Many animals make very long migrations to feed and breed. In episode 8 of The Blue Planet: A Natural History of the Oceans season 1, Attenborough describes the migratory movements of green sea turtle females. Each year up to 5,000 female green sea turtles that live off the coast of Brazil swim a long journey of over 2,200 kilometers to their traditional breeding site of Ascension Island in order to nest . The adult females return to their breeding sites every few years . While Attenborough mentions that how the turtles find the island is still a mystery, there has been research done to determine how they find their way back each year. Studies have been done that show that the turtles may take advantage of the earth’s magnetic fields to guide them in traveling these long distances at night . The turtles may also use the ocean currents and chemical cues to navigate their way to the island . Migration and the use of navigational cues is not just unique to sea turtles. For example, salmon also migrate to the same tributaries where they were hatched. They use odors or chemical cues to navigate back to their laying grounds. These olfactory cues are determined by the environment, such as the soil of the water they were born, and are part of their associative memory, allowing them to return to the same point of origin where they hatched two to three years earlier . The migratory abilities of these animals are truly phenomenal.
by Logan Schwartz and Garrett Halstein
The Blue Planet: A Natural History of the Oceans, Season 1, Episode 8, Coasts, starting at approximately 7:03
- Hasler A, Scholz A & RM Horrall. 1978. Olfactory imprinting and homing in salmon: recent experiments in which salmon have been artificially imprinted to a synthetic chemical verify the olfactory hypothesis for salmon homing. American Scientist 66: 347-355.
- Hays G, Åkesson S, Broderick A, Glen F, Godley B, Papi F & P Luschi. 2003. Island-finding ability of marine turtles. Proceedings of the Royal Society of London B: Biological Sciences 270: 5-7.
- Hays G & R Scott. 2013. Global patterns for upper ceilings on migration distance in sea turtles and comparisons with fish, birds and mammals. Functional Ecology 27: 748–756.
- Lohmann K & C Lohmann. 1996. Detection of magnetic field intensity by sea turtles. Nature: 380: 59-61.
- Luschi P, Hays G & F Papi. 2003. A review of long-distance movements by marine turtles, and the possible role of ocean currents. Oikos 103: 293–302.