The loggerhead sea turtle,
Besides monitoring the main rookeries, ARCHELON collects data on sporadic nesting, i.e., nesting events outside the monitored areas. We consider “nesting event” any of the following: (1) live adult sea turtles or hatchlings on the beach, (2) tracks of sea turtles (of adults or hatchlings) imprinted on the sand, or (3) sea turtle eggs or eggshells on the beach. Sporadic nesting events were initially reported by members and friends of ARCHELON, with related data collected in a paper file. Later on, with growing public awareness of sea turtle conservation, citizens started to report nesting events through ARCHELON phone numbers, usually via the 7 d–24 h telephone line at ARCHELON’s Sea Turtle Rescue Centre in Glyfada, Attica. Since 2024, reporting of nesting events has been upgraded through an electronic platform (in Greek and English) on ARCHELON’s website (
In the early years, the location of a nesting event was archived by the beach’s name and the corresponding municipality or the name of a nearby village or town. In some cases, more specific information (e.g., distance from a nearby conspicuous landmark) was provided. In recent years, GPS coordinates started to appear in citizens’ reports, which were augmented with the instigation of the electronic platform in 2024.
Citizens were asked to supply photographs of the nesting event, and in cases where a clutch of eggs may have been laid, they were encouraged to protect the nest site with any available appropriate material—usually bamboo sticks and red tape—to avoid trampling. We did not encourage validation of a possible nest, e.g., by excavating the sand to confirm the existence of eggs, as this could disrupt the clutch’s incubation. Occasionally, in cases of bright light sources close to a possible nest, citizens constructed makeshift shadings around the nest site against hatchling disorientation. Nest protection efforts were usually assisted by the local Coast Guard or municipality.
We scrutinized all collected reports from the 40-year period (1985–2024) to avoid duplication of the same event by checking the exact location, wherever possible, and the date of the event. In addition, we excluded reports of hatchlings or hatchling tracks after 45–60 days from a previously registered nest at the same location. Nesting events reported from regularly monitored areas were not considered.
In the 40-year period, we recorded a total of 583 nesting events along the Greek shores of the Ionian Sea (Fig.
Records of sporadic nesting events along the Greek coasts of the Ionian Sea (darker blue area), collected over 40 years (1985–2024). Records (red dots) are clustered per municipality or by proximity. Dark blue numbers show records per cluster. Green rectangles indicate areas of regular nesting, monitored annually by ARCHELON and other organizations.
Reported records contained all criteria for defining a nesting event, i.e., emergence tracks, live turtles, or exposed eggs (Fig.
Examples of nesting events, photographed by citizens.
Despite the opportunistic nature of data acquisition, we consider that the accumulated nesting events over four decades portray a realistic picture of the spatial distribution of sporadic nestings along the Greek shores of the Ionian Sea.
A similar study in the Aegean Sea revealed that nesting events in latitudes higher than 39°N are rather unusual (
A remarkable nesting event, reported in 2024, was recorded within Amvrakikos Gulf (Fig.
Improvised nest protection (Fig.
Nests protected
Loggerheads are noted for their relatively low nest site fidelity; hence, they may nest opportunistically on beaches other than their natal beach, and if they find suitable conditions, they may colonize new areas (
In an attempt to investigate the temporal distribution of nesting events across latitude, we positioned all citizen reports in 5-year bins south and north of 39°N. Our diagram showed clearly that northern events have increased in recent years (Fig.
Percentage of total reported nesting events north of 39°N, in 5-year bins, over the 40-year study period (1985–2024).
However, we cannot be certain that this represents an actual northward expansion of loggerhead nesting. Reporting of a nesting event is likely also influenced by a combination of increased citizens’ sensitization and increasingly easy communication—such as the promotion of social media and messaging platforms, enabling images to be instantly shared among citizens—which augments the likelihood of records reaching our recording platforms, as well as the increasing ease of human transportation and access to the coast. The fact that the Mediterranean loggerhead turtle population has undergone significant recovery in recent decades (
It is questionable, therefore, whether a hypothesized northward expansion of loggerhead nesting will be successful in Greece, as several beaches identified with relatively high numbers of sporadic nesting are becoming highly touristic. The colonizing loggerheads nesting in the western Mediterranean are already facing such threats, as beaches that traditionally held no turtle nesting and were urbanized or developed for tourism now host nests that are imperiled by anthropogenic influences (
Although it is generally not known whether nesting range expansions are undertaken by new recruits or old nesters, it might be ironic if loggerheads currently nesting successfully in the protected areas of Zakynthos and Kyparissia Bay were driven northwards by increased temperatures—which may render their current nesting sites unsuitable—and attempted to nest in Epirus and Corfu, amid a plethora of uncontrolled pressures. It took many years of unswerving efforts by NGOs and supranational entities to induce governments to establish these protected areas, and it seems challenging to reiterate anew similar efforts for other areas. However, there is room for action if needed—either by encouraging bottom-up measures, implemented voluntarily by coastal enterprises and other stakeholders, or through top-down administrative measures. Such measures would include stacking loungers at night, dimming bright lights, and protecting laid nests either