Project

Emys orbicularis

Goal: Ecology

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Ottonello Dario
added 15 research items
Ianieri Edizioni Via L. Da Vinci, 16-65124 Pescara-Tel. 085.2192404 www.ianieriedizioni.it-info@ianieriedizioni.it Nessuna parte di questo libro può essere riprodotta o trasmessa in qualsiasi forma o con qualsiasi mezzo elettronico, meccanico o altro senza l'autorizza-zione scritta dei proprietari dei diritti. Abstract Since 2000, a captive breeding and restocking program for the European pond turtle Emys orbicularis has been ongoing in Liguria, northern Italy, with the aim of preventing the extinction of the species in that region. In a previous study, we used a population model to predict the growth of a restocked population and to assess whether it would be better to release turtles of three, four or five years of age. However, that initial model was based on limited information, leading to uncertainty of our predictions. Here, we validate that initial study by analyzing the results of post-release monitoring for the first seven years of releases. We used a Cormack-Jolly-Seber (CJS) model to estimate survival of released individuals. We then updated the uncertain estimates of survival in the original model and assessed whether the best decision had changed and the benefits of having obtained empirical data from monitoring. Modelling results suggests that released turtles have sufficiently high survival, matching prior expectations, such that local extinction has been averted in the short-term. Survival was similar among candidate age classes for releases, suggesting the release of younger individuals can provide positive outcomes while reducing management costs. On the other hand, survival varied among sites, indicating the need for ongoing in-situ habitat management. In sites with less than ideal conditions, updated models of population viability suggest that long-term persistence depends on site conditions. Moreover, the late onset of sexual maturity in the species means reproduction of released animals cannot yet be determined with certainty. Captive breeding and reintroduction programs normally require long-term efforts; therefore, focused monitoring that is clearly linked to decision-making is necessary to continually refine and adjust management strategies.  Atti XI Congresso Nazionale della Societas Herpetologica Italica, Trento 2016 136 Riassunto Il progetto di riproduzione in cattività a scopo di restocking delle popo-lazioni di Emys orbicularis in Liguria è in corso con successo dal 2000. In uno studio precedente, un modello di popolazione per classi d'età veniva usato per determinare l'efficienza del rilascio di individui di tre, quattro o cinque anni d'età. A causa della scarsità di dati il modello originale de-notava incertezza nelle previsioni di viabilità e di conseguenza nella scelta della strategia di rilascio. In questo studio presentiamo una validazione del modello descritto precedentemente, sulla base dell'analisi dei risultati dei monitoraggi post-rilascio in Liguria dal 2008 al 2015. Usando un modello di marcatura-ricattura Cormack-Jolly-Seber, la sopravvivenza stimata risulta indipendente dall'età per gli individui tra tre e cinque anni, dimostrando la possibilità di rilasciare individui giovani senza pregiudicare la viabilità e permettendo di risparmiare risorse. D'altra parte, la sopravvivenza appare maggiormente legata al sito di rilascio, rafforzando l'importanza della ge-stione dell'habitat per garantire la viabilità a lungo termine. Un'ulteriore incertezza risulta dalla difficoltà del determinare il successo riproduttivo tra gli individui rilasciati, in particolar modo per la lentezza nel giungere a ma-turità riproduttiva. Le azioni fondamentali per il futuro saranno il concen-trare i monitoraggi su questa componente demografica e sviluppare strategie efficaci per il mantenimento e miglioramento dell'habitat. Keywords European pond turtle, ex-situ management, population viability analysis, uncertainty. Introduction and Methods e European pond terrapin Emys orbicularis was considered to have been extirpated from Liguria until the re-discovery of small, isolated populations in the Albenga plain (Jesu et al., 2004). Within a species recovery project, coordinated by the Savona Provincial Administration, a captive breeding centre was set up in 2000, and is now producing a significant number (about 60 juveniles each year) of individuals for restocking of the existing populations. Within the program, budget constraints influence management decisions, for example about the age of individuals to release. Among candidate age classes for release (three-, four-and five-year-olds), releasing older individuals may allow bypassing high-mortality juvenile stages and increase the chances of successful establishment , but the longer captive period would increase management costs. e benefits of releasing older turtles may also be offset by age-specific post-release mortality, for example if older turtles were more likely to disperse away from the site. In a previous study (Canessa et al., 2015) we used a stage-structured population model to predict the viability of a reintroduced population, focusing on management decisions about the age of individuals to release. However, that original model was based on limited information , introducing uncertainty about the model predictions and the best release strategy to adopt.
Ottonello Dario
added a project goal
Ecology