... Pacific Ridley Sea Turtle (Lepidochelis olivacea) ...
by Infocostarica Staff

The pacific olive ridley is probably the most abundant of the seven or eight currently recognized species of sea turtles. However they have been consistently neglected until this decade, are frequently misidentified, and are at present the least understood.

The olive ridley is widely distributed in circumtropical seas. Mayor nesting beaches identified in the Mexican states of Jalisco, Guerrero, and Oaxaca, the Nicoyan peninsula of Costa Rica , Surinam, Angola, Mozambique,Madras and Orissa, Sri Lanka, Malaysia, Pakistan, and the Andaman Islands.

Ridleys appear to prefer coastal areas, but large groups have been seen in the open ocean. Their behavior were more like bottom dwellers than others and frequented the shallow water between reef and coast line. In fact, very little is known of the habits of all sea turtles away from the nesting beaches where they have been observed and studied the most.

Food habits of olive ridleys is not well known. Early reports stated that their diet consisted primarily of vegetation. It seems likely, considering the frequent open ocean observations of ridleys and a few cursory examinations of stomach contents, that fish, mollusks, echinoderms, jellyfish, and especially pelagic crabs are important food items for this turtle.

The phenomenon of synchronized mass nesting, where several thousand turtles emerge together, is peculiar to the ridleys. Two sites of such activity, called arribadas in Latin America, are known on the Pacific coast of Costa Rica. At Playa Nancite in Santa Rosa National Park the species go by the name "carpintera". This name is used at least as far south Playas del Coco.

Local lore throughout the range of the ridleysis surprisingly consistent. The fleets are supposed to arrive during the last quarter moon, with a strong onshore wind and on a rising tide. However attempts to relate the occurrence of arrivadas to environmental parameters have not been successful.

The unpredictable nature of arribadas and the difficulty of correlating their occurrence with any known environmental factor suggest that they may be triggered by a pheromone. Their behavior is stereotyped and well documented. They generally prefer a fairly level beach free of flotsam above the high-water spring tide line. When nesting alone, ridleys are not nearly as selective as green turtles, although a steep sand embankment , the upper beach vegetation line, an estuary, or temporary tidal or freshwater impoundment will usually cause them to "half-moon" or return promptly to the ocean without nesting. During the march up the beach ridleys plow though the sand with their noses, implying that olfactory sensing may play a role in beach recognition or site selection on the beach.