A built-in magnetic map
The ability of a loggerhead sea turtle (Caretta caretta) to return to the beach where it was born is an impressive navigation. These turtles possess magnetoreception, a sense that allows them to perceive the Earth's magnetic field. Research indicates they use at least two distinct magnetic senses: a "compass sense" to determine direction and a "map sense" to ascertain their geographic position. This map sense relies on detecting variations in the magnetic field's intensity and inclination angle. Hatchlings are thought to imprint on the unique magnetic signature of their natal beach, creating a permanent reference point. This system is so precise that after migrating thousands of miles, a female can locate the specific stretch of sand where her life began decades earlier. The leading hypothesis for the physical mechanism behind this sense involves crystals of biogenic magnetite within the turtle's body that align with geomagnetic fields.
The beaches of Antalya
Turkey's Mediterranean coast is a important nesting area for loggerhead turtles, hosting roughly one-third of all their nests in the Mediterranean basin. Within the Antalya province, beaches like Belek, Çıralı, and Patara are among the most important nesting grounds. The nesting season runs from May through September. Under the cover of darkness, a female turtle will haul her 250-pound (113 kg) body ashore to dig a nest. She uses her powerful rear flippers to excavate a flask-shaped chamber in the sand, where she deposits a clutch of 100 to 120 soft, leathery eggs. A female may lay three to five nests in a single season, with a two-week interval between each nesting event. Conservation groups in the region, such as the Ecological Research Association (EKAD), monitor thousands of nests annually along dozens of kilometers of coastline.
A temperature-controlled nursery
The fate of the hatchlings is determined by the temperature of the sand during a period of incubation. This phenomenon is known as temperature-dependent sex determination (TSD). Sand temperatures consistently above 31°C (87.8°F) will produce almost all females, while temperatures below 27°C (80.6°F) will yield all males. The temperature, which results in a roughly 1:1 sex ratio, is around 29°C. After incubating for about 60 days, the hatchlings emerge from the nest, a process that usually occurs at night. They orient themselves toward the brightest horizon, which should be the moonlight reflecting off the sea. Artificial lighting from coastal development can disorient them, causing them to wander inland where their chances of survival are minimal.