Predation Rate on Olive Riley Sea Turtle (Lepidochelys olivacea) Nests with Solitary Nesting Activity from 2008 to 2021 at Corozalito, Costa Rica

SIMPLE SUMMARY: Understanding the mechanisms of predation dynamics in a sea turtle nesting beach is important in order to design a proper beach management plan and a valuable conservation strategy when working on sea turtle solitary nesting sites. We evaluated natural nest predation upon solitary Olive Ridley nesting events in Corozalito beach, a solitary and nascent arribada nesting beach on the Pacific in Costa Rica. Our results show a noticeable increase in predation rates close to 30% of nests predated throughout a 13-year study period. This could be an indicator of the increasing number of nesting events in this important nesting site. We suggest continuing to monitor the nesting activity at Corozalito, including the predation rates from other sea turtle species and mass nesting events to give a complete report of the threats that these species are facing in Corozalito and the impact on their population, combined with potential alternatives to manage predators’ impact. ABSTRACT: In Corozalito beach, Costa Rica, Olive Ridley turtles (Lepidochelys olivacea) nest both solitarily and in arribadas. The predation of solitary nests was monitored from 2008 to 2021, recording date, time, sector of the beach, zone, status of nest (predated or partially predated) and predator when possible. We recorded 4450 predated nests in total (N = 30,148 nesting events); predation rates showed a fluctuating trend, with recent percentages reaching up to 30%, with four distinctive dips in 2010, 2014, 2016 and 2017. The spatial distribution of predated nests along the beach showed significant differences among the sectors regardless of the seasons (Friedman test, chi-squared = 14.778, df = 2, p-value = 0.000), with most predated nests (47.62%) occurring in the northern sectors of the beach. Predators were identified by their tracks and/or direct observations (N = 896, 24.08%). The most conspicuous predators identified were raccoons (55.69%) and black vultures (22.77%). As seen in Corozalito, predation rates have increased in recent years despite established conservation efforts. A comprehensive assessment of all threats towards the overall hatching success for clutches is needed, considering predation during mass nesting events, poaching and beach erosion, among other factors, to fully understand the nesting dynamics occurring in this beach.