The Stephens’s kangaroo rat (Dipodomys stephensi; SKR) currently exists only in fragmented populations separated by urban landscapes. The species is listed as threatened by the state of California and endangered by the USFWS. The draft recovery plan for the species (1997) calls for conservation, funding and management within an established reserve system in Riverside and San Diego Counties. Species management plans are in place within some reserves and a translocation program is being established for the species to develop methods to reduce Take due to development (Shier 2009, 2010, 2011, Shier and Swaisgood 2012). Translocation may mitigate habitat fragmentation and restore historical gene flow by relocating animals between reserves or from areas slated for development projects onto reserves. It is not clear whether translocation is required to manage the species range-wide because, to date, the species landscape genetics and phylogeography are not well understood. To develop a successful range-wide long term management plan for the species that conserves extant genetic variation, it is critical to understand the genetic structure, dispersal characteristics and population histories of the fragmented populations in an evolutionary context.
In 2012, the U.S. Geological Survey (USGS) started a small animal connectivity study as part of
Connectivity Monitoring Strategic Plan (CMSP) developed by the San Diego Monitoring and
Management Program (SDMMP). The plan focused on small animals and their use of 8 underpasses
throughout San Diego County. Specialized infrared motion detection cameras were set up at each of the
underpasses and monitored from May 15 to October 1, 2102 and from March 19 to September 23, 2012.
After the first year, concrete structures were set up along the interior wall at 4 of the underpasses to
determine if the addition of structure would enhance the use of wildlife undercrossings by small
Over the two year period we collected over 3 million of pictures, developed specialized software
and methods for processing images, and documented the following species; Pocket Mouse (Chaetodipus
spp.), Kangaroo Rat (Dipodomys spp.), California Vole (Microtus californicus), Woodrats (Neotoma
spp.), Grey Shrew (Notiosorex crawfordi), Brush Mouse (Peromyscus boylii), California Mouse
(Peromyscus californicus), Deer Mouse (Peromyscus maniculatus), White footed Mouse (Peromyscus
spp.), Domestic Rat (Rattus rattus), Orange Throated Lizard (Cnemidophorus hyperythrus), Western
Whiptail (Cnemidophorus tigris), Western Fence Lizard (Sceloporus occidentalis), Granite Spiny Lizard
(Sceloporus orcutti), Side Blotched, Lizard (Uta stansburia), Red Diamond Rattlesnake (Crotalus
ruber)- outside only, Western Rattlesnake (Crotalus viridis), Bobcat (Lynx rufus), Coyote (Canis
latrans), Grey Fox (Urocyon cinereoargenteus), Mule Deer (Odocoileus hemionus), Greater
Roadrunner (Geococcyx californianus), Opossum (Didelphis marsupialis), Striped Skunk (Mephitis
mephitis), Raccoon (Procyon lotor), Spotted Skunk (Spilogale putorius), Jackrabbit (Lepus
californicus), Rabbit species (Sylvilagus spp.), California Ground Squirrel (Spermophilus beecheyi),
Chipmunk Species (Neotamias merriami).
This is the first study, to our knowledge, to show the use of underpasses by a community of
small vertebrates. Previous studies have lacked the sensitivity to document mice, lizards and snakes.
We have shown that these members of the community can be studied successfully using these passive
The results of modeling gave evidence to support the short-term effectiveness of the added
structure treatments on small vertebrate use and suggested that these rates changed on the specific side