N-mixture models reliably estimate the abundance of small vertebrates.

Sci Rep. 2018 Jul 9;8(1):10357. doi: 10.1038/s41598-018-28432-8. Ficetola GF1,2, Barzaghi B3, Melotto A3, Muraro M3, Lunghi E4,5,6, Canedoli C7, Lo Parrino E3, Nanni V8, Silva-Rocha I9, Urso A3, Carretero MA9, Salvi D9,10, Scali S11, Scarì G12, Pennati R3, Andreone F13, Manenti R3. Author information 1 Department of Environmental Science and Policy, University of Milan, Milano, Italy. francesco.ficetola@gmail.com. 2 Laboratoire d'Ecologie Alpine (LECA), CNRS, Université Grenoble Alpes, Grenoble, France. francesco.ficetola@gmail.com. 3 Department of Environmental Science and Policy, University of Milan, Milano, Italy. 4 Universität Trier Fachbereich VI Raum-und Umweltwissenschaften Biogeographie, Universitätsring 15, 54286, Trier, Germany. 5 Museo di Storia Naturale dell'Università di Firenze, Sezione di Zoologia "La Specola", Via Romana 17, 50125, Firenze, Italy. 6 Natural Oasis, Via di Galceti 141, 59100, Prato, Italy. 7 DISAT, Università degli Studi di Milano-Bicocca. Piazza della Scienza 1, 20126, Milano, Italy. 8 Department of Earth, Environmental and Life Science (DISTAV), University of Genoa, Genova, Italy. 9 CIBIO Research Centre in Biodiversity and Genetic Resources, InBIO, Campus de Vairão. 4485-661, Universidade do Porto, Vairão, Vila do Conde, Portugal. 10 Department of Health, Life and Environmental Sciences, University of L'Aquila, 67100, Coppito, L'Aquila, Italy. 11 Museo di Storia Naturale di Milano, Corso Venezia 55, I-20121, Milano, Italy. 12 Department of Biosciences, University of Milan, Milano, Italy. 13 Museo Regionale di Scienze Naturali, Via G. Giolitti, 36, I-10123, Torino, Italy. Abstract Accurate measures of species abundance are essential to identify conservation strategies. N-mixture models are increasingly used to estimate abundance on the basis of species counts. In this study we tested whether abundance estimates obtained using N-mixture models provide consistent results with more traditional approaches requiring capture (capture-mark recapture and removal sampling). We focused on endemic, threatened species of amphibians and reptiles in Italy, for which accurate abundance data are needed for conservation assessments: the Lanza's Alpine salamander Salamandra lanzai, the Ambrosi's cave salamander Hydromantes ambrosii and the Aeolian wall lizard Podarcis raffonei. In visual counts, detection probability was variable among species, ranging between 0.14 (Alpine salamanders) and 0.60 (cave salamanders). For all the species, abundance estimates obtained using N-mixture models showed limited differences with the ones obtained through capture-mark-recapture or removal sampling. The match was particularly accurate for cave salamanders in sites with limited abundance and for lizards, nevertheless non-incorporating heterogeneity of detection probability increased bias. N-mixture models provide reliable abundance estimates that are comparable with the ones of more traditional approaches, and offer additional advantages such as a smaller sampling effort and no need of manipulating individuals, which in turn reduces the risk of harming animals and spreading diseases. PMID: 29985399 DOI: 10.1038/s41598-018-28432-8 Free full text