Honors Project in Progress: Mechanisms Mediating Life History Trade-offs

In lab with a complete glucocorticoid sample

My name is Rachel Stafford-Lewis and I am currently involved with an honors research project in Dan Blumstein’s lab here at UCLA. My research project is a two quarter commitment that focuses on analyzing the trade-offs between reproduction and survival in yellow-bellied marmots. My research specifically focuses on glucocorticoid levels, the amount of white blood cells and parasites in the blood samples, and testosterone levels. I hypothesize that the more dominant and higher-ranking male marmots will have elevated testosterone levels, but that maintaining such rank will prove costly and will also result in high levels of glucocorticoid metabolites, white blood cells, and parasites. I hope to discover the correlation between these three factors, or lack thereof, and analyze my results so as to make sense of the compromise between health and fitness.

The extraction process-halfway through Day One

I will test my hypothesis using data collected in the field at RMBL in the Rocky Mountains of Colorado. I have spent the last seven weeks utilizing this data by collecting glucocorticoid levels from fecal samples in a precise three day extraction process. As seen in the picture above, the tubes contain a yellowish liquid that is a solution of the hormone, alcohol, and water. This mixture evaporates overnight in the vacuum centrifuge, as pictured in the photo below, so that the end result will only be the reconstituted hormone. The entire procedure involves three strict twenty-four hour sessions where I would repeatedly centrifuge and bathe the samples in a hot water bath, put them in a vacuum centrifuge, vortex, and then place them in the -20 degree freezer. The end result was then pipetted into exact sample sizes, as exemplified in the first picture at the top of the page, and shipped off for analysis.

Extractions at the end of day one in the vacuum centrifuge

Now that the extractions have been completed, the next step is to analyze blood smears for various neutrophils, leukocytes, monocytes, eosinophils, and any obvious parasites. This work is done using a microscope and will be measured by counting the number of white blood cells until we have one hundred total in each one of our samples. This portion of my project is especially important because it is the main indicator of health and will be used for comparisons with the glucocorticoid levels as well as the testosterone levels.

Once the blood smears have been examined I will begin the testosterone assays, which will reveal the relative levels of testosterone in each individual marmot. This will be the final component of my project and hopefully will reveal any connection between dominance and survival in regards to parasite and white blood cell count.

A happy marmot out and about in the Colorado sun

I went into this experience knowing very little about marmots and I have come to appreciate them as adorable creatures and as informative research subjects. I hope that this project will further my knowledge of the relationship between survival and health and how it affects marmot behavior in their natural setting. I look forward to completing my research and finding results that will benefit the extensive research that has already been completed in the Blumstein lab.