Challenges in confirming eradication success of invasive red-eared sliders

Biological Invasions

Authors: Pablo García-Díaz 1, 2, 3 *, David S.L. Ramsey 4, Andrew P. Woolnough 5, Marc Franch6, 7, Gustavo A. Llorente6, Albert Montori6, Xabier Buenetxea8, Asier R. Larrinaga9, Matthieu Lasceve10, Alberto Álvarez11, José María Traverso11, Aitor Valdeón12, 13, Ariñe Crespo13, Virginia Rada13, Enrique Ayllón11, Vicente Sancho14, J. Ignacio Lacomba15, José Vicente Bataller 16, and Miguel Lizana2

1 School of Biological Sciences and Centre for Conservation Science and Technology (CCoST), The University of Adelaide, North Terrace SA 5005, Australia.

2 Department of Animal Biology. University of Salamanca. Campus Miguel de Unamuno. E-37007 Salamanca, Spain.

3Present address: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand.

4 Arthur Rylah Institute, Department of Land, Water and Environment, 123 Brown Street, Heidelberg, VIC 3084, Australia.

5 Department of Economic Development, Jobs, Transport and Resources, 475-485 Mickleham Road, Attwood VIC 3049, Australia.

6 Section of Zoology and Anthropology, Department of Evolutionary Biology, Ecology and Environmental Sciences. Faculty of Biology University of Barcelona. Av. Diagonal 643, 08028 Barcelona, Spain.

7 CICGE - Centro de Investigação em Ciências Geo-Espaciais Observatório Astronómico Prof. Manuel de Barros Alameda do Monte da Virgem, 4430-146; Vila Nova de Gaia, Portugal.

8 BOLUE Ingurumen Ikerketak. Bolintxu Baserria, Ergoien Auzoa, 73. 48113-Gamiz-Fika, Bizkaia.

9 eNeBaDa, Rúa das Penas, 57, 15892, Aríns - Santiago de Compostela, A Coruña, Spain.

10Toulon Provence Méditerranée, Communauté d'Agglomération, France.

11Asociación Herpetológica Española, Apartado de correos 191, Leganés, Madrid 28911, Spain.

12 Departamento de Geografía y Ordenación del Territorio. Instituto de Investigación en Ciencias Ambientales (IUCA). Universidad de Zaragoza. Pedro Cerbuna, 12. 50009 Zaragoza. Spain

13 Department of Herpetology. Aranzadi Society of Sciences. Zorroagagaina 11, 20014 Donostia-San Sebastián, Spain.

14LIFE+Trachemys Project, Wildlife Service. Regional Ministry of Environment
Generalitat Valenciana, Spain.

15 Direcció General de Medi Natural, Generalitat Valenciana, Valencia, Spain.

16 Freshwater Species Conservation Centre, Wildlife Service. Regional Ministry of Environment. VAERSA-Generalitat Valenciana, Spain.

* Corresponding author: School of Biological Sciences and Centre for Conservation Science and Technology (CCoST), The University of Adelaide, North Terrace SA 5005, Australia. E-mail:

* Corresponding author present address: Landcare Research, P.O. Box 69040, Lincoln 7640, New Zealand. E-mail:

Supplementary methods

Bayesian removal model validation procedures

We validated the capture probability predictions from our removal model for net traps by using an independent trapping dataset from the river Tormes (city of Salamanca, central Spain; latitude: 40.96, longitude: -5.65). We conducted a capture-mark-recapture study of a population of sliders during 29 consecutive trapping occasions in 2012. Six net traps were deployed in a 500-metres section of the river (e.g., the trapping effort per occasion was constant, six trap nights). Traps were active during weekdays and removed on Friday morning every week during the experiment. All the traps were checked once per day (morning), and the turtles captured were individually marked using a white permanent marker. A total of 14 sliders were captured during the study. Although it was designed as a mark-recapture study, it is possible to analyse the capture data using a removal approach to validate our fitted models. We used our fittedremoval model for net traps to estimate the expected cumulative catch curve in Salamanca given the trapping effort undertaken and plotted this estimated curve alongside the actual cumulative catch curve (Fig. S4 in Online Resource 2). The result indicates that our removal model for net traps accurately predicted the independent trapping data for Salamanca, thus validating the removal model.

Supplementary acknowledgements

We thank all the collaborators of the Herpetology group of the Universitat de Barcelona for their help in undertaking the fieldwork, in particular, C. Feo and Escola Taller les Gavarres. We are grateful to the following institutions for providing us with the necessary authorisations for trapping turtles: Consejeria de Medio Ambiente (Junta de Castilla y León), Servei de Protecció i Gestió de la Fauna (Environmental Department of the Catalan Government), Diputacion Foral de Álava, D.G. de Medio Natural, Generalitat Valenciana, Government of Navarra, and Confederación Hidrográfica del Duero.The trapping fieldwork was possible thanks to the funding provided by the following institutions and research projects: Área de Conservación de Flora y Fauna de la Consejeria de Medio Ambiente de la Comunidad de Madrid, WWF Spain, Confederación Hidrográfica del Duero, Pamplona Council, Vitoria-Gasteiz Council, Government of Navarre, Bardenas Reales Council, Ganasa, Environmental Department of the Catalan Government (DMA) & Fundació Bosch i Gimpera (FBG302577) 2004-2007, Obra Social Caja Madrid (2007ma189), Land Stewardship Program - DMA & Emys Foundation (2009-2011), LIFE+Trachemys (LIFE09/NAT/ES/000529), projects Control by means of net traps of the population of exotic freshwater turtles in the Almendra’s reservoir and other localities in the Natural Park of Arribes del Duero and Study of the distribution and conservation status of the populations of freshwater turtles in Castilla y León of the Junta de Castilla y León. PG-D was funded by an IPRS/APA scholarship by the Commonwealth Government of Australia (DET) and an Invasive Animals CRC PhD scholarship. MF is funded by a grant (UMINHO/BI/175/2013) from the Foundation for Science and Technology, Portugal (FCT - PTDC/BIA-BIC/4296/2012). AV was funded by a pre-doctoral scholarship by the Department of Education of the Government of Navarre. The Balanced Researcher Program of the IA CRC provided additional funding for PG-D to attend the workshop ‘Bayesian Modelling using R’ (School of Mathematics and Physics, University of Queensland).

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