Olive Ridley Sea Turtle

Habitat
The olive ridley swims among the warm waters of the tropics.

Range
This turtle is found across the world's oceans. In Costa Rica, it only nests on the Pacific side, with the highest numbers in Guanacaste.

Nesting Sites
Playa Ostional, Playa Nancite, Santa Rosa National Park.

Physical Description
This is the smallest marine turtle that can be seen near Costa Rica's beaches. Its wide carapace (or shell) is heart-shaped and has 6 to 8 scutes (or plates) on each side of the center row. Two pairs of scales are on the face between the eyes and nostrils. On its upper sides the turtle is mostly an olive green color, with greenish-white on the undersides. Males have a long tail and a concave plastron (the belly side of the shell), while females have a short tail and a flat plastron.

Biology and Natural History
The olive ridley displays a spectacular behavior known as an arribada, which is a vast group of turtles collecting to nest at the same time and place. Only one other species, the critically endangered Kemp's ridley (Lepidochelys kempi) holds these arribadas of synchronized nesting, and Kemp's ridley is not found in Costa Rica. The olive ridley arribadas occur in five beaches in the world, and two of these are on the Pacific coast of Costa Rica. Olive ridley arribadas peak in September or October. In the off season, small arribadas of 500 to 10,000 females may congregate between January and June.

The arribada begins and ends abruptly. More than 150,000 sea turtles congregate offshore in shallow waters. Once the females begin moving towards the shore in droves, they do not stop, continuing through daybreak or disturbance. If the weather is extremely bad, they may delay for a time and retain their eggs until the sky clears. The arribada lasts four to eight days, bringing waves of turtles up the beach at each high tide. At Playa Ostional, 150,000 to 200,000 turtles come to nest in just four days.

With so many turtles nesting in a small area, a lot of eggs are dug up or destroyed by the females who arrive later in the arribada. Costa Rican legislation allows some egg harvesting on Playa Ostional at the beginning of the arribada to use the eggs that would otherwise be crushed.

Although the turtle is protected by law, the olive ridley is still suffering many deaths and the magnificent arribadas are getting smaller. Trawling and fishing during a single arribada can cause devastating losses for this sensitive species. The effects of such damage last a long time.

The olive ridley is a vulnerable species. It is protected by international policies and illegal to hunt. Read about Sea Turtles: Promises and Threats to learn more about the challenges facing this animal.

Diet
Some of the important food groups for the olive ridley are fish, crabs, jellyfish, and mollusks.

Height/Weight
This sea turtle is small compared to its relatives. The carapace (or shell) is usually between 60 and 70 cm long. An adult female can weigh just over 40 kg.

Taxonomy
Order: Testudines
Family: Cheloniidae

Sources
Cornelius, S. E., in: Janzen, Daniel H. Costa Rican Natural History. Chicago: University of Chicago Press, 1983.
Leenders, Twan. A Guide to Amphibians and Reptiles of Costa Rica. Zona Tropical, S.A, Miami, FL, 2001.

-Amy Strieter, Wildlife Writer