A female loggerhead turtle nested for the first time last summer on the Costa Brava. She laid 130 eggs and after 76 days they began to hatch until the hatchlings made their way to their natural habitat: the sea.

Do you remember these tracks? They're not from a tractor going in and out of the beach, but from the footprints of a sea turtle that came ashore to lay her eggs in the sand.

In the summer of 2023, a female loggerhead turtle chose Sa Riera beach in Begur to lay her eggs. She emerged from the sea at sunset on 18 July and made her way slowly into the sand, out of the reach of the waves: her body is designed to move nimbly in water, but it is ill-suited to moving across sand. It dug the nest with its hind flippers to a depth of about 50 cm and laid 130 eggs. It covered the nest with sand to protect the eggs from predators, regulate the temperature, and keep the surface clean.

Immediately it returned to the sea, paying no heed to the people who had already captured that moment. Seventy-six days later, the first eggs began to hatch and the little turtles made their way to the sea, swimming towards the brightest horizon created by the reflection of the stars and the moon on the water's surface. They will live the rest of their lives at sea. Only the females come ashore to lay their eggs.

Once in the sea, sea turtles embark on a journey full of dangers. They usually swim for around 20 hours to move away from the coast, and it is estimated that only one in a thousand will reach adulthood. An iron compound (magnetite) in their brains allows them to orient themselves from this very moment using the Earth's magnetic field, and it is a well-known fact that they return to nest on the beach where they were born. We would love for this “explorer” turtle to return next year to Sa Riera beach to lay another clutch of eggs, as well as for the newly hatched turtles that headed out to sea to return to the same place to breed. The answer is not clear. However, in the second case, we will have to wait, as female turtles experience their first reproductive cycle between the ages of 15 and 30!

The Catalan coast features a great diversity of marine habitats, home to a total of 94 protected marine species, including birds, cetaceans, turtles, sharks, algae, corals, etc. Marine pollution, accidental capture in large drifting fishing nets, the destruction and alteration of beaches, noise pollution and collisions with large vessels are some of the threats endangering these species, not to mention the consequences of climate change. It is very likely that female loggerhead turtles are beginning to seek out new nesting sites further north, in search of cooler temperatures.

Sometimes we are not aware of how valuable our surroundings are. That is why close-to-home, real-life stories often move us and inspire us to act and not give up. This is our desire!

On the Mediterranean coasts, three of the seven species of sea turtles can be observed. The loggerhead sea turtle or babaua (Careta caretta) is the most abundant on our coastline, followed by the green turtle (Chelonias mydas), both of the family Cheloniidae. The leatherback turtle (Dermochelys coriacea) is an occasional species, the only living representative of the family Dermochelyidae and the largest in the world, exceeds two metres in length and weighs over 600 kg. Only the loggerhead and green turtles nest in the Mediterranean, but the main breeding areas within the Mediterranean lie in the eastern part, on the beaches of Greece and southern Turkey. The western Mediterranean is a very important feeding area for juveniles and sub-adults from both the eastern Mediterranean and the Atlantic, although nesting by the loggerhead turtle on our coast is becoming less sporadic.

The loggerhead sea turtle, or babaua turtle, is the smallest in the Mediterranean. However, adults can weigh 120 kilos and exceed one metre in carapace length. They can live for up to 80 years. Sea turtles have their shells covered with large, hard scales called scutes. Characteristically, the loggerhead turtle has four or five prefrontal plates and a hard, heart-shaped shell made up of five vertebral scutes and five marginal scutes. Its head is quite long and broad in relation to its body.

It has a very robust neck and a strong, beak-shaped jaw. The colour of the head and the upper part of the shell can vary from yellow-orange to brownish-red, while the underside is usually pale yellow with some orange spots. The fore and hind flippers each have two claws. As with other sea turtles, neither its head nor its limbs are retractable.

The loggerhead turtle varies its geopositioning throughout its life cycle in response to nutritional and reproductive needs. Hatchlings head out into the open sea, where they feed for extended periods on small suspended organisms, as they cannot properly dive to feed underwater until their first year.

In the early stages of their life, they show a preference for deep pelagic habitats and, therefore, it is more common to encounter a juvenile individual in the high seas; whereas upon reaching maturity, they prefer neritic (shallow ocean) or coastal areas, associated with a change in diet. Large individuals feed on a wide variety of marine organisms, including crustaceans, molluscs, echinoderms, fish and cnidarians (such as jellyfish, which are one of their favourite foods!). They also consume algae and plants. In fact, the diet of sea turtles can contain more than 50 different species of marine animals.

Young and adult turtles often host a wide variety of organisms attached to their dorsal shell, which travel with them. These organisms, known as epibionts, include, for example, algae, tubeworms, barnacles and other sessile crustaceans. Thus, turtles act as an oasis, providing a resting and migratory habitat for other species. In fact, more than 150 animal and plant species have been described that can live on turtles.

Their bodies are designed to move through the water with agility. The younger ones (<400 g in weight) fold their foreflippers against the sides of their shells and propel themselves by kicking with their hind limbs. Adult turtles swim by dorsoventrally flapping their fore limbs during swimming, without using their hind limbs to propel themselves.

They swim swiftly and directly when passing through unsuitable habitats, and without a fixed course through places they favour and where food is abundant. Young loggerhead turtles spend just over half their time submerged, a period that increases as they grow. They surface to breathe for 15 to 30 minutes, although they can dive for up to four hours. Most of the time they remain at shallow depths, between 0 and 6 metres.

The female has the ability to store sperm from several males in her oviducts until ovulation. Thus, each clutch can have up to five different fathers. Females leave the sea and head for the beach, seek a safe spot above the high-tide line and dig a hole with their hind flippers about 40–70 cm deep, where they lay between 60 and 180 eggs. They cover it with sand and return to the sea. Sex is determined by the nest temperature during the central third of the incubation period.

An average temperature of around 29.5 °C balances the ratio of males to females. Higher temperatures accelerate embryonic development and produce more females, whereas lower temperatures extend the incubation period, resulting in a predominance of males. After around 80 days of incubation, the first hatchlings emerge, burrowing through the sand to the surface. They do so at different times, in what are known as events. This usually happens at night to avoid predators and extreme temperatures. As soon as they leave the nest, the turtles make their way swiftly to the water.

They find their way to the sea by means of visual cues, heading for the brightest spot and away from elevated silhouettes, such as dunes or vegetation. Once in the sea, they swim vigorously against the waves and from that moment on navigate by the Earth's magnetic field, which allows them to return to the beaches where they were born and to the various feeding areas.

Sea turtles are constantly on the move. Adults are capable of making long migrations from nesting areas to feeding grounds, often thousands of kilometres away and even to other continents. Some of the most common routes run from Cape Verde to the African coasts and along the entire eastern coast of the Americas towards the Mediterranean. Individuals have been found in the Balearic Islands originating from the Gulf of Mexico or the Caribbean Sea. These have managed to cross the Strait of Gibraltar and enter the Mediterranean Sea.

Thunderbird is the name of the loggerhead turtle that was caught in some ghost fishing nets in 2020 in Majorca, and released with a satellite tracking device. This enabled the tracking of the more than 6,000 km journey it made, crossing the Strait of Gibraltar despite strong currents and heavy maritime traffic, heading for West Africa, presumably returning to its place of origin. Unfortunately, Thunderbird was accidentally caught, this time by a trawler off Senegal, and her trace was lost. Thunderbird's story highlights both the problem of so-called ghost nets—remnants of nets in which turtles and other marine animals become trapped—and the bycatch by industrial fisheries.

Threat Factors

The loggerhead turtle is included in Annex IV. of the Habitats Directive (Council Directive 92/43/EEC of 21 May on the conservation of natural habitats and of wild fauna and flora) as a protected species. In addition, It is classified as vulnerable by both the International Union for Conservation of Nature (IUCN) and Decree 172/2022 in Catalonia..

In the early stages of its life, the loggerhead turtle has many predators. They face, among others, crabs and birds when they emerge from the nest, and large fish and sharks once they have entered the sea. Only one in every 100 turtles survives its first year in the wild, and very few of the hatchlings—only one in every 1,000—reach adulthood. Once they reach adulthood, they can only be attacked by sharks, sperm whales or orcas. However, it is undoubtedly we humans who have brought their population to critical levels.

Sea turtles play a crucial role in many marine ecosystems from an ecological point of view. However, many species of sea turtle are currently endangered worldwide due to habitat loss, the destruction of nests and nesting areas, pollution, collisions with vessels, and above all accidental capture by various fishing gear.. In the western Mediterranean, more than 50,000 loggerhead turtles are caught each year by trawling, gillnet and longline fishing. This phenomenon is regrettably repeated on a global scale. It is estimated that one in three turtles caught by longline fishing and released with the hook still embedded dies within the first three months.

On the other hand, many turtles, despite being released after accidental capture, die from what is known as decompression syndrome, caused by the rapid change in sea water pressure, a problem similar to that experienced by divers, and for which they also require a hyperbaric chamber to recover. Collaboration with fishermen is key and there is a protocol.A guide for fishermen for the management of accidentally caught specimens. We must not forget the problem of ghost nets that remain floating in the water and can ensnare them. It is estimated that, globally, 101 per cent by volume of marine litter consists of lost fishing gear.

Another significant threat to sea turtles is pollution in both the Mediterranean Sea and the oceans, caused by microplastics, macroplastics and other waste produced by us. Because of their limited ability to discriminate when feeding, many turtles in the western Mediterranean mistake these for food and ingest them.. Not only do floating plastic bags resemble jellyfish, a favourite food of many sea turtles, but there is new evidence suggesting that plastic and other marine debris can smell like food. It has been discovered that in just seven days, plastic debris in the ocean can become coated with a layer of algae and other microorganisms to the point that turtles mistake it for an appetising meal and swallow it.

90.1% of the sea turtles admitted to the CRAM (Foundation for the Conservation and Recovery of Marine Animals) in 2021 had microscopic plastics in their stomachs or faeces.. In fact, turtles are a good bioindicator of how polluted the sea is (and it's very polluted!). 

Another threat to loggerhead turtles directly related to humans is coastal overdevelopment and the destruction of the nesting habitat. The use of machinery for cleaning and levelling the sand can also destroy the nests, as they lie less than 50 cm below the surface. Light pollution from ports and roads can disorient the females laying their eggs and also the hatchlings, causing them to head inland across the sand and die before they can reach the sea, due to dehydration or predation at sunrise.

The loggerhead turtle nests for the first time on the Costa Brava

We know that turtles return to the same beaches where they were born to lay their eggs, a behaviour known as philopatry, the same pattern seen in salmon and some migratory birds. Nesting by the loggerhead turtle is common in the eastern Mediterranean. However, over the past ten years, an exponential increase in nesting has also been detected in the western Mediterranean. You can consult the sighting history on the scientific outreach project's website. Mask on sight! Nesting on the Catalan coast is the most abundant on the Iberian Peninsula. The first nest of the season was identified in Mallorca on 8 June 2023. And the nest detected on 18 July 2023 at Sa Riera beach, in Begur, is the most southerly located so far on our peninsula..

This “baby boom”, or the exponential growth in the number of loggerhead turtles observed nesting on the coasts of the western Mediterranean in recent years, has surprised experts and raises several questions. The increasing number of individuals breaking the pattern and exploring other nesting sites could be due to global warming, as the water and sand temperatures are rising. If they reach our coasts, it is likely due to the search for cooler areas in which to breed. Remember that a certain temperature is required for the eggs to hatch and to maintain a balance between the number of female and male hatchlings.. Therefore, if a beach produces mainly males, the return of females to the same site will be very small and a stable breeding population can never be established.

It has been observed that some turtles which had laid eggs on beaches in the Spanish Mediterranean and which have been fitted with satellite transmitters have followed a regular pattern and have returned to the area on two different occasions. On the other hand, some of the hatchlings hatched in captivity as part of Head-Starting programmes have been fitted with a microchip or satellite transmitter and released on the beach where their mother laid her eggs. This will allow the identification of any females that come ashore to nest. Recently, a total of 55 hatchlings from the nests at Begur, Malgrat de Mar, El Vendrell and the 5 nests in the Ebro Delta have been included in the Head-Starting programme, as well as hatchlings from the Balearic Islands.

Their return to our beaches will mean that this new nesting site on the Catalan coast is working for them and therefore, We must do everything possible to protect the areas that serve as refuges from climate change. These areas, such as Sa Riera cove, are often subject to heavy human pressure, leaving little room for nature; moreover, the breeding season coincides with the bathing season.. We know that the majority of nests that have failed to establish or have failed are due to human disturbance. Beaches are complex, vital and fragile ecosystems, and it is everyone's responsibility to look after them.

We humans have given this turtle its name (the babaua turtle) because of how easily it is accidentally caught by fishermen in their nets. Perhaps it is indeed true that this animal is completely trusting of everything, but that does not give us the right to disrespect its habitat: we are responsible for fishing catches, for all the plastics they ingest and mistake for food, and for the effects they suffer due to climate change, among others.

Protecting breeding areas, migratory corridors and reducing the causes of mortality resulting from human activities are fundamental to its recovery as a species.. Only in this way can we once again feel the excitement and the profound peace that these incredible animals convey in their natural habitat.

In the following video you can get to know the loggerhead turtle and learn how to identify its tracks. Remember that females usually nest from late May to August, and the hatchlings emerge between July and October. Avoid dazzling them, don't take photos with a flash, keep your distance and don't make noise 🙂

Date of article creation: 12/4/2024.

Header photo: Loggerhead sea turtle or babaua (Careta caretta). CC BY-SA 3.0.

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