Significance of Blarina brevicauda as a predator and source of trap-capture bias on small mammals

Abstract

Evidence on whether the northern short-tailed shrew (Blarina brevicauda) is a significant predator or a source of bias in trap-capture success of small mammals is contradictory. We compared subsequent captures of 2 murid rodent species (Clethrionomys gapperi and Peromyscus maniculatus) after capture of either murid species or B. brevicauda by using 4 years of capture-release data from New Brunswick, Canada. Capture success for P. maniculatus in a trap after occupancy by B. brevicauda was 65% lower than expected, and for C. gapperi, 67% lower than expected. The response by C. gapperi and P. maniculatus to odors of a different species was similar to their response to odor of B. brevicauda. Although we conclude that examination of odor-response data does not permit a conclusion as to whether B. brevicauda is a significant predator, the ubiquitous distribution of B. brevicauda implies that their influence on trap-capture success is significant, particularly in forests where small-rodent species are of similar weight to B. brevicauda. © 2005 American Society of Mammalogists.