Gould, W.R., Smallidge, S.T. & Thompson, B.C. 2005: Mark-resight superpopulation estimation of a wintering elk Cervus elaphus canadensis herd. - Wildl. Biol. 11: 341-349.
We executed four mark-resight helicopter surveys during the winter months January-February for each of the three years 199 -2001 at 7-10 day intervals to estimate population size of a wintering elk Cervus elaphus canadensis herd in northern New Mexico. We counted numbers of radio-collared and uncollared elk on a simple random sample of quadrats from the study area. Because we were unable to survey the entire study area, we adopted a superpopulation approach to estimating population size, in which the total number of collared animals within and proximate to the entire study area was determined from an independent fixed-wing aircraft. The total number of collared animals available on the quadrats surveyed was also determined and facilitated detectability estimation. We executed superpopulation estimation via the joint hypergeometric estimator using the ratio of marked elk counted to the known number extant as an estimate of effective detectability. Superpopulation size estimates were approximately four times larger than previously suspected in the vicinity of the study area. Despite consistent survey methodology, actual detection rates varied within winter periods, indicating that multiple resight flights are important for improved estimator performance. Variable detectability also suggests that reliance on mere counts of observed individuals in our area may not accurately reflect abundance.
Key words: aerial surveys, Cervus elaphus canadensis, detection, elk, helicopter, mark-resight, population estimation, superpopulation
William R. Gould, University Statistics Center, Box 30001, New Mexico State University, Las Cruces, NM 88003-8001, USA - e-mail: wgould@nmsu.edu Samuel T. Smallidge, New Mexico Cooperative Fish and Wildlife Research Unit, MSC 4901 Box 30003, Las Cruces, NM 88003, USA - e-mail: ssmallid@nmsu.edu Bruce C. Thompson*, New Mexico Cooperative Fish and Wildlife Research Unit, USGS Biological Resources, MSC 4901 Box 30003, Las Cruces, NM 88003, USA - e-mail: bcthompson@state.nm.us
*Present address: New Mexico Department of Game and Fish, P.O. Box 25112, Santa Fe, NM 87504, USA
Corresponding author: William R. Gould
Received 14 January 2004 , accepted 13 August 2004
Associate Editor: Nigel G. Yoccoz