BETA Technology Centre manages a record number of loggerhead turtle nests in Catalonia in 2021

In recent years, there has been an increase in sporadic nesting events outside the already stable populations

The year 2021 has broken the record for the number of loggerhead turtle nests detected in a single season in Catalonia. Between 18 June and 21 July, five nests were detected (four in Tarragona and one in Barcelona), but there were up to eight more nesting events: one on Platja Larga (Salou), one on Platja de Calafell (Calafell), three on Platja del Serrallo (St. Jaume d’Enveja), -Ebro Delta Natural Park-, one on Miracle Beach (Tarragona), one on Platja d’Aro’s beach, and another on Platja de la Picòrdia (Arenys de Mar). The BETA Technology Centre of the University of Vic – Central University of Catalonia (UVic-UCC) has collaborated with and supported the Rescue Network of the Servei de Fauna i Flora de Catalunya, the Parc Natural del Delta de l’Ebre (PNDE), and the local administrations in the tasks of detecting and managing these nests. It has also provided technical advice to CRAM, CRARC and Barcelona Zoo for the artificial incubation of eggs, and to non-profit organisations such as Cel Rogent, GEPEC and the PNDE volunteers in advising on the custody of the nests by environmental volunteers.

Elena Abella, Mireia Aguilera and Glòria Fainé, specialists in sea turtle conservation at BETA TC, have been responsible for guiding the technical staff of the administration and the environmental organisations that have participated in the management of these events. Some of the tasks carried out included: locating the nests; assessing whether a transfer was necessary to ensure viability; monitoring incubation temperatures to predict the emergence of hatchlings; assisting in the emergence and release of hatchlings; taking biometric data from the turtles and exhuming the nests after hatchling emergence. All these tasks will continue to be carried out during the year 2022.

A growing problem

In recent years, there has been an increase in sporadic nesting events outside the already stable populations (mainly Greece, Turkey and Cyprus). According to Elena Abella, “these events seem to be due to a change in the thermal conditions of our coasts, caused by the increase in temperature due to climate change, and to the dispersal behaviour of the animals; although it cannot be ruled out that factors such as chance or errors in the turtles’ behaviour may also be involved”.

In any case, colonisation of new nesting areas can be considered to be taking place. In loggerhead turtles, as in other reptiles, the sex of the hatchlings is determined by the incubation temperature of the nest. The higher the incubation temperature, the more females will hatch and, conversely, the lower the temperature, the more males will hatch. Therefore, “sea turtles are finding favourable conditions for nesting on the Catalan coast, causing nests to be incubated in colder latitudes, where it is more likely that in the future there will be more suitable conditions for the survival of the species in the face of a scenario of a global increase in temperature,” explains Abella.

Of the total of 309 hatchlings that hatched from these five nests, more than 60% were released at sea and the rest will be kept in captive breeding for one year, in a type of programme known as head starting. The aim of head starting is to release the hatchlings at a considerably larger weight and size than they were at birth. In this way, it is hoped that they will have a better chance of reaching adulthood, since it is estimated that only 1 in 1,000 sea turtle hatchlings reach sexual maturity. The CRAM, the Oceanográfico of Valencia, the Palma Aquarium, and the Marine and Aquaculture Research Laboratory of Mallorca (LIMIA) are also taking part in this project.

Coordination of the COMING project and collaboration with NIDOS-Caretta

During 2021, CT BETA coordinated the COMING project (funded by the MAVA Foundation in the framework of the MedPAN Small Projects call). The project activities focused on three main axes. One was the development of a common strategy for the monitoring and management of nesting events in the western Mediterranean. Another axis was based on carrying out scientific studies on the origin and viability of these events – including studies of beach temperature profiles to determine the viability of beaches to host nesting sites – and genetic studies to determine the region of origin of breeding individuals. Lastly, the third axis was the implementation of outreach and awareness-raising activities on the biology of Caretta caretta, in order to involve the public in the management of these events. This project was carried out in collaboration with the University of Barcelona, the Stazione Zoologica Anton Dohrn (Italy) and the Doñana Biological Station (EBD-CSIC).

On the other hand, the CT BETA has also collaborated in the NIDOS-Caretta project, which aimed to carry out a pilot test in Catalonia – potentially applicable in other Spanish regions – to maximise the success of nesting cases of this chelonian. The work includes scientific studies to understand why nesting episodes have increased and also to improve the protocols for the management and protection of these nests. This project was led by the University of Barcelona, with the collaboration of the Doñana Biological Station (EBD-CSIC), and is co-funded by the Biodiversity Foundation of the Ministry for Ecological Transition and the Demographic Challenge.