Rejection of Schmidt et al.'s estimators for bear population size.

Earl Becker,Aaron Christ

doi:10.1002/ece3.5134

Abstract

Aerial distance sampling of bears to estimate population size has been used throughout many parts of Alaska. The distance sampling models are complex since they need to account for undetected bears and differences in detection probabilities. This will require covariates and mark‐recapture data. The models proposed by Schmidt et al. do not use covariates or mark‐recapture data and are inappropriate for these surveys.

Highlights

Advanced distance sampling, using small 2‐person aircraft, has been successfully used to estimate brown and black bear (Ursus spp.) population size in Alaska (Becker & Christ, 2015)
Wilson, Thompson, and Reynolds (2017) presented a case for three alter‐ native bear population estimators that can be applied to this data that they claim are less complex and more precise than the mark– recapture distance sampling (MRDS) methods used by Becker and Christ (2015)
We found that ignoring mark–recapture data and covariates resulted in a −17.4% to −21.4% bias compared to the MRDS_2PN models (Table 2)

Summary

Introduction

Advanced distance sampling, using small 2‐person aircraft, has been successfully used to estimate brown and black bear (Ursus spp.) population size in Alaska (Becker & Christ, 2015). The second model pools data from sev‐ eral bear surveys into a hierarchical Bayesian CDS model that uses a half‐normal detection function (hereafter referred to as “CDS_HnBayes”), and estimates the population size of each study area.

Results

Conclusion