Loggerhead Sea Turtle Hatchlings Guided To The Sea

Hatchlings can lose up to 20% of their body mass due to evaporation of water as they journey from nest to ocean. They initially use the undertow to push them five to 10 m away from the shore. Once in the ocean, they swim for about 20 hours, bringing them far offshore. An iron compound, magnetite, in their brains allows the turtles to perceive the Earth's magnetic field, for navigation. Many hatchlings use Sargassum in the open ocean as protection until they reach 45 cm (18 in). Hatchling loggerheads live in this pelagic environment until they reach juvenile age, and then they migrate to nearshore waters.
• Maturation
When ocean waters cool, loggerheads must migrate to warmer areas or hibernate to some degree. In the coldest months, they submerge for up to seven hours at a time, emerging for only seven minutes to breathe. Although outdone by freshwater turtles, these are among the longest recorded dives for any air-breathing marine vertebrate. During their seasonal migration, juvenile loggerheads have the ability to use both magnetic and visual cues. When both aids are available, they are used in conjunction; if one aid is not available, the other suffices. The turtles swim at about 1.6 km/h (0.9 kn; 0.4 m/s) during migration.
Like all marine turtles, the loggerhead prepares for reproduction in its foraging area. This takes place several years before the loggerhead migrates to a mating area. Female loggerheads first reproduce at ages 28–33 in Southeastern United States and Australia, and at ages 17–30 in South Africa. Age at first reproduction in the Mediterranean, Oman, Japan, and Brazil are unknown. Nesting loggerheads have a straight carapace length of 70–109 cm (28–43 in). Because of the large range, carapace length is not a reliable indicator of sexual maturity. Their estimated maximum lifespan is 47–67 years in the wild.