Wood turtle (Glyptemys insculpta) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements

Wood Turtles are exceptionally terrestrial for a freshwater turtle species but are still semi-aquatic (Bishop, 1927; Breckenridge, 1944; Lazell, 1976; Thomas, 1983) and require water for several vital functions, including mating (Harding and Bloomer 1979; Ernst 1986; Farrell and Graham 1991); hibernation (Harding and Bloomer 1979; Green and Pauley, 1987; Farrell and Graham 1991; Hunter et al. 1992; Foscarini 1994; Arvisais et al. 2004; Trochu, 2004, Wesley, 2006), hydration (Kaufmann 1992) and thermoregulation (Dubois, 2006). They rarely move more than 300m from water (Harding and Bloomer 1979; Quinn and Tate 1991; Kaufmann 1992; Saumure and Bider 1998; Ernst 2001; Arvisais et al. 2002; Compton et al. 2002; Wesley 2006; Foscarini 1994; Arvisais 2002; Smith 2002, Wesley, 2006). Nesting habitat includes sand or gravel-sand beaches and banks (Hunter et al., 1992; Walde, 1998; Smith, 2002), but as in other turtles, Wood Turtles readily nest on gravel and dirt roads, gravel shoulders of paved roads, gravel pits, and similar anthropogenic structures.

Wood Turtles are associated with rivers and streams with sandy or gravely-sandy bottoms (DeGraaf and Rudis, 1983; Hunter et al., 1992; Daigle, 1997; Wesley 2006), and prefer clear, meandering streams with moderate current and frequent oxbows (DeGraaf and Rudis, 1983; Hunter et al., 1992; Ernst et al., 1994; Adams, 2003; J. Harding pers. comm. 2006; Wesley 2006).

Although Wood Turtles have been described as opportunistic with respect to habitat (Quinn and Tate, 1991), studies over their range have shown that they select particular habitat features (Harding and Bloomer 1979; Kaufmann, 1992a; Foscarini, 1994; Harding 1997; Smith, 2002, Arvisais et al., 2002; Compton et al., 2002; Arvisais et al., 2004; Trochu, 2004, Dubois 2006; Wesley, 2006; Y. Dubois pers. comm. 2005), virtually always associated with clear-water streams and their banks. Alder thickets and alder swale were the preferred or most-used habitats in Ontario (Smith, 2002; Cameron et al., 2002; Peiman and Brooks, 2003; Wesley et al., 2004), Quebec (Arvisais et al., 2004; Trochu, 2004), Nova Scotia (Adams, 2003), and Pennsylvania (Kaufmann, 1992). In late summer, forested habitats are important (Quinn and Tate, 1991; Cameron et al., 2002; Smith, 2002; Wesley et al., 2004, Wesley 2006). Other habitats used less often by Wood Turtles include bogs, marshy pastures, beaver ponds, oxbows, riparian and shrub areas, meadows, coniferous forests, mixed forests, hay and agricultural fields and pastures (Foscarini, 1994; Daigle, 1997; Compton et al., 2002; Smith, 2002; Cameron et al., 2002; Peiman and Brooks, 2003; Adams, 2003; Arvisais et al., 2004; Trochu, 2004; Wesley et al., 2004; Wesley, 2006).

Even though quantitative historic and contemporary data on changes in the area of available habitat suitable for the Wood Turtle are not available, it is evident that this habitat is declining over much of the species’ historic range in both Canada and the United States (Harding and Bloomer, 1979; Kaufmann, 1992a; Garber and Burger, 1995; Mitchell et al. 1997; Oldham, 1998; Galois and Bonin, 1999; Ernst, 2001).For example, only a very restricted number of creeks and rivers in the Carolinian region of southern Ontario retain clear water, undisturbed nesting sites, deep pools for overwintering, and undisturbed riparian zones (Mitchell et al., 1997; Boyd and Brooks, 1998; Wesley, 2006). This habitat loss and degradation is due to agricultural activities, shoreline development, channelization, dams, contamination, and forestry activities (Harding and Bloomer, 1979; Foscarini 1994; Garber and Burger, 1995; Mitchell et al. 1997; Oldham, 1998; Saumure and Bider 1998; Compton, 1999; Galois and Bonin, 1999; Natural Heritage Information Centre, 2004; Saumure 2004; Seburn and Seburn, 2004). The remaining populations in the Great Lakes/St. Lawrence faunal province in southern Quebec and Ontario persist at reduced levels on streams with reduced riparian areas, high disturbance, increased turbidity and exposure to people (Foscarini 1994; Mitchell et al. 1997; Boyd and Brooks 1998; Saumure 2004; Daigle and Jutras 2005; Dubois 2006)

For Wood Turtles, given their terrestrial habits, their unique vulnerability to collectors and their attractiveness for the pet trade, any increase in access to their populations constitutes a degradation of habitat even before direct habitat modification occurs.In addition, roads also remove habitat, alter adjacent areas, subdivide populations, and change hydrologic patterns (Kerr and Cihlar 2004; Hawbaker et al., 2006; Crowley 2006; Figure 4).For Wood Turtles though, the key threats come from increased access per se, and from roads and agricultural fields attracting turtles to nest thus acting as population sinks (Saumure pers. comm., 2006).To see this effect, one only has to look at the fates of Wood Turtles in southern Ontario and Quebec.Essentially, the species has disappeared from the southern parts of both provinces in conjunction with high road densities (Crowley 2006).Roads provide access (Crowley, 2006), and mortality to wildlife increases with increasing traffic speed (Farmer, 2006).At a more general level, land use is a strong predictor of densities of endangered species in Canada (Kerr and Cihlar, 2004), in particular there is a strong link between habitat conversion to agriculture and level of species endangerment.For the Wood Turtle, a similar link likely exists where forestry practices increase road access or alter riparian habitats.

Habitat protection/ownership

In Ontario, Wood Turtle populations are located mainly on Crown land. However, portions of three populations are in Provincial Parks (Smith, 2002; J. Trottier, 2004; R. Knudsen, 2004; D. Coulson, pers. comm. 2004). The remaining parts of these populations and other Ontario populations are on private land (some small segments are on federal lands and Nature Conservancy of Canada lands). One small population in Nova Scotia is in a National Park (Adams, 2003; Adams, 2004), and the remainder are on private or Crown lands (T. Herman, pers. comm. 2005). Part of one population in New Brunswick is in a National Park (E. Tremblay, pers. comm. 2004) and a second is on a military base (G. Forbes, V. Roy, pers. comm. 2004), but most reported locations are privately owned (McAlpine and Gerriets, 1999). In Quebec, part of one population is in a National Park (Bourgeois et al., 2004), but most studied populations are on private or public lands (Daigle, 1996; Walde et al., 2003; Trochu, 2004; Saumure, 2004). Therefore, no significant proportion of Canadian Wood Turtle habitat is under legal protection.

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