Seasonal and sexual differences in American marten diet in northeastern Oregon

Information on the diet of the American marten (Martes americana) is vital to understanding habitat requirements of populations of this species. The f requency of occurrence of prey items found in 1014 seat samples associated with 31 radiocollared American martens in northeastern Oregon included: 62. 7% vole-sized prey, 28.2% squirrel-sized prey, 22.4% insects, 19.5% birds, 13.3% plant material, and 2.4% lagomorphs. A significantly higher proportio n of voles (Microtus spp.), southern red-backed voles (Clethrionomys gapper i), and chipmunks (Tamias spp.) were found in the summer diet compared with the winter, and a higher proportion of northern flying squirrels (Glaucomy s sabrinus), unidentified squirrels, bushy-tailed woodrats (Neotoma cinerea ), and mountain cottontails (Sylvilagus nuttallii) were found in the winter diet compared with summer. Insects and plant remains represented a higher proportion of the diet in summer than winter. Females preyed on a higher pr oportion of shrews (Sorex spp.) and chipmunks, while males preyed on a high er proportion of southern red-backed voles.