Portland State University. Department of Geography
Date of Award
Master of Science (M.S.) in Geography
1 online resource (2, x, 136 pages)
Roadkill -- Oregon -- Clackamas County, Deer -- Oregon -- Clackamas County, Traffic accidents -- Oregon -- Clackamas County, Wildlife management -- Oregon -- Clackamas County
Road-kill of wildlife is common on Portland, Oregon's suburban fringe where development has increased road densities and traffic volume in rural areas. I identify the spatial and temporal patterns of black-tailed deer (Odocoileus hemionus columbianus) deer-vehicle accidents (DVA) at the suburban/rural interface of developing northwest Clackamas County using deer carcass pickup reports for county maintained roads for 1997-2004 and Oregon Department of Transportation deer-vehicle accident reports for 1996-2004. No black-tailed deer DVA models exist in the literature.
DVA increased 121% from 1997 to 1999 followed by a 26% decline by 2004. The initial DVA increase appears related to population growth and development into rural areas, an increase in the average daily vehicle-trip distance, and deer immigration from public lands. The subsequent decline appears related to DVA-induced decreases in deer populations, year-around hunting permits, growing predator populations, and fawning habitat loss.
Temporal OVA patterns for black-tailed deer show a minor peak in June-July and a major peak in October-November. Forty-two percent of DVA occur during the rut/hunt months of September, October, and November. This pattern corresponds to the black-tail's annual cycle and resembles patterns reported for white-tailed deer (Odocoileus virginianus) and mule deer (Odocoileus hemionus columbianus). Weekly DVA increased from a low on Sunday to a high on Friday and Saturday. DVA showed two daily peaks at 0500-0700 and 1800-2200, corresponding to dawn and dusk when deer activity is highest.
I identified 19 DVA hotspots with 16-27 DVA using CrimeStat III statistical clustering software. Hotspots occurring in rut/hunt months were separate from hotspots occurring in nonrut/nonhunt months. Similar to white-tailed and mule deer, black-tailed DVA hotspots commonly occurred where roads intersect or parallel water features, large forest blocks, and other areas of cover, or separate food sources from cover. Sixty-five percent of DVA occurred outside of hotspots with ≥ 10 DVA.
Deer-vehicle accidents have important ecological and economic costs and are frequent on northwest Clackamas County roads. Additional research supported by multi-agency carcass pickup repo1ting and the acquisition of precise DV A locations using a Global Positioning System (GPS) is needed to better identify wildlife movement corridors.
Anderson, Linda K., "Deer-Vehicle Accident Hotspots in Northwest Clackamas County, Oregon" (2006). Dissertations and Theses. Paper 4968.