Analysis of Raptor Pellets of the Arctic National Wildlife Refuge Reveals Multiple Producers of the Pellets across the Coastal Plain

Abstract

By Madison Wells, Geology

Advisor: Josh Miller

Presentation ID: 305

Abstract: The Coastal Plain of the Arctic National Wildlife Refuge, AK is one of the last remaining, largely un-anthropogenically modified stretches of coastal plain in the United States. While state and federal resources focus on understanding large mammals and migratory bird populations, we know less about small mammals which serve as the base of the food chain. Raptors generally eat their prey whole and will regurgitate packets of undigested material in the form of pellets. These pellets, particularly from owls, are useful for evaluating the composition of small mammal communities across space and through time. Recent work used pellets to establish the first survey of small mammals across the coastal plain. While snowy owls (Bubo scandiacus) were thought to be the source, no formal analysis has been done to evaluate the pellet producer(s). Identifying the pellet producer is key to fully understand the ecological data and biases associated with pellet records. I have measured 306 pellets for their length and width and compared that frequency distributions of those dimensions to known sizes of pellets from pellet producers that breed or summer along the Arctic Refuge Coastal Plain. Reference data was collected from literature and the Cornell Lab of Ornithology, Birds of the World website. The majority of Arctic Refuge pellets were shorter than those of snowy owl pellets and the distribution of pellet lengths and widths are inconsistent with a single producer. Pellets likely came from a mix of short-eared owls (Asio flammeus), snowy owls, and perhaps northern harriers (Circus hudsonius).