By Stacey Venzel
Snowbirds—Ohioans and avians—head south to Florida for the winter. Turtles have their own migratory patterns, too, but it is not always to warmer weather.
Variables affecting turtle migration include environmental suitability, age and size, nesting patterns and food behavior. Turtles have proven that they are capable of covering transoceanic distances in just one year.
Weather and habitat conditions can cause a turtle to relocate from one region to another. For example, during the summer, water sources can dry up and turtles can overheat. Red-eared sliders and common snapping turtles have scurried more than a mile toward more reliable water sources. To beat the heat, individuals can enter into a summer hibernation state called aestivation. The desert box turtle has been found in Arizona traveling to pastures in search of fresh cow dung, where the moisture helps it stay cool.
SIZE AND AGE MIGRATION
Size and age play a role in migratory routes among turtles, sometimes relative to feeding patterns, such as the green sea turtle’s preference for a carnivorous diet at a young stage but shift to herbivorous foraging in seagrass beds as an adult.
Much was not known about the early hatchling and juvenile stages of sea turtles until scientists recently discovered why these marine reptiles seemingly disappear for up to a decade. When sea turtle hatchlings make their way out to sea, they frantically swim miles out to regional ocean gyres. These currents are filled with camouflaging algae and pelagic food that hides and feeds the tiny turtle until it is large enough to avoid predators. Documented cases of these “lost years” in loggerheads show the babies head to a floating bed of Sargassum seaweed in an ocean current now dubbed the “Sargasso Sea.”
Female aquatic turtles that nest on land migrate anywhere from yards to miles by sea and terrain to lay their eggs. Loggerhead females are expert migrators, with one population documented swimming more than 7,500 miles from feeding zones off of Mexico to their nesting beaches in Japan. They make this initial trek as hatchlings, which can take up to six years.
Ever the food-motivated individuals, some turtles head to cooler waters instead of warmer ones. The leatherback sea turtle migrates as far as subarctic waters in pursuit of its prey. In these cold water zones, the jellyfish are much bigger, meaning less work is required for the leatherback to meet its monstrous daily dietary quota!
Sea turtles are master migrators moving between oceans halfway across the world, but once again, the leatherback sets the record. Satellite trackers have followed the turtles over 10,000 miles in a year, with the record holder traveling a distance of 12,774 miles. Marine biologists project one leatherback can cover hundreds of thousands of miles in a lifetime, essentially capable of circling the planet some 50 times!
Karen Eckert, David Gulko, Sea Turtles: An Ecological Guide (Honolulu, Mutual Publishing, 2004), 27, 29, 41, 75.
Carl J Franklin, Turtles: An Extraordinary Natural History 245 Million Years in the Making (St. Paul, Voyageur Press, 2007), 43-44.
Whit Gibbons, Judy Greene, Turtle: The Animal Answer Guide (Baltimore, The John Hopkins University Press, 2009), 42-43.