Habitat, movements, and behaviour of overwintering Blanding’s turtles (Emydoidea blandingii) in Nova Scotia

Abstract

The overwintering ecology of a disjunct population complex of Blanding’s turtles ( Emydoidea blandingii (Holbrook, 1838)) in southwestern Nova Scotia was studied from January 2005 to April 2006. Sites were visited biweekly. We recorded structural characteristics and dissolved oxygen (DO), pH, and water and substrate temperatures in 7 overwintering sites containing at least 46 turtles and 7 paired “control sites”. Twenty-five adult turtles were radio-tracked to record locations and movements. Median winter temperature ranged from 0.8 to 8.6 °C in the organic substrate and from 0.3 to 7.6 °C in the water column. In overwintering sites, median DO ranged from 2.8 to 11.3 mg/L and median pH ranged from 4.6 to 5.5. Blanding’s turtles can tolerate submergence under ice for at least 3 months in severely hypoxic conditions. Movement was positively correlated with water temperature. Although some moderate movements were made during winter, 90% were less than 5 m. Movement to overwintering sites (September to mid-November) was gradual, but departure (late March to April) was rapid. Physical characteristics and environmental variables varied dramatically among overwintering sites, and no consistent patterns were observed between overwintering and control sites. We suggest that Blanding’s turtles return to communal sites year after year because of site fidelity and mating opportunities.