Only six species of land mammals occur naturally within Kodiak National Wildlife Refuge. These include: Kodiak brown bear (Ursus arctus middendorffi), red fox (Vulpes vulpes), river otter (Lutra canadensis), ermine (Mustela erminea), tundra vole (Microtus oeconomus), and little brown bat (Myotis lucifugus). Kodiak bears have been extensively studied, and much is known of their biology and habitat requirements. In contrast, ecology of other native mammals is minimally documented. 
 

Between the 1920’s and 1960’s, several species of non-native mammals were introduced to increase subsistence and recreational opportunities in the archipelago. Eight species established, spread, and now commonly occur on the refuge. They are: Sitka black-tailed deer (Odocoileus hemionus sitkensis), mountain goats (Oreamnos americanus), Roosevelt elk (Cervus canadensis roosevelti), reindeer (Rangifer tarandus), beaver (Castor canadensis), red squirrel (Tamiasciurus hudsonicus), snowshoe hare (Lepus americanus), and pine marten (Martes americana). Populations of deer, elk, mountain goat, and snowshoe hare are now highly valued by sport and subsistence hunters. Some of these also are a source of management concern because of their potential to influence the quality of native fish and wildlife habitats.