Researchers are documenting the presence and behaviors of sea turtles in several areas in the ETPS, including Isla de Coco (Costa Rica). Free-swimming turtles are captured by researchers for thorough inspection and data collection. If they are among the few fortunate ones, like this male green turtle, they could also receive a satellite transmitter that researchers use to follow post-release turtle movements. Photo: Edwar Herrerano.
Like sharks, sea turtles are indifferent to geopolitical boundaries, instead relying on environmental cues at small and broad scales to carry out their life cycles. They inhabit several different marine habitats from wave-free mangrove estuaries to high-energy surflines and beaches to open ocean expanses, often traversing among them depending on their life phase.
Understanding how and why they use these different habitats is a key to constructing and implementing sound conservation strategies in a region like the Eastern Tropical Pacific (ETP) Ocean, where humans and marine species interact frequently.
Five of the world’s seven sea turtle species occur in the ETP, all of which are considered Vulnerable, Endangered, or Critically Endangered by the IUCN Red List of Threatened Species. Primary drivers of population declines have included incidental capture of sea turtles in fishing gear (i.e. bycatch) and human consumption of turtle eggs and meat.
In the ETP, conservation research on sea turtles focuses on population monitoring and assessment, as well as characterization of movements and habitat use of all species that appear in the region.
Migramar offers the unique opportunity to leverage the collective strength of several related projects to convey integrated information about where and why highly migratory species like sharks and sea turtles to varied audiences that share an interest in sensible management of marine resources and species in this unique pat of the world.
Population Assessments and Monitoring
Researchers take advantage of the rare occasions that sea turtle come on land to lay their eggs by recording behavioral and morphometric information, and by protecting the eggs and hatchlings. This hawksbill turtle also received a satellite transmitter and has been tracked in Ecuador’s Parque Nacional Machalilla. Photo: Bryan Wallace.
When thinking of assessing populations of highly migratory marine species, slogging along buggy beaches to count tracks made in the sand by massive expectant mothers probably doesn’t come to mind. But this is just what sea turtle researchers do regularly, taking advantage of sea turtles’ evolved dependency on land for their reproduction.
When adult female turtles crawl ashore on sandy beaches to lay their eggs, researchers throughout the ETP are there to register these events, conducting nocturnal censuses in search of nesting turtles or signs of their activities, record morphometric and behavioral data, and protect the eggs and hatchlings to ensure their safe passage to the next generation.
Although nesting females only represent a small fraction of overall sea turtle populations (adult males and juvenile turtles do not come ashore), counting nesting females or their nesting activities is the most common metric for monitoring sea turtle populations around the world.
Such efforts in the ETP in recent decades have resulted in highlighting the alarming declines of leatherback turtles, discovery of important hawksbill nesting areas, and the resurgence of olive ridley and green turtles.
Movements and Habitat Use
Despite the differences in how sea turtles and sharks are counted in the wild, how researchers determine their migrations, movements, and habitat use patters are quite similar.
Innovative technology has allowed typically land-locked researchers to virtually follow migratory marine species through their watery worlds from the dry safety of a boat deck or even their laptops. Sea turtle researchers in the ETP have employed telemetry techniques to gather information remotely about where turtles go, how they spend their time, and what managers should consider when developing conservation strategies.
For local telemetry studies, researchers use radio or acoustic tags to follow sea turtles. These tags, while requiring a great deal of demanding fieldwork, provide fine-scale data about movements and habitat use, allowing researchers to pry into the private lives of sea turtles.
For broad-scale, long-term studies, satellite-linked transmitters relay information about turtles’ whereabouts, as well as other information, to researchers’ email accounts, allowing them privileged access to the animals’ journeys across ocean habitats.
Throughout the region, researchers have been studying movement patterns of sea turtles, including internesting habitat use and post-nesting migrations, as well as juvenile foraging ground behavior, to improve our understanding of how sea turtles interact with a variety of habitats.
Results in Costa Rica
Researchers are documenting the presence and behaviors of sea turtles in several areas in the ETPS, including Isla de Coco (Costa Rica). Randall Arauz, of PRETOMA (Costa Rica), and Diego Amorocho, of CIMAD (Colombia) pose with a hawksbill turtle, which is outfitted with a satellite transmitter as well as an acoustic transmitter, which will allow researchers to follow it over broad- and fine-scales. Photo: PRETOMA.
In the waters around Isla de Coco – a National Park in Costa Rica and World Heritage Site – Migramar partner PRETOMA has led several expeditions to document the presence and behaviors of sea turtles. During 2009, 27 green turtles and one hawksbill turtle were registered during dives, 4 of which were tagged with both acoustic and satellite transmitters, 5 with only acoustic tags, and 2 with only satellite tags. Preliminary results show the importance of fishery-free Cocos Island as a nursery area for juvenile sea turtles.
On the Costa Rica mainland, a recent research initiative has helped unravel the mystery of the cryptic hawksbill turtle in the ETP. PRETOMA’s acoustic telemetry work with juvenile hawksbills off Punta Coyote – partially within a relatively new protected area (Refugio Nacional Vida Silvestre de Caletas Arío) designed for nesting olive ridley turtles – has been a critical advance.
Preliminary results show that these immature turtles appear to be residents to the area, remaining in relatively shallow water and not straying far from shore. This research has generated new questions about similar habitats along the Costa Rican coastline as well as other places where juvenile hawksbills might be.
Results in Ecuador
Researchers and officials from Parque Nacional Machalilla in Ecuador use tangle nets to catch free-swimming sea turtles. This technique is used in many places around the world so that scientists can get their hands on otherwise elusive animals. During the short time that turtles are held, they receive identification tags, are measured and weighed, and are sampled for genetic analyses. If they are among the few fortunate ones, they could also receive a satellite or ultrasonic tag that researchers use to follow post-release turtle movements. Photo: Bryan Wallace.
While Galapagos typically receives most attention, mainland Ecuador also plays host to many important migratory species in the ETP. In particular, the work of Equilibrio Azul has revealed that Parque Nacional Machalilla is the most important site for hawksbills in South America, and also is home to adult and juvenile green turtles.
Equilibrio Azul’s biologists have undertaken in-water monitoring of juvenile green turtles as well as nesting beach monitoring of nesting green turtles on PN Machalilla’s Isla de la Plata, showing that it is an important site for this species. Plans are underway to combine Equilibrio Azul’s efforts to use acoustic tracking to monitor manta rays around the island with acoustic tracking of green and hawksbill turtles as well.
Major advances in sea turtle monitoring have occurred near PN Machalilla’s shoreline, where 6 adult hawksbill turtles have been tracked with satellite transmitters. Tracks show that post-nesting female hawksbills appear to stay close to shore, and some migrate short distances to estuary systems characterized by mangrove habitats. Interestingly, a region-wide effort focusing on hawksbills is revealing a similar behavior by other post-nesting individuals, which is a paradigm-shifting discovery for hawksbill biology.
The Big Picture
Remote tracking studies have allowed researchers to challenge conventional wisdom about sea turtle behavior and life history, which helps us better understand why turtles go where they go, and therefore what is necessary for population persistence.
Specifically, these efforts show the importance of protected areas as sanctuaries for important life stages for imperiled sea turtle populations, and that maintenance of connectivity among these areas is crucial to ensure healthy populations of sea turtles and other migratory marine fauna.
Because shark researchers in the ETP are relying on an array of acoustic receptors in multiple marine protected areas throughout the region, there is tremendous potential for sea turtle researchers to take advantage of the technology and experience already in place to undertake joint research initiatives involving sharks and turtles alike.
Integrating results across species and habitats gives us a holistic understanding of sea turtle ecology and behavior, and provides solid scientific information to guide conservation efforts in the region.
