Analysis of Deer Population Movement Patterns Before and After Construction of Wildlife Crossing Improvements in Central Oregon
Wildlife & Ecosystems
Research Idea Scope
The threats to human safety posed by high rates of large mammal road-kill are well reported in the literature, as well as the adverse effects of road-kill on mammal populations; however, macro-scale studies of how large mammal populations interact with roads and certain types of wildlife crossing structures are wanting. In central Oregon, approximately 100 miles of the U.S. Highway 97 corridor south of the town of Bend is a well-known “hotspot” for mule deer/vehicle collisions and associated deer road-kills. In order to better understand deer population movement patterns and to identify appropriate locations for the installation of wildlife crossing structures along U.S. Highway 97, the Oregon Department of Fish and Wildlife (ODFW) and the Oregon Department of Transportation (ODOT) completed a mule deer tracking study between 2005 and 2010 which entailed fitting nearly 500 animals with collars and monitoring their movement patterns in the vicinity of U.S. Highway 97. The data collected during the ODFW/ODOT study likely represents the largest dataset of mule deer tracking data currently available for a single large population. In addition to the deer tracking data, existing road-kill data collected along the 100-mile stretch of U.S. Highway 97 confirms that mule deer road-kill is endemic and has been documented at nearly every mile point within the 100-mile long stretch. This information prompted ODOT to install two wildlife crossing structures on U.S. Highway 97. The wildlife crossing improvements included a dedicated wildlife undercrossing, a multi-purpose undercrossing, fencing and jump-outs designed to guide animals to the crossing structures, electro-mats at vehicle access points, and landscaping treatments designed specifically for moving animals quickly through the crossings.
The proposed research project would continue monitoring mule deer movements to determine the effectiveness of the wildlife crossing improvements installed on U.S. Highway 97, as well as monitoring wider population movement patterns in the vicinity of U.S. Highway 97. To collect sufficient information to evaluate movement in relation to the highway improvements, additional mule deer would be collared and a subsample of the collars would be set to collect short-interval GPS data points. These data would be used in combination with movement-triggered wildlife cameras to track actual use of the crossing structures by individual animals. The GPS data would be used to complete a geospatial analysis to compare the pre-construction mule deer population movement patterns to post-construction movement patterns. The geospatial analysis would identify landscape features and other principal components associated with the most common mule deer road-crossing locations. The proposed project would allow the investigators to 1) gain a better understanding of the effectiveness of the crossing structures, 2) understand individual animal behavior and learning patterns associated with using or avoiding the structures, and 3) continue monitoring large scale population movement patterns that could be used to identify other areas where crossing structures might be installed, further reducing deer/vehicle collisions and associated road-kill.
Urgency and Payoff
The proposed project would take advantage of an excellent existing data resource by allowing investigators to augment it and ultimately compare mule deer population movement patterns pre- and post-construction of crossing improvements on U.S. Highway 97. By tracking individual animal movement, ODFW and ODOT will be able to investigate use of the improvements and learn about individual animal use patterns. Through the larger geospatial analysis combined with the GPS data set gathered from the collared animals, the researchers will be able to analyze population-level movement patterns and how topographic features, including the new crossing improvements, might affect the movement patterns. The results of this analysis would inform the planning efforts of other transportation departments and wildlife management agencies that are faced with similar human safety risks and wildlife population threats.
Mindy Trask, Oregon Department of Transportation, Geo-Environmental Section