Raptor pellets of the Arctic National Wildlife Refuge Reveal Spatial Gradient in Small Mammal Communities

Abstract

Record ID: 105

Awards: Excellence in Research Mentoring; Excellence in Research Communication

Student Major: Geology

Project Advisor: Josh Miller

Abstract: Historical skeletal remains provide important resources for evaluating extant small mammal diversity. Many raptorial birds can consume prey whole and regurgitate pellets of indigestible remains. Resulting pellet accumulations faithfully record local prey diversity because these birds feed largely indiscriminately. Here, we use pellet-derived bone accumulations to evaluate changes in rodent communities across the Coastal Plain of the Arctic National Wildlife Refuge, Alaska. This region is dominated by three microtine rodents; collared lemming (Dicrostonyx groenlandicus), North American brown lemming (Lemmus trimucronatus), and tundra vole (Microtus oeconomus), but there are limited data on community composition. Since pellets can accumulate across decades or more, they may be particularly useful for establishing long-term population metrics for microtine rodents that undergo dramatic population cycles. Pellets were collected during taphonomic surveys of tundra habitats (near seven major river systems. Mammalian remains were identified based on tooth morphology and pellets were summarized by the minimum number of individuals for each species. We find significant changes in microtine community composition across the Coastal Plain. The community is strongly dominated by lemmings in the west and voles in the east. The shift in arcsine-transformed proportional abundance of voles is continuous across longitude and is highly significant (weighted linear regression; p < 0.01, R2 = 0.75). This dramatic shift in the Coastal Plain microtine species was previously unrecognized. Our results illustrate that (i) even in species-poor tundra settings, biological heterogeneity can be high, and (ii) conservation paleobiology can provide novel insights relevant to understanding cryptic diversity changes in modern ecosystem.