Sea turtle hatchlings can distinguish between coastal and oceanic seawaters

Abstract

Following their emergence on land, sea turtle hatchlings need to travel through the open ocean. Whether hatchlings can detect ecologically and functionally relevant chemical cues released in the marine habitat is unknown. We collected seawater at 6 and 27 km off the Brazilian coast, i.e. within and beyond the continental shelf. In a two-choice flume, we exposed post-emergent (<24 h old) loggerhead (Caretta caretta) turtles to these seawaters. Based on their life history, we posited that if hatchlings could distinguish between the seawater from these regions, they should prefer the oceanic seawater and/or avoid the coastal seawater. Hatchlings were tested singly and could access any parts of the flume. We recorded the seawater plume first visited and the time spent in each plume. Of all the first choices and time spent in a plume, nearly 70% involved the oceanic seawater. The ability of hatchlings to distinguish between seawaters could provide goal-recognition information.

Habitat use and distribution of the loggerhead sea turtle (Caretta caretta) in the Mediterranean Sea: Implications for marine planning strategies

“…Furthermore, it remains mostly unknown which environmental factors may influence small turtles in reaching their developmental areas after hatching. Previous studies tried do shed some light on these topics (i.e., Soeiro et al 2022); however, survival estimates, post-hatchling dispersal, high-density areas and habitat suitability for small oceanic juveniles have essentially relied on numerical simulations of particle distribution (Hays et al 2010, Casale and Mariani 2014, Maffucci et al 2016, Cardona and Hays 2018.…”