Sydney Stephens, University of Utah
Dipodomys microps, the chisel-toothed kangaroo rat, is a small desert rodent occurring in a region that has undergone substantial ecological changes due to rangeland expansion. Although generally considered a saltbush specialist, the natural diet of D. microps consists of saltbush (Atriplex confertifolia) a C4 plant and blackbush (Coleogyne ramosissima) a C3 plant. To determine if human-driven environmental change has impacted the natural diet of D. microps we took advantage of natural differences of carbon stable isotopes between C4 and C3 plants. We predicted that increased abundances of blackbush due to rangeland expansion and corresponding decreases of saltbush will have led to diet shifts in D. microps. To test this prediction we sampled fur of kangaroo rats from Inyo County, California housed in the Museum of Vertebrate Zoology from three time periods: before the landscape change (1917, N=10), during the disturbance (1973-1978, N=10), and recent samples (2008-2009, N=8). We observed minor shifts in percent of saltbush in diets of D. microps. In 1917 saltbrush consumption averaged 48%, in the mid 1970s saltbrush ingestion averaged 47i%, and by the late 2000s the average consumption dropped to 37%. These observations are consistent with my prediction that environmental factors caused kangaroo rats to favor blackbush. However, the low percentage of C4 reliance suggests this species may not be a true Atriplex specialist as previously thought.