An 18-Year Mark-Recapture Study of Wood Turtles (Glyptemys insculpta) in Michigan

Abstract

Wood Turtles (Glyptemys insculpta) occupy forested streams at midlatitudes in eastern North America and are listed as endangered by the International Union for Conservation of Nature, but few populations have been rigorously studied. We studied a population of Wood Turtles in Michigan for 18 yr, individually marking 260 different turtles (146 females, 88 males, and 26 unsexed juveniles), including 118 turtles that we followed for one or more years using radiotelemetry. We analyzed our encounter data using a Cormack-Jolly-Seber model in Program MARK; and we estimated total population size using a Bayesian integrated population model that combined Horvitz-Thompson estimates of annual population size, mark-recapture estimates of annual survival, and derived estimates of annual recruitment. Annual adult survival was 0.970 ± 0.016 SD and annual recruitment to age 15 (mean age of first capture) was 0.058 ± 0.019 SD. Over the 18-yr study, estimated population size grew from 770 (95% CI 631-928) to 1,196 (95% CI 977-1,444) individuals.