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In Corsica, a French island located 164 km southeast of mainland France, and 83 km south of mainland Italy, nesting evidence had been reported until the 1950s (Casale et al. 2018; Pascal et al. 2003), but after this period, there were no accounts of nesting or nesting attempts, suggesting that turtles had abandoned Corsica’s beaches for nesting. For the first time in 50 years, a nest was discovered in 2002, on the Palombaggia beach in southeastern Corsica (Fig. 1) where eggshells were found and remaining embryos sampled (Delaugerre & Cesarini 2004). In 2014, one individual turtle was observed twice (recognized by its shell and scale patterns) attempting to climb onto the San Nicolao and Meria beaches in the northeastern part of Corsica on two occasions in July and August (Gerigny et al. 2016). Unfortunately, human disturbances (touching and lights) probably led the turtle to return to the sea and no egg deposition was observed (Fig. 1). In June 2016 in Palombaggia, a night watchman of a beach restaurant took pictures of a female crawling past the beach furniture during the night. In July and August 2016 three events were reported on the western Corsican coast located near Ajaccio (Fig. 1). On 30 July 2016, on the private beach of a hotel (Plage du Maquis - Porticcio), a turtle was observed attempting to climb on the upper beach among the sunbeds (Fig. 2a) and it started digging in the sand, but no nest was found. The beach furniture may have been a disturbance in this instance (RTMMF, unpublished data). The same day on a nearby beach (Pointe Sud - Porticcio), tracks were observed that indicated another female emergence. Eventually, on 16 August further north of Ajaccio on a very short sandy and rocky beach (Capo di Feno), members of the RTMMF observed three tracks (Fig. 2b), that were probably several days old. One of these tracks resulted in a nesting attempt, but it was possibly aborted due to rocks in the nesting substrate (<http://gtmf.mnhn.fr/16-aout-2016-trois-nouvelles-traces-de-montee-en-corse/>). In 2017 and 2018, no marine turtle nesting activity was reported in Corsica.

Figure 1. Locations of egg-laying and hatching events of loggerhead turtles in Corsica (red diamond).

On 18 August 2019 at 8:17 pm, the emergence of a Caretta caretta hatchling (Figs. 3a-b) was reported to the RTMMF by a local resident, in Pinia, close to Ghisonaccia (42.0337 °N, 9.4844 °E) (Fig. 1). The nest was located 3 m above sea level on the upper- beach section that was characterized by a moderate slope at the edge of a littoral pine tree and a juniper forest (Natura 2000 site, <http://inpn.mnhn.fr/collTerr/commune/2B123/tab/natura2000>, code FR9400580). There were tire tracks of an ATV (All Terrain Vehicle) over the nest, representing a potential danger to the nest and hatchlings. Protection of the nest with natural material (driftwood) was implemented to prevent destruction from further ATV use while allowing the emergence of hatchlings. Appropriate surveillance was organized during the following days to keep the nest safe.

Later on 18 August 2019, 23 hatchlings were observed leaving the nest and going to the sea, while 64 hatched egg shells were collected, suggesting that another 41 turtles emerged before the observer arrived. Furthermore, 56 eggs, whose hatching was estimated to be pending, and four unfertilized or non-mature eggs were also counted in the nest (Fig. 3c). The unhatched eggs were left in the nest.

Figure 2. Marine turtle nesting tracks observed on the sand on (A) 30 July 2019 on Plage du Maquis and (B) 16 August 2019 on Capo di Feno beach. Photos by P. Moisson.

Figure 3. (A) Loggerhead turtle hatchling after emergence from the nest and heading toward the sea; (B) hatchling loggerhead turtle tracks observed on the sand on 18 August 2019 on Pinia, an eastern beach of Corsica; (C) dead loggerhead turtle embryo pipped halfway out of its eggshell. Photos by O. Gérigny.

On 19 August, no emergence activity was observed by the guards. However, a hatchling with an unabsorbed yolk sac, which had been observed out of the nest the night before, was found dead near the nest. On 20 August, fragments of eggs were found around the nest, probably due to the action of predators such as foxes or dogs. On 21 August, the nest was observed to have been dug up, probably by a fox according to the prints on the sand, and egg remains were found up to three meters around the nest. Tracks of hatchlings were also observed. On 22 and 23 August, no signs of emergence or predation were observed, and on 24 August, the nest was excavated and inventoried by RTMMF members. They observed that the bottom of the central chamber was positioned 55 cm deep, and 31 eggs (unfertilized or undeveloped) were counted but due to the predator disruption there may have been more than 31 unhatched eggs. Eighty-nine hatched eggs were found, but there may have been some that were consumed by predators. All remaining eggs were sampled for genetic analysis and as odorous print sources for the turtle nest detection program by sniffing dogs, recently launched by Centre d’Etude et de Sauvegarde des Tortues marines de Méditerranée - Center for the Study and Protection of Mediterranean Sea Turtles (CESTMed) and RTMMF, on selected French Mediterranean beaches (Gambaiani & Senegas, pers. comm. 2019). Indeed, dogs can be trained to detect species for conservation purposes (Smith et al. 2001; Hurt & Smith 2009) and appear to be effective in detecting sea turtle nests (Witherington et al. 2017). In 2018, CESTMed and RTMMF carried out a survey using a sniffing dog to find sea turtle nests on two Natura 2000 beaches of the Mediterranean coast of mainland France. Before surveying French beaches, the sniffing dog was trained by the Rogue Detection Teams, thanks to the collaboration of ARCHELON, on nesting beaches of Greece.

On 01 October 2019, there was an observation of a hatchling lost in the littoral vegetation of a western beach in Corsica. Over the last 15 years, the three successful hatched nests confirm that Corsican beaches are still adequate nesting habitats for loggerheads. Furthermore, the single October 2019 hatchling event suggests that nests and emergences may be overlooked. Moreover, no systematic beach monitoring is carried out on Corsican beaches and observations depend on public alerts received on the RTMMF permanent “green line,” which is a hotline for reporting environmental observations.

While sandy beaches are present all around the island, the eastern coast might be more suitable than other areas of Corsica, as it has more documented nesting and topography that features very long sandy beaches. The eastern beaches of Corsica were regularly used for sea turtle nesting until the beginning of the 20th century (Fretey in Pascal et al. 2003). For example, eggs that are currently stored in the collections of the Oceanographic Museum in Monaco, were collected in Cervione, Moriani and Aleria between 1923 and 1932. Moreover, there are records of egg harvesting taking place between 1935 and 1940 in Aleria and Favone (Fretey in Pascal et al. 2003).

Habitat degradation along with the fragmentation of the long sandy eastern shores as a result of anthropogenic development and urbanization might explain the lack of documented nesting events for 50 years in Corsica. The disturbances may also explain the decline of nesting in the Mediterranean until recent times (Casale 2015).

The recent occurrence of nesting events on Corsica may be explained by several factors, such as an increase in loggerhead population size, or environmental changes. The International Union for the Conservation of Nature (IUCN) has changed the conservation status of Caretta caretta from Vulnerable to Least Concern (LC) for the Mediterranean subpopulation. However, the current population status is conservation-dependent and results from decades of intense conservation programs (Casale 2015). The population increase could explain changes in the geographic distribution of nesting females and the recent nesting events in Corsica. Also, the effects of climate change on the phenology and distribution of loggerhead nesting are being investigated in the Mediterranean (Mazaris et al. 2009; Mazaris et al. 2017; Almpanidou et al. 2018). Those studies indicated that the phenological and latitudinal adjustment of nesting to warming conditions could be the most effective short-term adaptation to climate change. However, in the western Mediterranean Sea, oceanic conditions would not favor hatchling survival (Maffucci et al. 2016).

It would be interesting to investigate if climate change (e.g., sand temperatures and moisture levels, sea surface temperatures, beach profiles, etc.) could make the habitat of Corsica more suitable for nesting loggerheads than in past years. For other Mediterranean regions, habitat may become less suitable.

In France, sea turtle species and their habitats are protected by law (Ministerial decree of 14 October 2005). The revised IUCN LC status of Caretta caretta in the Mediterranean includes in its definition that this status remains dependent of maintaining current conservation efforts.

The Caretta caretta nesting and hatching observations in the western Mediterranean summarized here emphasize that conservation measures should not only be maintained at the eastern Mediterranean major nesting sites, but must also be initiated or reinforced in the western basin where rare reproductive activity is reported, for example, in Corsica.

The measures that should be implemented should at least consist of: i) monitoring selected beaches during the nesting and hatching periods; ii) informing the adjacent coastal cities; iii) reducing anthropogenic pressures (e.g., prohibiting ATVs, night-lighting, and removing beach furniture at night on nesting beaches during the nesting/hatching season, etc.); iv) raising public awareness (e.g., through informative signs describing sea turtle tracks and respectful observer behavior (e.g., no flash cameras, touching, or moving turtles, etc.); and v) using predator cages over nests.

Acknowledgements. Thank you to all volunteers for providing the necessary data for writing this note. We are grateful for S. Catteau, C. Filippi, J. Sacchi & J.B. Senegas for their personal communications. Thanks to N. Defrance and T. Limongi for reporting the presence of the nest in Pineto; to Daria Giustiniani and G. Becmeur-Mattei for providing information about the hatchling found on 01 October 2019 in La Maraninca. Thanks to V. Claro Hergueta for her English corrections.

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