Ecology of solitary nesting olive ridley sea turtles at Playa Grande, Costa Rica

Abstract

Olive ridley turtles (Lepidochelys olivacea) have two distinct mating systems: independent (solitary) and synchronized and mass assemblages (arribadas). Arribada nesting beaches have been the focus of most research, even though solitary nesting is the most common behavior. The purpose of this study was to assess the contribution of solitary nesting turtles to the olive ridley turtle population. We studied the nesting ecology of solitary nesting olive ridley turtles within the national park Parque Nacional Marino Las Baulas (PNMB) in Playa Grande, Costa Rica (10°20′N, 85°51′W) and compared these turtles to nearby arribada turtles. Between 2009/2010 and 2013/2014, an estimated 933 nesting activities occurred within PNMB. This number of turtles has not changed significantly since 1995. During this study, 285 females were tagged; of these, 30 females were encountered nesting on more than one occasion. Significantly, more females emerged (31.1 % of tracks) during the third-quarter moon, often a predictor of arribada events, than any other moon phase. However, there was no significant change in nesting activity at PNMB during nearby arribada events. Mean hatching success (78.5 ± 23.4 % SD) was higher, and incubation temperatures were lower (ranging from 28.3 to 33.4 °C) than at nearby arribada beaches. Thus, clutches are relatively successful and may produce males. These data suggest that solitary olive ridley turtles are important. Currently, PNMB protects turtles from October to March; however, hatching success was highest and 40 % of nesting activity occurred during the rainy season (August–November). More turtles could be protected by increasing the temporal scope of park protection.