title: Optimizing occupancy surveys by maximizing detection probability: application to amphibian monitoring in the Mediterranean region.
abstract: Setting up effective conservation strategies requires the precise determination of the targeted species' distribution area and, if possible, its local abundance. However, detection issues make these objectives complex for most vertebrates. The detection probability is usually <1 and is highly dependent on species phenology and other environmental variables. The aim of this study was to define an optimized survey protocol for the Mediterranean amphibian community, that is, to determine the most favorable periods and the most effective sampling techniques for detecting all species present on a site in a minimum number of field sessions and a minimum amount of prospecting effort. We visited 49 ponds located in the Languedoc region of southern France on four occasions between February and June 2011. Amphibians were detected using three methods: nighttime call count, nighttime visual encounter, and daytime netting. The detection nondetection data obtained was then modeled using site-occupancy models. The detection probability of amphibians sharply differed between species, the survey method used and the date of the survey. These three covariates also interacted. Thus, a minimum of three visits spread over the breeding season, using a combination of all three survey methods, is needed to reach a 95% detection level for all species in the Mediterranean region. Synthesis and applications: detection nondetection surveys combined to site occupancy modeling approach are powerful methods that can be used to estimate the detection probability and to determine the prospecting effort necessary to assert that a species is absent from a site.
authors.affiliation: Les Ecologistes de l'Euzière, Domaine de Restinclières 34730, Prades-le-Lez, France.
authors.forename: Maud
authors.initials: M
authors.lastname: Petitot
authors.affiliation: Les Ecologistes de l'Euzière, Domaine de Restinclières 34730, Prades-le-Lez, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Manceau
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (UMR 5175), Ecole Pratique des Hautes Etudes, Biogéographie et Ecologie des Vertébrés campus CNRS, 1919 route de Mende, 34293, Montpellier Cedex 5, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Geniez
authors.affiliation: Centre d'Ecologie Fonctionnelle et Evolutive (UMR 5175), Ecole Pratique des Hautes Etudes, Biogéographie et Ecologie des Vertébrés campus CNRS, 1919 route de Mende, 34293, Montpellier Cedex 5, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Besnard
keywords: Anuran; detection probability; occupancy probability; sampling methodology; species phenology; urodela