Estimating species' absence, colonization and local extinction in patchy landscapes: an application of occupancy models with rodents


Alessio Mortelliti, Dipartimento di Biologia Animale e dell'Uomo, Università‘La Sapienza’, Viale dell'Università 32, 00185, Rome, Italy.


Making an inference on the absence of a species in a site is often problematic, due to detection probability being, in most cases, <1. Inference is more complicated if detection probability, together with distribution patterns, vary during the year, since the possibility of inferring a species absence, at reasonable costs, may be possible only in certain periods. Our aim here is to show how such challenging situations can be by tackled by applying some recently developed occupancy models combined with sample size (number of repeated surveys) estimation. We thus analysed the distribution of two rodents Myodes glareolus and Mus musculus domesticus in a fragmented landscape in central Italy pointing out how it is possible to identify true absences, non-detections, extinctions/colonizations and determine seasonal values of detection probability.