Olive ridley sea turtle conservation & research in Ostional Wildlife Refuge, Costa Rica. by Alexandra Briere
December 13, 2019
Open gallery
In January of 2015 I travelled to the Ostional Wildlife Refuge of Costa Rica to embark on a 10-week sea turtle volunteer/internship experience. The sea turtle species I predominately worked with was the Olive Ridley Lepidochelys olivacea, the species which I will discuss in this blog, however I should mention during my 2.5 month experience I worked occasionally with leatherback sea turtles Dermochelys coriacea and green sea turtles Chelonia mydas as well.
Sea turtles are definitely one of the most adored reptiles on the planet, however, many of us are unaware of the complexity of their life cycles and biology which are partly what make them fascinating but unfortunately at the same time vulnerable. Male sea turtles spend their entire lives in the ocean except while on the journey they make between hatching and arriving at the ocean for the first time while on the other hand female turtles return to sand to release their fertilized eggs either a few times per year or once every 1-3 years. Therefore, since only mating takes place in the ocean and the rest of reproduction occurs on land a large portion of research and conservation work is necessary outside of the water.
Ostional Wildlife Refuge is a critical nesting site for Olive Ridley sea turtles due to the utilization of the beach by solitary olive ridleys on a nightly basis and by aggregate olive ridleys during a phenomenon called the “arribada” which is a mass nesting event that takes place every 3-4 weeks around the new moon. The arribada occurs over a 3-5 day period in which hundreds of thousands of olive ridley’s leave a nest buried in the sand with roughly 70-100 eggs which add up to around 1 million eggs by the end of the arribada.
Before getting into more of the science I think it’s important to mention the social aspects of the refuge, there is a unique arrangement that the local community of Ostional and governmental environmental organizations have which helps the local economy and conservation of the olive ridleys. During the first 72 hours of the arribada locals harvest a certain percentage of the eggs, a portion are sold and the rest are consumed by families. You are probably wondering how taking more eggs could possibly help conservation efforts, well I mentioned that the eggs are only harvested during the first 72 hours of the arribada and the reason for that is there are so many waves of nesting turtles that the clutch’s nested have a high probability of becoming crushed by other nests laid on top. Researchers have found that after 20 years of this program the number of female nesting turtles has increased. This may indicate that this project has been successful for conservation since it takes 15 years for a female turtle to reach reproductive age and female sea turtles generally return to their home beach to lay their eggs.
Anyway, back to the facts on clutch size, so at first the fact that olive ridley females can lay eggs a couple of times a year and have clutch sizes of around 70-100 eggs may make us think there is no reason to worry about the conservation of this species or other sea turtle species which have similar reproduction statistics, however, currently only roughly 1 out of 1,000 – 10,000 of hatched sea turtles will make it to adult hood due to threats such as predators, poaching (eggs & adult turtles), disease, fishing/boating accidents, and pollution. On top of the wide range of threats sea turtles are faced with climate change is now becoming a threat to sea turtles before they are even born. Due to the sea level rising there are less available nesting sites for female nesting turtles and the overall rise in temperature is causing a higher proportion of female sea turtles to male sea turtles since the sex of an egg is determined by the sand temperature.
Since sea turtles are overall so complex and the olive ridley species is classified as threatened with declining numbers as a volunteer/intern I had a wide range of responsibilities/duties to assist the refuge site with data collection and conservation. As I previously mentioned olive ridley sea turtles nested at the refuge on a nightly basis therefore, data needed to be collected every night. For 4 hours every night around high tide nightly patrols were performed volunteers & interns would split into small groups and patrol different areas of the beach for two reasons: to discourage poachers, and to collect data. Patrols were performed without the use of any light since non red light can confuse and scare a turtle, and additionally tracks were easier to spot without the use of any light. Once tracks and then a turtle was found the weather conditions, location, nest, clutch, and the turtle’s measurements were taken. During the arribadas the same type of data was taken as when patrolling for solitary turtles but many more turtles were recorded. In addition to nightly beach patrol & data collection I assisted in beach clean ups, hatchery vigilance & maintenance, excavations, geological surveys, tagging, hatching release, and community outreach/education.
My experience as an intern/volunteer was truly incredible, I was able to work up close with wild olive ridley sea turtles to assist in research and conservation for the species which is not always possible in research and or conservation. Not only was it incredible to see a female sea turtle up close because of the sheer fact it is a species that humans rarely interact with but also the probability of the female sea turtle before my eyes making it to that moment where she came back to her place of birth to lay her eggs was extremely low which made the sight so magical. The odds of an egg hatching are not very high and the odds of a sea turtle making it to adult hood are very low (to review: 1 out of 1,000 – 10,000). Sea turtles face a mostly solitary life with constant threats which I find to be somewhat sad since as a human I am a social being with relatively less threats. These fascinating ancient sea turtles would leave solitarily for the open ocean after dropping off their sons and daughters in the sand to incubate until born and then they will have the same journey alone through the open ocean.
Additionally, seeing how the olive ridley turtles are so woven into the existence of the local community of Ostional Wildlife Refuge and in some sense a symbiotic relationship was very interesting, and I hope that other conservation sites that formed after the establishment of a community are able to make arrangements that serve both the local community and conservation efforts. I am grateful that at such an early point in my career working in the ecology field I was able to have such a well-rounded experience that touched on all aspects of ecology!
***If you ever get a chance to visit Costa Rica visit Ostional Wildlife Refuge to see either solitary nesting olive ridleys or the arribada (if it is happening while you are there)!