Ontogeny

Sea Turtles

Hatchling logger head sea turtles begin life in the darkness of their nest.  Once they emerge from the nest of sand they must find their way across the dangerous beach and into the deep ocean water.  Many studies in the 1990s have sought to answer the question of how sea turtles manage to cope with all of the obstacles that stand in the way between the nest and the safety of the North Atlantic Gyre.  Early studies indicated that sea turtles are in fact able to use magnetic orientation, however, later studies indicated that hatchlings often do not rely on their magnetic senses except as a last resort.  Instead, it was found that hatchlings are able to use light from the moon, beach slope, and wave direction as more immediate ways of navigating from the beach to the deep ocean.  There is little evidence that suggests why these turtles make this ontogenetic switch in navigation systems, though it has been suggested that hatchling sea turtles can use these other environmental cues in order to "set" their magnetic compass and develop their map sense [3,17].
Proposed schematic of the navigational transitions that hatchling
loggerhead sea turtles experience [3, 18]