Abstract
Abstract: This study monitored marine turtle nests in a region known as the Potiguar Basin, which stretches from the northern region of Rio Grande do Norte State (5°4’1.15” S, 36°4’36.41” W) to eastern Ceará State (4°38’48.28” S, 37°32’52.08” W) in Brazil. We collected data from January 2011 to December 2019 to identify species of sea turtles that spawn in the basin, to analyze the nesting spatial-temporal pattern and nests characteristics, and to record effects of environmental and anthropic factors on nests. A field team examined sea turtle tracks and nests signs. Turtle clutches were monitored daily until hatchings emerged from the nests. We monitored nests of hawksbill (Eretmochelys imbricata; n = 238) and olive Ridley turtles (Lepidochelys olivacea; n = 103). The nesting season for E. imbricata occurred between December and May and for L. olivacea from March to August. Hawksbills had clutch size, incubation time, number of unhatched eggs, and dead hatchlings higher than olive Ridley turtles; nevertheless, they presented lower hatching success. Precipitation between 0 and 22 mm and relative humidity (RH) higher than 69% increased the hatching success rate for E. imbricata; however, rainfall above 11 mm and RH 64% had the same effect for L. olivacea. Signs of egg theft and human presence (e.g. vehicle traffic and plastic residues on the beach) were recorded and are considered threats to nests. The results of our long-term monitoring study in the Potiguar Basin provide basis for the implementation of mitigation measures and adoption of management policies at nesting beaches in this Brazilian region.
Highlights
Sea turtle species are distributed around the globe throughout tropical, subtropical, and temperate oceans, migrating to and from their nesting beaches
Characteristics of nests adapted from Miller (1999): (a) clutch size: total number of eggs laid by turtles; (b) incubation time: from the day of egg laying until emergence of hatchlings, when we found tracks of hatchlings on the beach; (c) unhatched eggs: total number of unhatched eggs with no obvious embryo + unhatched eggs with obvious embryo; (d) dead hatchlings: total number of dead hatchlings found in nests; (e) live hatchlings: total number of live hatchlings found in nests + number of empty shells counted (>50% complete); and (f) hatching success = × 100
Most nests of E. imbricata and L. olivacea were recorded between Macau/Rio Grande do Norte (RN) (207/341; 60.70%) and Guamaré/RN (71/341; 20.82%) along 46 km (Figure 2)
Summary
Sea turtle species are distributed around the globe throughout tropical, subtropical, and temperate oceans, migrating to and from their nesting beaches. There are seven sea turtles species and five of which are found in Brazil, namely hawksbill turtle (Eretmochelys imbricata: Linnaeus 1766), olive Ridley turtle (Lepidochelys olivacea: Eschscholtz 1829), loggerhead turtle (Caretta caretta: Linnaeus 1758), leatherback turtle (Dermochelys coriacea: Linnaeus 1766), and green turtle (Chelonia mydas: Linnaeus 1758) (Santos et al 2011). According to the Red List of Threatened Species of the International Union for Conservation of Nature, sea turtles are classified as critically endangered (E. imbricata), vulnerable (L. olivacea, C. caretta and D. coriacea), and endangered (C. mydas) (Seminoff 2004, Abreu-Grobois & Plotkin 2008, Mortimer & Donnelly 2008, Wallace et al 2013, Casale & Tucker 2017). Carapace commerce was the main threat (Castilhos et al 2011, Marcovaldi et al 2011)
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