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1 December 2008 Efficacy of Three Types of Live Traps Used for Surveying Small Mammals in the Pacific Northwest
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Capture rates of 3 trap types were compared at 5 sites in and around Portland, Oregon, USA: Sherman traps, custom-made steel-mesh traps, and pitfall traps. Simpson and Shannon diversity indices were calculated for various combinations of trap types and compared for differences. Sherman and mesh traps also were evaluated for mortality rates before and after the use of a rain shield during the rainy winter months. Of the 5 species of small mammals caught in all 3 types of traps, pitfalls were the most effective trap, followed by Sherman traps, with mesh traps a very distant third. Sherman traps significantly outperformed mesh traps overall when compared for larger species that were not contained by pitfall traps. Different combinations of trap types yielded significantly different Simpson and Shannon diversity indices, with pitfalls having the highest measures for small mammals, and a combination of Sherman and pitfall traps having the highest measures when considering both larger and smaller mammals. Use of rain shields with Sherman and mesh traps did not affect mortality rates. However, mortality was affected by trap type, with significantly higher death rates in mesh than Sherman traps.

Laurie Dizney, Philip D. Jones, and Luis A. Ruedas "Efficacy of Three Types of Live Traps Used for Surveying Small Mammals in the Pacific Northwest," Northwestern Naturalist 89(3), 171-180, (1 December 2008).
Received: 23 April 2008; Accepted: 1 June 2008; Published: 1 December 2008

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