Nesting activity of Lepidochelys olivacea, and the effect of artificial shade at Cascajilloso beach, a newly inhabited nesting site in Pacific Panama

Abstract

Sea turtle nesting activity on newly monitored beaches yield important data to support future regional and global conservation assessments. Here, we report on nesting activity of Olive Ridley (Lepidochelys olivacea) at Cascajilloso beach in Pacific Panama based on data from a new hatchery during seasons 2019, 2020 and 2021. Further to this, we conducted a field experiment analyzing the effects of artificial shade versus unshaded treatments on hatchlings' biometric characteristics, hatching success, incubation success and the incubation period. The analyses of three seasons showed that nesting activity, based on number of egg clutches transferred to the hatchery, reached a peak between September (33%) and October (25%). Curved carapace length (CCL) of nesting females (64.3–66.2 cm) was similar to other populations of the Eastern Tropical Pacific (ETP). The number of eggs clutches were 80 in 2019, 73 in 2020 and 108 in 2021; however, the clutch size was slightly smaller (93.92 ± 18.78 eggs) compared with other populations of the ETP. This could be a phenotypic variation of nesting females at this beach. The ability to move egg clutches to the hatchery was affected during 2020 season due to COVID19 restrictions. Heavy rainfall during the incubation period caused a reduction in ambient temperature resulting in cooler (maximum average 29.9°C) nest temperatures registered under artificial shade and unshaded treatments. This could result in males hatchlings during the 2020 season. The warmer temperatures in our experimental nests produced heavier hatchlings contrary to general assumptions, but this was also related to straight carapace length only after a threshold value of 40 mm. Hatchlings under the artificial shade were able to grow to a certain size but potentially at the costs of storing less mass (trade-off). Ongoing beach patrolling and hatchery management techniques with long-term baseline data collection are needed to secure the nesting population of L. olivacea in this recently surveyed beach.