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

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.

Illegal take of nesting sea turtles in Tortuguero, Costa Rica: Conservation, trade, or tradition?

Tortuguero, Costa Rica is considered the second largest green turtle (Chelonia mydas) rookery in the world. By 1950, Tortuguero was one of the sites with the greatest take of green turtles in the Caribbean. Currently, Tortuguero is a worldwide example for ecotourism-based on sea turtle conservation. However, illegal take of nesting turtles still occurs. We aimed to describe the illegal take at Tortuguero, estimating the minimum number of sea turtles taken using data collected during daily and weekly track surveys from 2005 to 2021. Additionally, we conducted 12 semi-structured interviews with key informants to obtain a better understanding of this activity. We documented 735 nesting turtles illegally taken at Tortuguero, being the green turtle the most affected species; these findings were also supported by our interviewees. Respondents stated that in Tortuguero the take of sea turtles has always occurred and traditions regarding sea turtle meat consumption are still present, even though it is considered shameful in the village. However, our interviewees affirmed that most of the sea turtles taken are traded to other locations away from Tortuguero. Our findings represent the minimum of illegal take (documented only at the beach), as not all the sea turtles taken were observed. Finally, despite long-standing conservation efforts carried out in Tortuguero, further changes in the National Park's management plans are needed, including more personnel and increased law enforcement. This may be necessary to reduce the impact on the Tortuguero green turtle nesting population in the near future.

Dynamics of human take and animal predation on sea turtle nests in Northwest Costa Rica.

Many conservation projects relocate sea turtle eggs to hatcheries to protect the sea turtle nests from the anthropogenic and natural threats they face in the early stages of development. The Rescue Center for Endangered Marine Species (CREMA) manages four sea turtle conservation projects on the nesting beaches of the Southern Nicoya Peninsula in Costa Rica, where the predominant nesting activity is from olive ridley turtles (Lepidochelys olivacea). Two of these nesting projects are based in Costa de Oro and San Miguel, which are adjacent beaches divided by an estuary. In this study, we compared the dynamics and rates of human and animal predation of nests prior to being relocated to the hatchery on both nesting beaches from 2012 to 2018. We hypothesized that human take and animal predation were compensatory threats, meaning that lower human take may result in higher animal predation, and vice versa, resulting in a similar number of nests lost to predation overall. We discuss the community-based conservation programs on both beaches, one of which has been monitored since 1998 (San Miguel) and the other of which has been monitored since 2012 (Costa de Oro). We found that Costa de Oro exhibited high rates of human take with up to 51% of nests being extracted per season, which has decreased since the conservation project was established. Human take was significantly higher than animal predation on both beaches and human take was significantly higher in Costa de Oro. While San Miguel exhibited higher animal predation, the difference was not statistically significant. Higher depredation by animals corresponded to higher overall nest abundance on both beaches. We were unable to find evidence that human take or animal predation increased in the absence of the other threat, suggesting a lack of compensatory effects of predation. Our findings support further analysis of animal predation and a continuation of patrol-based conservation efforts as well as community outreach to attempt to merge cultural values with sea turtle conservation.

Corozalito: a nascent arribada nesting beach in Costa Rica.

Costa Rica hosts two renowned olive ridley (Lepidochelys olivacea) arribada beaches: Nancite and Ostional. In addition, the country hosts a third nascent arribada beach in Corozalito. We documented the frequency of arribada events in Corozalito (9°50'55.40″ N; 85°22' 47.67″ W) from 2008 to 2021 and the abundance of egg-laying females during 12 arribadas. Moreover, we report on tag recaptures at Corozalito that were initially deployed at other nesting beaches in Costa Rica. Finally, we estimated incubation temperature, and performed quadrat and nest excavations to estimate hatching rates. We registered 29 arribadas at Corozalito since 2008, all between August and January. We estimated more than 150,000 olive ridleys nested during 12 arribadas from 2019 to 2021. Mean hatching success was 65% in quadrats and 59% for in situ marked nests. The mean incubation temperature was 32.3 °C. We found turtles tagged at other locations on the Pacific coast of Costa Rica nesting at Corozalito, providing evidence of philopatric plasticity. We suggest nascent arribada rookeries form rapidly via recruitment from regional turtle aggregations. Our findings show that hatching success is far higher at Corozalito than Ostional or Nancite. Continued monitoring of nesting dynamics at this site may shed light upon the mechanisms that rule how arribada beaches are born and evolve. Corozalito offers a unique opportunity to study and understand the arribada phenomenon and warrants official protection under official National Wildlife Refuge status.

Using GPS-enabled decoy turtle eggs to track illegal trade.

The insatiable human appetite for wildlife products drives species to extinction, spreads disease and has negative consequences for the economies of source countries [1,2]. As a major transnational enterprise, illegal wildlife trade is valued between eight and 26.5 billion US dollars annually [3,4]. Because law enforcement is often only reactive, information on trafficking routes is key to disrupting trade and curtailing wildlife crime. In our efforts to uncover trade routes of trafficked sea turtle eggs, we developed and field-tested the InvestEGGator, a 3D-printed decoy turtle egg embedded with a GPS-GSM transmitter (Supplemental Information). Illegally collected clutches of turtle eggs containing a decoy transmitter enabled us to track the movements of traffickers, and thus gain a better understanding of illegal trade routes. The decoys, set to emit a signal once an hour, provided five tracks, the most detailed of which identified an entire trade chain, covering 137 km. Using data provided by the decoys, we identified trafficking routes and on two occasions properties of potential interest to law enforcement. Decoys also yielded anecdotal information, furthering our understanding of trafficking routes.