they created a database covering 19
years of loggerhead sea turtle nesting
along Florida’s east coast, the largest
sea turtle rookery in North America.
Earth’s magnetic field, which acts as an
invisible shield to protect our planet
from solar radiation, changes over time.
The molten metal surrounding Earth’s
core sloshes around, causing changes
in the magnetic field, with some areas
strengthening and others weakening.
Researchers wanted to determine
if the naturally occurring changes in
Earth’s magnetic field might influence
where the turtles nest. Their studies
provided strong evidence that sea
turtles find their nesting place at least in
part by navigating to unique magnetic
signatures along the coast. Scientists
believe it is possible that tiny magnetic
particles in sea turtles’ brains help them
process these magnetic signatures. If
there is no shift in the magnetic field,
sea turtles return to their birthplace.
If the magnetic field shifts, turtles will
likely respond to that change and may
not return to their exact birthplace.
Kiawah’s Turtle Patrol started in the
1970s. Lynn Sager, the current leader
of the Turtle Patrol, has worked with
the organization for almost 20 years
and is responsible for all Turtle Patrol
volunteers. The dedication of these
volunteers is quite amazing. The official
nesting season runs from May 1 through
WINTER/SPRING 2020 • VOLUME 42
October, and the volunteers show up
every day, rain or shine. The nesting
patrol rides the beach each morning
in the turtle patrol truck, investigating
every crawl from the previous night.
Not every crawl results in a nest, but
each one must be investigated. The
hatching patrol examines each nest for
the next 50 to 60 days, while the turtles
are incubating. Nests have an average
of 100 to 125 eggs.
One of the Turtle Patrol’s
responsibilities is checking the nests for
predators. Some islands and beaches
are predated by coyotes and armadillos.
Fortunately, nest predation is not a
significant issue on Kiawah. Our main
predators are raccoons and ghost
crabs. Screening the top of the nests
prevents the raccoons from reaching the
eggs, but ghost crabs dig deep and are
impossible to stop.
On April 26 of this year, the first
nest in the state was found on Kiawah.
Turtles nest in intervals of 2 to 4
years, laying 3 to 6 nests per season
approximately 2 weeks apart. The eggs
incubate for roughly 60 days. When the
nesting season is over, females return
to their usual feeding sites. Male turtles
never come ashore, and females do not
nest every year.
Turtle Patrol takes one egg from
every nest on the date it is laid. At that
early point, the female’s DNA is on the
outside of the shell. In addition to the
eggshell, the yoke is also examined.
The yolk reveals what the turtle fed on
before the mating season. Through this
investigation researchers can determine
how many nests a female lays in a
season which may be as many as 5. The
nest temperature determines the sex of
the turtles. The warmer part of the nest,
the top layer, becomes female and the
cooler part becomes male. An easy way
to remember this is: hot chicks, cool
dudes.
The website seaturtles.org has a great
deal of information about the status
of sea turtle nests around the world.
It gives the number of nests for each
beach that is documented. The number
of sea turtle nests on the Atlantic coast
from North Carolina to Florida is up
dramatically this year. Several articles
have stated the numbers have increased
because the sea turtle conservation
movement has been active for the
past 30-40 years, and we are only now
reaping its benefits.
But perhaps there’s another
possibility. The year that Hurricane
Hugo struck, there were only 59
turtle nests laid. This year there were
a record number of nests. Wouldn’t it
be interesting if, in addition to their
geomagnetic sensing capability, sea
turtles can also detect the likelihood
of a hurricane strike? NK
47