Occurrence of the Maritime Shrew (Sorex maritimensis) in Black Spruce (Picea mariana) Forest Stands in Southeastern New Brunswick (original) (raw)

2012, Canadian Field-Naturalist

The disjunct eastern population of the Arctic Shrew (Sorex arcticus) has recently been recognized as a separate species, the Maritime Shrew (S. maritimensis) (Wilson and Reeder 2005), based on genetic analysis by Stewart el al. (2002). Before the taxonomic division, most information on either species was based on studies conducted in the western population (S. arcticus), and few publications exist on habitat use by the eastern population, now S. maritimensis. Sorex arcticus occurs in meadow environments and wet Tamarack (Larix laricina)-Black Spruce (Picea mariana) forest (Clough 1963; Buckner 1966; Wrigley et al. 1979), whereas S. maritimensis has been characterized as an associate of grass-sedge marshes, lowlying floodplain, wet meadows, and marsh margins (Herman and Scott 1994; Perry et al. 2004; Scott and Hebda 2004; McAlpine et al. in press). The type specimen of Sorex maritimensis was captured in marsh (Smith 1939), and the sampling by Perry et al. (2004) focused on alder (Alnus sp.) in wet areas. A recent study (Dawe and Herman 2005*) working in open wetland habitat concluded that S. maritimensis is associated with open wetlands with abundant graminoids, particularly Calamagrostis canadensis (Bluejoint Reedgrass), and low tree cover. Maritime Shrew specimens were collected during a study of the effects of pre-commercial forest thinning on small mammals in southern New Brunswick. Study Area Our work was conducted in Black Spruce forests of southeastern New Brunswick, a habitat considered atyp ical for S. maritimensis. Maritime Shrews were collected from nine naturally regenerating clear-cuts, ranging in age from 16 to 29 years since harvest. The sites were open coniferous forest on moist substrates with minimal grass. The sites would not be categorized as wet forest or wetlands (Warner and Rubec 1997), and there were no grassy meadows for a distance of at least several kilometres that would be typical of sites where Dawe and Herman (2005*) reported capturing S. maritimensis. Dominant tree species were Black Spruce, Balsam Fir (Abies balsamea), and Eastern White Pine (Pinus strobus), with smaller amounts of Red Maple (Acer rubrum), birches (Betula spp.), and alders (Alnus spp). Four of nine capture sites had been pre-commercially thinned 5 to 10 years prior to the survey. Our study sites are characterized by moist, semiproductive soils on moderate-poorly drained sites and would be classified as Eco-site 2 in the New Brunswick Ecological Land Classification (Zelazny 2007). Methods We surveyed relative abundance of small mammals in 45 sites with 16 Sherman (H. B. Sherman Inc., Talla hassee, Florida) live traps (dimensions 7.6 ¥ 8.9 ¥ 22.9 cm) and 16 pitfall traps (8.9 cm diameter, 10.8 cm depth) per site, spaced at 20-m intervals along a single 300-m transect. Trapping was conducted between June and September 2005 and between May and early October 2006. Traps were set for seven consecutive nights in each site. Shrews were removed from the sites unless captured alive (<5% captured alive). Sorex maritimensis specimens were identified by examining external morphology and dentition (van Zyll