Abstracts

Presented by Joshua T. Ackerman - Email: jackerman@usgs.gov

Mammalian predation on ground-nesting waterfowl often is the primary cause of nest failure. Understanding how individual predators interact with duck nests and move through different habitats may inform management practices and improve nest success. We quantified movement and habitat use of raccoons (Procyon lotor; n=29) and striped skunks (Mephitis mephitis; n=25), using GPS collars in Suisun Marsh, CA. Mesopredators were collared prior to duck nesting (20162019), with locations recorded during the nesting period every 15 min (raccoons) and 7.5 min (skunks). At monitored nests, iButton temperature dataloggers recorded temperature every 8 min. We identified temperature decreases associated with hen departure from a nest, using a camera-validated algorithm. Nocturnal hen departures likely indicate response to a predator, allowing us to use them as further evidence for the timing of depredations. Raccoons and skunks differed in upland habitat use, although all mesopredators were captured within or along the edges of upland fields. Raccoons and male skunks primarily moved along habitat edges, specifically roads, levees, and canals. Raccoons spent most of their time in managed wetlands adjacent to, and occasionally within, upland fields. Female skunks remained almost entirely within upland fields. Furthermore, raccoons demonstrated a high level of territoriality, with limited overlap between individuals of the same sex. Collared raccoons were observed < 25m from 17% of monitored nests and depredations occurred at 32% of those nests. Collared skunks were concentrated within a smaller area of the upland nesting fields, were observed < 25m from only 4% of monitored nests, and depredations occurred at 53% of those nests. We revealed sections of upland nesting habitat more commonly frequented by mesopredators, which can inform habitat management to potentially decrease encounters between mesopredators and duck nests.