Differential Effectiveness of Standard and Long Sherman Livetraps in Capturing Small Mammals

Most studies of small-mammal populations rely on livetrapping, yet relatively few studies compare different types of traps. We placed one standard-length (22.9 cm) and one long (30.5 cm) Sherman livetrap at each station of a trapping grid in oldfield habitat in eastern Kansas and compared rates of capture of small mammals over a 5-year period (1985–1990). Nine of 10 species were captured more often in long traps. Of the five most commonly trapped species, only Sigmodon hispidus and Microtus ochrogaster varied seasonally in proportion of captures in long traps. Species having lower adult body mass were captured proportionately more often in long traps, suggesting that long traps might have more sensitive trigger mechanisms. However, long traps closed without capturing an animal significantly less often; furthermore, proportions of captures in the two types of trap did not differ among mass classes of S. hispidus or M. ochrogaster , so size differences alone cannot account for differential capture success. Not only were capture rates higher in long traps, but also mortality due to predators and winter exposure was lower.