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Carnivore activity and movement in a Southern California protected area, the North/Central Irvine Ranch.

Released: 2006
Lyren, LM, GM Turschak, ES Ambat, CD Haas, JA Tracey, EE Boydston, SA Hathaway, RN Fisher, KR Crooks. 2006. Carnivore activity and movement in a Southern California protected area, the North/Central Irvine Ranch. U.S. Geological Survey Technical Report, 115 p.

Connectivity and wildlife corridors are essential for biodiversity conservation in fragmented landscapes, and large carnivores are ecologically pivotal species whose status can be indicative of functional connectivity of ecosystems. Our primary research goals were 1) to assess movement patterns of wildlife in the North/Central Irvine Ranch (NIR), with a focus on large carnivores, and 2) to identify and monitor key movement corridors for large carnivores near potential arterial roads that are proposed to cross the NIR, including the Jamboree Road extension and North Lake Road construction. In Phase 1 (summer 2002-fall 2003), we completed track and remotely-triggered camera surveys to evaluate distribution, relative abundance, and movement patterns of wildlife species. Track and camera transects detected nine wildlife species each throughout the study area, including the three target species [(mountain lion (Puma concolor), bobcat (Lynx rufus), coyote (Canis latrans)] as well as six non-target species [(mule deer (Odocoileus hemionus), gray fox (Urocyon cinereoargenteus), raccoon (Procyon lotor), striped skunk (Mephitis mephitis), spotted skunk (Spilogale gracilis), and the non-native opossum (Didelphis virginiana)]. Track and camera surveys also detected various human recreationists, as well as domestic animals including dogs (Canis familiaris) and horses (Equus caballus). In addition, we conducted GPS (Global Positioning System) radio telemetry surveys on 10 bobcats, 6 males and 4 females, within the study area. In Phase 2 (fall 2003-summer 2005), we conducted radio telemetry surveys on six more bobcats, two males and four females, within the study area. In addition, we carried out radio telemetry surveys on three adult female mountain lions. With the exception of one mountain lion, we successfully retrieved all collars and downloaded the stored location data. In total, we recorded 4469 high-resolution GPS locations for bobcats (X¯ = 279 locations; range = 181 to 359 locations per individual) and 3118 GPS locations for mountain lions (X¯ = 1039 locations; range = 371 to 1637 locations per individual). Mountain lions, and to a lesser extent bobcats, traveled widely throughout the study area; the 100% Minimum Convex Polygon (MCP) and 95% Fixed Kernel (FK) home range sizes for bobcats ranged from 1.54 to 9.42 km2 (X¯ = 3.62 ± 0.56 SE) and 1.34 to 13.39 km2 (X¯ = 3.72 ± 0.35 SE), respectively, and the 100% MCP and 95% FK home range sizes for mountain lions ranged from 97 to 181 km2 (X¯ = 132 ± 25.3 SE) and 83 to 125 km2 (X¯ = 105.4 ± 12.4 SE), respectively. Mountain lions and bobcats frequently encountered potential barriers such as urban edges and roadways. Indeed, although we recorded mountain lion and bobcat use of existing underpasses along CA-241 and Santiago Canyon Road, two of the GPS radio collared mountain lions were killed by vehicles while attempting to cross these roadways. Overall, core habitat blocks within the NIR appear to serve as critical components of a network of wildlands in the region, and with continued urban development and road construction in the area, it is critical to maintain and restore connectivity within and outside the NIR to ensure long-term persistence of carnivore populations and the systems in which they live

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