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Turtle conservation update from Costa Rica

Sea turtles are one of the oldest reptilian species at over ten million years old, yet the survival of the species is under threat. The Osa Conservation and Frontier Costa Rica turtle project has been producing some interesting results over the last survey phase, which has allowed the team to gather once again data regarding the mysterious ecological behaviour of these fascinating animals.

Learn more about the Frontier Costa Rica Big Cats, Primates & Turtles Conservation project and how to get involved.

Video courtesy of Alex Prior, Costa Rica Big Cats, Primates & Turtles Conservation

Since 2003, Osa Conservation have been patrolling the beaches of the Osa Peninsula aiming to deter poachers and predators to ensure the long–term conservation of turtles nesting on these shores. Subsequently their team was joined by Frontier with the objective of patrolling the beaches and gathering together important data on turtles coming to nest on these sites.

The overall aim of the project is to be able to create a database with relevant annual information on the nesting cycles of various species of turtle present on this peninsula. In addition, data is being gathered relating to hatchling success, predation levels and methods of protection, location of the nesting sites and size, health and species of turtle and flipper tagging individuals. The patrol area covers approximately 8 kilometres, and comprises a stretch of land between Playa Piro and Playa Pejeperro.

Image courtesy of Helen Walters, Costa Rica Big Cats, Primates & Turtles Conservation

There are two species of marine turtle known to nest frequently on Playa Piro and Playa Pejeperro: the Olive Ridley turtle (Lepidochelys olivacea) and the Pacific Black turtle, also known as Pacific Green (Chelonia mydas agassizii). Leatherbacks (Dermochelys coriacea) and Hawksbill turtles (Eretmochelys imbricate) have been seldom sighted as they nest less frequently on these beaches. The Olive Ridley turtle is the more commonly sighted of the two species. Pacific Greens come ashore to nest between December and March, whereas Olive Ridley Turtles tend to nest from July until September. In some areas the two species will tend to nest together, where hundreds of turtles swim ashore at one given time. This extraordinary event is known as “arribadas” (Gaos et al, 2006; Savage, 2002).

Image courtesy of Costa Rica Big Cats, Primates & Turtles Conservation

Over the past few weeks, the team has been concentrating solely on morning patrols as the Oliver Ridley turtles which nest during the night have stopped arriving at the beaches, as their season is now over. The Pacific Green season however, is currently ongoing and this species tends to lay its eggs during early morning hours. The team had also explored the difference in nest position between the two species. As predicted the Pacific Greens tend to nest much closer to vegetation stands with respect to the Olive Ridleys. An interesting finding of the study was the very high proportion of false crawls present on the beaches during this phase with respect to previous ones. False crawls, or unaccomplished nesting attempts, may be occurring due to a number of different factors, usually strictly related to the environment. The higher proportion or false crawls by Pacific Greens during this phase could be related to their sensitive nature when choosing a nesting site and their low tolerance to disturbance.

The team also recorded the presence of leatherback turtles during this phase. This species is usually very rarely seen, which makes the outcomes of this phase extremely successful. Furthermore, predated nests have not been recorded so far this year on either beach, although it is early in the year. There have also been some changes especially with regards to the domestic dogs on Pejeperro beach. A house formerly inhabited by locals is no longer occupied and therefore it is possible that the dogs have moved further away in search for food. Tracks are still seen regularly however, predated nests have dropped in numbers. Hopefully this will continue throughout the year.

By Eleonora Arcese

Discover conservation volunteering in the Osa Peninsula with the Costa Rica Big Cats, Primates & Turtles Conservation project, or see all Frontier's opportunities to volunteer.

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