Estimating Population Size of a Threatened Turtle Using Community and Citizen Science

Abstract. Blanding's turtles (Emydoidea blandingii) are considered threatened or endangered throughout most of their range. A critical step in determining appropriate conservation actions for this species is assessing the status of remaining populations. The long-term surveys required to adequately document population trends are lacking, as they are generally labor-intensive and time-consuming. We used community and citizen science–collected data and free pattern-recognition software to conduct a mark–recapture study on female Blanding's turtles in a northwest Ohio wetland. Over a 5-yr period, community and citizen scientists gathered 155 images of 65 individual female Blanding's turtles. Our results suggest the wetland has a population of 87 (95% CI = 74–116; SE = 10.1) adult female Blanding's turtles. Deriving preliminary population estimates from photographic recapture data is an example of how the efforts of community and citizen scientists can benefit ongoing research projects and conservation efforts.