Ecological Trap or Favorable Habitat? First Evidence That Immature Sea Turtles May Survive at Their Range-Limits in the North-East Atlantic

Abstract

Unusual environmental events can push marine animals outside their physiological tolerances through changes in trophic and/or thermal conditions. Such events typically increase the risk of stranding. Rescue Centers offer a unique opportunity to report animals in distress and satellite track rehabilitated individuals to identify potential new habitats and support an effective conservation of these endangered species. By combining sightings (1988–2020) and tracking data (2008–2020) collected along the French Atlantic and English Channel coasts, our study assessed if the Bay of Biscay is an ecological trap or a favorable habitat for immature sea turtles. The largest tracked individuals migrated westward to pelagic waters, likely toward their natal beaches, while smaller individuals remained within the Bay of Biscay (BoB) and crossed colder (mean: 17.8 ± 3.0°C) but more productive waters. The turtles’ directions differed from the ones of ocean currents, excluding a passive advection to these unexpected habitats. Although the BoB might be thermally unsuitable in winter, the higher micronekton biomass predicted in this region could offer a productive foraging habitat for immature turtles. However, the majority of the sightings referred to individuals stranded alive (75%), suggesting this area could also act as an ecological trap for the smallest individuals that are mostly reported in winter suffering cold-stunning. Assumed to be outside the species range, our results reveal a potential foraging ground in the North-East Atlantic for these young turtles, confirming the crucial role of the rehabilitation centers and the need to continue prioritizing conservation of these endangered species, particularly vulnerable at this stage and at such temperate latitudes.

Loggerhead turtle oceanic-neritic habitat shift reveals key foraging areas in the Western Indian Ocean

“…Oceanographic data from the GLORYS12 global ocean reanalysis (Lellouche et al, 2021) and the Low and Mid-Trophic Levels (LMTL) predictions (Lehodey et al, 2010;Lehodey et al, 2015) that use components of the SEAPODYM dynamical population model (Lehodey et al, 2008) were extracted at interpolated turtle locations (Table 1). Considered variables, chosen for their potential relevance in the behavioral ecology of loggerhead turtles (e.g., Frick et al, 2009;Vandeperre et al, 2019;Chambault et al, 2021b), include the velocity of surface currents, sea surface temperature, net primary production and micronekton biomass. Taking the vertical diel migration of mesopelagic micronekton into account, the total biomass of micronekton potentially available in the epipelagic zone, mnkc tot , was estimated from the following formula:…”