Small mammal diet indicates plant diversity, vegetation structure, and ecological integrity in a remote ecosystem

We evaluated patterns of herbivory and predation/scavenging by a small mammal, the arctic ground squirrel ( Urocitellus parryii ), as an indicator of biological diversity, vegetation structure, and ecological integrity on two contrasting islands in the vast and remote Alaska Maritime National Wildlife Refuge. Using DNA metabarcoding techniques, we assessed the taxonomic composition of vertebrates, vascular plants, and bryophytes at family and growth form levels in arctic ground squirrel fecal samples collected on the ecologically intact island of Chowiet, which supports diverse seabird and vegetation communities, and the degraded island of Chirikof, which has incurred centuries of disturbance from introduced arctic fox ( Vulpes lagopus ) and cattle ( Bos taurus taurus ). We also evaluated whether fecal samples collected across the growing season (May—August) could act as indicators of herbivore-plant phenology. We did not detect any vertebrate taxa, however, observed herbivory patterns closely matched known differences in island plant diversity based on independent surveys. Diets from the ecologically intact island exhibited higher taxonomic richness, greater evenness, and higher shrub content than the ecologically degraded island, which is a grass- and forb-dominated ecosystem. On Chowiet Island, diets changed seasonally, likely in response to changing availability, nutritional quality, and toxin content associated with primary production. Small mammal diet served as an effective indicator of plant diversity, vegetation structure, and ecological integrity when compared against known composition and status of these remote island ecosystems. Non-invasive fecal sampling and dietary analyses using genetic techniques may provide a useful strategy for monitoring biological diversity, particularly in remote areas where widespread intensive sampling is unfeasible.