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 Four
species of endangered or threatened sea turtles crawl ashore and nest
on the Gulf beaches at Gulf Islands National Seashore. Loggerhead and
green sea turtles are the most frequent nesters. In 1998 the first Kemp's
Ridley nest was documented in the park, and in 200 the first leatherback
nest was documented in the park. For most of the summer the Seashore's
biologists plus 25 volunteers locate sea turtle nests in over 21 miles
of beaches in the Florida District. Covering these distances requires
early morning ATV patrols and legwork to search for turtle crawls. Nests
are marked, dated, and watched. About 60 days later, tiny turtles burst
from the sand and struggle toward the glowing horizon. Too often, the
brightest glow comes from artificial lights.
Hatchling
Disorientation
Light pollution from developed areas causes hatchlings to crawl in the
wrong direction at night. Hatchlings are drawn to the brightest horizon,
which historically was the moonlit waters of the Gulf of Mexico to the
south, but is not the artificially lit urban area to the north. Disoriented
hatchlings that crawl northward away from the water typically fall prey
to ghost crabs, foxes or other predators; die from desiccation in the
sand dunes; or are hit by passing cars. To help save disoriented hatchlings,
volunteers and staff watch nests closely during hatch time, intervening
and moving disoriented hatchlings closer to the Gulf of Mexico where they
can crawl into the surf and swim seaward.
Nest
Relocation
Hurricanes Erin and Opal (1994), Danny (1997), Earl and Georges (1998)
altered parts of the beach and primary dune line so that some nest are
vulnerable to flooding in high tide cycles that occur during strong southerly
winds. If the nest floods during a high tide, the eggs drown. To mitigate
this situation, biologists relocate approximately 25% of the nests each
year to higher ground. Relocation involves placing the eggs on a layer
of sand in a cooler one by one, taking care not to roll the eggs. A new
nest cavity similar to the original nest cavity is dug on higher ground,
usually just to the north of the original site. The eggs are placed in
the new nest cavity so that the original bottom eggs are on the bottom
and the original top eggs are on the top. The nest is covered with sand
and packed in to simulate the original nest cavity. Relocated nests have
about a 70% hatch rate, considerably higher than the rate for nests left
in their original sites (due mostly to mortality from flooding and hurricanes).
For up-to-date
information on turtle nesting in the park and adjacent areas in Escambia
and Santa Rosa counties, go to http://escambia.ifas.ufl.edu/marine/seaturtles.htm.
Recent
Scientific Studies in the Park
For four years temperatures of loggerhead nests were recorded using small
temperature data loggers placed in and adjacent to the egg chamber. Incubation
temperatures determine the sex of the turtle hatchlings. This study provided
data on percentages of each sex produced in park nests, information critical
to the survival of this threatened species. A thorough understanding of
the male to female ratio of the Gulf coast population of loggerheads is
needed to avoid a possible future shortage of females. This study was
conducted in part with the Universities of West Florida and Florida. In
a 3-year post-nesting migration study, the park tagged several turtles
in the Florida District and tracked them by satellite. Five female loggerhead
and one green sea turtle were outfitted with satellite transmitters after
nesting in the park. When the swimming sea turtle breaks the surface,
the transmitter sends a signal, which is picked up by satellite. The transmitter
operates for about 12-18 months until the battery fails. All the tracked
sea turtles stayed within the confines of the Gulf of Mexico. Two turtles
traveled as far as the Marquesas Islands, but one turtle only migrated
a few miles from its nesting beach.
Turtle
Strandings:
Each
year several adult and sub-adult turtles are found dead in the park and
surrounding waters. These turtles are examined for possible causes of
death. Species, size and sex are also recorded. Mortalities in the past
have occurred from fishing hooks and line, boat hits, natural causes and
drowning caused by entrapment in fishing nets.
Please remember
all sea turtles are fully protected under federal and state laws. Do not
disturb sea turtles or their nests. Report all information concerning
sea turtles to park rangers, or call 850-934-2600.
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