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Defining the danger zone: Critical snow support thresholds for predator-prey interactions
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  • Benjamin Sullender,
  • Calum Cunningham,
  • Jessica Lundquist,
  • Laura Prugh
Benjamin Sullender
University of Washington

Corresponding Author:[email protected]

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Calum Cunningham
University of Washington
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Jessica Lundquist
University of Washington
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Laura Prugh
University of Washington
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Snowpack dynamics have a major influence on wildlife movement ecology and predator-prey interactions. Specific snow properties such as density, hardness, and depth determine how much an animal sinks into the snowpack, which in turn drives both the energetic cost of locomotion and predation risk. Here, we quantified the relationships between 15 field-measured snow variables and snow track sink depths for widely distributed predators (bobcats [Lynx rufus], coyotes [Canis latrans], wolves [C. lupus]) and sympatric ungulate prey (caribou [Rangifer tarandus], white-tailed deer [Odocoileus virginianus], mule deer [O. hemionus], and moose [Alces alces]) in interior Alaska and northern Washington, USA. We first used generalized additive models to identify which snow metrics best predicted sink depths for each species and across all species. For species occurring in both sites, we then tested whether the snow metric-sink depth relationship differed across regions. Finally, we used breakpoint regression to identify thresholds for the best-performing predictor of sink depth for each species (i.e., values wherein tracks do not appreciably sink into the snow). Near-surface (0-10cm) snow density was the strongest predictor of sink depth across species. This relationship varied slightly by region for wolves and moose but did not differ for coyotes. Thresholds of support occurred at snow densities of 230 kg/m3 for coyotes, 280 kg/m3 for bobcats, 290 kg/m3 for wolves, 340 kg/m3 for deer, 440 kg/m3 for caribou, and 550 kg/m3 for moose. Together, these critical thresholds define the bounds of “danger zones,” the range of snow density in which carnivores have a comparative movement advantage over ungulates. These results can be used to link predator-prey relationships with spatially explicit snow modeling outputs and projected future changes in snow density. As climate change rapidly reshapes snowpack dynamics, these danger zones provide a useful framework to anticipate likely winners and losers of future winter conditions.
08 Dec 2022Submitted to Oikos
08 Dec 2022Submission Checks Completed
08 Dec 2022Assigned to Editor
08 Dec 2022Review(s) Completed, Editorial Evaluation Pending
11 Dec 2022Reviewer(s) Assigned
25 Jan 2023Editorial Decision: Revise Major
23 Mar 20231st Revision Received
24 Mar 2023Assigned to Editor
24 Mar 2023Submission Checks Completed
24 Mar 2023Review(s) Completed, Editorial Evaluation Pending
31 Mar 2023Reviewer(s) Assigned
19 Apr 2023Editorial Decision: Revise Minor
04 May 20232nd Revision Received
08 May 2023Assigned to Editor
08 May 2023Submission Checks Completed
08 May 2023Review(s) Completed, Editorial Evaluation Pending
16 May 2023Editorial Decision: Accept