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Nail varnish helps solve ancient mystery

A chance brainwave allows scientists to chart the intriguing peregrinations of the giant marine turtle, writes PETER FROST

Marine turtle sightings are rare in British waters but last month's severe storms washed a live juvenile loggerhead turtle ashore in Pembrokeshire.

Just under seven inches (17cm) long, "Stormy" as the turtle has been named is thought to be about three-years-old. He is now recovering at Bristol Aquarium being tube fed and treated with antibiotics.

Last August a four foot long adult loggerhead turtle (right) was spotted off Portland Bill, Dorset. It may have been lured here by unusually warm sea temperatures and a particularly good crop of jellyfish.

Visits to British waters from loggerheads are incredibly rare, with the last previous reported sighting off Dorset in 1938. Sightings are slightly more frequent off the west coast of Ireland.

In 2012 there were 45 sightings in Britain of the more common leatherback turtles, which can grow as large and heavy as a VW beetle car, but only four of loggerheads and all were dead.

Loggerheads (Caretta caretta) are listed as endangered by the International Union for the Conservation of Nature and their migrations have long been a mystery to scientists.

They nest on beaches and get their name from their unusually large heads. They feed on crabs, mussels, clams and jellyfish and can weigh up to 400lbs.

Jeanette Wyneken of the Florida Atlantic University and her fellow researchers have always had a problem tracking young turtles. The animals have what are known as the lost years, which is the time a new sea turtle leaves the nesting beaches until many years later when they return as juveniles.

During these years Atlantic loggerheads are thought to make their way around the Atlantic, but scientists had no idea where exactly they were or what they were doing.

They tried attaching satellite tracking tags to the newly hatched young turtles but however sophisticated the adhesives used to stick them to the rapidly growing turtle's shell they fell off in days.

Some of the glues interfered with the growth of the turtles' shells and had to be removed. New thinking was needed.

Then Wyneken talked to her manicurist. "My nails are made of keratin. And a turtle's shell is made of keratin" she told us.

She experimented with an over-the-counter acrylic fingernail kit and it fixed the light-weight solar-powered tags in place perfectly. The acrylic also helps reduce the peeling of the turtles' shells, enabling the tags to remain in place for many months.

This helped Wyneken and her colleagues fill in many details of the animal's amazing life cycle including the lost years.

Adult females bury their eggs on the beach in an area above the high-tide line near the water so the hatchlings can scramble to the sea.

The loggerhead's gender is dictated by the temperature of the underground nest. Eggs that incubate at 32°C become females, those at 28°C become males and a temperature of 30°C results in an equal number of male and female hatchlings.

After incubating for around 80 days, the tiny hatched babies - under two inches long - dig through the sand to the surface, usually at night, when darkness increases the chance of escaping predation and damage from extreme temperatures.

They navigate toward the reflection of the moon on the ocean's surface and once they reach the water they use the tidal undertow to sweep them out to sea where they will swim for 20 or so hours to get as far from the dangers of the shoreline as possible.

 

An iron compound in their brains allows the turtles to use the Earth's magnetic field for global navigation.

The new tracking techniques have now revealed that they spend some years hidden from predators far from shore in the Sargassum Sea's rich-in-food floating rafts of weed where they grow into 18-inch (45cm) juveniles before they return to waters much nearer the shore to grow to adult size.

The loggerhead takes between 17 and 33 years to reach sexual maturity and can live between 47 and 67 years.

An average adult measures around three foot (90cm) but they can grow to nearly nine foot long. Average weights can be 300lb (135kg) with the largest specimens weighing in at more than a thousand pounds (450kg).

The skin ranges from yellow to brown in colour, and the shell is typically a handsome reddish-brown.

They are found in the Atlantic, Pacific and Indian oceans, as well as the Mediterranean and, very rarely, here in Britain.

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