Record nesting of sea turtles on the coasts of the Western Mediterranean this season

This increase may correspond to a process of colonisation of the species as a consequence of climate change

In the last decade, western Mediterranean beaches have been experiencing an increase in the frequency of loggerhead turtle (Caretta caretta) nests. This increase may correspond to a process of colonisation of the species as a consequence of climate change, something that is considered to be of great importance for their survival due to evidence and predictions of feminisation and reduced viability of hatchlings on the nesting beaches of their original nesting areas.

However, this emerging colonisation is occurring in areas with a high level of human occupation, as is the case on the Spanish coastline, which is why appropriate management is necessary to favour the success of these clutches in coexistence with the human presence.

The recent appearance of this colonisation process means that, over the last few years, it has been necessary to develop new capacities on the part of all the agents involved, both at the scientific level and in public administrations. The main factors that can negatively affect this growing population are the lack of public awareness, the scarcity of scientific information, the alteration of the laying beaches for the successful incubation of eggs and the effectiveness of the management measures that are being implemented.

Very active start to the 2023 season

The first sea turtle nest detected this season on a Spanish beach appeared at the beginning of June on Can Pere Toni beach in Palma, in the Balearic Islands. Within a few weeks it was quickly followed by more nests detected on beaches in Catalonia, Valencia, Murcia and Andalusia. Some nesting attempts have also been detected. In the face of these events, the action teams have been able to observe and work with several nesting female turtles.

In Catalonia, three of the nests have been located in the Ebro Delta, which may indicate the growing importance of this natural area as a new nesting site. Another noteworthy fact in 2023 is that the nest detected on Sa Riera beach, in Begur, is the most southerly nest located to date on the Iberian Peninsula.

All this activity is posing a great challenge for the monitoring networks, local and regional governments and academic institutions involved, which in each case activate the protocols recently drawn up both in Catalonia and in the rest of the Spanish coastal communities for their conservation and for the collection of scientific data.

This increase in nesting activity on Spanish beaches is in line with what is also happening in other areas of the Western Mediterranean, Italy being the paradigmatic case: in the first weeks of the season, nearly 100 nests have been detected. Regions such as Campania have detected increases of more than 50% compared to previous years.

Start of the InGeNi-Caretta project

Thanks to funding from the Biodiversity Foundation, a consortium formed by the BETA Technology Centre of the University of Vic-Central University of Catalonia, the University of Barcelona and the Biodiversity Research Institute (IRBio) of the University of Barcelona, the Polytechnic University of Valencia, with the collaboration of the University of Valencia, and the Doñana Biological Station has begun work on InGeNi-Caretta.

This multidisciplinary project is made up of a research team made up of leading sea turtle experts with the aim of generating the scientific knowledge necessary to understand this unique colonisation phenomenon in the world and to facilitate decision-making in the planning and management of this endangered species along the Spanish coastline. All the results of InGeNi-Caretta will help to improve conservation measures for the species, particularly with regard to nesting activity on the Spanish Mediterranean coast.

The project encompasses several actions. It will enable a detailed study to be carried out on the potential suitability of Spanish coastal beaches for nesting sea turtles, considering their physico-chemical characteristics and better defining the environmental parameters on nesting beaches. On the other hand, it will make it possible to analyse the number, origin and behaviour of breeding individuals through genomic studies of the nests, as well as their biological efficiency, the number of eggs, the rate of embryonic development and the viability of the hatchlings. Finally, by combining all the data obtained, it will also be possible to assess the impact of brood genotype on dispersal, viability and growth.

The consortium also hopes to examine the behaviour of females and offspring through the use of satellite telemetry and stable isotope studies. This will make it possible to infer, from their movements, the feeding areas and habitat use of the females prior to laying and their subsequent dispersal, in order to determine important nesting areas. Finally, the success of ex situ conservation will be studied to assess hatching percentage, growth parameters and viability of hatchlings in captivity in order to facilitate head-starting practices.

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