Estimating Abundance and Occupancy of Northern Barrens Tiger Beetles in an Isolated New York Population

Abstract

Reliable monitoring of abundance of rare species across space and time is critical to determining their status and risk of extinction. For Cicindela patruela patruela (Notrthern Barrens Tiger Beetle), we determined whether mark–recapture estimates of abundance or site occupancy probability were sufficiently precise, unbiased, and efficient to be used for long-term monitoring of population status for this imperiled species in the Shawangunk Mountains, NY. Over 2 years, the estimated population size grew from 81 ± 5.7 to 109 ± 6.4 individuals. Consistent with a space-limited but potentially growing population, seasonal occupancy models (3-season model with year = season) indicated site-colonization probability remained constant, site extinction probability decreased, and detection probability increased among years—the latter indicating the need to account for variation in detection probability when monitoring population trends. Both occupancy and mark–recapture methods were promising for monitoring change in populations of Northern Barrens Tiger Beetle in this region.