The status of turtle populations in Point Pelee National Park: a 20 year update

Abstract

Long-lived species such as turtles may appear to have healthy persistent populations if adults are consistently observed; however, study of size structures can reveal declining populations left vulnerable by limited juvenile recruitment. Longterm studies can provide insight into community and population structure changes as well as test the efficacy of previously implemented mitigation measures. Two intensive turtle studies that included trapping occurred in Point Pelee National Park (PPNP) prior to my work: Rivard and Smith (1973) and Browne (2003). Browne (2003) studied the populations, capturing six species, and started the PPNP nest protection program to mitigate heavy nest predation causing limited juvenile recruitment in Snapping and Blanding’s Turtle populations. I captured 1834 individuals of five native and one introduced turtle species in 2022–2023 and compared my results with the results from Rivard and Smith (1973) and Browne (2003). The objective of my thesis was to estimate population sizes and compare community structure, relative abundance, sex ratios, and size structures from 2022–2023 with 1972–1973 and 2001–2002 to determine the status of PPNP turtle populations and the efficacy of the nest protection program. A total of 882 nests were protected between 2001–2021; 480 Snapping Turtle nests and 33 Blanding’s Turtle nests. I found an increased catch-per-unit-effort (CPUE) and a more evenly distributed size structure with a significantly lower median MCL (mm) than Browne (2003) for Snapping Turtles. I found a decreased CPUE and a size structure with no significant changes since Browne (2003) for Blanding’s Turtles. [...]