Bender, L.C., Myers,W.L. & Gould,W.R. 2003: Comparison of helicopter and ground surveys for North American elk Cervus elaphus and mule deer Odocoileus hemionus population composition. - Wildl. Biol. 9: 199-205.
Both ground and helicopter surveys are commonly used to collect sex and age composition data for ungulates. Little attention has been paid, however, to whether data collected by each technique are similar. We compared helicopter and ground composition data for both elk Cervus elaphus and mule deer Odocoileus hemionus across a variety of habitats in the state of Washington, USA. We found that ground and helicopter counts differed (P’s < 0.002) consistently in male age structure estimates for elk, and that the two survey methods differed in estimates of adult sex ratios for mule deer (P = 0.023). Counts from helicopters provided larger sample sizes, tended to be more consistent annually in their results, and were corroborated by other demographic studies of the test populations. We conclude that helicopter and ground surveys differ for male age structure and perhaps male:female ratios, but are similar for young:female ratios. Managers should maintain a standardized technique using the same survey vehicle for trend analysis of composition data.
Key words: age structure, elk, ground surveys, helicopter, mule deer, population composition, sex ratios, surveys
Louis C. Bender*,Washington Department of Fish and Wildlife, 2950 Ley Road, Cle Elum,Washington 98922, USA - e-mail: lbender@nmsu.edu
Woodrow L. Myers,Washington Department of Fish and Wildlife, 8702 North Division, Spokane,Washington 99216, USA - e-mail: myerswlm@dfw.wa.gov
William R. Gould, University Statistics Center, Department of Economics, New Mexico State University, Las Cruces, New Mexico 88003, USA - e-mail: wgould@nmsu.edu
*Present address: U.S. Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit, PO Box 30003 MSC 4901, Las Cruces, New Mexico 88003, USA
Corresponding author: Louis C. Bender
Received 19 December 2001, accepted 5 December 2002
Associate Editor: John P. Ball