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 c
reates
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. 
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).
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