STAND OCCUPANCY BY FISHER AND TREE SQUIRRELS IN NORTHERN CALIFORNIA: INVESTIGATING THE INFLUENCE OF MASTING HARDWOODS.
Andria M. Townsend; Humboldt State University; 1 Harpst Street, Arcata, CA, 95503; (630) 487-9319; amd94@humboldt.edu; Aaron Facka, Sean Matthews, Micaela Szykman Gunther
Sciurids are an important prey species for fisher (Pekania pennanti), especially when other prey species are absent. In California, Western gray squirrel (Sciurus griseus) and Douglas squirrel (Tamiasciurus douglasii) should be highly ranked prey where they occur. Masting trees including black oak (Quercus kelloggii) and tanoak (Notholithocarpus densiflorus) produce an important food source for tree squirrels, therefore forested stands containing these trees may be useful to fishers for efficient foraging. We tested the hypotheses that rates of tree squirrel and fisher occupancy and detection would be greatest in stands that should produce the most mast. We collected data for 44 weeks throughout 2017 using remote cameras in 87 stands in the northern Sierra Nevada Mountains. Stands were dominated by compositions of conifer, or co-dominant with conifers and tanoak or black oak. We constructed competing models in a single species occupancy framework testing the effect of stand type and other co-variates. Detection and occupancy rates varied among species and stand types. Douglas squirrels had high occupancy rates (0.96-0.99) irrespective of stand type. Gray squirrels and fishers had the highest rates of occupancy and detection in tanoak-dominated stands. Our data highlight the value of specific mast-bearing species for the conservation of carnivores.
Ecology and Conservation of Mammals IV   Student Paper