Modeling long‐term population viability to inform recovery of a functionally extinct urban Blanding's turtle population

After being assessed as functionally extinct, Toronto Zoo and Parks Canada have been working since 2012 to recover the Rouge National Urban Park (RNUP) population of Blanding's turtle ( Emydoidea blandingii ) through ex situ incubation of eggs and headstarting. To evaluate progression toward recovery goals and identify which demographic factors most strongly affect long‐term population persistence, we performed a population viability analysis using the program VORTEX. Analyses used demographic data from 2014 to 2022 to evaluate population trajectory over the next 150 years and to compare the influence of various management strategies and model uncertainties on population growth rate, population size, and probability of extinction. Completing the remaining 12 years of the 20‐year headstarting program is projected to result in a population that is roughly twice the size compared to if headstarting is stopped immediately. Given uncertainty in some demographic parameters, sensitivity analyses highlight juvenile survival has the largest influence on stochastic growth and extinction risk, and even small reductions in juvenile mortality could greatly increase population growth. Overall, results highlight that continued headstarting efforts along with additional management interventions will be needed to meet project goals and support the long‐term persistence of the population. Further investigation of demographic parameters as this population ages and grows will help address current knowledge gaps and inform future adaptive management.