conducting some independent research as part of this larger project. We are studying the effects of climate factors such as average daily temperature and aridity on the population density and the measured fecal stress levels (glucocorticoids) of pikas found in talus patches that we sample. As conditions in lower elevation talus patches are becoming hotter, pikas have been migrating uphill to higher elevation talus patches. We predict that we will find higher population densities of pikas in higher elevation patches and higher stress levels in pikas that reside in hotter, drier talus patches. 

In addition to this larger study, I will be conducting my own GIS analysis of how factors such as elevation, average daily temperature, precipitation, and aspect (the direction the patch faces which influences how much sunlight the patch receives) affect population density and stress levels of the pikas the reside in these patches. I plan to compare the relationships between each one of these individual climate factors to population density and stress levels as well as looking at the relationships that these factors have on one another. For example, one map of a mountain range may overlay the average precipitation against population density and average stress levels to examine the relationship between aridity and lower population/higher stress. Another map of the same mountain range will highlight how average temperature, precipitation, elevation and aspect work together to impact population density and stress levels. That map may have different color schemes for each of these variables to show how they affect one another, and comparing that map to our field data might show that for example, there is a strong relationship between lower elevation, lower precipitation and higher temperatures in lower population density and higher stress levels of pikas that live in patches where all three of these factors apply, but aspect isn’t a significant predictor of pika population or stress.

We will be travelling to six mountain ranges across South West Montana and South Eastern Idaho to see how pikas are doing in different elevations/areas with different climate patterns. These ranges are as follows; the Donkey Hills (ID), the Lehmi Mountains (MT), the Highland Mountains (MT), the Lima Peaks (MT), the Black Tail Mountains(MT), and the Tobacco Root Mountains (MT). While we have not yet begun our field season, I have been using the satellite data on the mapping website CalTopo to outline talus patches that we will sample at. Using the polygon tool, I draw an outline around talus patches that follow an elevational gradient, usually up creek drainages where the patches are at increasingly high elevations to map out where we will need to collect samples. For the maps of the Tobacco Roots, Lima Peaks, and the Black Tail Mountains, which we have not sampled yet, purple outlines show the locations of patches we plan to sample. For the Highland Mountains, which Peter did some sampling in last summer, green patches mean that there were pikas found to be living there, blue patches mean that pikas were found to be living there, and red patches have not been sampled yet.

This map of the Highland Mountains show the patches (red) that we still have to sample. Most of the red patches are at higher elevations.

This map of the Black Tail mountains shows patches that will be mapped on an increasing elevational gradient. The white areas are largely talus as well (they were covered in snow for this satellite image), but they are pretty inaccessible since there are not many trails through the Black Tails.

This map of the Lima Peaks shows talus patches on a pretty large elevation gradient and has patches on different aspects (slopes facing different directions). We are sampling higher elevations here because these mountains are more accessible.

We are going to be doing a lot of sampling in the Tobacco Roots, so this zoomed out image shows every place we plan to go in this range.

This more zoomed in image of an area of the Tobacco Roots shows patches going up one creek drainage to the crest, and then down the creek drainage on the other side. The Tobacco Roots are a very accessible range with lots of trails and roads, so sampling there will be relatively easy.

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