Of land and sea
There is one day that will be embedded in my memory forever.
I awoke to voices calling, “Baula baula baula!” getting increasingly louder outside the window at the Ostional National Wildlife Refuge Field Station in Costa Rica. An adult leatherback female, una baula, had begun emerging from the ocean to lay her eggs on the beach half a mile from the station. I sprinted down the beach, unable to contain my excitement for this long-anticipated encounter and not wanting to miss a single second. Watching her haul her body onto the beach while exhaling heavy, prehistoric breaths left me awestruck. She was a torpedo-shaped, white-spotted, Volkswagen-sized mother, moving with determination. What first struck me was the unwieldy and burdened nature of her movement on land, despite being a 1,000-2,000 pound ocean dweller with flippers.
Every nesting female that returns to the place of her birth to lay eggs is a miracle. Only 40-60% of leatherback nests hatch worldwide, and approximately one in 1000 hatchlings survives the gauntlet of threats awaiting these reptiles in their adolescent years. Every sexually mature individual has beaten the odds, making it all the more disturbing when adults are prematurely removed from the population due to the many threats facing this species. Historically, months spent patrolling the beach in Ostional with Bioma Travel would have resulted in a number of encounters with nesting females. Due to the devastation of the critically endangered Eastern Pacific leatherback sea turtle subpopulation, this was the only night I saw one. It was predicted that the 2014/15 nesting season could be the last in Ostional, and I realised then that I was personally witnessing the extinction trajectory of an ancient reptilian population. That night I didn’t really feel like I adopted a mission, but like a mission adopted me. I had to do something.
The latest estimates from Laud OPO, the network dedicated to East Pacific (EP) leatherback conservation, indicate that at current rates of decline, there are only about 10-15 years until the leatherback sea turtle is functionally extinct in this region. The threat most affecting the decline of the EP population of leatherback sea turtles is bycatch, or accidental catch, in artisanal fisheries. Leatherback sea turtles can hold their breath for approximately 85 minutes, but the set times of nets in some of these fisheries can be as long as 24 hours. Fisheries in the Southeast Pacific are thought to catch more than 46,000 turtles of all species per year. In the 1980s and 1990s there were as many as 35,000 leatherbacks occupying the East Pacific Ocean subpopulation, but current estimates report that there are less than 1,000 individuals left.
Leatherback conservation is particularly important because leatherbacks are a keystone species. Leatherbacks feed only on jellyfish species like gelatinous zooplankton, moon jellies, and sea nettles, which are opportunistic predators that consume juvenile fish species and fish larvae. Leatherbacks have special papillae in their throat to assist with swallowing their slippery prey. Able to eat their weight per day, they help to regulate jellyfish populations. By protecting leatherbacks, we can therefore naturally regulate jellyfish populations, support the recovery of fish stocks and subsequently contribute to international food security. Leatherbacks are the largest reptile by weight in the world and they are also characterised by the widest reptilian range, both geographically and thermally. The leatherback sea turtle is the only sea turtle species that does not have a hard, bony carapace made of keratin. Their teardrop-shaped carapace is made of cartilage and has seven ridges, a body design that makes them very hydrodynamic in the water. They often travel as far as 35km per day as part of their cyclic oceanic migrations. The deepest dive ever recorded was to about 4,000 feet, which is deeper than some whale species dive. There is fossil evidence to suggest that this species has remained majorly unchanged for more than 110 million years. They have survived the time of the dinosaurs and are only now facing extirpation from different ocean basins due to extreme and long-term pressures caused by the human race.
Leatherbacks have been referred to as a polar reptile. They have a remarkable layer of insulating fat. They are not warm- or cold-blooded but exhibit something that has been termed Gigantothermy. Gigantothermy is thought to be a body life history characteristic exhibited by polar bears, panda bears, and even dinosaurs. One of the mechanisms observed in their physiology is something called counter-current heat exchange, which occurs when veins carrying oxygen-poor, cooler blood heading back to the heart, and arteries carrying oxygen-rich warmer blood coming from the heart, are located close to each other. This arrangement allows heat to be conserved in the extremities. When leatherbacks dive, they can withstand temperature differences that other sea turtles cannot and are therefore found at latitudes that none of the other more tropical sea turtles can be found at. Other sea turtle species are ectotherms, meaning they use the environment to regulate their body temperature. In leatherback sea turtles, when they are overheated, their skin turns a pinkish color as they flush blood to the outside of their body in an effort to cool down. The body temperature of individuals measured off the coast of California is typically six to seven degrees higher than the temperature of the ambient environment, providing further evidence that this species is able to regulate the temperature of its body to utilise foraging habitats at latitudes where jellyfish can be found and where no other marine turtle species can thrive.
There are a few constraints of being a sea turtle: you must breathe air, you must lay your eggs on land, and you must spend the majority of your life in the ocean. This use of both oceanic and terrestrial habitat presents unique and expansive conservation challenges for sea turtles in general, but specifically for leatherbacks. Leatherbacks do not occupy nearshore foraging habitats during their developmental period like other sea turtles but spend all of their developmental life stages as a pelagic species, occupying the open ocean. This behaviour makes protecting them from fishing efforts even more of a challenge. Oftentimes already protected reefs and seagrass beds do not provide protection for this species, and we know very little about their movements across life stages in the open ocean.
Leatherbacks are symbolic as a flagship species. They are affected by almost all of the greatest threats facing our ocean today including climate change, plastic pollution, unsustainable fisheries bycatch, and also threats facing coastal habitats such as sea level rise, beach erosion, temperature increases and ocean acidification. They exemplify and put a charismatic face to these issues. Plastic bags floating in the water column resemble the leatherback’s primary prey, and leatherbacks have the lowest natural nest hatching success rate of all sea turtle species, which is only decreasing with observed global increases in nest temperatures. Leatherbacks are one of the species of sea turtles that do not nest close to or behind the vegetation line, making their nests more susceptible to rising tides and beach erosion. By studying leatherback sea turtles and the threats facing their survival, we can open the doors to conversations about the biggest threats facing our oceans today.
After my time in Ostional, I spent several months in Latin America and the Caribbean through Latin American Sea Turtles, The Leatherback Trust, and the St. Kitts Sea Turtle Monitoring Network gaining experience working with and studying marine turtles. I pursued a Master’s degree through Purdue University and The Bioko Marine Turtle Program under the direction of Dr. Shaya Honarvar and Dr. Frank Paladino and conducted my thesis research on Bioko Island, Equatorial Guinea. On Bioko I walked the beaches every night for five months with a team of Equatorial Guinean university students, local community members and US biology graduates, acting as a passive protection for nesting sea turtles against poachers. We were located in the Gran Caldera Scientific Reserve, in remote jungle habitat. Apart from participating in the long-term monitoring program, the goal was to collect data on the various environmental characteristics that affect reproductive success in sea turtles on the island. We profiled the five main nesting beaches to model sea level rise, evaluated hatching success rates, and studied environmental nest-site characteristics like pH, conductivity, sand moisture content, location, temperature, etc. Our results indicate that the beach experiencing the most anthropogenic pressures, including a public entrance from a newly built road leading from the city, increased poaching, and potential construction plans are all occurring on the beach that is likely to maintain nesting habitat and allow for highest reproductive success for the longest period of time. Hopefully our results will be useful to the Equatorial Guinean government in considering the vulnerability of its endangered wildlife populations when planning for future development.
One night we stumbled upon an overturned leatherback carapace at the waterline. It had been completely carved out of all the muscle and fat, just lying there, moving slightly with each of the lapping waves. All that was left inside the overturned carapace was her heart. It was still warm. I remember staring at it in shock, everything else around me fading away. I looked up with tears in my eyes and shown my headlamp down the beach. There were three sets of footprints and an egg trail disappearing into the darkness. Some sights change your life forever and light a fire in your soul to take action.
In April 2019, I started an NGO called The Leatherback Project (TLP) for the global protection of this species through community empowerment, research and advocacy. The Leatherback Project initiatives include a global citizen science and artificial intelligence photo identification program for leatherbacks, a sea turtle conservation and wildlife trafficking reduction program in Panama, an international investigation of in-water leatherback behavior and habitat use, a fisheries bycatch reduction program in Ecuador, and an international campaign for Rights for Nature.
There are seven subpopulations of leatherback sea turtles in the world. On the International Union for Conservation of Nature Red List, each subpopulation is evaluated separately based on the likely number of individuals left in the population, their total available habitat, current threats, and the rate that the population is increasing, decreasing or remaining stable. Four of the subpopulations are critically endangered (West and East Pacific, Southwest Atlantic and Southwest Indian), one is Endangered (Northwest Atlantic) and two are data deficient (Southeast Atlantic and Northeast Indian).
The EP subpopulation of the leatherback sea turtle is arguably the most endangered sea turtle subpopulation in the world, which is why TLP’s efforts are currently focused on preventing East Pacific leatherback’s local extinction, or extirpation. To accomplish this goal, TLP has joined forces with various branches of the government of Ecuador to launch a pilot project to test bycatch reduction technology, specifically the use of green LED lights, within the artisanal gillnet fleet. In several other countries around the globe, LED lights have been successful in decreasing the bycatch of sea turtles species by up to 93%. The idea is that we can exploit the differences in visual spectra between sea turtles and target fish catch. Sea turtles are able to see the lights on the nets and subsequently avoid them, whereas bony fish species are not able to visually distinguish between the green LEDs and surrounding ocean, resulting in a decrease in bycatch with no significant effect on target catch. The project will involve grassroots community partnerships and campaigns, bycatch reduction technology research, delineation of coastal habitat use, and the development of effective management plans and implementation proposals. Working collaboratively with fishermen to test the lights and analyse experiential feedback will be key to the success of the pilot project. Fishermen have been collaborating with TLP through participating in surveys and documenting bycatch events of endangered species for over a year, and we have already collected several data points on leatherback fisheries interactions.
The hope is that the results from the pilot project in Ecuador are consistent with results seen around the world, and that Ecuador can move forward with country-wide implementation of the lights. This type of broad sweeping legislation and implementation is what EP leatherbacks need, and it seems to be within the realm of possibility. If we are willing, as a regional, polysector society, to take the targeted actions necessary to address their devastating decline, East Pacific leatherbacks still have a fighting chance.
Photographs by Jonah Reenders, courtesy of the Bioko Marine Turtle Program.
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