Loggerhead sea turtles (Caretta caretta) nest globally on sandy beaches, with hatchlings dispersing into the open ocean. Where these juveniles go and what habitat they rely on remains a critical research question for informing conservation priorities. Here a high-resolution Earth system model is used to determine the biophysical geography of favourable ocean habitat for loggerhead sea turtles globally during their first year of life on the basis of ocean current transport, thermal constraints and food availability (defined here as the summed lower trophic level carbon biomass). Dispersal is simulated from eight major nesting sites distributed across the globe in four representative years using particle tracking. Dispersal densities are identified for all turtles, and for the top 15% ‘best-fed’ turtles that have not encountered metabolically unfavourable temperatures. We find that, globally, rookeries are positioned to disperse to regions where the lower trophic biomass is greatest within loggerheads' thermal range. Six out of the eight nesting sites are associated with strong coastal boundary currents that rapidly transport hatchlings to subtropical–subpolar gyre boundaries; narrow spatial migratory corridors exist for ‘best-fed’ turtles associated with these sites. Two other rookeries are located in exceptionally high-biomass tropical regions fuelled by natural iron fertilization. ‘Best-fed’ turtles tend to be associated with lower temperatures, highlighting the inverse relationship between temperature and lower trophic biomass. The annual mean isotherms between 20°C and the thermal tolerance of juvenile loggerheads are a rough proxy for favourable habitat for loggerheads from rookeries associated with boundary currents. Our results can be used to constrain regions for conservation efforts for each subpopulation, and better identify foraging habitat for this critical early life stage.

红海龟 ( Caretta caretta) 全球在沙滩上筑巢，幼体分散到开阔的海洋中。这些青少年去哪里以及它们依赖什么栖息地仍然是告知保护优先事项的关键研究问题。在这里，高分辨率地球系统模型用于根据洋流运输、热限制和食物供应（此处定义为总和较低的营养级碳生物量）。使用粒子跟踪模拟了四个代表性年份分布在全球的八个主要筑巢地点的扩散。确定了所有海龟的扩散密度，以及没有遇到代谢不利温度的前 15% 的“最佳喂养”海龟。我们发现，在全球范围内，栖息地分布在低营养生物量最大的区域，这些区域在赤蠵的温度范围内。八个筑巢地点中有六个与强大的沿海边界洋流有关，这些洋流将幼龟迅速运送到亚热带-亚极地环流边界；与这些地点相关的“最佳喂养”海龟存在狭窄的空间迁徙走廊。另外两个栖息地位于以天然铁施肥为燃料的生物量异常高的热带地区。“吃得最好”的海龟往往与较低的温度有关，突出了温度与较低营养生物量之间的反比关系。年平均等温线介于 20°C 和幼年赤蠵的耐热性之间，可以粗略地代表与边界流相关的巢穴中的蠼螈有利栖息地。我们的结果可用于限制每个亚种群的保护工作区域，并更好地确定这一关键早期生命阶段的觅食栖息地。