San Diego Management & Monitoring Program


A Field Study of Small Vertebrate Use of Wildlife Underpasses in San Diego County, 2014

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File description: LAG report for small animal underpass study

File owner: San Diego Management and Monitoring Program

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Type: report

Article abstract: 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 vertebrates. 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 methods. 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

Number of pages: 80

Authors: Brehme, Cheryl; Clark, Denise; Fisher, Robert N.; Rochester, Carlton; Tracey, Jeff;

Year: 2014

Publisher: U.S. Geological Survey

Prepared for: California Department of Fish and Wildlife;

Prepared by: U.S. Geological Survey, Western Ecological Research Center;

Keywords: 1996 Harmony Fire; connectivity; connectivity corridors; habitat connectivity; small mammals; underpasses;

Species: Red Diamond Rattlesnake; Stephens' kangaroo rat; California bobcat; Northwestern San Diego pocket mouse

Threats: Loss of connectivity