forests-11-01085.pdf - Article Comparison of Two Sampling Methods to Estimate the Abundance of Lucanus cervus with Application of n-Mixture Models

forests-11-01085.pdf - Article Comparison of Two Sampling...

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Article Comparison of Two Sampling Methods to Estimate the Abundance of Lucanus cervus with Application of n-Mixture Models Francesca Della Rocca 1, * , Pietro Milanesi 2 , Francesca Magna 1 , Livio Mola 3 , Tea Bezzicheri 1 , Claudio Deiaco 4 and Francesco Bracco 1,5 1 Departement of Earth and Environmetal Sciences, University of Pavia, Via Ferrata 9, 27100 Pavia, Italy; [email protected] (F.M.); [email protected] (T.B.); [email protected] (F.B.) 2 Swiss Ornithological Institute, Seerose 1, 6204 Sempach, Switzerland; [email protected] 3 Via Madonna del Boschetto, 16, 25030 Castel Mella, Italy; [email protected] 4 Via San Rocco 3, 24060 Predore, Italy; [email protected] 5 Botanical Garden, University of Pavia, Via S. Epifanio 14, 27100 Pavia, Italy * Correspondence: [email protected] Received: 28 August 2020; Accepted: 6 October 2020; Published: 12 October 2020 Abstract: Monitoring programs should be based on the measurement of two main pillars for evaluating the conservation status of a species: population size and geographical distribution. To date, the only way reported in the literature to obtain detailed information on L. cervus population size is to use the capture-mark-recapture method. This is an expensive and time-consuming technique that implies physical capture and handling of individuals, which could a ff ect their survival. Therefore, in this study we tested and compared two non-invasive sampling approaches, namely evening walk transects and diurnal tree trunk surveys, to derive accurate abundance estimates by means of N-mixture models in a Bayesian framework. In our study, both methods showed relatively high detection probability ( 56%). However, tree surveys performed better than walk transects ( 80%), especially with the progression of the sampling season. Tree surveys proved to be more e ff ective than walk transects in providing data for an accurate population density estimate (much smaller 95% Bayesian Confidence Intervals). In light of a cost and benefit assessment, the tree survey is undoubtedly more convenient, as well as more e ff ective, as it is more time consuming but less expensive than a walk transect (one operator for 2–3 h vs. two operators for 30 min each). Moreover, it needs fewer expert operators because of the greater proximity to the species, increasing the probability of correctly identifying it, i.e., reducing type I error (false positive or overestimation of counts). For the first time, we applied N-mixture models for estimating population abundance of L. cervus . Overcoming all the limits imposed by the use of the capture-mark-recapture method, in this study we performed a further step forward in the planning of monitoring aimed at the conservation of L. cervus and the evaluation of its demographic trend.

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