George Shillinger, Hopkins Marine Station, Pacific Grove, CA -- We're keeping our eyes on the four remaining Great Turtle Race leatherbacks whose satellite tags are still transmitting: Turtleocity, Genevieve, Freedom and Billie. In case you're new to TOPP, we co-sponsored the Great Turtle Race last April, in which eleven leatherback turtles "raced" from Playa Grande, Costa Rica, to the Galapagos for 14 days. Although the official race ended there, that was just the beginning of the three-year migration of the turtles. We've been watching their journeys for the last year, and something strange is happening.

But first, I'm sad to say that seven of the eleven leatherbacks' satellite tags are no longer transmitting. They began going silent from shortly after the race to last December. Stephanie Colburtle stopped transmitting first, after 925 miles; Drexelina after 932 miles; Windy after 1,508 miles; Saphira after 2,474; Champira after 2,616; Purple Lightning after 2,695 miles; Sundae after 3,276 miles; and Drexelina. In a five-part series starting last September 10, when four of the seven turtles' tags stopped transmitting, we examined the possibilities of what could have happened to them: tag failure, being killed in long lines or nets by commercial fishermen, being killed on purpose for food, their tags temporarily being covered by algae, eating plastic bags or dying of old age.

Three of the four remaining turtles -- Genevieve, Freedom, and Billie, the turtle who won the Great Turtle Race -- are hunting jellyfish where we expected them to go -- in the South Pacific Gyre.

Image from NASA SEAWIFS and SIMBIOS projects

It's an area the size of a continent that stretches from South America to New Zealand. Although it's called the world's largest ocean desert, food is patchily distributed. The water temperature is cooler than around the equator, and the turtles don't have to fight the currents.

Turtleocity's heading toward the equator! What gives? She's traveled 5,266 miles since she was tagged last year.

But Turtleocity's doing something strange: she's heading toward the equator. If she crosses it during this time that we call the inter-nesting phase -- the months when she's living at sea and before she heads back to Costa Rica (and crosses the equator then) to lay eggs in 2010 -- that will be news to us researchers. See, we've been thinking that the turtles that nest along the west coast of Central America stay south of the equator during the inter-nesting phase, and the leatherback turtles that nest in Indonesia and Malaysia stay in the North Pacific. If Turtleocity crosses the equator and heads to Indonesia in the next few months...well, that'll get our attention. But, she's probably just finding lots of jellyfish in the Intertropical Convergence Zone, where the northeast and southeast trade winds converge and force moist air upwards. The ITCZ, as it's known, moves back and forth across the equator with the seasons, always hovering over where the sun is most intense, hence where the waters are warmest.

Genevieve's traveled the farthest: 6,263 miles since last year.

Billie, the winner of the Great Turtle Race, has stroked a respectable 5,168 miles in the last 13 months.

Freedom, one of only four Great Turtle Race leatherbacks whose tag is still sending a signal, has traveled 4,859 miles.

For you Great Turtle Race fans, you may remember that we knew we could do this race when we saw where the leatherbacks that were tagged in 2005 went -- nearly on a straight line to the Galapagos before turning south.

The turtles return to their nesting beaches every fourth year, so this year, we were looking for the turtles tagged in 2005. We couldn't look for turtles wearing harnesses with satellite tags. Their harnesses automatically dropped off after about 18 months, when the batteries on the satellite tags run out of juice. But Jim Spotila has a crew of researchers who live in Playa Grande during the nesting season and who look for turtles every night from late November through February. And they found one of the turtles who had been tagged in 2005. She doesn't have a name. The researchers know her as "Turtle 56276."

She's 4.3 feet long (133 centimeters), and 3.3 feet wide (101 centimeters). She laid six nests in the 1999-2000 season, six in 2002-2003, and 10 nests in the 2004-2005 season.

We were able to follow her for 433 days -- from February 4, 2005 to April 13, 2006 -- before her satellite tag went silent and her harness released from her body. She made her deepest dive on May 3, 2005, to 1,660 feet (506 meters) in water that was just over two miles deep.

Total distance traveled while she was tagged: 5,197 miles (9,523 kilometers)! Here's her track: