FUXJAGER, M.J.*; MANGIAMELE, L.A.; DAVIDOFF, K.R.B.; LOHMANN, K.J.; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill; University of North Carolina, Chapel Hill: Effects of the Magnetic Environment of Sea Turtle Nests on Magnetic Orientation Behavior in Hatchlings

Magnetic orientation has been documented in numerous animals, yet little is known about the ontogeny of magnetic sensing abilities. We studied whether the magnetic environment in which loggerhead sea turtle (Caretta caretta) hatchlings develop affects their subsequent magnetic orientation behavior. Clutches of eggs deposited by nesting females on the beach were permitted to develop in one of two ambient magnetic fields. Half of the clutches were subjected to an altered magnetic field generated by an array of magnets buried around the eggs. The field at different locations within these nests ranged from approximately 1-7 times Earth-strength. The other half of the clutches were treated identically, but surrounded by an array of non-magnetic aluminum bars so that the eggs developed in the natural ambient magnetic field. Hatchling turtles from both groups were subjected to several behavioral assays designed to assess both their orientation behavior and general health. The results indicated that developing in an altered magnetic field affected the way in which hatchlings responded to a regional magnetic field that exists along their migratory route and is normally used as an open-sea navigational marker. However, turtles that developed in the altered field did not differ from controls in other assays of orientation behavior and health unrelated to magnetic field perception. The findings imply that the magnetic environment in which sea turtles develop affects subsequent magnetic orientation behavior and may also affect their ability to exploit the Earth�s magnetic field as a navigational marker during their trans-Atlantic migration.