Lights down low, or off, for nesting sea turtles

Loggerhead turtles are the most frequently observed turtles in Florida waters, with more than 90 percent of the nesting activity in the world occurring on Florida’s beaches.

Now is the time for boaters to navigate carefully off of the coastline and keep an eye out for the mating loggerhead sea turtles. Nesting season begins on May 1, with courtship activity occurring several weeks before the actual nesting season. Females nest a few weeks after mating.

Nesting on Marco Island usually occurs between May and August, with hatchlings emerging through Oct. 31.

Loggerhead nesting occurs on sandy beaches above the high-tide line. Most females return to the same nesting beach each year.

The female crawls ashore at night, digs a shallow pit and then, using her hind flippers, makes a nest cavity, called a clutch, where she deposits the 100 ping pong ball-shaped eggs. The depth of the cavity is determined by the length of the stretched hind flipper.

The eggs are white, soft and round, measuring about 1¾ inches. The eggs are surrounded by a thick, clear mucus covering. Once the eggs are deposited, the rear flippers fill and cover the nest with sand and the turtle returns to the sea.

Females may nest every two to three years, resulting in one to seven nests per season. The female can storage sperm from one or more males in the oviducts without additional mating needed to fertilize her eggs.

Sometimes a turtle may arrive and for many reasons return to the sea without digging a clutch. This is commonly known as a false crawl.

On Marco Island, this is normal, with about 50 percent of the turtles visiting the beach before actually laying a nest.

The incubation time varies with species, clutch size, and temperature and humidity in the nest.

Recent research indicates the sex of the egg is determined as the embryo develops, and may be temperature dependent. Lower nest temperatures produce more males; higher temperatures produce more females.

Between 45 to 75 days after the mother lays her nest, the dull-brown hatchlings erupt. Their average size at hatching is 45 mm long; average weight is 20g.

Hatchlings use the moon’s reflection on the water to navigate to the water’s edge. Therefore beach lighting can cause confusion for hatchlings if not addressed in coastal communities.

Although eliminating beach lighting would be the most effective way to reduce disorientation of hatchlings, studies have shown that low pressure sodium vapor lights have a lesser effect on loggerhead and green sea turtle hatchlings. Many beach communities like Marco Island have encouraged the use of these lights.

When a hatchling reaches the surf, it dives into a wave and rides the undertow out to sea. The small hatchlings begin a true test of survival with a “swim frenzy” of continuous swimming for 24 to 48 hours after they enter the water. This frantic activity gets the young turtle into deeper water, where it is less vulnerable to predators.

Loggerhead turtles are essentially carnivores, feeding primarily on crabs, horseshoe crabs, shrimp, jellyfish and a variety of mollusks. The strong beak-like jaws are adapted for crushing thick-shelled mollusks. Although loggerhead sea turtles are primarily bottom feeders, they also eat sea jellies obtained while swimming and resting near the sea surface.

Loggerhead turtles are one of the largest of the hard-shell turtles, with adults measuring 36 to 38 inches in length, and a weight range of 200 to 350 pounds. The upper shell is widest near the front, just behind the front flippers, then tapers toward the rear. The shell is colored reddish-brown with some yellow markings, with the underneath a creamy yellow color.

The limbs are paddle-shaped and each bears two claws. The adult male has a long tail. The tail of the female is short.

As loggerheads mature, they travel and forage through near shore waters until the breeding season, when they return to the nesting beach areas. Maturity is reached at between 16-40 years. The majority of mature loggerheads appear to nest on a two- or three-year cycle. Therefore protection efforts are important.

Any lights visible to the beach after 9 p.m. should be turned off, shielded, or otherwise modified between the dates of May1 through Oct. 31.

To ensure compliance, property managers, beach vendors, and/or residents, please step out on the beach at 9 p.m., view the building or vendor area to determine what lights need shading or turned off.

If you can see your shadow on the beach, the light is too bright!

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Nancy Richie is Environmental Specialist for the city of Marco Island.

© 2007 All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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