Assessment of the nesting population demography of loggerhead turtles (Caretta caretta) in La Roche Percée: First long‐term monitoring in New Caledonia

Abstract

1. Population monitoring is essential to assess, manage, and protect threatened species. Although the South Pacific loggerhead turtle (Caretta caretta) subpopulation is classified as Critically Endangered by the International Union for Conservation of Nature (IUCN), monitoring data are scarce. 2. This study reports the results of the first long-term monitoring of the nesting population of loggerhead turtle held by Bwärä Tortues Marines on La Roche Percée beach, New Caledonia.3. From 2006 to 2020, capture-mark-recapture was used to identify nesting individuals. Time and nesting success were recorded on site.4. A total of 452 different females were observed and tagged over 14 years. The number of different nesting individuals observed each year showed a significant increase over the time frame of the study. A remigration interval of 3.34 years was observed, and the overall nesting success was 59.02%. This study also reports the internesting intervals and monthly and hourly variabilities in visits to the nesting site.5. The conservation actions led by Bwärä Tortues Marines appear to be correlated with a higher nesting success. This study provides encouraging results and highlights the need to pursue the monitoring and conservation actions implemented by Bwärä Tortues Marines. Further management recommendations are also provided.

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“…territorial knowledge prior to this study [17,20]. The mean number of nests 437 (95% CI = 328-582) surpasses that of the estimated number of loggerhead turtle nesting activities in New Caledonia.…”

“…2.2.1 Nesting data count type. Seasonal survey events were conducted during austral summer in the 'GLS' area to match the reproductive phenology of the loggerhead turtle in New Caledonia [20]. They consisted in a series of 1 to 2 days missions at sea, in which a set of islets were monitored by a minimum of two persons in order to reduce observer bias.…”

“…It benefits the highest monitoring effort, with a minimum of six survey events throughout the nesting season. Surveys were conducted with a two to three weeks interval in between them in order to (1) take into account the loggerhead inter-nesting interval, which varies between 12 to 25 days based on available sources [20,25], (2) efficiently assess the primary nesting phenology parameters, prerequisite key knowledge to the use of statistical methods to quantify total seasonal number of nests, and (3) provide valuable and whenever possible exhaustive counts from one survey event to another, considering the decrease of the nest detection over time. The 16 remaining islets, composing the B-set, were monitored only twice during the season, with a two to three weeks interval at the peak of the nesting season [26], i.e.…”

“…The 16 remaining islets, composing the B-set, were monitored only twice during the season, with a two to three weeks interval at the peak of the nesting season [26], i.e. from mid-December to mid-January [20]. It would later benefit from the nesting phenology knowledge generated…”

“…They combine for the greatest concentration of all reproductive individuals in the South Pacific region, as the remainder of the nesting population is dispersed at a large number of small aggregations with 10s or <10 nesting females per year. In New Caledonia, only one important coastal nesting site with several 10s of nesting females every year has been identified on the west coast of the mainland, in the 'Roche Perce ´e' beach, commune of Bourail [20,21]. Numerous other smaller nesting beaches have been inventoried on dispersed coral islets along the coastline, forming large aggregations off the northwestern coast of the mainland and in the 'Grand Lagon Sud' (GLS) provincial park, at the meridional end of the mainland.…”