Connectivity of deer populations across San Diego County
Summarized by Jahaira Correa, Roy Little Fellow
Researchers with the US Geological Survey, including Dr. Amy Vandergast, a UC San Diego alumna, investigated the movement and gene flow of several groups of Southern mule deer (
Odocoileus hemionus fuliginatus) in a USGS 2019 report. Scat and select tissue samples were used to approximate the range and paths traversed by Southern mule deer across northern San Diego County, including samples taken from our own
Dawson-Los Monos Canyon Reserve. DNA fingerprinting was used to identify individual mule deer and construct pedigrees for analysis, important for analyzing the genetic health of the population.
This survey corroborated previous work identifying two genetic clusters, the "Inland/Mountain" and “Coastal” mule deer clusters, where Dawson-Los Monos Canyon Reserve is a part of the latter. Comparing their effective population sizes revealed more genetic diversity in the Inland/Mountain cluster. It is suggested that gene flow is being maintained under the I-15 overpass near Daley Ranch Preserve and San Diego Safari Park, where sampled mule deer derived approximately 50 percent of their genetic background from each cluster. Maintaining gene flow is important for the health of the population because it diversifies the gene pool, which improves the population’s adaptability and allows for better offspring. The survey found that these large herbivorous mammals use tunnels, culverts, and freeway underpasses to cross swathes of land, some traveling distances of up to 4.6km, or 2.85 miles. They were also found to cross roads with at-grade vehicular traffic, a risky deed for both drivers and deer alike. Future surveys with more locales and more samples would allow us to further analyze the connectivity of Southern mule deer and their relationship with urban infrastructure. The continued presence of our furry, four-toed neighbors highlights the importance of safe and accessible crossings for wildlife and reminds us to be mindful of the space we take up as humans.
Read the full USGS report here:
Mitelberg, Anna, Julia G. Smith, and Amy G. Vandergast. DNA fingerprinting of Southern Mule Deer (Odocoileus hemionus fuliginatus) in North San Diego County, California (2018-19). No. 2019-1138. US Geological Survey, 2019.
