Townsend's mole (Scapanus townsendii) COSEWIC assessment and status report: chapter 5

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Habitat

Habitat requirements

Townsend’s mole is found in medium-textured silt loam soil with good humus content as found in fields, meadows, lawns and other grassy habitats, preferring manured pastures and hayfields (Pedersen 1963, Giger 1973, Nagorsen 1996) where earthworms are abundant (Edwards and Lofty 1972). About 30 km² of silt loam soil exists in the Fraser Valley (Figure 3), although all but about 13 km² has undergone urban development (Sheehan and Galindo-Leal 1996). Townsend’s mole will also venture into open forests and light sandy soils (Dalquest 1948, Johnson and Yates 1980, Nagorsen 1996). Population densities vary considerably in different habitats according to the availability of earthworms.  Numbers are lowest in gravelly soils and highest in manured pastures and hayfields (Pedersen 1963, van Zyll de Jong 1983).

It typically inhabits low lying pastures, farmland and lawns. This habitat extends from the Fraser Valley across the border into Washington State (see aerial photographs in Appendix showing contiguous farmland and residential development and lowland habitat extending to Nooksack, Wa.). The grass cover supports a greater biomass of its preferred food, the large earthworm Lumbricus terrestris, than do to arable land and forests (Gorman and Stone 1990). The grass insulates the ground from frost that decreases earthworm numbers (Edwards and Lofty 1972). Grassland soils are also highly structured and better suited to support an underground network of tunnels.

Townsend’s mole seems to prefer moister soil than the coast mole (BC Ministry of Environment, Lands and Parks 2001). The habitat requirements and food requirements for Townsend’s and coast moles appear to be similar, and it is not readily apparent why Townsend’s mole is not found throughout the same range as the coast mole in Canada.

Population trends

It has been suggested that the numbers of Townsend’s and coast moles in the Pacific northwest have increased in the past several hundred years. This is likely due to more farmland created by diking wetland meadows and the availability of the larger introduced species of earthworms (Glendenning 1959, Schaefer 1978). However, new habitat is no longer being created. On the contrary, mole trapping, intensive agricultural practices, the conversion of farmland through urban sprawl and habitat fragmentation may all contribute to lower mole population numbers.

Protection/ownership

The habitat in which moles occur in Canada is largely privately owned. The land between Riverside and Angus Roads, which holds 3 of the 16 territories recently located, has undergone urban development. The remainder of the range is in the Agricultural Land Reserve (ALR) and is somewhat protected from development (British Columbia Agricultural Land Commission 1996). However, intensive agriculture kills moles and land is constantly removed from the ALR.

Townsend’s mole is considered an agricultural pest, and may be trapped in residential areas where it destroys lawns.  It is protected by the BC Red List Schedule A.

Figure 3. Soil map of the Huntingdon-Abbotsford region (Geological Survey of Canada, 1976, map 1485A, Surficial Geology, Mission, BC). Note the distribution of Sab soils right of center (organic sediments overlain by up to 1 m of silt loam, silt and sand), the location of most Townsend’s mole records around Huntingdon. The two records east of Abbotsford are in Saq silt to clay soil overlaying Fraser River Sediments.