Colonisation by sea turtles on the coasts of the Spanish Mediterranean continues

The beaches of Spain's coastline and the rest of the western Mediterranean have been experiencing a rise in the numbers of nests by loggerhead turtles detected (Caretta caretta) over the last decade. The increase in the number of nests in these regions is due to the fact that the sea turtles are starting to colonise new areas as a result of climate change. This colonisation is very important to the species, as forecasts suggest that climate change could prevent the birth of males and reduce the survival rates of their young in the areas where they used to nest.

The nesting season is from the beginning of June to the end of August, and the young turtles are born until October. Despite increased monitoring by volunteers, and awareness and education campaigns, the nests identified so far have been scattered, although they are now beginning to be concentrated in some areas of the coast. Some nests are found after the turtles have hatched, which suggests that the actual number of nests may be higher.

Furthermore, this new colonisation is taking place in areas with high levels of human habitation, such as the Spanish coast, and as such appropriate management is required to ensure the success of these eggs in an unnatural environment. Public ignorance of the issue, the lack of scientific information about the factors that govern it, changes in the conditions of beaches due to their use for leisure and a lack of knowledge about the effectiveness of measures for the management of nests and hatchlings by beach authorities may compromise hatching in nests and the survival of hatchlings.

In this situation, it is necessary to increase vigilance on beaches and cooperation with local, regional and national authorities in order to protect the nests and make high levels of tourism compatible with the conservation of sea turtles during the summer months. Engagement by the public is also essential for detecting females that come to the beaches to make their nests, to locate of their tracks in order to find the eggs, and to locate the young and their tracks. Public awareness of these events is crucial for the conservation of sea turtles on the Spanish coastline. The growing trend observed and the presence of females nesting in different years suggests that the nesting of sea turtles on the Spanish Mediterranean coasts has entered a new era, in which migrants from distant populations could live alongside individuals already resident on the Spanish coastline.

Start of the InGeNi-Caretta project

This multidisciplinary collaborative project began in May 2023, thanks to funding from the Biodiversity Foundation. InGeNi-Caretta is a consortium consisting of the BETA Technological Center at the University of Vic - Central University of Catalonia, the Biodiversity Research Institute (IRBio) at the University of Barcelona, the Polytechnic University of Valencia in partnership with the University of Valencia and the Doñana Biological Station. The project's objectives are to detect and study nests on the beaches on the Spanish coast, to assess the quality of beaches by studying temperatures, to undertake monitoring through telemetry, genetic analyses and to monitor stable isotopes of females and hatchlings (to identify their origin). The project's objectives also include the study and assessment of management actions in order to refine the action protocols.

The research team is made up of sea turtle specialists, who produce the scientific knowledge necessary to understand this unique phenomenon of colonisation in the world, and also pass it on to the authorities in order to facilitate decision-making in the planning and management of the Spanish coast. InGeNi-Caretta's results provide important scientific information to improve the nesting and management of the species.

InGeNi-Caretta's actions on the ground began in 2023, when data and samples were collected from twenty-nine nests. Nine adult females were marked for movement tracking by satellite telemetry during the project. The information analysed by the InGeNi-Caretta consortium, and especially that obtained from the genetic studies of nestlings and satellite telemetry of the females, has made it possible to identify turtles that always come to the same area to nest, as well as exploratory turtles that nest in different regions in different years.

The actions will continue throughout the 2024 nesting season, which began in early June. So far this year, the activity of at least six females, some of which had already visited Spanish beaches in previous years, has been recorded in the Valencian Community, Catalonia, Murcia, Andalusia and the Balearic Islands. Three nests, two of which are in the Valencian Community and one in Catalonia, have also been located and protected. Nesting is expected to increase in July, as the temperature of the sea water rises.

InGeNi-Caretta is supported by the Biodiversity Foundation of the Spanish Ministry for Ecological Transition and the Demographic Challenge (MITECO) within the framework of the Recovery, Transformation and Resilience Plan (PRTR), funded by the European Union – NextGenerationEU.