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Winter Severity and Wolf Predation on
a Formerly Wolf-free Elk Herd

L. David Mech, Douglas W. Smith, Kerry M. Murphy, and Daniel R. MacNulty

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Abstract: We studied wolf (Canis lupus) predation on elk (Cervus elaphus) in Yellowstone National Park from 17 March to 15 April 1997 (severe winter conditions) and from 2 to 31 March 1998 (mild winter conditions) 2-3 years after wolves were reintroduced to the park. Elk composed 91 % of 117 kills. Data comparisons for 1997 versus 1998 were: hunting success rate, 26% versus 15%; kill rate, 17.1 kg/wolf/day versus 6.1; percent of kill consumed in first day, 7 versus 86; percent femur marrow fat of adult kills, 27 versus 70; calf:adult ratios of kills, 2:33 versus 17:23; sex ratio of kills, 14M:19F versus 17M:6F; mean age of elk killed, males 6.1 years, females 15.2 versus males, 4.8, females 13.0. Winter severity influenced the wolf-elk relationship more than the naivete of the elk herd to predation by wolves.

Key words: Canis lupus, Cervus elaphus, elk, nutritional condition, predation, snow, winter severity, wolf, Yellowstone National Park.

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This resource is based on the following source (Northern Prairie Publication 1145):

Mech, L. David, Douglas W. Smith, Kerry M. Murphy, and Daniel R. MacNulty.  
     2001.  Winter severity and wolf predation on a formerly wolf-free 
     elk herd.  Journal of Wildlife Management 65(4):998-1003.

This resource should be cited as:

Mech, L. David, Douglas W. Smith, Kerry M. Murphy, and Daniel R. MacNulty.  
     2001.  Winter severity and wolf predation on a formerly wolf-free 
     elk herd.  Journal of Wildlife Management 65(4):998-1003.  
     Jamestown, ND: Northern Prairie Wildlife Research Center Online.  
     http://www.npwrc.usgs.gov/resource/mammals/severity/index.htm  
     (Version 03JUN2002).

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Table of Contents

• Introduction
• Study Area
• Methods
• Results
• Discussion
• Management Implications
• Acknowledgements
• Literature Cited

Tables and Figures

• Table 1 -- Success rates of Yellowstone National Park wolves hunting elk.
  
• Table 2 -- Sexes and ages of adult elk killed by 3 wolf packs on the northern range of Yellowstone National Park.
  
• Table 3 -- Yellowstone National Park wolf mean minimum kill rates.
  
• Table 4 -- Percent of Yellowstone National Park wolf-killed elk eaten.
  

• Figure 1 -- Map of the northern range study area in northeastern Yellowstone National Park with wolf pack territories defined, 1997-1998.

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L. David Mech, Biological Resources Division, U.S. Geological Survey, Northern Prairie Wildlife Research Center, 8711 37th Street, S.E., Jamestown, ND 58401, USA.  Mailing address: University of Minnesota, Gabbert Raptor Center, 1920 Fitch Street, St. Paul, MN 55108, USA.  E-mail: mechx002@tc.umn.edu
Douglas W. Smith and Kerry M. Murphy, National Park Service, Yellowstone Center for Resources, P.O. Box 168, Yellowstone National Park, WY 82190, USA.
Daniel R. MacNulty, Department of Fisheries and Wildlife, University of Minnesota, St. Paul, MN 55108, USA.

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