Assessment of critical habitat for common snapping turtles (Chelydra serpentina) in an urbanized coastal wetland

Critical habitats such as nesting areas and overwintering sites are specific areas used by organisms to carry out important life functions. In many urbanized centers, critical habitats of at-risk species have often become degraded and/or fragmented because of human activities. Such is the case for the population of common snapping turtles (Chelydra serpentina) in Cootes Paradise Marsh, a highly urbanized ecosystem located at the western tip of Lake Ontario. In addition to these threats, mortality from collisions with cars on a four-lane highway at the western end of the marsh has greatly reduced wildlife populations. Here, we examine long-term changes in critical habitat distribution that has accompanied urbanization of Cootes Paradise Marsh from 1934 to 2010. We delineated potential nesting habitat for snapping turtles in 7 digitized aerial photos, using literature information and 2017 nesting surveys as guides. Between 1934 and 2010, total area of potential nesting habitat decreased by almost 50%. Nesting surveys confirmed that snapping turtles were disproportionately using created nesting mounds and this suggests that availability of natural nesting habitat is limited. We also radio tracked 11 snapping turtles to identify use of overwintering habitat. Temperature loggers monitored in-situ water temperatures at each turtle’s location and other unconfirmed habitats. The snapping turtle population overwintered in a wide range of upland terrestrial habitats and we found consistent characteristics regarding water temperature across both confirmed and unconfirmed sites, therefore suggesting overwintering habitat may not be limiting within the marsh.