Demographic Assessment of a Freshwater Turtle Assemblage in an Urban Protected Area in the Context of Ongoing Threats and a Mass-Mortality Event

Chronic threats and mass-mortality events in urban areas impact wildlife and can disproportionately affect turtle populations because their slow life history limits population recovery. Demographic studies of urban turtles are important, especially where ongoing conservation efforts (e.g., headstarting) occur and historical data on species status are absent. Our study focused on a community of headstarted Blanding's (Emydoidea blandingii) and naturally occurring painted (Chrysemys picta) and snapping (Chelydra serpentina) turtles that inhabit a wetland complex in an urban area of Toronto, Ontario, Canada. We assessed demography and biomass at 3 sites using mark-recapture data collected from 2018 to 2021. Abundance estimates were highest for painted turtles, followed by Blanding's and snapping turtles, while survival estimates varied depending on the species. Sex ratios of Blanding's turtles in human care and postrelease were similar. Both painted and snapping turtles displayed unbiased sex ratios, except at 1 site, where painted turtles displayed a female-biased sex ratio. The Blanding's turtle population was juvenile-biased because they are part of an ongoing headstarting program, whereas the painted and snapping turtle populations were adult-biased. Biomass of snapping turtles was the highest despite low abundance, highlighting their functional role in the ecosystem. Our findings indicate that turtle communities can persist in urban habitats; however, ongoing threats and catastrophes may pose a risk to population stability.