Lethal and non-lethal effects of predators and temporal trends in activity
We observed 12 mortalities of tree voles at nest platforms, of which seven were attributed to short-tailed weasels (M. erminea ), one to a long-tailed weasel (M. frenata ), two to flying squirrels, one to a small owl (northern saw-whet owl; Aegolius acadicus ), and one to a Steller’s jay (Cyanocitta stelleri ; Table 1). Of the 12 mortalities, eight were adult tree voles and four were juveniles. In addition, we observed one flying squirrel mortality which we determined was a young animal during an annual climbing inspection, and one case where a barred owl (Strix varia ) used the nest platform as a perch to consume a brush rabbit (Sylvilagus bachmanni ).
Table 1. Summary of temporal patterns at nest platforms.Summary of different species or groups detected at 168 nest platforms monitored by remote cameras for up to 177 weeks (670 ± 264 days; (x̄ ±SD ) at 23 young forest sites in the central Oregon Coast Range, Oregon, USA. Italics indicate species that represent a subset of a taxonomic group. Data represent weekly detections (# of detections per week) during the sampling period in which each nest platform was monitored (n = 15,510 monitoring-weeks). Predation rate is the proportion of detections resulting in an observed mortality of a red tree vole attributable to a given nest predator.