Sound production in sea turtle nests and hatchlings (Eretmochelys imbricata and Caretta caretta) in Northeast Brazil

ABSTRACT

Sea turtles have been considered the least vocal of living reptiles, but recent studies are changing this perception. Here, we aimed to investigate the acoustics of hatchlings of, Eretmochelys imbricata and Caretta caretta in Northeast Brazil, to describe their acoustic signals and compare sound structure within and between species. We monitored 13 km in Ipojuca, southern coast of Pernambuco State. We recorded five nests of each species and the hatchlings’ walk to the sea in 2020/2021. We recorded 12 sonotypes in C. caretta and 5 in E. imbricata, increasing the number of described signals. Nevertheless, not all sonotypes were produced by all or in the different developmental stages. Some of the sounds for both species reached ultrasonic frequencies. The sound structure varied between C. caretta nests, suggesting a potential vocal signature, but the sound structure had no variation between E. imbricata nests. The sound structure varied between species. Despite their reputation for being silent, this study shows a diverse acoustic repertoire in the target species, further supporting speculations of acoustic signals mediating the potential synchronisation of hatchlings’ departure to the sea. Our signal descriptions could be used for future passive acoustic monitoring of the target species. Future studies should focus on understanding the functionality of acoustic signals in the different life stages.

KEYWORDS:

• Vocal signature
• bioacoustics
• incubation
• Testudines
• vocalisation

Acknowledgements

We thank the staff at the NGO Ecoassociados, who provided logistical support for the development of this work. We also thank professors Pedro Murilo Sales Nunes, Ednilza Maranhão dos Santos, Thyara Noely Simões, Artur Campos Dália Maia and Frederico Simão Hintze de Oliveira, for fruitful discussion during the Master dissertation defence and the comments on an earlier version of this manuscript. This study complied with Brazilian law and data collection was conducted under the SISBIO Licence number 75658. SM is supported by a Capes scholarship (Financial code: 001). BMB and the study were supported through FACEPE grants (BFT-01602.04/17; BFT-0014-2.05/20; APQ-1230-2.05/22) and CNPq productive grant (Grant number 309256/2019-4).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data can be made available upon reasonable request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/09524622.2023.2251936.

Additional information

Funding

This work was supported by CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) through a scholarship to SM (Financial code 001), and grants from FACEPE (Fundação de Amparo a Ciência e Tecnologia do Estado de Pernambuco; grant codes: [BFT-01602.04/17; BFT-0014-2.05/20]) and from CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico; Grant number [309256/2019-4]) to BMB.