Assessing the Distribution of Eastern Moles (Scalopus Aquaticus) in Canada in Relation to Loam Soils and Forest Cover
Ritchie, Louise E., Nocera, Joseph J., The American Midland Naturalist
We assessed the distribution of Eastern moles Scalopus aquaticus in relation to loam soils under the hypothesis that the species' Canadian distribution is limited by soil type. We also explore the relationship between mole occurrence and the amount of forest cover at a local (49 m) and landscape (305 m) scale. We resurveyed 46 sites dispersed across much of the species' Canadian range in southern Ontario. These sites initially were inspected for mole sign (e.g., surface tunnels and earth mounds) in 1997, allowing us to compare between study periods to assess changes in species distribution. Eastern moles were eight times more likely to occur at sites with loam or sandy loam soils than at sites with other soil textures (e.g., coarse sands, clays). The likelihood of mole sign no longer occurring at a site in 2008 increased in the absence of loam or sandy loam soils. At sites with loam or sandy loam soils, including the proportion of forest cover within the surrounding landscape increased our ability to discriminate between sites with and without mole sign. We noted a 26% decrease in mole occurrence across our study area since it was surveyed more than a decade ago.
Talpid moles are relatively common in North America, yet they remain surprisingly understudied and are among the most poorly understood North American mammalian taxa (Hartman and Yates, 2003). The Eastern mole (Scalopus aquaticus Linnaeus, 1758) has the largest range of all North American moles (Yates and Schmidly, 1978). It is a conservation concern in several states (Colorado, West Virginia and Wyoming) and has a very limited distribution within Canada (NatureServe, 2008). The Canadian race is geographically restricted to the vicinity of Essex County and Chatham-Kent municipality in Southern Ontario (see Waldron et ai, 2000) and has the largest individuals of the species (Banfield, 1974).
Currently, there are few quantitative data describing the occurrence patterns, habitat associations and population stability of Eastern moles. This species is the most subterranean of North American moles (Banfield, 1974), rarely straying from underground tunnel networks. Individuals rarely are observed directly but their tunnelling behaviour provides an index of species occurrence and activity. Such surface indices are frequently used for broad scale studies of species abundance and distribution (Hartman and Krenz, 1993; Rosenblatt et al, 1999; Duhamel et al, 2000; Waldron et al, 2000; Berthier et ai, 2005; Delattre et al, 2006). Eastern moles construct two distinct types of tunnels; surface tunnels (<10 cm) that are foraging runways and deep (10-40 cm) tunnels that are less noticeable, more permanent structures. Deep tunnels are typically associated with earth mounds caused by animals piling soil removed during tunnel construction. Eastern moles are intolerant of openings in their burrow system and will persistently repair damaged tunnels (Hartman and Yates, 2003).
Soil type, condition and moisture levels may be important limiting factors affecting mole distribution. Individuals of the species reportedly prefer moist loams, may use sandy soils, but avoid clay, stony or gravely soils and arid lands (Arlton, 1936; summarized in Yates and Schmidley, 1978; Waldron et al, 2000). However, quantitative data for these relationships are lacking because authors fail to provide support or cite largely descriptive studies that did not quantify the relationship (Arlton, 1936; Davis, 1942; Banfield, 1974; Yates and Schmidly, 1978; Hartman and Yates, 2003 and references therein). It has been suggested that the distribution of Eastern moles may be affected by proximity to forest cover. Banfield (1974) indicated that the species "prefers moist friable loams in open woodlands and pastures." Waldron et al (2000) found mole signs most frequently in forested areas, along hedgerows, watercourses and open drains. Species are influenced in different manners by processes operating at different scales, resulting in the emergence of scale-dependent patterns (Wiens, 1989). …