Loggerhead turtles are quietly nesting on Greek beaches far north of their strongholds

Along the Greek coasts of the Ionian Sea, loggerhead sea turtles have been nesting in places where nobody thought to look for them. A new 40-year analysis, published in the journal Herpetozoa, has compiled 583 sporadic nesting events recorded between 1985 and 2024 — evidence of nesting or attempted nesting outside the systematically monitored rookeries of Zakynthos and Kyparissia Bay. Most of these records came not from professional surveyors but from ordinary citizens who stumbled upon tracks in the sand, an emerging female, or a scatter of exposed eggs, and picked up the phone to report it.

The findings carry particular weight because Greece hosts the largest loggerhead nesting grounds in the Mediterranean. The two Ionian rookeries, Kyparissia Bay and Zakynthos, anchor the species’ breeding in the region, and the conservation organization ARCHELON has monitored them annually for decades with trained volunteers. That long-term effort has underpinned site-specific legal protection and the inclusion of key beaches in European protected-area networks. But monitoring the main rookeries leaves vast stretches of coastline unwatched — and that is precisely where the new dataset fills a gap.

The authors defined a nesting event broadly: a live adult turtle or hatchling on a beach, tracks imprinted in the sand by adults or hatchlings, or eggs or eggshells exposed on the surface. Reports initially flowed in through members and friends of ARCHELON and were kept in paper files. As public awareness grew, citizens began calling the organization’s 24-hour telephone line at its Sea Turtle Rescue Centre in Glyfada, Attica. Since 2024, an electronic reporting platform in Greek and English has streamlined the process, and GPS coordinates increasingly accompany citizen submissions.

Citizens were asked to photograph what they found and, where a clutch might have been laid, to protect the site with improvised materials — usually bamboo sticks and red tape — to prevent trampling. The researchers deliberately discouraged digging into the sand to confirm the presence of eggs, since excavation could disrupt incubation. Where bright artificial lights shone near a possible nest, some residents built makeshift shadings around the site to guard against hatchling disorientation, often with help from the local Coast Guard or municipality. Many of these improvised protections proved effective, producing hatchlings that scrambled successfully to the sea.

After scrutinizing four decades of reports to eliminate duplicates — checking locations and dates, and excluding hatchling sightings that could be attributed to nests registered at the same spot 45 to 60 days earlier — the team arrived at 583 verified events. Some areas concentrated nesting events repeatedly over the years, a pattern the authors say deserves closer examination. All photographed adults and hatchlings were confirmed as loggerheads. Exposed eggs typically resulted from nest predation, primarily by foxes and secondarily by stray dogs and jackals, or from beach erosion.

The geography of the records is where the story becomes scientifically provocative. A comparable study in the Aegean Sea found that nesting above latitude 39°N is rather unusual. Not so in the Ionian. Here, nesting events are not uncommon north of 39°N — beyond the Amvrakikos Gulf — and loggerheads are known to nest even further north in the Adriatic, in Albania and Italy. The discrepancy, the authors suggest, likely reflects the different temperature regimes of the two seas, with the Ionian running warmer than the Aegean.

Several records stand out. In 2024, a remarkable nesting event was documented within Amvrakikos Gulf itself — a well-studied developmental and foraging habitat for loggerheads where breeding had never previously been recorded. Three unusual events were also reported at the eastern end of the Gulf of Corinth. When the researchers binned all citizen reports into five-year periods south and north of 39°N, the diagram showed clearly that northern events have increased in recent years.

Yet the team is careful not to overclaim. An apparent northward spread could partly be an artifact of better reporting: growing public sensitization, social media and messaging platforms that let images circulate instantly, easier transportation and coastal access, and the significant recovery of the Mediterranean loggerhead population in recent decades. All of these factors could inflate records, especially in northern latitudes where nesting was until recently uncommon. Whatever the driver, these nests — despite makeshift protection efforts — remain without formal safeguards, and many may fail to incubate through to hatching.

That vulnerability is sharpened by a bitter irony. The loggerhead nesting season in Greece coincides with the peak tourist season from June to September, and beaches along the Epirus coast and Corfu Island — where sporadic nesting is now relatively frequent — are seeing booming tourism and coastal development. Beach furniture, bright lights, mechanized beach cleaning, and speedboats are well-documented threats to nesting turtles. Loggerheads are known for low nest-site fidelity and can colonize new beaches opportunistically, and the species’ Mediterranean breeding range has already expanded westwards and northwards under global warming. But if turtles pushed north by rising temperatures arrive on heavily developed shores, they may find themselves in what one researcher has described as an ecological trap — nesting on beaches where incubation success is undermined by human pressures.

The authors even raise the possibility that turtles now nesting successfully in the protected areas of Zakynthos and Kyparissia Bay could be driven northwards if warming renders their current sites unsuitable, only to attempt nesting in Epirus and Corfu amid uncontrolled pressures. It took years of sustained effort by NGOs and supranational bodies to establish the existing protected areas, and replicating that achievement elsewhere would be challenging. Still, there is room for action: bottom-up measures implemented voluntarily by coastal enterprises — stacking loungers at night, dimming lights, protecting or relocating laid nests — draw on vast experience from ARCHELON’s long-running programs. The researchers’ prescription is vigilance: beaches with frequently reported sporadic nesting should be surveyed systematically over multiple seasons to assess their true nesting magnitude, because such surveys may reveal the next areas of regular nesting, as has already happened in Calabria and Sicily. It may be a long way before colonizing loggerheads establish new rookeries, but the red dots on the map are multiplying — and someone should be watching.

Subject of Research: Loggerhead sea turtle (Caretta caretta) nesting ecology and conservation in the Ionian Sea, Greece

Article Title: Sporadic nesting events of loggerhead sea turtles Caretta caretta along the Greek coasts of the Ionian Sea

Article References: Margaritoulis, D., Fytilis, D., Manias, N., Panagopoulou, A., Theodorou, P., & Rees, A. F. (2025). Sporadic nesting events of loggerhead sea turtles Caretta caretta along the Greek coasts of the Ionian Sea. Herpetozoa, 38, 225-230. https://doi.org/10.3897/herpetozoa.38.e159978

Image Credits: AI Generated

DOI: 10.3897/herpetozoa.38.e159978

Keywords: loggerhead sea turtle, Caretta caretta, Greece, Ionian Sea, nesting ecology, citizen science, climate change, range expansion, ARCHELON, Mediterranean, conservation, sea turtle nests