Estimating red deer (Cervus elaphus) population size based on non-invasive genetic sampling

Cornelia Ebert,Bernhard Thiele,Bettina Welter,Julian Sandrini,Ulf Hohmann

doi:10.1007/s10344-021-01456-8

Abstract

Some deer species are of conservation concern; others are officially managed as a food source or for their trophies, whereas in many regions, deer are regarded as overabundant or even as a nuisance causing damages. Regardless of local management issues, in most cases, reliable data on deer population sizes and sex ratios are lacking. Non-invasive genetic approaches are promising tools for the estimation of population size and structure. We developed and tested a non-invasive genetic approach for red deer (Cervus elaphus) population size and density estimation based on faeces collected from three free-ranging red deer populations in south-western Germany. Altogether, we genotyped 2762 faecal samples, representing 1431 different individuals. We estimated population density for both sexes separately using two different approaches: spatially explicit capture-recapture (SECR) approach and a single-session urn model (CAPWIRE). The estimated densities of both approaches were similar for all three study areas, ranging between total densities of 3.3 (2.5–4.4) and 8.5 (6.4–11.3) red deer/km2. The estimated sex ratios differed significantly between the studied populations (ranging between 1:1.1 and 1:1.7), resulting in considerable consequences for management. In further research, the issues of population closure and approximation of the effectively sampled area for density estimation should be addressed. The presented approach can serve as a valuable tool for the management of deer populations, and to our knowledge, it represents the only sex-specific approach for estimation of red deer population size and density.

Highlights

Assessing ungulate population size and density is of central importance for monitoring programmes and managementNon-invasive genetic approaches represent a powerful tool for population size and density estimation of animals that are elusive and difficult to survey (Woods et al 1999; Beja-Pereira et al 2009; Ferreira et al 2018; Skrbinšek et al.27 Page 2 of 13Eur J Wildl Res (2021) 67: 272019)
DNA contained in hair or faecal samples can be used for identification of individual animals, and these data can be used for population size estimation, e.g. implemented in a capture-recapture (CR) framework
Of the 1156 samples that did not yield useable red deer consensus genotypes, 83 (7.1%) were excluded because they had been identified by their genotypes as originating from roe deer

Summary

Introduction

Assessing ungulate population size and density is of central importance for monitoring programmes and managementNon-invasive genetic approaches represent a powerful tool for population size and density estimation of animals that are elusive and difficult to survey (Woods et al 1999; Beja-Pereira et al 2009; Ferreira et al 2018; Skrbinšek et al. Page 2 of 13Eur J Wildl Res (2021) 67: 272019). Capture-recapture can yield accurate and precise population estimates (Otis et al 1978; Seber 1982; Pollock et al 1990), and non-invasive genetic CR offers the advantage that animals do not have to be captured physically, but are detected through their genotypes. This can reduce some sources of bias that are problematic in traditional CR, those related to the behaviour of animals towards being captured like, e.g. Care must be taken to reduce genotyping errors, e.g. by repeating analyses several times and by using effective error-checking protocols (Broquet and Petit 2004; McKelvey and Schwartz 2004)

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