Terrestrial food web dynamics in an old-growth forest
This project constitutes the primary components of Marie Tosa's PhD research and involves studying the terrestrial food web to better understand how old-growth forest ecosystems are structured and function in the Pacific Northwest. We are focusing this research in and near the HJ Andrews Experimental Forest, with particular focus on carnivore space use and diet. We are also collecting data on a range of other components of the food web, including invertebrates, fungi, small mammals, and vegetation.
We are investigating the dietary overlap and prey preferences of 7 mammalian carnivores: mountain lion (Puma concolor), black bear (Ursus americanus), bobcat (Lynx rufus), gray fox (Urocyon cinereoargenteus), western spotted skunk (Spilogale gracilis), long-tailed weasel (Mustela frenata), and short-tailed weasels (M. erminea). To date we have collected 876 scats and identified prey items using DNA metabarcoding and mechanical sorting. Preliminary results indicate that mule deer are main prey items for mountain lions and small mammals are main prey items for bobcats and gray foxes. Vegetation and invertebrates were large components of spotted skunk and black bear diets. With the exception of black bears, prey size scaled with carnivore biomass, and with the exception mountain lions, there was a high degree of dietary overlap between all of the carnivores.
Western spotted skunk spatial ecology
Marie and her technicians are trapping and tracking western spotted skunks to quantify their space use and sites used for denning and resting.
We are collecting data from an array of camera traps in and around the HJ Andrews forest to be used to fit models to quantify spatial and temporal partitioning of carnivores in this forest.