Some nest only during the day, others only at night, and still others throughout both the day and night. But regardless of what time of day nesting occurs, the turtles are present at the beach for only a few (2-7) days and then, as suddenly as nesting started, it stops. About a month later, the turtles return and mass nesting occurs again.
A map (Figure 3) shows where both species of ridley turtles nest. As far as we know, Kemp’s ridley turtles have a single arribada beach located on the east coast of Mexico,
Figure 4. Hypothesis to account for the balance between solitary and arribada nesting in ridley turtles. Solitary nesting is favored when few turtles nest on any beach, making it difficult for predators to find the nests. However, when more females nest at those sites predators are attracted, destroy the nests, reduce female fitness and make solitary nesting a less favorable strategy. That promotes an increase in arribada nesting. Initially, those nest have high survival probabilities because few predators are aware of places where synchronized nesting activity and hatchling emergence occurs over such a short time period (a week or less). As a result, more females are recruited to the the arribada site, increasing the density of nests. Females returning to the site a month later begin to dig up and destroy the nests of the females that nested earlier, reducing female fitness. The pendulum then swings back in the opposite direction to favor solitary nesting. The result is a balance between the females that opt for each strategy (modified from Bernardo and Plotkin, 2007, op. cit.).
a place called Rancho Nuevo. Olive ridleys have several arribada beaches on the west coast of Mexico, Nicaragua, Costa Rica and Panama, and another arribada in the Caribbean located close to the border between Suriname and French Guiana. Ridley turtles also nest as solitary individuals on the northeastern coast of Mexico, southwestern Texas, and in Brazil. Solitary nesters on occasion nest at sites in close proximity to arribada sites but never at arribada sites. The arribada females nest only at those sites, even when another beach that appears suitable (at least to a human) is close by – in fact, next door!