Course:CONS200/2025FL1/Olive Ridley Sea Turtle Conservation in Costa Rica

Introduction

Olive ridley sea turtles are a species currently facing a multitude of threats including natural stresses such as predation but also because of being directly or indirectly impacted by humans. This had led to the species being classified as threatened, and an increased focus being placed on their protection and conservation. This article will focus on the olive ridley sea turtle populations of Costa Rica, which faces some unique challenges such as the commodification of sea turtle eggs. Multiple government and non-government organizations are currently working towards protecting these Costa Rican turtles, using a variety of methods such as reducing bycatch, closing active sea turtle areas from fishing, creating wildlife refuges, and allowing the sustainable and legal extraction of eggs by locals. Conservation efforts still need to be developed and refined, since the olive ridley populations in Costa Rica are continuing to decline.

Background and Species Information

Olive ridley sea turtle resting on a beach

Olive ridley sea turtles are a very widespread species found primarily in the tropical regions of the Pacific, Atlantic, and Indian Oceans. They get their name from the olive colouration of their heart-shaped shells, which have 5 to 9 lateral scutes. The size of this species varies from region to region with the West African populations being the largest. Still, olive ridleys are among the smallest sea turtles.

Like all sea turtles, olive ridleys are omnivorous seagoing reptiles that have to breathe air. They typically feed on algae, crustaceans, tunicates, and mollusks. Additionally, they return to their hatching site in order to lay eggs. Unique though, is their tendency to nest synchronously in exceptionally large groups of hundreds to thousands in events called arribada nesting.

Olive ridley populations are listed under the Endangered Species Act as endangered on the Pacific Coast of Mexico and threatened in all other locations. Historically, it is estimated that there were up to 10 million olive ridleys roaming the Pacific Oceans but there has been a 30 to 36% reduction in their population worldwide. Sea turtles are important members of marine ecosystems for their ability to contribute to many ecosystem functions. Olive ridleys are no different, and improve water circulation, facilitate biodiversity of marine plants, act as prey for other species, regulate jellyfish and sponge populations, prevent algal blooms, among others. For these reasons as well as cultural significance, conservation of sea turtles including olive ridleys is essential.

Threats to Population

A large nesting event, known as an arribada, of olive ridley turtles.

This is an example of a turtle caught in fishing equipment.

Olive ridley sea turtle nesting behaviour.

Olive ridleys are currently under threat from many different factors. For example, accidentally catching turtles in fishing gear has become increasingly common. This can result in drowning or life threatening injury from swallowing hooks, and becoming entangled. Secondly, increased marine pollution poses similar hazards to fishing gear. Many plastic items get mistaken by turtles as food and can become a choking hazard when ingested. They can also result in turtles becoming entangled and drowning. Additionally, one of the biggest threats faced by olive ridleys and other sea turtle species is the potential rise in sea level due to climate change caused by human activities. It has been estimated, through examining 8 sea turtle rookeries in the northern Great Barrier Reef, that sea level rise could inundate 38% of crucial nesting habitat. Olive ridleys are disproportionately vulnerable to this due to their preference for nesting closer to the shoreline than other species of turtles. Another incredibly influential threat to breeding populations is the extraction and sale of olive ridley sea turtle eggs. 80% of sea turtle eggs sold in the market come from olive ridleys. Many female turtles are also killed in the process of collecting eggs, or simply to be used for meat. Separate from humans, olive ridleys are also vulnerable to predation of their eggs and hatchlings. In fact, despite conservation efforts, predation of olive ridleys has increased in Corozalito, Costa Rica in recent years. It is agreed that understanding predation of sea turtle hatchlings is crucial to creating an effective beach management and conservation program.

Conservation Methods

There are many conservation measures being taken by various government and non-government bodies. One of the more concrete conservation efforts is being headed by NOAA with a goal to reduce bycatch, a significant contributor to the endangerment of the species. The NOAA focuses its efforts in implementing measures such as fishing gear modification, changes to fishing practices, and temporal/geographical closures of certain areas that have a high number of turtles. In order to better understand the impact that bycatch has on the turtles, NOAA implements fisheries observers, whose job is to observe and record the instances of bycatch aboard fishing boats. The NOAA also responds to strandings and entanglements through regional networks dedicated to documenting and rescuing strangled or entangled turtles. There are many international partnerships across the world dedicated to the conservation of the turtles, mainly involving governments, non-profits, and private entities, which helps scientists and policymakers make informed decisions about conservation

Despite current conservation efforts, the olive ridley turtle is still endangered, which highlights shortcomings in the current approach to protecting the turtles. Current wildlife trade regulations are insufficient for reducing the capture and sale of ridley turtles through illegal streams. Further expansion of already existing conservation methods is crucial to ensure the safety of the turtles. Nasja et al. identify artificial light pollution to be a key area that needs stricter enforcement, which can be done by making coastal development more sustainable, and limiting artificial light around known breeding grounds. Further engagement with local communities in promoting awareness and conservation efforts would improve the outlook for the olive ridley turtles.

Olive Ridley Refuges in Costa Rica

Overview of Olive Ridley Nesting Behaviours

Olive ridleys tend to nest in very large groups, which are referred to as arribadas, meaning arrivals in Spanish. The species is unique amongst sea turtles, thanks to its ability to host synchronized events, where many thousands of females arrive at the same time to a nesting beach and nest during one shared 3-7 day period.

When females return to these beaches to reproduce every 1-3 years, they first dig nests in the sand, then deposit roughly 90-130 eggs each. After covering the nest up, they return to sea. Incubation will take around 50 days, varying based on temperature. The sex of the turtle depends on the temperature of the sand—when it's around ~29-30°C, this results in an evenly distributed male and female ratio. However, when climate patterns shift, the balance of males and females can be disrupted. Sand temperatures that fall under ~28°C lead to more male hatchlings, while temperatures between ~30-31°C result in majority female hatchlings. Temperatures higher than that can result in unsuccessful embryos.

Ostional Wildlife Refuge

The Ostional Wildlife Refuge was established in 1984 in the Nicoya Peninsula in the Guanacaste province of Costa Rica, and it protects one of the world's most crucial nesting sites for the olive ridley. This refuge safeguards around 7 km of the beach for the main nesting area, and the surrounding area of the coastline. Most of the peak nesting events happen around between August and December, and the largest ever recorded arribada occurred in November 1995, with around 500,000 females having nested at once.

An important note about Ostional (and other arribada-based beaches) is how its hatching success is lower, on average, compared to solitary nesting sites. Research observes that the hatching success is between 0-32% at arribada beaches, compared to between 74-81% at solitary nesting beaches. This is potentially due to the increased microbial abundance in the sand. Destroyed eggshells break down and increase microbial activity, which negatively impacts oxygen diffusion, heat, and embryo vitality.

Ostional is unique because it's the only beach in the world where a legal harvest of turtle eggs would be allowed by the local community. This harvesting would occur during the first few days of an arribada, and is only permitted for a limited amount of turtle eggs. Allowing harvesting is a thoughtful choice since it is likely that a number of eggs would be destroyed by trampling anyways. In allowing this to occur, local livelihoods are supported and funds can be used towards conservation initiatives.

Why Refuges Matter

Arribadas are important to the long-term viability of the olive ridley species. They help concentrate enormous amounts of eggs in one space, leading to significant amounts of hatchings at once. Refuges, like Ostional, protect arribadas and ensure the beaches they return to nest are preserved for generations to come. Refuges also offer opportunities for communities to get involved and reduces illegal harvest, which encourages stewardship. Through the hosting of arribadas, refuges also provide educational insights to people passionate about conservation and inspire awareness for marine ecology.

The Impact of Commercialization and Urbanization

The Impact of Commercialization of Turtle Eggs

Commercialization means the large-scale collection and trade of turtle egg for economic benefits. This activity is common in the Central America, Southeast Asia and West Africa. Because the long sexual maturity term and low survival rates of offspring, commercialization will substantially decrease reproductive output and the replenishment of the population by new individuals. The long-term excessive commercialization has declined the population and altered the age structure.

The commercialization of turtle eggs are impacted by both cultural and economic factors. In coastal communities, turtle eggs are considered as traditional food, but with the increase of demands and illegal trades, the activity gradually transfers to commercial enterprise. The illegal networks even connect with organized crime like drug dealing, undermining enforcement of conservation plans. Overall, the commercialization directly decrease the reproductive success rate, emphasizing the sustainable pressure to ocean ecosystem from human’s commercial activities.

The Impact of Urbanization to Turtles

The urbanization of coastal areas has seriously threatened the reproduction of olive ridley Turtles. The expansion of urban areas declines and fragments the beaches for turtle reproduction. The urbanization prevents the natural migration of beaches, speeding up the coastal erosion and decrease the beaches for laying eggs.

Otherwise, the light pollution from urban area will disturb the awareness of direction. The newborn turtles depend on the natural light to climb into the ocean, but artificial light will misguide them to land, causing dehydration and predation.

The urban area has also altered the temperature and humidity condition of the beaches.The heat island effect and deforestation increase the sand’s average temperature. Meanwhile, the gender of turtle babies depends on the temperature, therefore, the abnormal temperature will cause lower survival rate and imbalance gender structure in population.

Conclusion

The olive ridley sea turtle is an important keystone species within marine ecosystems, but its survival remains uncertain due to the compounding pressures of urbanization, bycatch, and commercial exploitation. While unique conservation strategies such as the authorized harvests at the Ostional Wildlife Refuge and international regulatory frameworks demonstrate progress, the persistent vulnerability of populations highlights the insufficiency of current protections. Securing a future for these turtles ultimately demands a more aggressive, multi-pronged approach that bridges local community engagement with stricter enforcement of environmental policies.

To increase the chances of long-term recovery for the olive ridley turtle, conservation programs should address the sources of population decline—such as the lack of strong wildlife trade regulations and presence of coastal development projects. Community-based governance in Costa Rica can work in tandem with scientific monitoring, and this collaborative action helps uplift both local livelihoods and species resilience for generations to come.

References

This conservation resource was created by Course:CONS200.