Prior to removal of pest species from an area, resource managers must determine if re-immigration from another population is possible. Voles inhabiting Saddle Rock on the southern Oregon coast are suspected to be partially responsible for declines in the Leach's storm petrel colony on the island. The island is very close to the mainland, and it is potentially accessible during below-average low tides. USGS scientists Mark Miller and Susan Haig and colleagues used genetic techniques to assess island vole population connectivity.