ASSESSING TOP-DOWN AND BOTTOM-UP EFFECTS ON INTERACTIONS BETWEEN DUSKY-FOOTED WOODRATS AND SPOTTED OWLS IN THE SIERRA NEVADA

Corbin C Kuntze; University of Wisconsin - Madison; kuntze@wisc.edu; Jonathan N. Pauli, John J. Keane, Brian P. Dotters, Kevin N. Roberts, Sarah C. Sawyer, Ceeanna J. Zulla, M. Zachariah Peery

Understanding the extent to which species are governed by top-down (predation) versus bottom-up (resource) limitations can benefit the management of both predator and prey. The dusky-footed woodrat (Neotoma fuscipes) is an important prey species for California spotted owls (Strix occidentalis occidentalis), yet the relative importance of bottom-up versus top-down controls for woodrat populations remains uncertain. Based on a sample of 109 radio-collared individuals, we found that predation on woodrats was uniformly low within spotted owl territories that featured a mosaic of forested seral stages. Nevertheless, video monitoring at 15 spotted owl nest sites revealed frequent deliveries of woodrats to dependent young. To reconcile this apparent dissonance and understand the proportion and number of woodrats consumed by pairs of spotted owls we used a combination of woodrat trapping data, occupancy models, and mark-recapture analyses. Our results suggest that the top-down effects of predation on woodrats are relatively weak but, in conjunction with other studies, woodrat abundance is likely a key driver of spotted owl populations. Collectively, our findings can inform forest management practices intended to promote woodrat populations and improve spotted owl conservation in Sierra Nevada forests.

Spotted Owl Ecological Associations   Student Paper Zoom Presentation