DOI: 10.5061/dryad.cjsxksn3d
title: Data from: Predator-prey interactions in the canopy

description: Small mammal abundances are frequently limited by resource availability,
 but predators can exert strong lethal (mortality) and non-lethal (e.g.,
 nest abandonment) limitations. Artificially increasing resource
 availability for uncommon small mammals provides a unique opportunity to
 examine predator-prey interactions. We used remote cameras to monitor 168
 nest platforms placed in the live-tree canopy (n = 23 young forest
 stands), primarily for arboreal red tree voles (tree voles; Arborimus
 longicaudus), over three years (n = 15,510 monitoring-weeks). Tree voles
 frequently built nests and were detected 37% of monitoring-weeks, whereas
 flying squirrels (Glaucomys oregonensis) built nests infrequently but were
 detected 45% of monitoring-weeks. Most nest predators were detected
 infrequently (&lt;1% of monitoring-weeks) and were positively
 correlated with tree vole presence. Weasels (Mustela spp.) were highly
 effective predators of tree voles (n = 8 mortalities; 10% of detections)
 compared to owls (n = 1), flying squirrels (n = 2), and Steller’s jays (n
 = 1). Tree vole activity decreased from 84.1 (95% confidence interval
 (CI): 56.2, 111.9) detections/week 1-week prior to a weasel-detection to
 4.7 detections/week (95% CI: 1.7, 7.8) 1-week post detection and remained
 low for at least 12 weeks. Interpretations of predator-prey interactions
 were highly sensitive to how we binned continuously collected data and
 model results from our finest bin-width were biologically
 counter-intuitive. Average annual survival of female tree voles was
 consistent with a previous study (0.14; 95% CI: -0.04 [0.01], 0.32) and
 high compared to many terrestrial voles. The relative infrequency of
 weasel detections and inefficiency of other predators did not provide
 strong support for the hypothesis that predation per se limited
 populations. Rather, predation pressure, by reducing occupancy of already
 scarce nest-sites through mortality and nest abandonment, may contribute
 to long-term local instability of tree vole populations in young forests.
 Additional monitoring would be needed to assess this hypothesis.
description: We added 598 nest platforms at a height of 16 ± 4 m to 23
 randomly selected young forest sites (17 in 2015, six in 2016) that were
 located adjacent to old forests that contained sign of tree vole presence
 (Linnell et al. 2018). At each site, we randomly selected two 100
 m<sup>2</sup> circular plots per hectare and constructed 1
 nest platform in the tree at plot center within the live canopy (live
 limbs vertically above and below). To construct a nest platform, we
 stretched a length of hexagonal wire mesh (2.54 cm openings) between two
 or three branches to form an open basket and placed ~8 liters of conifer
 branch tips and moss within the basket. We used two
 sources of data: annual nest platform inspections (<i>n</i> =
 1640) that occurred each summer 2016 – 2018, and photographic data from
 nest platforms monitored with a remote camera (<i>n</i> = 168)
 June 2015 – October 2018. Each nest platform was inspected annually for
 diagnostic sign of arboreal rodent nests. Tree vole nests, especially
 female nests, are frequently large (0.06 m<sup>3</sup>) and
 consisted of tunnels and nest chambers formed within discarded resin
 ducts, fecal pellets, and conifer branch tips whereas flying squirrels
 primarily built smaller cup-shaped nests from collected moss (Lesmeister
 and Swingle 2017; Swingle 2005). Tree vole nests were inhabited primarily
 by one adult except for breeding female nests which often contained
 juveniles (Swingle 2005). We deployed remote cameras at
 a random selection of ~10% (2015) or ~20% (2016) of nest platforms
 (<i>n</i> = 96). In addition to the randomly selected nest
 platforms, we placed cameras at 72 nest platforms built in 2015 and
 containing a tree vole nest identified during the first-year annual
 inspection in 2016. We combined data collected from randomly
 (<i>n</i> = 96) and non-randomly (<i>n</i> = 72)
 placed cameras for all analyses (<i>n</i> = 168 monitored nest
 platforms). Remote cameras were mounted 0.6 – 1.0 m
 above nest platforms and faced down such that the entire nest platform and
 some adjacent branches were within the field of view of the camera sensor
 and included in each image. We set each camera to record photos when
 triggered by motion with a five minute (2015 – 2016) or one-minute (2016 –
 2018) quiet period. We tagged each photo with species identity, and for
 tree voles we also identified age class (juvenile, adult) and, if present,
 we noted the unique external marking on the tree vole. We tracked photo
 tagging and estimated a rate of 2616 photos per hour (95%
 <i>CI</i>: 2406, 2826;<i> n</i> = 175 sessions).
 Using this rate, we estimated that tagging the 852,000 photos in our data
 set required 326 hours (95% <i>CI</i>: 301, 354).
description: Meta-data is uploaded in tab with main data set.