Fig 1.
Spatial overview of the Rouge National Urban Park in Toronto, Ontario, Canada.
The exact location of the study site is excluded to protect at-risk species from poaching. The map was created by compiling data available from https://geohub.lio.gov.on.ca/ on QGIS (3.20.1-Odense) [29–32].
Table 1.
Number of headstarted Blanding’s Turtles included in the Jolly-Seber open population model.
Headstarted turtles were grouped based on release year (release cohort) and further subdivided based on number of years tracked, which resulted in 23 groups.
Fig 2.
Simplified conceptual framework of the Jolly-Seber open population model used to estimate abundance and survival of headstarted Blanding’s Turtles in the Rouge National Urban Park.
The analysis included 260 released headstarted turtles, of which 139 had capture histories from mark-recapture and radio-telemetry surveys. Survival and detection parameters were indexed by time and by acclimation (acc), which had two levels: ‘New’, for newly released turtles and Exp. (experienced) after more than one year in the wild. Probability of entry (b) was indexed by time and release cohort. b0 occurs prior to the first sampling occasion. RHyear refers to the size and year of each release. refers to population size in each year. Implementation of this model included partitioning of release cohorts into smaller groups according to telemetry duration so that detection probability, p, could be fixed at 1 on specific occasions when turtles were tracked.
Fig 3.
Conceptual diagram of how survival, telemetry, and detection were represented in encounter histories and using parameter fixing of detection probability, p, for a subset of potential scenarios.
Scenarios are illustrated for a single Blanding’s Turtle release cohort over three sets of annual surveys. Hollow turtle symbols indicate an individual was not observed, a solid turtle symbol indicates that the turtle was observed. The red X indicates mortality, and the blue “wifi” symbol indicates a radio transmitter. Sampling by trapping and opportunistic detection were collapsed into one occasion per year with survival occurring during intervals between occasions. Telemetry observations of live individuals in May were considered live encounters during the corresponding annual occasion; otherwise, we considered telemetry observations during the rest of the year to occur during intervals, which are not represented directly in encounter histories. *Detection probability is conditioned on survival; †Jolly Seber models use only live encounter data, even when mortality is observed; §Encounter history is a binary sequence: 1 when an individual is observed alive, 0 when not observed; ‡Conditional on being released, turtles are encountered according to the product of current detection probability and previous survival. Certain detection (p = 1) but no encounter, implies no survival over a previous occasion, which informs survival estimation.
Fig 4.
Population size of headstarted Blanding’s Turtles in the Rouge National Urban Park estimated using the Jolly-Seber open population model.
The blue shading indicates the 95% confidence interval for population size.
Fig 5.
Headstarted Blanding’s Turtle abundance in the Rouge National Urban Park based on release year.
The population size () increased each year but the number of turtles in each cohort decreased each year as a result of mortality. The total abundance in 2020 was 218 headstarted turtles.
Table 2.
Summary of Jolly-Seber POPAN model ranking.
Φ and p refer to apparent survival and recapture probabilities, respectively for Blanding’s Turtles in the Rouge National Urban Park. ‘acc’ refers to the effect of acclimation with two levels: newly released headstarted turtles and those in their first year following release.
Table 3.
Densities of adult Blanding’s Turtle in populations from Canada and the USA.