Scientists Place Transmitters on Leatherbacks
GANDOCA, Limón – Since being fittedwith a satellite transmitter nearly twoweeks ago, Purra, a large female leatherbackturtle, appears to have been content tostay near Costa Rica’s southern Caribbeancoastline.That’s according to data from the transmitter,which scientists from the CaribbeanConservation Corporation (CCC) and theAssociation ANAI attached to Purra (shortfor purruja, which means “sand flea”) atabout 1:30 a.m. on May 30.Now, they hope the transmitter willcontinue to send valuable data regardingthe animal’s migratory behavior.It was the third such transmitter theCCC attached that week, having fitted twoturtles in Tortuguero with the devices justdays before.SEBASTIAN Troëng, scientific directorof the CCC, said the data the teamhopes to obtain from the transmitters willassist them in coordinating internationalconservation efforts by showing themwhere the turtles are located around theglobe at different times of the year.Leatherbacks, the world’s largest reptiles,are indeed international animals. Onetracked by the CCC in 2003 traveled some5,000 miles in seven months, and Troëngsaid that researchers occasionally encounterthe turtles in Spain, West Africa and Canada.The leatherback population on theAtlantic coast of Costa Rica has remainedstable in recent years, Troëng said, but theturtles have suffered drastic losses in theEastern Pacific. For example, the numberof leatherbacks nesting at Playa Grande, onCosta Rica’s Pacific coast, dropped fromthousands in 1990 to just 68 last year.IN spite of this, Troëng said, manypopular guidebooks still list Playa Grandeas one of the best places to see aleatherback nesting.According to Didiher Chacón, a marinebiologist and the director of the SouthernCaribbean Sea Turtle Conservation Program,global populations of the leatherback(Dermochelys coriacea) havedropped 80% in the past 10 years.Leatherbacks in the Pacific are ofteninadvertently caught by long-line fishingvessels after swordfish or sharks. Theyare also caught in the nets of fishermenwho neglect to use Turtle ExclusionDevices (TEDs) on their trawl nets. CCCofficials mentioned that fishermen theyhad consulted said TEDs are cumbersometo install and can affect catches, and thusare often not used unless fishermen knowof a government inspection.SCIENTISTS hope to determinewhether the leatherbacks’ migratory patternscoincide with periods of heavy fishingelsewhere in the world, thus increasing thethreat to this already-endangered animal.Troëng said CCC research has shownthat leatherbacks have a tendency to varytheir nesting locations widely, meaningthat protecting only certain beaches –while certainly helpful – won’t provide thekind of long-term solution the turtles need.“Our efforts here may be compromisedby what’s happening in places very faraway from here,” Troëng said. “That’s whythe transmitter is important – to find outwhere they are, when.”The transmitter was attached by meansof a harness made of silicon and nylon thatwraps around the turtle’s belly and over itsshoulders. For other species of turtles, thisis not necessary, since their carapaces arehard and the transmitters can be attachedwith epoxy. Leatherbacks, on the otherhand, are named for their soft shells supportedby bony plates. Epoxy could seriouslyharm them, said Dan Evans, CCC’seducational coordinator.Evans said the turtle’s soft, cartilagerichbody could aid it in suffering theextreme depths it dives to feed.LEATHERBACKS, the world’s thirddeepest-diving air breathing animal(behind the elephant seal and the spermwhale), have been recorded at depths of1,000 meters, he said. Their diet consistsmostly of jellyfish.The harness and transmitter combinedweigh around five pounds, an amountshadowed by that of the leatherbacks,which have been recorded at weights ofup to 2,000 pounds.“It increases the drag somewhat, butnot enough to seem to affect it significantly,”Evans said. “It’s designed to not interferewith the turtle’s swimming.”The silicon will degrade within twoyears, he said, and the rest of the harnesswill subsequently fall off.The transmitter will automaticallypower on and off in alternating 24-hourcycles, he said. It will emit a signal eachtime the turtles, which can remain underwaterfor about 20 minutes at a time, surfacefor air. In older models, batteries lastedaround seven months.THE transmitters attached last monthare of a newer model, and while they shouldlast longer, no one is quite sure how longthey will continue to provide information.The devices cost around $2,500 eachand the harnesses $500, but the equipmentisn’t the most expensive part of theprocess, Troëng said. Rather, it’s thesatellite time, which can cost up to$5,000 per turtle if the transmitters continueto emit readable signals.Evans said Purra’s movements areposted in the Internet at www.cccturtle.org. The information will always be a fewdays old by the time it is posted, he said.Troëng also authored a recent studypublished by the World Wildlife Fund(WWF) that showed that sea turtles areworth more alive than dead. Troëng foundthat non-consumptive use of turtles fortourism can generate nearly three times therevenue consumptive uses can.The study reported that TortugueroNational Park, with an average annualincome of $6.7 million, brought in moreturtle-based revenue than any other locationon earth.Attaching a Transmitter: No Job for the SluggishWHILE they’re on land, sea turtlesaren’t exactly the most nimble, speedycreatures in the world.Just the same, attaching a satellitetransmitter to a leatherback turtle requiresscientists to work quickly and efficiently.But first they have to find one.Two weeks ago, CCC scientists satinto the night, with a transmitter and harnessready, waiting for one of two beachpatrols to radio in and tell them they hadfound a turtle ready to nest.There was no electricity at theirresearch station, provided by theAssociation ANAI, so biologists conversedby candlelight about other turtle taggingexperiences they had, what wasnew in Gainesville, Fla., or which speciesof sloth was the more aggressive.Emma Harrison, a CCC biologist, saidthe massive turtles remain calm while layingtheir eggs, affording researchers theironly viable opportunity to attach the harness.“We’ll have to start work the minuteshe starts laying her eggs,” Harrison said.The first call came just after midnight.The team rushed out to the beach, beforeturning back after being informed the turtlewas already laying her eggs and it wastoo late.The next call came around 1:30 a.m.Scientists waited patiently until the turtlefinished digging her nest and convergedon her to attach the harness immediatelyafter she laid her first egg. They dug outthe sand under the leatherback’s bellyand shoulders to attach the harness,tightened it and then used metal bands tosecure the transmitter.The operation seemed a first-timesuccess, until one of the nylon strapssnapped loose from a securing D-ring.The scientists jumped back on the animalto reattach the harness, just after she hadfinished laying her eggs. It was thenapparent why there is such a narrow windowof opportunity to attach a transmitterto a giant turtle.Four of them, using their full bodyweight, were not able to fully stop thepowerful animal from moving toward thewater.They were able to successfully securethe transmitter.Harrison also said the flippers of aleatherback aren’t quite as soft as theylook, and it’s common for researchers togo home rather bruised after attaching atransmitter. On one occasion, she said, aleatherback knocked a man clean off hisfeet with one of its front flippers.
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