Evaluation of Putative Hybrid Hatchlings between Hawksbill Sea Turtle (Eretmochelys imbricata) and Green Sea Turtle (Chelonia mydas) in Tortuguero, Costa Rica

Abstract. Although hybridization processes in the Cheloniidae family have been documented since the 19th century, detailed reports of these occurrences are scarce. Therefore, the record of a hybridization between Green Sea Turtles (Chelonia mydas) and Hawksbill Sea Turtles (Eretmochelys imbricata) signifies an important event. In this study, we report the third known record of hybridization between C. mydas and E. imbricata in the Caribbean Sea. In Tortuguero, Costa Rica, we marked and monitored several nests from both species during the 2020 nesting season. Offspring from two E. imbricata clutches showed morphological characteristics corresponding to both species. We compared 20 individuals from each of these nests to large groups of pure C. mydas and E. imbricata individuals. We measured carapace length and mass of each hatchling and documented other morphological properties such as scale patterns on the head to better identify the species. Because these hatchlings presented different combinations of representative characteristics of each species, we concluded that they are hybrid individuals. Our findings provide a new record of a C. mydas · E. imbricata hybridization event.