The intentional and unintentional movement of plants and animals by humans has transformed ecosystems and landscapes globally. Assessing when and how a species was introduced are central to managing these transformed landscapes, particularly in island environments. In the Gulf of Alaska, there is considerable interest in the history of mammal introductions and rehabilitating Gulf of Alaska island environments by eradicating those mammals classified as invasive species. The Arctic ground squirrel (Urocitellus parryii) is of concern because of its effect on vegetation and seabirds on Gulf of Alaska islands. This animal is assumed to have been introduced by historic settlers, however, ground squirrel remains in the prehistoric archaeological record of Chirikof Island, Alaska challenges this timeline, suggesting that they colonized the islands long ago. This study uses three lines of evidence to address this problem: 1) direct radiocarbon dating of archaeological squirrel remains; 2) evidence of prehistoric human use of squirrels; and 3) ancient DNA analysis of dated squirrel remains. The results suggest that squirrels have been on Chirikof longer than previously assumed and that the current population of squirrels is closely related to the ancient population. This challenges the assumption that ground squirrels were a recent, human-mediated introduction and supports the hypothesis that they may have colonized the island via a natural dispersal event or an ancient human translocation. This article is protected by copyright. All rights reserved.
