Chemical, thermal, and physical properties of sites selected for overwintering by northern wood turtles (Glyptemys insculpta)

Abstract

Northern ectotherms must seek refuge from winter conditions for a large portion of their annual activity cycle. The objective of this study was to quantify physical properties of overwintering sites selected by wood turtles ( Glyptemys insculpta (LaConte, 1830)) at the species’ northern range limit. We mapped all structural features (e.g., root balls and log jams), water depth, and sediment types along a 1.5 km stretch of river that was available to turtles outfitted with radio transmitters (N = 8) during winter. Temperature selection was assessed by comparing thermal profiles from data loggers on turtles and temperature stations within the river and other riparian habitats (e.g., ephemeral pools and oxbows). Dissolved oxygen (DO) was measured at each temperature station and turtle location. Wood turtles overwintered in the river, which was colder (~0 °C), had more stable temperatures, and provided higher DO (12.64 ppm) compared with adjacent habitats. Some turtles selected structured refuges for overwintering. Winter movements were not related to temperature or DO, but may be related to maintaining a certain distance from shore and water depth to protect against accidental relocations during winter. We discuss hibernacula as potential factors limiting the northern distribution of wood turtles, a species at risk in Canada.

Spatial and Temporal Habitat-Use Patterns of Wood Turtles at the Western Edge of Their Distribution

“…Wood Turtles were reported to hibernate in the main river rather than tributary streams or oxbows at a site in northern Ontario (Greaves andLitzgus 2007, 2008). The main river was colder (about 0 degrees Celsius) and had more stable temperatures and higher levels of dissolved oxygen (12.6 parts per million) than adjacent aquatic habitats (Greaves and Litzgus 2008). Within the river, Wood Turtles remained in locations under about 1 metre in depth and less than 2 metres from shore (Greaves andLitzgus 2007, 2008).…”

The Ecology of the Wood Turtle (Glyptemys insculpta) in the Eastern Panhandle of West Virginia

“…While Wood Turtles have been observed overwintering exposed on stream beds in Massachusetts (Farrell and Graham 1991) and in Ontario (Greaves and Litzgus 2008), individuals at our site used some type of cover.…”

Hibernation Ecology of an Isolated Population of Bog Turtles,Glyptemys muhlenbergii

“…This is especially important in eutrophic environments since lower temperatures result in an increased ability to depress metabolic demands and therefore oxygen demands (Ultsch, 2006;Edge et al, 2009). Studies of aquatic turtles indicate the importance of maintaining a constant body temperature, just above freezing, for successful hibernation (Greaves and Litzgus, 2008;Edge et al, 2009;Rasmussen and Litzgus, 2010). In some species of aquatic turtles, like Snapping Turtles (Chelydra serpentina), temperature has been found to be the most important factor in a hibernaculum (Paterson et al, 2012).…”