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A seasonal pulse of ungulate neonates influences space use by carnivores in a multi-predator, multi-prey system
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  • Joel Ruprecht,
  • Tavis Forrester,
  • Nathan Jackson,
  • Darren Clark,
  • Michael Wisdom,
  • Mary Rowland,
  • Joshua Smith,
  • Kelley Stewart,
  • Taal Levi
Joel Ruprecht
Oregon State University

Corresponding Author:[email protected]

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Tavis Forrester
Oregon Department of Fish and Wildlife
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Nathan Jackson
University of Nevada Reno
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Darren Clark
Oregon Department of Fish and Wildlife
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Michael Wisdom
USDA Forest Service Pacific Northwest Research Station
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Mary Rowland
USDA Forest Service Pacific Northwest Research Station
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Joshua Smith
Oregon Department of Fish and Wildlife
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Kelley Stewart
University of Nevada Reno
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Taal Levi
Oregon State University
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Abstract

Understanding the extent to which predators engage in active search for prey versus incidentally encountering them is important because active search can exert a stabilizing force on prey populations by alleviating predation pressure on low-density prey and increasing it for high-density prey. Parturition of many large herbivores occurs during a short and predictable temporal window in which young are highly vulnerable to predation. Our study aims to determine how a suite of carnivores responds to the seasonal pulse of newborn ungulates using contemporaneous GPS locations of four species of predators and two species of prey. We used step-selection functions to assess whether coyotes, cougars, black bears, and bobcats actively searched for parturient females in a low-density population of mule deer and a high-density population of elk. We then assessed whether searching carnivores shifted their habitat use toward areas exhibiting a high probability of encountering neonates. None of the four carnivore species encountered parturient mule deer more often than expected by chance suggesting that predation of young resulted from incidental encounters. By contrast, we determined that cougar and male bear movements positioned them in proximity of parturient elk more often than expected by chance which is evidence of searching behavior. Although both male bears and cougars searched for neonates, only male bears used elk parturition habitat in a way that dynamically tracked the phenology of the elk birth pulse suggesting that maximizing encounters with juvenile elk was a motivation when selecting resources. Our results support the existence of a stabilizing mechanism to prey populations through active search behavior by predators because carnivores in our study searched for the high-density prey species (elk) but ignored the low-density species (mule deer). We conclude that prey density must be high enough to warrant active search, and that there is high interspecific and intersexual variability in foraging strategies among large mammalian predators and their prey.
17 Mar 2022Submitted to Ecology and Evolution
22 Mar 2022Submission Checks Completed
22 Mar 2022Assigned to Editor
22 Mar 2022Review(s) Completed, Editorial Evaluation Pending
11 May 2022Editorial Decision: Revise Minor
27 Jul 20221st Revision Received
28 Jul 2022Review(s) Completed, Editorial Evaluation Pending
28 Jul 2022Submission Checks Completed
28 Jul 2022Assigned to Editor
28 Aug 2022Editorial Decision: Accept
Oct 2022Published in Ecology and Evolution volume 12 issue 10. 10.1002/ece3.9389