July 15, 2008
The beach is empty, but the deserted stretch was obviously
full of activity the night before, as evidenced by turtle crawl tracks
zigzagging from the surf to nest sites in the dunes. A joint research
effort can now tell biologists which turtles made these tracks.
Loggerhead sea turtles are returning to Georgia’s beaches and so are their
offspring and possibly even the next generation of offspring. New research
methods developed by researchers at the Applied Conservation Genetics Lab
at the University of Georgia are allowing the Department of Natural
Resources (DNR) to identify the nesting turtles and their offspring as they
return each year.
The research based on DNA samples taken from the turtles’ eggs will help
determine the population structure and genetic diversity of loggerheads
nesting on the Georgia and Florida coasts.
Genetic diversity is important for adaptation to environmental changes. A
certain amount of diversity is necessary for the health, longevity and even
survival of a species.
“We’re really excited about the possibilities the new genetic markers and
technique have unlocked,” said UGA doctoral student Brian Shamblin. “In
partnership with Georgia DNR and cooperators all along the Georgia coast,
we’re generating nesting data on a scale unimaginable a few years ago.”
Loggerheads, federally listed as threatened, are Georgia’s primary nesting
sea turtle. Research from a DNA pilot study done in 2006 revealed four
instances of mother-daughter pairs nesting on the beaches.
“This is an important development because loggerheads do not become
sexually mature until sometime between 30 and 35 years of age,” said Mark
Dodd, a senior wildlife biologist with the DNR’s Wildlife Resources
Division. “If you have a mother-daughter pair nesting on the coast, then
you know the mom is at least 60-70 years old and has been reproductively
active for 30 years or longer. That is an incredibly long period to be
DNA samples from the nesting turtles are entered into a database at the UGA
genetics laboratory. The genetic research is led by Shamblin, a student in
Dr. Joe Nairn’s lab. The database will help researchers determine
differences in the current population. The research can also provide
details on how long the turtles live, how long they are capable of
reproducing, how many times they nest and where they nest (this “site
fidelity” is important to gauging the health of the reproductive
“For example, if they assume that each female nests four times per season
and in truth the females nest five times, then they have far fewer turtles
than they thought and the population is much smaller than originally
thought,” Dodd said. “These are critical questions to consider when
creating a plan for conservation.”
The DNA from the samples is a genetic fingerprint that identifies
individuals. “We are able to determine parents and offspring and even
‘cousins’ in each turtle family,” Dodd said.
In the past, researchers relied on tags and transmitters to track specific
turtles. But the devices sometimes fail and eventually fall off. DNA
research creates a permanent link, a database in which all nesting turtles
can be compared.
The new methods are also much easier and more reliable. Although night
patrols are still done to collect data, researchers no longer have to catch
a female turtle in the act of nesting. Samples can be taken from every nest
found. One egg from each nest is collected and as long as the egg is
recovered before embryonic contamination, which usually occurs 24 hours
after deposition, the mother and lineage can be determined.
“This project is really exciting for us,” said Nairn, an assistant
professor in UGA’s Warnell School of Forestry and Natural Resources. “The
new genetic techniques and the partnership with Mark Dodd and Georgia DNR
enable us to gather information about Georgia’s loggerhead population that
we could never obtain with traditional approaches.”
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