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Survival and dispersal routes of head-started loggerhead sea turtle (Caretta caretta) post-hatchlings in the Mediterranean Sea


Several loggerhead sea turtle (Caretta caretta) nesting events have been recorded along Spain’s Mediterranean coast, outside its known nesting range, in recent years. In view of the possible expansion of its nesting range and considering the conservation status of this species, management measures like nest protection and head-start programs have been implemented. To study the dispersal behavior and survival of head-started loggerheads, 19 post-hatchlings from three nesting events were satellite tracked after their release in three consecutive years (2015–2017). This paper presents the first study of survival probabilities and dispersal movements of loggerhead post-hatchlings in the Mediterranean basin. Monitored post-hatchlings dispersed over large areas using variable routes, mainly off the continental shelf. Nonetheless, post-hatchlings dispersed to high-productivity warmer areas during the coldest months of monitoring. These areas might be optimum for their survival and development. We observed differences regarding dispersal orientation and routes among individuals, even from the same nest, release date, and location. Our survival models contributed to improving current survival estimates for sea turtle post-hatchlings. We observed a high probability of survival in head-started individuals during the first months after release, usually the most critical period after reintroduction. The data did not support an effect of habitat (neritic or oceanic) in survival, or an effect of the region (Balearic sea or Alboran sea) in survival probability. Differences in survival between nests were observed. These differences might be related to parasitic infections suffered during the head-starting period. This study shows that nest management measures may contribute to the conservation and range expansion of the loggerhead turtle population in the western Mediterranean.

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This satellite study was funded by Universitat Politècnica de València, Ministerio de Agricultura y Medio Ambiente (ref: 16MNSV006), Ministerio de Economía, Industria y Competitividad (ref: CGL2011-30413), Fundación CRAM, Fundación Hombre y Territorio and Eduardo J. Belda. Corresponding author, S. Abalo, was supported by a Ph.D. grant (FPU) from Ministerio de Educación, Cultura y Deporte (Spain). J. Tomás is also supported by project Prometeo II (2015) of Generalitat Valenciana and project INDICIT of the European Commission, Environment Directorate-General. We are extremely thankful to the entities that have collaborated: we thank all professionals at the Oceanogràfic, especially at the ARCA Rehabilitation Center, for their many efforts and whole-hearted dedication to the best animal care. In particular, we are grateful to the Conselleria d’Agricultura, Medi Ambient, Canvi Climàtic i Desenvolupament Rural of the Valencia Community Regional Government. We also thank the professionals at Centro de Recuperacion de Animales Marinos (CRAM) for their dedication and animal care. We are thankful to the Marine Zoology Unit of the University of Valencia, NGO Xaloc, EQUINAC, Aquarium of Sevilla, Doñana Biological Station (EBD-CSIC) and to involved professionals at Consejería de Medio Ambiente y Ordenación del Territorio (CMAOT) of Junta de Andalucía, especially at the Andalusian Marine Environment Management Center (CEGMA) for their efforts with animal care, logistics for release events and necropsy of “Rabiosa”. We are particularly grateful to the people who called 112 to report a nesting event and to the nest custody volunteers. Thanks are due to the staff of Parador de El Saler for volunteering logistical support. The authors wish to acknowledge the use of the Maptool program for analysis and graphics in this paper. Maptool is a product of SEATURTLE.ORG (Information is available at Also, we acknowledge the use of the Douglas Argos Filter (DAF) utility in Movebank ( and especially David Douglas for his help and recommendations. Finally, we thank the reviewers for their reviewing efforts.

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Correspondence to Sara Abalo-Morla.

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The authors declare that there is no conflict of interest and that consent was obtained from all parties. The authors declare that animals were treated according to all applicable international, national, and/or institutional guidelines for the care and use of animals. Animal ethics approval was granted by Universitat Politècnica de València. Tagging of post-hatchlings was done under permit from local environmental authorities (Generalitat Valenciana, Generalitat de Catalunya, and Consejeria de Medio Ambiente y Ordenación del Territorio de la Junta de Andalucía).

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Responsible Editor: P. Casale.

Reviewed by N. F. Putman and an undisclosed expert.

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Abalo-Morla, S., Marco, A., Tomás, J. et al. Survival and dispersal routes of head-started loggerhead sea turtle (Caretta caretta) post-hatchlings in the Mediterranean Sea. Mar Biol 165, 51 (2018).

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