Evaluating trap performance and volunteers’ experience in small mammal monitoring programs based on citizen science: The SEMICE case study

Abstract

Citizen science projects have proliferated in the last decades, becoming a critical form of public engagement in science. However, monitoring based on citizen science must take special care on the analyses and/or standardization of volunteer’s variation in sampling and identification skills. Key aspects such as detectability of species and ability to determine individual traits (i.e., sex and reproductive state) are expected to vary with observer’s experience. We analysed how volunteer experience influenced results of a small mammal monitoring program (SEMICE) based on a standardized trapping design. This protocol aims at monitoring common species easy to catch with the two most widely used commercial live traps (Sherman and Longworth traps). We analysed sampling inaccuracies due to problems with trap performance according to trap type and observer experience, and how experience influenced the ability to determine sex and reproductive state of individuals trapped. Sampling inaccuracies were low (4.0 inaccuracies/100 traps-night) and were not influenced by experience, so that experience did not affect abundance estimates. Aptitude to sex shrews Crocidura russula and Sorex spp. was positively influenced by experience (31% sexed by short-experienced people vs. 78% by people with longer experience), but not for sexing rodents (> 90% individuals sexed irrespective of experience). No differences among volunteers and professionals were evident despite longer experience by professionals (9.32 ± 0.54 vs 18.42 ± 0.62 sampling sessions, respectively). Data collected by volunteers provided accurate information on species abundance, but less information than professionals provided for some biological traits such as shrews’ sex and reproductive condition. Effect sizes of experience were small enough to utilize volunteer’s data to obtain unbiased monitoring results. Overall, the SEMICE protocol can be validated for its use as a small mammal monitoring program based on citizen science.