Reproduction and Life History

            Loggerhead sea turtles migrate to warmer water for mating grounds and to lay their eggs (Drakes, 2012).  For example, in the United States, nesting season usually happens in June and July, but ranges from April through September (U.S. Fish and Wildlife Service, 2013). Before loggerheads migrate to a nesting beach they store energy and nutrients for the breeding season (Tiwari and Bjorndal, 2000).  Rarely will you see a loggerhead leave the water, except to lay eggs (MarineBio, 2014). Loggerheads usually reach sexual maturity at age 17 to 33 years or when they reach 90 cm, but it varies in each habitat (MarineBio, 2014; Drakes, 2012).
    Once a male loggerhead finds a mate he will circle her before potential courtship (Drakes, 2012; Duermit, 2007).  The male loggerhead will then bite her neck or shoulder (Duermit, 2007). Using his claws, the male loggerhead grabs onto the female to maintain grip. He also maintains his grip by putting his head on the females shell. Next, the male curls his tail under the female to bring their cloaca’s (reproductive opening) closer together (Duermit, 2007; Drakes, 2012). The male needs to maintain grip because mating may last for hours and other males may try to remove him from the female. A female can reject the male however. If the female does reject the male loggerhead she will close her cloaca and swim to the bottom of the water (Duermit, 2007).
    After mating, females return to the beach they were born on for 12 to 17 days to lay their eggs (Drakes, 2012; Duermit, 2007).  The female could lay multiple clutches and between each clutch a female will re-mate once or several times. If a female mates multiple times between a clutch it could be produced by more than one male (Drakes, 2012; Duermit, 2007). Loggerheads are known for nesting one to seven times during a nesting season every 2 or 3 years. Nesting can take up to three hours (U.S. Fish and Wildlife Service, 2013; MarineBio, 2014).  The nesting size must be a certain size to protect the eggs from predators and so the hatchlings can safely make it to the water (Drakes, 2012).
    The female cLoggerhead Sea Turtle laying eggsreates the nest by digging out a hole with her hind legs and then laying her eggs (MarineBio, 2014; Drakes, 2012).  A female loggerhead typically lays 50 to 200 eggs. After the eggs are laid, the female erases any sign of a nest by covering the eggs with sand with her plastron (bottom part of the shell) (MarineBio, 2014). Watch the video of a female loggerhead covering her nest below! Incubation of the eggs is usually around two months (42 to 75 days) (NOAA, 2013; U.S. Fish and Wildlife Service, 2013). The sex and characteristics of the hatchling are affected by environmental variables such as temperature of the sand they were laid in (Warner et al., 2010; Drakes, 2012). High temperatures create females and cooler temperatures form males (Drakes, 2012).  If you want to learn more about the life history of a loggerhead and their habitats click here. ARKive video - Female loggerhead turtle buries eggs and returns to the ocean
    Not only does the location of the nesting beach affect the temperature of incubation, but it also affects length of the nesting season and egg development (Tiwari and Bjorndal, 2000).  Developing embryos, their developing rate and timing of hatching, are affected by maternal and environmental factors.  Many factors create variation in the embryo and its survival (Warner et al., 2010). Factors like the turtle’s biology, predation, and environmental factors like climate. The female loggerheads try to lay their nests in a safe and suitable home, but sometimes these factors happen outside the control of the female turtle since they do not care for their young (Warner et al., 2010).
    An example of how egg development is impacted by the location of the nesting beach is shown between Greek turtles (Mediterranean population), Florida turtles (temperate population), and Brazil turtles (tropical population) (Tiwari and Bjorndal, 2000). According to Tiwari and Bjorndal, Greek loggerhead turtles produce the largest clutches compared to body size; however, Greek turtles produced the smallest eggs (2000). The Florida population produced the largest eggs (Tiwari and Bjorndal, 2000). Egg size can be used to see how much investment was put in by the female turtle to make her offspring. A turtle’s size can be predicted by the size of the egg. The bigger the hatchling is, the higher the offspring’s fitness or survival (Warner et al., 2010). Warner et al., found that a female loggerhead’s investment in the yolk of the eggs influences egg survival (2010).
    Location of nesting also affects the quality and availability of food a loggerhead has access to. The energy a turtle puts into egg production depends on the food and the energy used in migration and reproduction (Tiwari and Bjorndal, 2000). This may be why Greek, Florida, and Brazil turtles have different egg development. Size of the turtle also can determine how much energy is put into egg production. The larger the turtle, the more energy the turtle puts into egg production (Tiwari and Bjorndal, 2000).  Nest dimensions were also different between the three populations.  An example is the nest dimensions between Florida and Greece were similar and only was the width of the nest between Florida and Brazil was similar (Tiwari and Bjorndal, 2000).
    The nesting season is also affected by the location of the nesting beach. For example, nesting season is shorter at higher latitudes and longer at lower latitudes according to Tiwari and Bjorndal, (2000).  A shorting nesting season would restrict the number of clutches made, but would lead to a larger clutch size to make up for the shorter nesting season (Tiwari and Bjorndal, 2000). Limited resources and an uncontrolled environment limit the amount of eggs a turtle can produce. Differences among populations show that each population of loggerheads experience and react to different factors (Tiwari and Bjorndal, 2000).