We conducted our research at the RNUP in Toronto, Ontario, Canada (43.8188° N, 79.1728° W). The RNUP is the first urban national park in Canada and is part of a pilot project carried out by Parks Canada to conserve urban biodiversity, Indigenous cultural landscapes, and agricultural heritage of the area [27 ]. It is an ecologically protected zone established in 2015 under the Rouge National Urban Park Act [28 ] that encompasses 80 km2 of forests, meadows, rivers, wetlands, and fragments of rare habitats such as oak savannah and Carolinian woodlands [27 ]. Situated at the center of the Canada’s largest metropolitan area (Fig 1 ), the park is surrounded by major highways, freight and passenger railways, residential, commercial, and industrial developments, and agricultural lands [27 ].
Our study site is situated in the southern portion of the RNUP. In the early 1990s, the area was restored to a wetland complex of vernal pools, and more permanent ponds of various sizes with littoral vegetation including alders (Alnus spp.), cattails (Typha spp.), sedges (Carex spp.), and willows (Salix spp.) [21 ]. More recently, invasive species, such as European common reed (Phragmites australis), garlic mustard (Alliaria petiolate), purple loosestrife (Lythrum salicaria), and reed canary grass (Phalaris arundinacea) have become ubiquitous. Once restoration efforts were completed, the Toronto Zoo’s Adopt-A-Pond Wetland Conservation Program began wetland surveys to evaluate species occurrence in the area. The surveys found three at-risk turtle species: Painted Turtle (Chrysemys picta), Snapping Turtle (Chelydra serpentina), and the globally endangered [33 ] Blanding’s Turtle. In Canada, Painted and Snapping turtles are designated as ‘Special Concern’ by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) [34 , 35 ], and Blanding’s Turtle is designated as ‘Endangered’ [36 ].
In 2005, the Blanding’s Turtle population within the park boundary was known to be comprised of three adult turtles (two males and one female) and a juvenile. Two additional adult turtles (one male and one female) were discovered in 2006 in an adjacent creek approximately 4 km from the RNUP (Toronto Zoo [Unpublished]). Given that the Blanding’s Turtle population in the RNUP was presumed functionally extinct, the Toronto Zoo initiated a headstarting program in 2012 to supplement the wild population [21 ]. A preliminary population viability analysis (PVA) showed that 40 headstarted turtles with 1:1.5 male:female sex ratio would need to be released each year for 20 years to reach a self-sustaining population of 150 adult Blanding’s Turtles (Toronto Zoo [Unpublished]). The first release occurred in 2014 with 10 juveniles, followed by 21 in 2015, 36 in 2016, 49 in 2017, 49 in 2018, 48 in 2019, 57 in 2020 for a total of 270 headstarted turtles released to date (Toronto Zoo [Unpublished]). An additional 184 hatchlings were released without headstarting because the number of eggs that hatched exceeded the capacity of the Toronto Zoo rearing facility.
Our study site is situated in the southern portion of the RNUP. In the early 1990s, the area was restored to a wetland complex of vernal pools, and more permanent ponds of various sizes with littoral vegetation including alders (Alnus spp.), cattails (Typha spp.), sedges (Carex spp.), and willows (Salix spp.) [21 ]. More recently, invasive species, such as European common reed (Phragmites australis), garlic mustard (Alliaria petiolate), purple loosestrife (Lythrum salicaria), and reed canary grass (Phalaris arundinacea) have become ubiquitous. Once restoration efforts were completed, the Toronto Zoo’s Adopt-A-Pond Wetland Conservation Program began wetland surveys to evaluate species occurrence in the area. The surveys found three at-risk turtle species: Painted Turtle (Chrysemys picta), Snapping Turtle (Chelydra serpentina), and the globally endangered [33 ] Blanding’s Turtle. In Canada, Painted and Snapping turtles are designated as ‘Special Concern’ by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) [34 , 35 ], and Blanding’s Turtle is designated as ‘Endangered’ [36 ].
In 2005, the Blanding’s Turtle population within the park boundary was known to be comprised of three adult turtles (two males and one female) and a juvenile. Two additional adult turtles (one male and one female) were discovered in 2006 in an adjacent creek approximately 4 km from the RNUP (Toronto Zoo [Unpublished]). Given that the Blanding’s Turtle population in the RNUP was presumed functionally extinct, the Toronto Zoo initiated a headstarting program in 2012 to supplement the wild population [21 ]. A preliminary population viability analysis (PVA) showed that 40 headstarted turtles with 1:1.5 male:female sex ratio would need to be released each year for 20 years to reach a self-sustaining population of 150 adult Blanding’s Turtles (Toronto Zoo [Unpublished]). The first release occurred in 2014 with 10 juveniles, followed by 21 in 2015, 36 in 2016, 49 in 2017, 49 in 2018, 48 in 2019, 57 in 2020 for a total of 270 headstarted turtles released to date (Toronto Zoo [Unpublished]). An additional 184 hatchlings were released without headstarting because the number of eggs that hatched exceeded the capacity of the Toronto Zoo rearing facility.
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