Vol. 64, 2025

Exponential Increase in a Loggerhead Sea Turtle Nesting Population: Investigating the Role of Multi-decadal Nest Protection in Kyparissia Bay, Greece

Dimitris Margaritoulis^1,*, ALan F. Rees¹, and Thomas E. Riggall¹

¹ARCHELON, the Sea Turtle Protection Society of Greece, Solonos 113, GR-10678 Athens, Greece. *Correspondence: E-mail: margaritoulis@archelon.gr (Margaritoulis)
E-mail: alanfrees@gmail.com (Rees); tomriggall@gmail.com (Riggall)

(Received 3 March 2025 / Accepted 15 May 2025 / Published -- 2025)
Communicated by Chien-Hsiang Lin

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.

Keywords: Caretta caretta, Conservation, Population trend, Predation, Monitoring

Citation: Margaritoulis D, Rees AF, Riggall TE. 2025. Exponential increase in a loggerhead sea turtle nesting population: Investigating the role of multi-decadal nest protection in Kyparissia Bay, Greece. Zool Stud 64:29.

Supplementary materials: Table S1