Colomera was unlucky. This loggerhead turtle (Caretta caretta), a magnificent specimen weighing one hundred kilos, fell three times into the nets of fishing boats off the Valencian coast. But she was also lucky: the fishermen who hooked her were aware of the importance of the species and took her three times to the recovery center of the Oceanogràfic Foundation in Valencia, where veterinarians succeeded to recover it and put it back into the sea. The last received a satellite beacon which allowed him to follow his life course. For two years, Colomera managed to avoid more accidents and wandered around the Mediterranean until the device stopped transmitting.
“This is a symptomatic case of the pressure this species is under,” explains José Luis Crespo, head of the Foundation’s Conservation and Marine Fauna Area. Threatened by man, by fishing, by its natural predators, by climate change which heats up its usual nesting places, the Caretta caretta look for a new home.
The common, or loggerhead, turtle is a very vulnerable species and one of two types of turtle, along with the green turtle, included in the EU catalog of controlled species. These animals can lay 300 eggs at a time, but at the same time, they have minuscule success rates: only one in 500 specimens reaches adulthood. It needs help and, although this is due to external circumstances, Spain acquires a fundamental role in its conservation due to the changes that the planet is undergoing: it is the only country in the world that produces more males than females, a fundamental factor. value than the species.
It is increasingly common to see these turtles coming out of the sea on a Spanish beach to lay their eggs. Their presence has been relatively normal on the coast, but they came as visitors. However, over the past two decades, Caretta caretta It is moving towards our coasts to nest under the effect of climate change, explain Oceanográfic scientists. This animal reproduces in certain temperature conditions and the warming experienced by countries like Turkey or Greece pushes it towards slightly cooler places. Since 2014, 70 nesting episodes have been detected in the Valencian Community, whereas 20 years ago they were sporadic. In 2023 alone, 29 nests were located across the country and in 2024 this dropped to 11, but scientists believe this is because each female only lays eggs once every two or three years and it hit fallow.
An indicator of global warming
Researchers have made the journeys of these turtles a reliable indicator of global warming, says Jesús Tomás, of the Department of Zoology of the University of Valencia, who, with Eduardo Belda, of the Polytechnic University of Valencia, carries out the main program of research. and followed by the Generalitat Valenciana. “We see the evolution live,” he explains, between enthusiasm and concern. “We see how an animal with a 20-year life cycle adapts to climate change. » Crespo confirms the idea, established in the scientific community: “This is a serious alarm signal.” The more Caretta caretta Towards the west, the worse the planet.
Currently, the southernmost point in Spain where nests have been found is Marbella (Málaga). Satellite tags, small devices with an antenna stuck to the top of the turtle’s shell, have recorded them traveling through the Strait of Gibraltar, perhaps in an attempt to cross the Atlantic, Tomás explains, but the Surface currents are too strong for young people. specimens and push them back towards the Mediterranean.
Tomás and Crespo attend this Friday on the beach of Almassora (Castellón) the release of 22 specimens recovered by the Fundació Oceanográfic in the presence of a group of journalists invited by the Foundation for Biodiversity, the Ministry of Ecological Transition and Demographic Challenge (MITECO). The outing takes place within the framework of the Life Intermares project, coordinated by the Foundation and in which various administrations, the CSIC, certain universities and organizations such as the Spanish Fishing Confederation or WWF Spain participate. The turtle program is just one of many they run.
The 22 specimens released Friday were recovered from a nest on this same beach just a year ago. Weighing between one or two kilos and measuring 30 or 40 centimeters long, they are in better conditions to survive immersion in a hostile environment after 12 months, gaining strength and presence in small tanks of the Océanogràfic. Under natural conditions, they would have entered the sea fresh from the egg, weighing 20 grams and smaller than the palm of your hand. 99% of them would not have succeeded. In the right scenario.
This is why MITECO, in collaboration with the autonomous communities and various institutions, monitors every turtle that leaves the sea in Spain. When a nest is seen or located (the mark it leaves in the sand is characteristic), it is protected, 20% of the eggs are taken to incubate them in recovery centers and their evolution is monitored. Although there is no global data, scientists ensure, by monitoring those they mark and release, that the chances of survival multiply when they enter the sea at a certain size.
“Spanish society must begin to get used” to seeing turtles coming out of the water in search of a suitable place to nest, scientists say. Our country has become a favored nesting place for turtles due to the increase in temperature in their usual habitats.
“Spanish society must start to get used to seeing turtles coming out of the water in search of a suitable place to nest,” explains Daniel García, technical director of the Oceanogràfic Foundation. In addition to the movement that is recorded, because the species is philopathic: it returns to the place of birth, or where it entered the sea, to look for suitable areas to make nests and lay its eggs. Although it is not yet clear whether philopathy works the same for those raised in captivity as it does for hatchlings left on the beach, some studies suggest that the point of return is incubation, not entry. in the sea, explains Tomás.
Regardless, the phenomenon is expected to be recurring, if it cannot already be considered as such. Not all turtles always return to the same place and there are also some that lay several eggs in different places, explains the researcher on the beach. In their research they have examples of all kinds: there was a turtle that nested during the same season in Catalonia, in the Valencian Community and in Andalusia, the three places in Spain with the Balearic Islands where nesting occurred been recorded. There was another one that made three nests on the same beach in Catalonia. The number of clutches and the number of eggs depend on the “energy” (food) that each female has managed to accumulate, explains Tomás.
This Friday’s release is particularly relevant because of the 22 turtles, 21 are males. And they are starting to become rarer. The sex of turtles depends on the temperature at the time of incubation, Crespo explains: When it’s around 29 degrees, the mix is about 50 percent. If it increases, it begins to shift in favor of women. If it drops, it’s among males. Global warming is destroying the balance of the species and scientists have identified nests where 90% of the specimens were female. The problem this creates is obvious.
But not in Spain, “the only country in the world where more men than women are born,” explains García, from Oceanogràfic. “We need females to come and produce males,” he says.
Recovery programs can’t tell females to come nest in Spain, but they can improve the survival of the species as a whole so that it happens naturally in terms of numbers. Work is being carried out on several fronts, and much of it concerns awareness. Raising awareness among society in general when it sees a nesting episode, but also among fishermen, explains Crespo. It works: more and more specimens are sent to the recovery center. More than a hundred people come to Oceanogràfic every year and they have already served nearly a thousand.
“We should not demonize fishermen, but it is true that it is an impactful activity,” explains the veterinarian. The institutions have created agreements and protocols so that when a specimen is caught in fishing nets, they take it to a conservation center (in the case of the Valencian Community, the Oceanogràfic) to be treated by experts, as happened three times. Colomere. These animals are resilient and, although the nets are devastating and can amputate limbs, if they are treated, they survive. Three-finned turtles have been recorded transmitting for years (and the fact that the device stops transmitting simply means that it has stopped working, not necessarily that the turtle is dead).
This care also allowed the team of García and Crespo, from Oceanogràfic, to discover that turtles can suffer from air embolism and decompression syndrome, like divers, which scientists did not know. “It happens to some when they come into contact with fishing equipment,” says García. It is not known if this was due to stress or why, but they detected that some turtles were apparently fine when the fishermen untangled them and after a while their condition began to worsen until they are almost in a coma despite the absence of apparent symptoms. injuries.
This led to another discovery, a small point of pride for the Oceanogràfic team: they discovered that turtles responded extremely well to hyperbaric chambers. Like people. And they have integrated one into their work materials with a very high success rate. “They are very strong animals, with a very slow metabolism which makes them very tolerant of hypoxia,” explains García. In any case, he adds, it is not a realistic solution: it is about prevention. But in the meantime, a time in front of the camera, a season in a recovery center, a marking to follow his progress and collect information and ready to go back to sea. Let’s hope it happens again.
