Thursday, June 30, 2011

Loggerhead Turtles

Loggerhead turtle
via http://upload.wikimedia.org/wikipedia/commons/8/8e/Loggerhead_sea_turtle.jpg


A recent review on movies.nytimes.com of the new film Turtle: The Incredible Journey got me thinking about this endangered species that visits New Jersey waters.

Though the reviewer is critical of special effects enhancements in the film, there's no doubt that the story is compelling.
The journey of the loggerhead turtle is, by any measure, an amazing life voyage, one that here reaches from the beaches of Florida to the eerie calm of the Sargasso Sea and the watery speedway known as the Gulf Stream before heading to Africa and then the call of motherhood. It’s a trip that eats up thousands of miles, takes some two dozen years and is fraught with dangers, though sometimes in the movie that threat may be more imaginary than actual, as when a basking shark, the second largest fish in the world, cruises by with its weird wide mouth open, yawning in water and prey. Armed with little teeth, the basking shark feeds on krill and plankton, but its size and cavernous mouth do make for dramatic viewing.

In 1978, loggerheads were listed as threatened and in 1979 the state of New Jersey classified four marine turtles - the Atlantic hawksbill, loggerhead, ridley and leatherback turtles - as endangered. (Also the Atlantic green turtle as threatened.)

Adult Atlantic loggerhead turtles, Caretta caretta, weigh from 170 pounds (77 kg) to 350 pounds (159 kg) and measure 31 inches (79 cm) to 45 inches (114 cm). The loggerhead sea turtle is omnivorous, feeding mainly on bottom dwelling invertebrates. Its large and powerful jaws serve as an effective tool in dismantling its prey.

The greatest concentration of loggerheads is along the southeastern coast of North America and in the Gulf of Mexico, but they are common throughout the temperate and tropical zones around the globe.

Scientists from the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration proposed last year a reclassification of the loggerhead sea turtle’s designation from “threatened” to the more critical “endangered” category. That tells you that most efforts to protect the species have been ineffective.

The loggerhead sea turtle is found in the Atlantic, Pacific, and Indian oceans as well as the Mediterranean Sea. It spends most of its life in saltwater and estuarine habitats, with females briefly coming ashore to lay eggs.

One problem the loggerhead sea turtle encounters today is that it has a low reproductive rate. Females lay an average of four egg clutches and then become quiescent, producing no eggs for two to three years. The loggerhead reaches sexual maturity within 17–33 years and has a lifespan of 47–67 years.

Untended fishing gear is responsible for many loggerhead deaths. Turtles may also suffocate if they are trapped in fishing trawls. Turtle excluder devices (TEDs) have been implemented in efforts to reduce mortality by providing the turtle an escape route.

Two other problems are the increasing loss of suitable nesting beaches, and the introduction of exotic predators has also taken a toll on loggerhead populations.

It is also more difficult to protect this species because it requires international cooperation since the turtles roam vast areas of ocean and critical nesting beaches are scattered among several countries.

The young loggerheads are threatened by a number of predators and the eggs are especially vulnerable to terrestrial predation.

Once the turtles reach adulthood, their formidable size limits predation to large marine organisms such as sharks.

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