Predation of nests by a multitude of terrestrial predators is a major threat to sea turtle populations worldwide. Destruction of eggs decreases hatching success and reduces hatchling recruitment. The 43.5-km beach of Kyparissia Bay in Greece, hosting a large nesting population of loggerhead sea turtles (Caretta caretta), is subject to heavy nest predation by canids. Over 50% of nests were annually depredated in the 1980s and this triggered in 1992 an intensive long-term nest protection program through which the predation rate was reduced to about 13%. Continuous beach monitoring over decades revealed that nest numbers started to increase after 17-20 years from the onset of nest protection and in recent years reached exponential dimensions. Similarly, yearly tagging of nesting turtles showed, in the last decade, a significant increase in the percentage of neophyte turtles, i.e., those considered to be nesting for the first time. We attribute this extraordinary increase of nests largely to the maturing of hatchlings saved due to the intensive nest protection, since the time lag of 17-20 years falls within the boundaries of the maturation time of Mediterranean loggerheads. Our conclusion is further discussed in relation to the evolution of nest numbers at the nearby predator-free Zakynthos rookery that over the same time frame shows no significant increase of nests, although both populations share the same foraging habitats, and exhibit low nesting interchange, similar temperature regimes and female mortalities.

Here we present 38 yrs of nesting data of the loggerhead population in Laganas Bay, Zakynthos, Greece, adding data for 2010-2021 to existing published data for 1984-2009. This rookery, encompassing 6 discrete beaches of 5.5 km total length, features the highest nesting density in the Mediterranean. The annual nest numbers, ranging from 667 to 2018, showed no significant long-term trend. Beach nesting contributions increased on some public-accessed beaches (as did nesting success), but decreased on a remote beach that previously held > 50% of all nests. These changes might be attributed to management actions by the National Marine Park of Zakynthos that improved conditions for sea turtles (e.g., restricting nighttime access to the public), indicating that the previously recorded high nesting density on the remote beach may have been atypical. Although no significant phenological changes were detected with the available data in the 20-yr period 2002-2021, the date of the first hatched nest shifted significantly toward earlier dates in the 38-yr data set. Clutch size and body size of nesting turtles exhibited significantly decreasing trends. Hatching success, hatchling emergence success, and in-nest hatchling mortality showed significantly increasing trends. The number of viable hatchlings decreased over the seasons, albeit not significantly, possibly a result of the decreasing clutch size. Incubation durations were revealed as shortening on all beaches, a potential sign of global warming, with a consequent suggested increase of female primary sex ratio. Continuation of this long-term monitoring program is expected to provide further insights in the reproductive traits of this regionally important loggerhead population.

Following a multi-decadal tagging program at loggerhead nesting areas in Greece, 28 individual turtles have been identified with reproductive longevities greater than 21 yrs, ranging from 22 to 33 yrs. Continuation of this long-term tagging program, along with improvement of tag retention through usage of PIT tags, are expected to increase the herein reported maximum reproductive longevity of loggerhead turtles.

Foraging success affects reproductive output in sea turtles, and is therefore an impor- tant factor to measure in order to understand population dynamics. During 2010 and 2011, we used satellite telemetry to track the at-sea behavior of 20 post-nesting loggerhead turtles Caretta caretta from Rethymno, Crete, Greece. Nineteen transmitters provided location and dive data throughout the turtles' migration towards their foraging grounds and the transition into foraging behavior. We identified 3 foraging regions: (1) 9 turtles migrated southwest towards the North African coast, with 8 concentrated in the region of the Gulf of Gabes, Tunisia; (2) 6 turtles migrated north towards the Aegean Sea; and (3) 4 turtles did not take long-distance migrations, instead remaining resident within the waters of Crete. Two fitness proxies were associated with differ- ences in post-nesting strategies. Turtles foraging in northern waters had significantly larger curved and straight carapace lengths and clutch sizes than turtles foraging near Crete or Africa. Those differences reflect the disparity in benthic prey abundances among the 3 regions. The Aegean had a higher abundance of macrobenthic fauna than the other 2 regions, and the Gulf of Gabes had an increased level of eutrophication. Deterioration of the aquatic resources in the Gulf of Gabes region may be a contributing factor in the observed steady decline in clutch size and total nests per season in 2 critical nesting beaches for loggerheads in Greece.

Much is still to be learned about the spatial ecology of foraging marine turtles, especially for juveniles and adult males which have received comparatively little attention. Additionally, there is a paucity of ecological information on growth rates, size and age at maturity, and sex ratios at different life stages; data vital for successful population modelling. Here, we present results of a long-term (2002–2011) study on the movements, residency, growth and sex ratio of loggerhead turtles ( Caretta caretta ) in Amvrakikos Gulf (39°0′N 21°0′E), Greece, using satellite telemetry ( N = 8) and ongoing capture–mark–recapture (CMR; N = 300 individuals). Individuals encountered at sea ranged from large juvenile to adult (46.2–91.5 cm straight carapace length) and demonstrated growth rates within published norms (<2.7 cm yr −1 ) that slowed with increasing body size. We revealed that an unexpectedly high proportion of animals were male (>44 % of captures above 65 cm straight carapace length), compared to region-wide female-biased hatchling production, indicating sex-biased survival or possible behavioural drivers for likelihood of capture in the region. Satellite tracking confirmed that some turtles establish discrete, protracted periods of residency spanning more than 1 year, whilst others migrated away from the site. These findings are underlined by CMR results with individual capture histories spanning up to 7 years, and only 18 % of individuals being recaptured.