![]() Detection is never complete because some animals are obscured by shadow, in vegetation, or otherwise hidden from view (Figure 3), and are thus missed during survey flights (Samuel et al., 1987). Sightability models estimate population size by correcting the number of observed elk or deer groups by the numbers missed due to incomplete detection. Herding individuals, viewing from many different angles, and low flight capability all greatly increase the accuracy of herd composition counts. Using a helicopter provides many advantages for wildlife surveys. Thus, sightability models are the most useful and easily applied of the accurate methods for monitoring population size, and should be the tool of choice for landowners in New Mexico and similar habitats.įigure 2. Sightability model surveys can be expensive to conduct because they require the use of a helicopter (Figure 2), but they probably produce the best data for management of deer and elk populations and are the least complicated population estimator to use on wildlife enterprises. The most commonly used and probably best method is an aerial sight-bias (sightability) model (Samuel et al., 1987 Otten et al., 1993). Similarly, many methods are used to estimate the size of big game populations, including distance sampling, mark-resight estimators, and sight-bias or sightability models (Keegan et al., 2011). ![]() Consequently, these methods are seldom used by management agencies to monitor populations because of the inherent problems and inaccuracies in these methods. Unfortunately, most of these commonly used trend indices have many assumptions that usually result in trend information of uncertain value, and very few have been calibrated to actual population size (Keegan et al., 2011 Bender, 2020a). The most common trend indices used by landowners include minimum counts, spotlight or ground counts, and pellet group surveys (Bender, 2020a). Ultimately, it is the per capita resource (food, water) availability that determines individual body condition and thus population productivity, harvestable surplus, and animal (trophy) quality (Bender, 2011). Second, population estimates can be converted to densities, and relationships between resource availability (forage, etc.) and population size can be determined. First, they allow direct calculation of harvestable surplus. Population estimates are preferable to trend estimators for several reasons. Methods range from trend indices (Bender, 2020a), which provide information on whether a population is increasing, stable, or declining, to abundance estimators, which provide a population estimate (Lancia et al., 1996). Many methods have been used to monitor the status, composition, and trends of deer and elk populations. Managing populations for optimal yields requires accurate monitoring of population size and composition. Wildlife such as mule deer can contribute significantly to ranch income through well-managed wildlife hunting enterprises. ![]() This is particularly true in arid habitats where annual changes in population productivity, and thus sustainable harvest and trophy quality, can be pronounced (Heffelfinger et al., 2003 Bender, 2011).įigure 1. Sustainable management of these resources requires monitoring of populations. ![]() Wildlife (hunting) enterprises are important sources of revenue for property owners in New Mexico, and consequently elk (Cervus elaphus) and mule deer (Odocoileus hemionus) are vital economic resources for private landowners (Figure 1). Senior Research Scientist (Natural Resources), Department of Extension Animal Sciences and Natural Resources, New Mexico State University. Guidelines for Monitoring Elk and Mule Deer Numbers in New MexicoĬollege of Agricultural, Consumer and Environmental Sciences, New Mexico State University
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