Tuesday, September 17, 2013

Do Snakes Stress Out Squirrels?: Guest Post by Lauren Kong

Lauren is a graduate of Mills College where she was a Barrett Scholar last year. Her scholarship through the Barrett Research Program funded her stay with us at the Blue Oak Ranch Reserve. Her adviser at Mills, Dr. Jennifer Smith, is collaborating with me on a project examining the sub-lethal effects of snakes on ground squirrels. Lauren was in charge of data collection and organization for this project. She describes her research below: 

My research question focused on whether California ground squirrels (Otospermophilus beecheyi) were becoming stressed out after interacting with predatory snakes- the northern Pacific rattlesnake (Crotalus oreganus) and the Pacific gopher snake (Pituophis catenifer). To test our hypothesis we staged interactions between snakes and squirrels. We baited focal squirrels near snakes using sunflower seeds (their favorite food). After baiting the area, we waited until our desired ground squirrel approached and interacted with the snake. After the interaction, we trapped the squirrel using humane traps and collected their feces for the rest of the day. As a control treatment, we trapped the squirrel without having it interact with a snake and collected its feces to see if being in a trap affected their stress levels. To analyze the stress levels of squirrels that have and have not interacted with snakes, we will extract stress hormones (glucocorticoids) from their fecal material.

Ground Squirrel Perches on a Rock

It takes approximately 4-6 hours for the glucocorticoids to pass through the digestive system of the squirrel so it’s important to hold the squirrels long enough to get a complete sample. We placed the fecal deposits in tubes on ice or in liquid nitrogen. It’s important to collect the feces as soon as it is expelled because glucocorticoids are subject to degradation once they leave the body. Now that my internship is over, the fecal samples will be transported to the Smith Lab at Mills College for further analysis. We hope to see if venomous, and presumably more dangerous, rattlesnakes induce a greater stress response in squirrels than non-venomous, less dangerous gopher snakes.


We placed the squirrels onto plastic trays to collect their feces. Look at how many squirrels we did trials on in one day!

Although behavioral ecology can be taxing, this experience has opened my eyes to field biology. This research would not have been possible without the help of my fellow internists and Bree. Together we are a group of animal loving, enthusiastic, and intelligent people striving to elucidate the mysteries of animal life. This was a truly amazing experience. 

Looking over the edge of the Arroyo. Our study site is truly beautiful!