Loggerhead Crisis Brewing?
Surprising Study Results Show More Females Than Males Hatching
in Northern Population
by Scottee Cantrell
Marine biologist Larry
Crowder stands beside a round concrete tub in
the Duke Marine Lab's turtle ranch.
Ten small loggerhead turtles, each splashing in a brightly
colored surplus Easter basket, vigorously flap their front
fins and open their mouths hoping to be fed.
Crowder points to spots of fingernail polish on their shells
that let him know these turtles hatched on a beach in Georgia.
Over the course of this past summer, volunteers caught 500
baby loggerheads for Crowder as the hatchlings emerged from
their nests on four beaches in the Carolinas and Georgia.
They were packed in wet beach sand and quickly transported
by Crowder's research team to the ranch on the Beaufort, N.C.,
campus for one of the largest-scale projects of its kind aimed
at preserving the threatened turtles.
Crowder and Jeanette Wyneken from Florida Atlantic University
(FAU), who studied another 700 turtles that hatched on six
beaches as far south as Miami, are gathering information about
how many males and females are hatching in the northern and
southern loggerhead turtle subpopulations.
Their early results show a surprisingly small percentage
of males among the turtles that Crowder's team collected in
the Carolinas and Georgia, which may have serious implications
for the future of the entire Southeastern population. (The
Florida population alone makes up about a third of the world's
total loggerhead population.)
The researchers expected that the males would dominate in
the north, and instead they found that the "girls"
had the advantage: for every two males there were three females.
"The results we have seen so far are surprising and
even alarming," said Crowder, who is Stephen Toth Professor
of Marine Biology in the Nicholas School.
The project to study the gender ratios began in earnest last
summer (2002) under Crowder's direction at the Duke Marine
Lab, and under Wyneken's direction at FAU in Boca Raton and
the Mote Marine Laboratory in Sarasota, Fla. It is part of
a three-year research study funded mainly by a $350,000 grant
from the U.S. Environmental Protection Agency. This is the
first time so many loggerhead hatchlings have been raised
and studied so intensely.
They began by enlisting volunteer turtle watchers who monitored
the nests along the Atlantic, checked nest temperatures and
alerted the research teams when the 2-inch hatchlings were
getting ready to make a break for the ocean.
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