string: Arctic ground squirrel populations in the boreal forest are smaller (Donker and Krebs 2011) and appear to exhibit demographic characteristics indicative of sink habitat types. The extirpation of ground squirrels from the boreal forest (Gillis et al. 2005; Donker and Krebs 2011), poor active-season survival, low recruitment rates, immigration from nearby low elevation-meadow habitat and population growth rates <1.0 provide convincing evidence that the boreal forest functions as a sink habitat for arctic ground squirrels. Conversely, arctic ground squirrel populations in nearby low elevation-meadow habitat appear to be stable and self-sustaining and appear to function as sources for populations in the boreal forest. Juveniles in the present study moved from low elevationmeadow habitat into boreal forest habitat, which suggests that low-elevation meadows have the capacity to support a nearby population sink. These findings also validate Gillis et al.’s (2005) suggestion that boreal forest populations are functioning as population sinks and that nearby meadow habitats may provide the immigrants required to sustain arctic ground squirrel populations in the forest.