By Stacey Venzel
While a human giving birth to quintuplets makes headlines, turtles should really be the ones on the cover page. They can lay hundreds of eggs in a nesting season—thousands in a lifetime!
Among species, scientists have determined that turtles lay their eggs in the same time and place but not necessarily returning year after year. The age at which a turtle can start laying eggs also differs between species and even within a species.
Turtles have regionally specific nesting seasons, some stretching for many months, others only a few or in the case of snapping turtles, less than a month. Outliers exist in every given year but scientists have established generalized nesting times for turtles. Loggerheads in the southeastern Atlantic shores of the United States reportedly nest from late May through early August, the majority of the egg laying occurring in June and July. Most North American turtles are spring and summer nesters, but chicken turtles in South Carolina are documented as fall and winter egg-layers. While turtle-nesting parameters are well established, they shift annually by a few days depending on weather conditions, such as rainfall and temperature.
Many species return to the same approximated nesting area for each bout of egg laying. Female diamondback terrapins dig nests in the same dune region throughout their lifetime. Turtles do, however, dig a new nest with every clutch. Female sea turtles even return to lay their eggs on the same beach where they were born!
On top of laying eggs in the same season and place, turtles also nest at a specific time of day. Many species lay eggs under the cloak of darkness for added protection from predators and reduced heat stress. At high tide, there is also less beach to traverse for shoreline nester, and therefore less time and energy to expend. The majority of sea turtles embrace this nighttime egg-laying phenomenon but other aquatic and terrestrial species, like the female three-toed box turtle, nest at night, too.
Some turtles nest in back-to-back years while others skip a year before laying eggs again. Sea turtles commonly wait at least two years before returning to the nesting beach. Green turtles have been known to let five years pass before nesting again.
The number of clutches laid annually changes from species to species. The common snapping turtle has only been recorded laying one clutch per year. On the other hand, sea turtles average three to six clutches a season but have been known to lay up to 12 clutches in a year!
Age of sexual maturity varies greatly among species but small turtles—who generally also have shorter lifespans—typically peak earlier than large turtles. North American wood turtles take 10 years to reach fertility whereas loggerhead sea turtles become viable after 20 to 30 years but mud turtles can reproduce at only six years old.
Variation of sexual maturity occurs even within species. For example, some green sea turtles have been documented nesting at 20 years old while other females record their first nesting at 50 years.
Karen Eckert, David Gulko, Sea Turtles: An Ecological Guide (Honolulu, Mutual Publishing, 2004), 24, 28, 30, 64.
Carl J Franklin, Turtles: An Extraordinary Natural History 245 Million Years in the Making (St. Paul, Voyageur Press, 2007), 33.
Whit Gibbons, Judy Greene, Turtle: The Animal Answer Guide (Baltimore, The John Hopkins University Press, 2009), 63-66, 74.