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An Assessment of Highway Effects on Flying Squirrel Movement and Population Genetics, at I-90 Snoqualmie Pass East, WA

Started: February, 2010 Ended: September, 2012 Project ID #4W2988 Status: Completed

Results & Findings

Results of this research suggested that flying squirrel populations on either side of the highway were well connected demographically and genetically, and that connectivity can be maintained if gaps in forest canopy associated with the highway are kept to a width within the gliding range of flying squirrels.


The goal of this study is to collect baseline genetic and movement information for flying squirrels, and to assess the extent to which I-90 currently represents a barrier to the movement of individuals and the genetic connectivity of the population.


As part of an ambitious effort to improve a 15-mile stretch of Interstate 90 (I-90) east of Snoqualmie Pass, Washington, the Washington State Department of Transportation is planning to install more than 20 wildlife underpasses, 3 overpasses, and wildlife fencing. Crossing structures have been designed and located with a broad range of species in mind—from amphibians to wide-ranging mammals. A key component of the I-90 project is its commitment to extensive wildlife monitoring. The long-term and multi-phased nature of this project makes it possible to collect valuable baseline data prior to construction. Ultimately, wildlife monitoring data will help researchers evaluate whether the crossing structures provide an effective means for wildlife to cross I-90. The Western Transportation Institute is currently overseeing the wildlife monitoring program at Snoqualmie Pass East. The flying squirrel project in particular is evaluating the current barrier effects of I-90 on flying squirrels, including if and how often squirrels cross the highway, and to what extent the highway is a barrier to gene flow for this species. Future studies conducted after the construction of crossing structures will evaluate whether the structures have helped increase connectivity for flying squirrels.


Files & Documents

Sponsors & Partners

  • U.S. Forest Service (FS) Sponsor
  • Washington Department of Transportation (WSDOT) Partner

Part of: Road Ecology

Project Tagged In: wildlife monitoring, road ecology, flying squirrel

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