Using Long‐Term Data to Compare Two Sizes of Sherman Trap

Abstract

Live traps are commonly used to inventory, monitor, and sample populations of small mammals. Due to the variety of available trap types, understanding differences between traps is important to minimize bias and plan future studies. Sherman traps (H. B. Sherman Trap, Inc., Tallahassee, FL, USA; hereafter Sherman traps) are a popular live trap that come in a variety of sizes. However, studies comparing the relative efficacy of different‐sized Sherman traps often focus on a single species or are limited by a lack of temporal and spatial replication, leading to contradictory or ambiguous results. Therefore, to better understand the relative efficacy of two commonly‐used sizes, we used a paired design and 10 years of trapping data to compare species richness, capture numbers, and mortality rates between small Sherman traps (5.1 × 6.4 × 16.5 cm) and large Sherman traps (7.6 × 8.9 × 22.9 cm) across 55 preserves in northeastern Illinois. Despite wide annual variation, we captured more small mammals in large traps except for the smallest taxa (Sorex spp.), the proportion of captures in large traps increased with body size, and large traps significantly reduced mortality rates for Peromyscus spp., meadow voles (Microtus pennsylvanicus), and short‐tailed shrews (Blarina brevicauda). We recommend the 7.6 × 8.9 × 22.9 cm Sherman trap for monitoring surveys in the midwestern USA when research or monitoring objectives include maximizing captures and species richness while minimizing mortality. However, we note the smaller‐sized trap may be useful to minimize bycatch when smaller species are being targeted. Finally, managers and biologists conducting short‐term or pilot studies should be wary of year effects, as we found substantial annual variation in relative capture rates between trap sizes. © 2021 The Wildlife Society.

Relative efficiency of two models of snap traps for sampling boreal small mammals

“…A limitation of our design was that traps were paired at each station, which does not allow a comparison of capture rates or detectability for each trap type if only one trap type was available. Our paired design was similar to that commonly used for trap comparison studies (Anthony et al 2005, Jung 2016, Torre et al 2016, Korslund 2018, Vanek et al 2021). However, an alternate design that randomly assigns a trap type to each station would provide additional inference on the comparative ability of each trap type to estimate abundance or detection probability.…”

Distribution of Four Vole Species through the Barn Owl Tyto alba Diet Spectrum: Pattern Responses to Environmental Gradients in Intensive Agroecosystems of Central Greece

“…In extensive agricultural ecosystems, the live trapping of small mammals cannot answer large-scale questions since the method is time demanding, applied mainly in small scale monitoring studies even in multiannual efforts, and mostly focuses on population dynamic assessments [ 15 ]. On the contrary, Barn Owl diet analysis has been proven to be an ideal proxy to assess the composition, distribution, and abundance patterns of small mammals on large geographical scales [ 16 , 17 ].…”