Data from: The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behavior of hatchlings

Loggerhead sea turtle hatchlings (Caretta caretta) use regional magnetic
fields as open-ocean navigational markers during trans-oceanic migrations.
Little is known, however, about the ontogeny of this behaviour. As a first
step towards investigating whether the magnetic environment in which
hatchlings develop affects subsequent magnetic orientation behaviour, eggs
deposited by nesting female loggerheads were permitted to develop in situ
either in the natural ambient magnetic field or in a magnetic field
distorted by magnets placed around the nest. In orientation experiments,
hatchlings that developed in the normal ambient field oriented
approximately south when exposed to a field that exists near the northern
coast of Portugal, a direction consistent with their migratory route in
the northeastern Atlantic. By contrast, hatchlings that developed in a
distorted magnetic field had orientation indistinguishable from random
when tested in the same north Portugal field. No differences existed
between the two groups in orientation assays involving responses to
orbital movements of waves or sea-finding, neither of which involves
magnetic field perception. These findings, to our knowledge, demonstrate
for the first time that the magnetic environment present during early
development can influence the magnetic orientation behaviour of a neonatal
migratory animal.