Beach rebuilding may aid survival of sea turtles
Published: Thursday, January 11, 2007 at 6:01 a.m.
Last Modified: Thursday, January 11, 2007 at 12:00 a.m.
FORT LAUDERDALE — Researchers at Florida Atlantic University have found that beach nourishment projects may aid the survival of endangered sea turtles by increasing the distance between the reptiles' nests and a major predator, the fire ant, researchers at Florida Atlantic University have found.
Stinging fire ants are common on many South Florida beaches, and are known for attacking and killing hatchling reptiles and birds.
"People have a hard time believing that ants have an impact on wildlife," said James K. Wetterer, an FAU ecology professor and the study's chief author.
"They are a big problem on the beach."
The findings are significant in part because beach renourishment projects often prove to be detrimental to the success of sea turtle nesting.
Sand dredged from offshore is often dark in color, and becomes more compacted on the beach than natural sand, Wetterer said. Dark sand can contribute to higher temperatures that affect hatching, and compacted sand makes digging difficult for the nesting turtle.
Beach renourishment also can create escarpments that prevent sea turtles from getting onto the beach.
But ants are also troublesome, according to Larry Wood, curator of the Loggerhead Marine Life Center, in Juno Beach, and wider beaches may lessen the danger.
A single sting to a hatchling can be fatal, he said.
"The study suggests we still have to look at the bigger picture," said Wood, a study co-author. "We first have to learn how to renourish beaches in ways that allow turtles to get onto the beach in the first place."
Escarpments, or steep banks, can be leveled or angled so that turtles can get to nesting spots.
Female sea turtles come ashore in May through October to dig a nest to deposit dozens of eggs. Loggerheads travel an average distance of 50 feet from the surf to nest, Wood said.
After covering the eggs with sand, the turtle returns to the sea.
The eggs normally hatch after 50 to 60 days.
In addition to ants, common hatchling predators include ghost crabs on land and tarpon in the ocean, researcher have found.
The FAU study, conducted in the summers of 2000 and 2001, focused on a 6-mile stretch of Atlantic Ocean beach between Jupiter and Juno Beach that is considered an important nesting site for endangered green and leatherback turtles, and loggerhead turtles, which are listed as threatened under the Endangered Species Act.
In between those summers, the beach was replenished with offshore sand, increasing the average width of the beach by about 40 feet.
That change allowed Wetterer and his team to evaluate the influence of beach width on the incidence of ants on sea turtle nests.
The survey looked at 909 turtle nests in the summer of 2000, and 639 nests the following year to conclude that "sea turtle nests closer to the dune vegetation were much more likely to have ants present."
"This is because most ant species do not nest on open beaches," the researchers wrote. "Instead, they nest in adjacent vegetated areas and make forays out into the beach in search of food."
The study has been submitted to the Journal of Applied Ecology.
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