EN
Seasonal fluctuation and its causes for three species of Sorex shrews and the shrew-mole Neurotrichus gibbsii Baird, 1857 were investigated in three sites with high amounts of coarse woody debris (CWD) and three sites with low amounts of CWD in managed forests of western Washington, USA. Sorex trowbridgii Baird, 1857 was more abundant on sites with high amounts of CWD (captures per 100 trapping nights), and had higher reproductive rates than in sites with low amounts of CWD. Sorex monticolus Merriam, 1890 showed higher reproductive rates on sites with high amount of CWD. Population of Sorex vagrans Baird, 1857 fluctuated greater and abundance was higher in sites with low amounts of CWD. Most reproduction occurred from January to April and declined rapidly in May. Previous studies also have shown an early onset of breeding in Coastal California and Oregon. It seems that local species of soricids and Neurotrichus gibbsii gain reproductive benefits by breeding primarily in January through May.