Water Shrew 131 



Table 7. Taxonomic richness and mean percent contribution (1 SE and range) of 

 macroinvertebrate taxa occuring in four streams at which S. palustris was found 

 in Virgina, 1974-1993. 



Taxon 



Number of 

 Genera 



Mean Percent 

 Abundance 



SE 



Range (%) 



Hydracarina 



1 



<1 



<1 



0-1 



Decapoda 



1 



1 



<1 



0-2 



Ephemeroptera 



6 



26 



10 



6-54 



Odonata 



1 



1 



<1 



1-2 



Plecoptera 



6 



26 



2 



20-31 



Trichoptera 



8 



22 



4 



14-31 



Coleoptera 



3 



3 



2 



1-8 



Diptera 



8 



22 



4 



11-32 



Pelecypoda 



1 



<1 



<1 



0-1 



Chimneys or Clarks Cave sites. These include the rock vole {Microtus chrotor- 

 rhinus), in the Little Back Creek area of Bath County (Pagels 1990), and the 

 northern flying squirrel (Glaucomys sabrinus), at the Highland County sites 

 (Pagels et al. 1990). Handley (1992:159) suggested that these species, along 

 with a few others, probably "...represent the last stages of the recoil of high bore- 

 al species from southern latitudes into higher latitudes in the United States and 

 Canada— north and west of Virginia." 



Sorex palustris was found only at sites where cool, mesic conditions 

 occurred along with considerable cover on the banks of swift-flowing streams. 

 Beneski and Stinson (1987) observed that although it is found in a variety of 

 habitats, rocky crevices, logs, and abundant overhanging areas along stream 

 banks are typical of S. palustris habitat throughout much of its range, and likely 

 are critical in warmer, southern areas to provide cool, mesic microhabitats for the 

 shrews. Also, the full canopy of mature forests, as occurred at the sites where 

 the shrews were found, probably is essential for maintaining the cool conditions. 



Habitat conditions also are important in affecting the food resources 

 available to the shrews. Both terrestrial and aquatic invertebrates are consumed 

 by water shrews (Beneski and Stinson 1987). Wrigley et al. (1969) suggested 

 that a mesic microhabitat along stream banks was important for supporting ter- 

 restrial invertebrates that at times can compose a significant portion of the diets 

 of the shrews (Hamilton 1930, Whitaker and Schmeltz 1973). The primary 

 aquatic organisms consumed by shrews, including stoneflies, mayflies, and cad- 

 disflies (Conoway 1952, Conoway and Pfitzer 1952, Sorenson 1962, Linzey and 



