Are abundance indices derived from spotlight counts reliable to monitor red deer Cervus elaphus populations?
Mathieu Garel, Christophe Bonenfant, Jean-Luc Hamann, François Klein & Jean-Michel Gaillard
Management of large herbivores could be improved by investing less effort in estimating absolute abundance and more effort tracking variation over time of indicators of ecological change (IEC) describing animal performance, herbivore impact on habitat, and relative animal abundance. To describe relative changes in animal abundance, monitoring trends in numbers through indices may constitute a useful and low cost method, especially at large spatial scales. Reliability of indices to detect trends should be evaluated before they are used in wildlife management. We compared population trends estimated from spotlight counts, a standard census method for deer populations, with population size estimates of a red deer Cervus elaphus population monitored using Capture-Mark-Recapture (CMR) methodology. We found a strong negative effect of conditions of observation (e.g. rainfall) on both the number of animals (-24.4%) and the number of groups (‑1.6%) seen per kilometre. After controlling for observation conditions, we found that these two abundance indices were linearly correlated withCMRestimates, with the group-based index being better correlated (r = 0.75) than the individual-based index (r = 0.68). These consistent trends between indices and CMR estimates provide support in using standardised spotlight counts as an IEC describing relative changes in abundance for the monitoring and management of red deer populations.
Key words: abundance index, Capture-Mark-Recapture, census method, Cervus elaphus, count data, indicators of ecological change, red deer
Mathieu Garel, Office National de la Chasse et de la Faune Sauvage, Centre National d’E´tude et de Recherche Appliquée Faune de Montagne, 5 allée de Bethléem, Z.I. Mayencin, F-38610, Gières, France, and Université de Lyon, Université Lyon 1, CNRS,UMR5558, Laboratoire de Biométrie et Biologie Evolutive, Bâtiment G. Mendel, 43 boulevard du 11 novembre 1918, F-69622 Villeurbanne, France - e-mail: mathieu.garel@oncfs.gouv.fr
Christophe Bonenfant&Jean-Michel Gaillard, Universite´ de Lyon, Université Lyon 1, CNRS,UMR5558, Laboratoire de Biométrie et Biologie Evolutive, Bâtiment G. Mendel, 43 boulevard du 11 novembre 1918, F-69622 Villeurbanne, France - e-mail addresses: bonenfan@biomserv.univ-lyon1.fr (Christophe Bonenfant); gaillard@biomserv.univ-lyon1.fr (Jean-gaillard@biomserv.univ-lyon1.frMichel Gaillard)
Jean-Luc Hamann & François Klein, Office National de la Chasse et de la Faune Sauvage, Centre National d’Étude et de Recherche Appliquée Cervidés Sanglier, 1 place Exelmans, F-55000 Bar le Duc, France - e-mail addresses: petitepierre@oncfs.gouv.fr (Jean-Luc Hamann); francois.klein@oncfs.gouv.fr (François Klein)
Corresponding author: Mathieu Garel
Received 16 March 2009, accepted 11 September 2009
Associate Editor: Leif Egil Loe
Wildl. Biol. 16: 77-84 (2010)
DOI: 10.2981/09-022
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