By Jenell Black and Christian Díaz Chuquisengo. Captured by drone, a leatherback returns to the ocean after nesting in Playa Grande, Las Baulas National Marine Park. Recommendations to visitors are important to reduce threats.
This year, as Field Manager at The Leatherback Trust, I was lucky enough to witness an extraordinary event in Las Baulas National Park (Parque Nacional Marino Las Baulas) on Costa Rica’s Pacific coast. Leatherbacks typically nest under the cover of darkness, but once in a rare while our team out conducting a morning survey happens upon a sea turtle that is up late enough she may still be on the beach as the sun rises. Since light disrupts nesting sea turtles, photographs may not be taken of nesting sea turtles at night, but sea turtles that are up under the bright morning light are free game to take photos of respectfully and without the use of flash. Our project has been making large efforts to be at the lead of exciting new research methods conducted with drones, and I was lucky enough to remember to bring one out with me so you could witness this exciting event of a leatherback returning to the sea after completing her nesting process. What is so very exciting about using the drone is that we are able to not only see how the leatherback moves on land, but how graceful she is once she’s in the water clear of the shore.
Parque Nacional Marino Las Baulas remains the largest nesting location for the Eastern Pacific leatherback, a population that has declined by more than 98% since 1990. Organizations such as The Leatherback Trust, MINAE (Ministerio Ambiente y Energía, or Ministry of Environment and Energy)’s rangers, schools and universities, and even local restaurants are working tirelessly to prevent further decline of this population. Threats to these animals include climate change - where increased temperatures can cause nest mortality, pollution with plastics – which get lodged in digestive systems and nasal passages causing mortality, fisheries – where turtles are accidentally caught on long lines or in shrimp trawling traps and drown, known as bycatch, and habitat loss – leaving our girls with no place to lay their eggs. Fortunately there are many ways you can help save this species, and all other flora and fauna protected found in our national park.
Playa Grande, the largest of the beaches in Las Baulas National Park, is not only well known for surf breaks and stunning sunsets but also for visits from nesting turtles like critically endangered East Pacific leatherbacks.
Every year, during the leatherback nesting season (between October and March), leatherbacks come ashore to lay their eggs at night; up to 60 days later, the eggs hatch and the hatchlings start their race to the ocean. Black and olive ridley turtles also nest here, and portions of their nesting seasons overlap with the leatherback nesting season.
There are seven different species of sea turtles in the world, and Playa Grande is regularly visited by the aforementioned three species. The leatherback turtle (baula in Spanish) can measure up to 130 – 190 cm (52 – 75 in) and weigh 250 – 500 kg (550 – 1100 lbs). Since leatherbacks exclusively feed on jellyfish species, it’s incredible to think they can grow this large on jellyfish alone! East Pacific leatherbacks migrate from as far south as the waters off Chile and Peru, where they forage in the cold upwellings of the Humboldt current, to tropical waters offshore nesting beaches where they lay their eggs, such as here in Guanacaste province.
The East Pacific Green turtle, also known as the black turtle (negra in Spanish), can measure approximately from 80-122 cm (32 – 48 inches) and weigh 65-204 kg (144 – 450 lbs). This turtle’s main diet is sea grasses and algae, and occasionally jellyfish. They travel along the coast of Central America and venture as far south as the Galápagos Islands.
The olive ridley (lora in Spanish) measures around 55 – 75 cm (22 – 30 inches) and weighs 36 – 45 kg (85 – 95 lbs). Olive ridleys are considered to be the most abundant sea turtles in the world, although the current global population is only 0.2% of the species’ historical abundance. Females often nest together in large aggregations, known as arribadas, which only occur on certain beaches, like the local Ostional. Scientists have recorded arribadas of up to 200,000 turtles at once. Olive ridleys forage along drift lines for crabs, jellyfish, clams, squid, snails and algae.
Playa Grande, Playa Ventanas and Playa Langosta, are all part of Las Baulas National Park (Parque Marino Nacional Las Baulas). The Park protects the last mass-nesting beach for the East Pacific leatherback turtle, a population designated as critically endangered by the International Union for Conservation of Nature (IUCN). Park Rangers, local guides, members of local communities, and researchers are working hard to save these turtles from extinction, as well to protect the local wildlife and flora.
Las Baulas National Park was created more than 20 years ago to protect the sea turtles and other ecosystems, including estuaries, wetlands, dry forests and the marine habitat extending 12 nautical miles offshore.
In the late 1980s, when The Leatherback Trust scientists began collecting standardized data on nesting turtles on Playa Grande and Playa Ventanas, they documented hundreds of turtles nesting on the beach each night during the nesting season. At that time, egg poachers had organized themselves in groups and divided up the beach to collect every last leatherback egg. Unfortunately, the result was the loss of an entire generation of East Pacific leatherbacks.
The Leatherback Trust’s founders, Dr. Jim Spotila and Dr. Frank Paladino, worked with Mario Boza to create The Leatherback Trust to stop egg poaching at Playa Grande and Playa Ventanas and their support helped lead to the creation of Las Baulas National Park. Our organization’s scientists and volunteers continue to conduct monitoring activities at Playa Grande and Playa Ventanas, in communication with Park officials, and we are proud to say that today, there is virtually no poaching in Las Baulas National Park. Nevertheless, there are still other threats that compromise the survival of this species.
For every 1,000 hatchlings, only one sea turtle reaches adulthood. Climate change, pollution, nest disturbance, fishing and habitat loss are now the main threats to leatherbacks and other sea turtles. Increases in sand temperature due to climate change can kill hatchlings in the nest before they fully develop. Around 30°C the mortality starts to increase and by 33°C the mortality rate is close to 100%.
Plastic, lights, and water pollution can compromise the survival of sea turtles. Turtles can confuse plastic bags, straws, or utensils with food. Plastics can get stuck in their digestive systems or lodged in their nasal passageways, as our scientists have seen. Light pollution disorients the hatchlings trying to reach the ocean, making them more vulnerable to predation or dehydration; adult turtles trying to find their way to the beach to nest are also disoriented by coastal lighting. Water pollution from leaky septic tanks, agricultural runoff, oil spills, or even runoff of oily residue from streets can lead to respiratory inflammation, gastrointestinal ulceration, organ damage and reproductive failure.
Longline fisheries for tuna, swordfish, and mahi-mahi, as well as shrimp trawling present one of the most serious threats to sea turtles in the ocean. Although turtles are not targeted by these fisheries, they get stuck in weighted nets used by trawlers or entangled on the miles of lines with baited hooks set by longliners, becoming “bycatch” and often drowning when they are unable to surface for air. Costa Rica has taken action to improve fisheries practices, for example by phasing out bottom trawling for shrimp, but consumers must not only demand strong fishing regulations to protect sea turtles but also reduce demand for unsustainably captured fish.
Finally, habitat loss at nesting beaches can leave sea turtles with no place to nest. The shade beachfront trees produce can help cool nests, which impacts the gender of hatchlings. Loss of coastal vegetation also increases compaction of sand, preventing turtles from digging, and erosion, exposing nests to danger.
Las Baulas National Park, The Leatherback Trust and other organizations, companies, and neighbors are working together to help save sea turtles. How can you help? Here some tips from The Leatherback Trust’s Outreach Manager, Christian Díaz Chuquisengo: