From the Science Blogs

From the Science Blogs

Leatherback turtles: going where few air-breathers dare

Playa Grande neighbors go to court for damage to leatherback turtles

On July 1, an appeal for protection was filed before the Constitutional Court by the Playa Grande Neighbors Association, arguing serious damage is being caused to the leatherback turtles that come to nest on the Guanacaste beaches of Playa Grande and Playa Ventanas.

Julio Saenz, a member of the community group, said he was going “to present proof that scientific research led by the organization The Leatherback Trust (President Jim Spotila), has made it so that these endangered turtles are not coming back to nest on these beaches, which are part of the Las Baulas Marine National Park.”

The experiment being questioned was conducted for scientific reasons. However, the Playa Grande Neighbors Association has indicated that none of the turtles fitted with the radio transmitters returned to their nesting site. That’s the main reason for the appeal for protection (recurso de amparo) that they filed with the Constitutional Court, and which is now being reviewed by its magistrates.
Of the 27 turtles that were outfitted with the devices in the 2003-2004 season, none returned to their nesting site, despite the fact that leatherbacks return to their nests, on average, 3.7 years after the time they migrated.

This information was presented in the reports issued by researchers with The Leatherback Trust, and which the Playa Grande neighbors have copies of. Meanwhile, 40 other turtles that were not given a transmitter, also on the 2003-2004 season, did return to their nests the following season.

In this sense, the appeal for protection accuses The Leatherback Trust of violating a series of international agreements ratified by Costa Rica for the protection of flora and fauna, according to article 7 of the country’s Constitution. The complainants are asking the Constitutional Court to ban experiments done with the turtles, as they could generate “an irreversible effect against the environment, according to the appeal presented against SINAC, the Tempisque Conservation Area, and the Ministry of the Environment and Energy (MINAE).

Bryan Wallace, In response to Pedro Vargas:

First, our project has a 20 year history of research efforts that have contributed to conservation of leatherbacks in Costa Rica, including the formation of the National Park, and the ELIMINATION of egg poaching, which was one of the main drivers in the population decline of these animals. Thus, our reputation for important, reliable scientific research and consistent, dedicated conservation efforts speaks for itself -in Costa Rica and around the world.

Second, as conservation scientists working with endangered species, we have a responsibility to maximize the conservation applications of our research while minimizing the impacts of that research on our study animals. The very nature of field research is such that it is impossible NOT to have some impact -however small- on one's study subjects. Despite this unavoidable fact, we used the most widely accepted, proven technique available to us at the time of the study to attach transmitters to leatherbacks (the harness) to study their movements and the environmental influences of those movements throughout the Pacific Ocean. No tracking study had ever been conducted on this population on the scale of this one, and no tracking study had ever obtained so much crucial information to be used for conservation of leatherbacks in Costa Rican waters, and international waters as well.

Third, speaking of conservation importance, through high-level analyses of these high-quality data, we were able to outline clear, pertinent recommendations for conservation of leatherbacks in their marine habitats. In addition to egg poaching, incidental capture of leatherbacks in fishing gear also has been implicated as a major driver of this population's decline. Thus, mitigating the interactions between leatherbacks and fishing gear is now the most important conservation issue facing us and the leatherbacks we are trying to save from extinction. The information we obtained in this study has allowed us, for the first time, to describe in great detail where leatherbacks go, why they go there, when they go there, and what can be done to keep them out of fishing gear.

Fourth, as a technical point, contrary to the claim in his post, there are currently no data clearly demonstrating adverse impacts of the harnesses on leatherbacks. The only studies that have explored this possibility have arrived at tentative, suggestive conclusions that harnesses might result in slightly slower travel rates or might be related to earlier start of migration. What is needed is a rigorous test of various techniques to figure out what the impacts actually might be.

Fifth, we have identified almost 2000 individual leatherbacks over the past 15 years of monitoring, but have seen fewer than 500 return to the beach after being counted for the first time. Thus, we have an unfortunately, but consistently, low rate of return of our turtles (about 25%). In fact, during the years that we put harnesses on turtles, we counted 417 individual turtles, of which only 18% have returned so far. The turtles that we put harnesses on (46 total) are in the proportion that haven't returned yet, but still might. Leatherbacks take between 2 and 7 years to return to the beach to nest, and in some cases, we've recorded turtles returning after intervals of more than 10 years! Everyone can rest assured that when these turtles come back, our patient field biologists will be waiting to count them.

The take-home message is this: we care about saving these turtles more than almost anyone, and we always try to do the best job we can to find out what we need to know to save them, and to take the actions necessary to save them. We hope that others will join us in saving the leatherbacks in the Eastern Pacific!

Thanks for reading,
bw

Posted by: Bryan Wallace | August 8, 2008 2:45 PM