Keywords

Introduction

Sea turtles have been traveling the oceans for millions of years and with an incredible resilience have survived to the present day. This is probably why they are much appreciated and arouse so much interest in the general public and scientists, alike. Turtles belong to the most ancient line of living reptiles, first appearing more than 200 million years ago, in the late Triassic. But it was probably around some 110 million years ago, in the Jurassic, during the reign of dinosaurs, that turtles entered the sea and shared the ocean with several other air-breathing reptiles, such as ichthyosaurus and plesiosaurus. While the end of the Cretaceous was the scene of the mass extinction of large reptiles that dominated the earth, sea turtle lineages persisted until the present day (Lutz and Musick 1997; Motani 2009).

These large marine reptiles are well adapted to life in the ocean, performing vast migrations between foraging and nesting areas that can be thousands of kilometers apart, and inhabiting a variety of neritic and pelagic habitats of tropical and subtropical waters globally (Carr 1982). The oceanic islands of the Gulf of Guinea, particularly São Tomé and Príncipe, harbor important breeding and foraging grounds for sea turtles. Sea turtle nesting grounds on Annobón, the smallest island in the Gulf of Guinea, are limited with only a few suitable beaches available, although important foraging grounds might exist (Castroviejo et al. 1994; Fretey 2001).

It was only in the 1990s that the presence of five sea turtle species in São Tomé and Príncipe was confirmed (Fig. 20.1): the Green Turtle Chelonia mydas (Linnaeus, 1758), the Olive Ridley Turtle Lepidochelys olivacea (Eschscholtz, 1829), the Hawksbill Turtle Eretmochelys imbricata (Linnaeus, 1766), the Leatherback Turtle Dermochelys coriacea (Vandelli, 1761), and the Loggerhead Turtle Caretta caretta (Linnaeus, 1758). Research in the past decade has greatly improved our knowledge of these populations, highlighting their regional and global importance. Simultaneously, there have also been significant efforts towards their protection. Since data regarding sea turtles in Annobón is scarce and that there are no conservation initiatives targeting these species on that island, this chapter will focus on Príncipe and São Tomé.

Fig. 20.1
A photograph of five sea turtle species in Sao Tomé and Principe. It includes the Green Turtle Chelonia mydas, the Olive Ridley Turtle Lepidochelys olivacea, the Hawksbill Turtle Eretmochelys imbricata,the Leatherback Turtle Dermochelys coriacea, and the Loggerhead Turtle Caretta caretta.

Sea turtles of the Gulf of Guinea islands: (1) Female Green Turtle Chelonia mydas; (2) Green Turtle hatchlings; (3) Female Leatherback Turtle Dermochelys coriacea; (4) Leatherback Turtle hatchlings; (5) Female Olive Ridley Turtle Lepidochelys olivacea; (6) Juvenile Hawksbill Turtle Eretmochelys imbricata; (7) Male Loggerhead Turtle Caretta caretta; (8) Mating Green Turtles. Photo credits: (1) Maria Branco | Programa Tatô, (2, 4, 7) Ana Besugo, (3) Ivana Tacikova, (5) Joana Meneses, (6) Victor Jimenez | Programa Tatô, (8) Lara Baptista | Fundação Príncipe

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History of Sea Turtle Conservation in São Tomé and Príncipe

The first references to sea turtles in São Tomé and Príncipe date back to 1883. At this time, sea turtles were described as being common and were exploited by local communities, with carapaces used in the manufacture of jewelry and other ornamental items (Greeff 1884; Bocage 1903). The first sea turtle surveys of the Atlantic coast of Africa started as early as 1957 (Carr 2002), but it was only between 1985 and 1994 that the first attempts were made to describe the status of sea turtles in São Tomé and Príncipe (Stuart and Adams 1990; Schneider 1992; Atkinson et al. 1994; Castroviejo et al. 1994; Graff 1996).

Between 1994 and 1996, a more comprehensive survey was initiated on São Tomé Island thanks to a collaboration between ECOFAC (European Commission Program for the Conservation and Sustainable Use of Forest Ecosystems in Central Africa) and the U. S. Peace Corps. This survey confirmed the sea turtle species occurring in São Tomé and Príncipe, identified the main nesting beaches, assessed the impact of harvesting by the local communities (Graff 1996) and resulted in the baseline information being used to implement a monitoring and protection program on the main nesting beaches (Graff 1996; Rosseel 1997). This project gave rise to Programa Tatô (Tatô refers to the Olive Ridley Turtle in the local language) in 1998. Led by ECOFAC until 2001, it included the monitoring of the main nesting beaches, training of local community members as beach rangers and the construction of hatcheries (Dontaine and Neves 1999; Fretey and Dontaine 2001; Formia et al. 2003). In 2002, MARAPA (Mar, Ambiente e Pesca Artesanal), a national NGO created in 1999, took responsibility for Programa Tatô’s conservation activities. This program survived until 2008 under the jurisdiction of the Central Africa Protected Areas Network (RAPAC) in partnership with the regional network PROTOMAC (Protection Tortues Marines Afrique Centrale), when it suddenly collapsed. Since then, several groups have kept sea turtle conservation efforts going on both islands.

In Príncipe, the Center for the Biodiversity Conservation of Príncipe Island (CBioP), an international research center under the responsibility of the University of Algarve’s CCMar—Ocean Sciences Center in Portugal and the Regional Government of Príncipe, started Programa Sada (Sada refers to the Hawksbill Turtle in the local language) in 2009. The program aims to ensure sea turtle protection and conservation actions in partnership with the regional government and local communities of Príncipe, and focuses on the populations of the Critically Endangered Hawksbill Turtle. In 2010, the Government of the Autonomous Region of Príncipe approved the creation of the Sea Turtle Commission (Comissão Tartaruga Marinha) by the Natural Park of Príncipe, with the main goal of promoting and reinforcing sea turtle protection and their sustainable use on Príncipe.

In 2012, the Natural Park of Príncipe joined efforts with Here Be Dragons Príncipe (HBD, a tourism investment company established in 2010 for the sustainable development of Príncipe Island) and the Association for the Research, Protection, and Conservation of Sea Turtles in Lusophone Countries (ATM, a Portuguese NGO) to develop a comprehensive sea turtle monitoring and protection program on Príncipe Island. After two extremely successful seasons in Príncipe, ATM in 2014 combined efforts with the NGO MARAPA on São Tomé and their partnership reinitiated Programa Tatô. This resulted in the growth of Programa Tatô’s team. In 2018, Programa Tatô was no longer just a MARAPA project. The coordination team, with the support and encouragement of its technical and financial partners, decided to give more autonomy and sustainability to this program and created an International NGO, Association Programa Tatô—the original name, which was well known to all local communities, national authorities, civil society as well as international partners, was preserved.

Meanwhile, on Príncipe, with the transition of ATM to São Tomé Island in 2014, Protetuga Project was created and managed by Fundação Príncipe (FP), a national NGO, established to support environmental and social actions by the HBD group with funding from the South African private-investor and businessman Mark Shuttleworth. At the end of 2016, due to budget cuts from the main donor, FP started to work with its regional, national, and international partners to become independent. Today, FP is independent and has a strategic plan focused on the conservation of biodiversity and the social and economic development of the communities on the island, with more than 15 different donors and projects directed at marine and terrestrial conservation.

Regarding Annobón, although classified as a Nature Reserve since 2000, there is no information or knowledge of any sea turtle conservation efforts on the island.

Species and Status

The modern marine turtles are placed in two families and are the only living members of what had been a large and diverse fauna: the family Dermochelyidae, which consists of a single species, the Leatherback Turtle, and the family Cheloniidae, which comprises six species of hard-shelled sea turtles: the Loggerhead Turtle, the Green Turtle, the Hawksbill Turtle, the Olive Ridley Turtle, the Kemp’s Ridley Turtle Lepidochelys kempii Garman 1880, and the Flatback Turtle Natator depressus (Garman, 1880).

Five of the seven modern species are found in São Tomé and Príncipe, all of which are listed as threatened (IUCN 2021): the Olive Ridley, the Leatherback and the Loggerhead Turtles as Vulnerable, the Green Turtle as Endangered), and the Hawksbill Turtle as Critically Endangered. All of these five species nest on the beaches of the islands, except for the Loggerhead, which is occasionally found at sea (unpublished data). The Green Turtle is the most common sea turtle in the archipelago, nesting on virtually all sandy beaches of both islands (unpublished data). This nesting population exhibits relatively high levels of genetic diversity and distinctiveness, representing an important genetic pool in the region (Hancock 2019). The Olive Ridley Turtle is the second most numerous species on São Tomé, while only sporadic nesting occurs on Príncipe (unpublished data). These islands harbor one of the last remaining Hawksbill Turtle nesting aggregations in the region, which have a unique genetic haplotype and low genetic variability (Monzón-Argüello et al. 2011) and are one of the 11 most threatened sea turtle populations in the world (Wallace et al. 2011), emphasizing the high degree of isolation and vulnerability of this population. The Leatherback Turtle is the least abundant nesting species in the archipelago (unpublished data).

Distribution and Habitat

São Tomé and Príncipe are unique islands with clear warm oceanic waters surrounded by shallow rocky reefs sparsely colonized by hard and soft corals, vast beds of rhodoliths, and great diversity of macroalgae and seagrass meadows, which are more common in São Tomé. Coastlines change from an extensive shallow shelf and low wave exposure in the northern coasts to short and deeper shores more exposed to waves in the southern coasts of both islands. Freshwater enters the sea from small streams and rivers, forming small estuarine habitats in a few areas with mangroves bordering some of the river mouths (Bollen 2017; Cowburn 2018; Airaud et al. 2020; Ferreira-Airaud et al. 2021).

São Tomé has a diversity of beaches ranging from golden yellow sand to dark gray sandy or rocky stretches and varying between 0.17 and 2.11 km in length. Coastal vegetation is shaped by a wide range of precipitation and relatively homogeneous temperature (daily average of 27 °C): coastal meadows and a savanna-type ecosystem can be found on the northern coast, where rainfall is less than 700 mm a year, while in the south yearly rainfalls over 7000 mm feed luscious rainforests (Ceríaco et al. 2022; Dauby et al. 2022). Mangroves can be found on sheltered coasts along this gradient. Príncipe displays a luxurious green wilderness with a magnificent topography of volcanic landscapes. The forest is omnipresent and, in most places, falls directly into the ocean from high cliffs with several narrow beaches up to 1.4 km in length ranging from white, golden to black sand or rocky stretches.

This exceptional environment offers optimal conditions for colonization by sea turtles, both on the nesting beaches and on foraging sites at sea.

Nesting Beaches

Sea turtle nesting occurs on almost all the sandy beaches of both islands that offer suitable conditions for nesting, even though distribution and density vary between species. The nesting season on both islands coincides with the rainy season, which runs from October to May, providing suitable conditions for nesting and incubation.

In São Tomé, nesting occurs on the northern, eastern, and southern coasts (Fig. 20.2). The northern and eastern coastal areas host large human settlements, whereas the southern (particularly southwestern) beaches are relatively remote. The lack, or very low prevalence, of nesting on the western coast of São Tomé is likely due to the rocky beaches characterizing this stretch of coast.

Fig. 20.2
A diagram illustrates four geographical distributions of the average number of nests of the turtles in Sao Tome between 2017 and 2020 for green turtle Chelonia mydas,olive Ridley, Hawksbill, and leatherback turtle Dermochelys coriacea.

Distribution of the average number of nests per species in São Tomé, from 2017 to 2020: (a) Green Turtle Chelonia mydas; (b) Olive Ridley Turtle Lepidochelys olivacea; (c) Hawksbill Turtle Eretmochelys imbricata; and (d) Leatherback Turtle Dermochelys coriacea

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In Príncipe, nesting occurs mainly on the northern and southeastern beaches (Fig. 20.3). Most of the southern beaches are particularly remote with almost no human settlements.

Fig. 20.3
Three maps illustrate the geographical distributions of the average number of nests of the animals in Principe from 2017 and 2020, for Green turtle mydas, Hawksbill turtle Eretmochelys imbricata, and Leatherback turtle Dermochelys coriacea.

Distribution of the average number of nests per species in Príncipe, from 2017 to 2020: (a) Green Turtle Chelonia mydas; (b) Hawksbill Turtle Eretmochelys imbricata; and (c) Leatherback Turtle Dermochelys coriacea

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In Annobón, nesting is limited due to the availability of only a few suitable beaches (Castroviejo et al. 1994), this oceanic island.

Green Turtle

The Green Turtle is the most common species in the archipelago. Its nesting has been confirmed on virtually all sandy beaches of both islands, ranging from 49 to 1177 nests per year on São Tomé and from 287 to 2050 nests per year on Príncipe (from data collected by our team between 2014 and 2020). Data collected since 2014 confirm what was observed during the initial surveys in the 1990s, namely that Green turtles on São Tomé nest mainly in the south, with Praia Jalé being the preferred beach (70% of the total nesting by the species), followed by Praia Grande, both in the region of Porto Alegre, in the Caué district (Fig. 20.2a). This area is characterized by high rainfall, dense tree cover, beaches with steeper slopes and high wave exposure. On Príncipe, green turtles nest mainly in Praia Grande do Norte in the northern part of the island and in Praia Infante in the south (Fig. 20.3a). Green turtle nesting occurs year-round (except June), with a nesting peak in December and January.

Olive Ridley Turtle

Major nesting grounds of Olive Ridley Turtles in West Africa are in Angola and Gabon (Metcalfe et al. 2015; Morais and Tiwari 2022). Nevertheless, this is the second most numerous species on São Tomé, ranging from 326 to 683 nests per year between 2014 and 2020 (unpublished data). On Príncipe only two nesting observations were recorded on Praia Macaco in 2012, and on Praia Grande do Norte in 2018. This species nests year-round (except June), with a nesting peak in November and December. Olive Ridley Turtles seem to prefer the northern area of São Tomé from Praia Juventude to Praia das Conchas, adjacent to the fishing communities of Micoló, Fernão Dias, and Morro Peixe, where 90% of the nesting occurs (Fig. 20.2b). This area is characterized by lower rainfall, gentle sloping beaches, an extensive shallow shelf and low wave exposure shores. The northern part of São Tomé is also notable for the presence of seagrass meadows, an ecologically valuable marine habitat and feeding grounds for the Green Turtle.

Hawksbill Turtle

The Hawksbill Turtle is the most threatened turtle species on São Tomé and Príncipe and, nowadays, its distribution is less extensive due to the indiscriminate harvesting for its meat and shell (Fretey et al. 2000). Nevertheless, the number of nests appears to be increasing slightly, ranging from 13 to 246 nests per year on São Tomé and from 43 to 118 nests per year on Príncipe (unpublished data collected between 2014 and 2020). Most of its nesting (60%) on São Tomé occurs on Rolas Islet, south of São Tomé, highlighting the importance of this islet as a priority site for the conservation of this Critically Endangered species (Fig. 20.2c). On Príncipe, the preferred beaches are Praia Infante in the south and Praia Grande do Norte in the north (Fig. 20.3b). Hawksbill nesting occurs from August to April with a nesting peak in December and January. Like Green Turtles, Hawksbill Turtles seem to prefer beaches characterized by dense tree cover, steeper slopes, high wave exposure and high rainfall.

Leatherback Turtle

One of the major nesting grounds for Leatherback Turtles is in Gabon, approximately 300 km from São Tomé and Príncipe, with as many as 36,185–126,480 nests, and 5865–20,499 breeding females per year (Witt et al. 2009). In São Tomé and Príncipe, it is the least abundant nesting species with 15–155 nests per year in São Tomé and 3–44 nests per year in Príncipe, (unpublished data collected between 2014 and 2020). Nesting occurs from September to March with a nesting peak in December. Although this species has a more heterogeneous distribution, there is a certain preference for the southeastern beaches on São Tomé (Fig. 20.2d) and the northern and eastern beaches on Príncipe (Fig. 20.3c).

Loggerhead Turtle

Extensive surveys in the eastern Atlantic suggest that the only significant nesting aggregation is in Cabo Verde (Fretey 2001; Ehrhart et al. 2003; Marco et al. 2012). Historically, in São Tomé and Príncipe there have been only a couple of observations of Loggerhead Turtle nesting on São Tomé, but there is no evidence that this species has ever nested frequently on the islands (Fretey 2001). Since 2014, only one nesting event (82 cm CCL—curved carapace length) has been registered on São Tomé, in January 2017 at Praia Inhame in the south of the island (Porto Alegre region; our data). In addition to these isolated events, Loggerhead Turtles are occasionally observed at sea (our data).

Foraging Grounds

After hatchlings emerge from the nest and make it safely to the sea, they swim in a frenzy to reach the open ocean. The “lost years” characterize this lesser-known period when young sea turtles stay away from coastal areas until they become juveniles. Foraging habitats vary among species (Musick and Limpus 1997). All species occurring in São Tomé and Príncipe are found foraging year-round in coastal waters.

Green Turtle

Local fishermen have indicated several foraging or aggregation sites of Green Turtles around both Príncipe and São Tomé, which have been confirmed through in-water surveys developed by the sea turtle conservation programs (our data). Both islands host two distinct immature groups of foraging green turtles: small immature, likely to have recruited recently from the oceanic to the neritic zone, and larger immatures that explore the local resources for extended periods.

On São Tomé, Green Turtle immatures hand-captured at sea since 2014 during Programa Tatô in-water surveys ranged from 34 to 45 cm CCL (Curve Carapace Length; Hancock et al. 2018), which is consistent with historical records from the 1990s of small immatures ranging from 33 to 45 cm CCL (Fretey and Dontaine 2001). This is within the expected size range at recruitment for post-pelagic turtles of this species (Musick and Limpus 1997) but slightly smaller than other locations in the Atlantic (Reisser et al. 2013) and Pacific (Arthur et al. 2008).

Small immature Green Turtles are more commonly found in a foraging ground identified in the south of São Tomé; it is possible that the rocky substrate of southern São Tomé is well suited for omnivores because it is rich in macroalgae and benthic invertebrates and provides more resting or hiding sites for the smallest individuals than the exposed seagrass beds located in the north foraging ground. Large immatures range from 45 to 75 cm CCL, since the minimum size observed in nesting females on São Tomé ranges between 72 and 75 cm CCL. These large immatures are more often found feeding upon green algae and seagrasses in the northern foraging ground, where there are large seagrass meadows.

On Príncipe, the recruitment size for small immatures is lower than on São Tomé, with the smallest individual observed having 28 cm CCL; large immatures on Príncipe have a maximum CCL over 70 cm. Individuals are observed, mainly in rocky reefs covered with macroalgae all around Príncipe, but to date the main green turtle foraging grounds on Príncipe have not been identified. Analysis of stomach contents of stranded immature green turtles revealed that these animals feed on several algae species present on rocky reefs around the island. Transmitters with cameras placed on adult females nesting in Praia Grande do Norte, north of Príncipe, in 2018, confirmed that these females feed on algae during the inter-nesting period in the bays near the nesting beach.

These foraging sites clearly indicate that these islands are important recruitment and development habitats for immature Green Turtles in the region, and that after reaching maturity, adults move to other foraging sites in the region. Ongoing satellite telemetry studies will refine our understanding of adult foraging grounds and migration routes.

Olive Ridley Turtle

Globally, Olive Ridley Turtles may use a wide range of foraging habitats, primarily neritic in relatively shallow benthic waters or sometimes in major estuaries as recorded in Australia (Whiting et al. 2007), Oman (Rees et al. 2012), French Guiana (Plot et al. 2015), and Brazil (Santos et al. 2019). They are also known to feed in oceanic deep waters, as seen in Costa Rica (Plotkin 2010), India (Ram et al. 2009), Gabon and Angola (Maxwell et al. 2011).

The foraging behavior of Olive Ridley Turtles in São Tomé and Príncipe is largely unknown, with only a few observations in the past few years during in-water surveys. However, recent incidental fishery bycatch records, beach strandings, and fishermen testimonials revealed that the coastal waters of both islands may host important foraging areas for both adults and immatures throughout the year. Small immatures were observed on a few occasions at both islands. The smallest were registered in 2014 on São Tomé with a CCL of 20 cm, and in 2015 on Príncipe with a CCL of 18.8 cm; others individuals within the same size range have been observed since then. According to a local fisherman, they can be seen feeding on eggs of flying fish (Exocoetus spp.) that breed on the southwest coast of São Tomé from June to August.

Hawksbill Turtle

As with Green Turtles, shallow waters of both islands host year-round Hawksbill Turtle foraging aggregations of small and large immatures, and of mature males and females in rocky reef and coralline algae (rhodolith) habitats. On São Tomé, the main foraging grounds are in the south, at Rolas Islet, and on the northwest coast, adjacent to Neves and Santa Catarina. On Príncipe, most of the rocky reefs are used by the species, where it can find a variety of suitable food items, such as rhodoliths and macroalgae, hard and soft corals and other invertebrates.

While immature Hawksbill Turtles found in shallow waters are assumed to be residents for certain periods, ongoing satellite telemetry studies on nesting females have revealed that most of the adults migate from nesting to foraging grounds, adults may.

On São Tomé, the smallest Hawksbill Turtle hand-captured at sea was 30 cm CCL, while the minimum size observed for nesting females was 55 cm CCL on São Tomé.

On Príncipe, the smallest immature had 26.5 cm CCL (Ferreira et al. 2018).

Leatherback Turtle

Leatherbacks are the most pelagic sea turtle species, spending much of their life in the open sea, but foraging over continental shelves where environmental conditions favor the presence of gelatinous zooplankton, their favorite prey (Dodge et al. 2014).

In São Tomé and Príncipe there are no recent records of Leatherbacks foraging in the coastal waters, besides sightings and bycatch by local fishermen during the nesting season. Older records mention three immatures in Príncipe, ranging from 17 to 21 cm CCL, and a of 14 cm CCL one on São Tomé (Fretey et al. 1999). However, since there are no recent records of small immatures, these are thought to be occasional, even though there has been no concerted effort to record immatures of this species.

Loggerhead Turtle

In São Tomé and Príncipe, sporadic observations at sea of adult loggerheads have been recorded over the years during in-water surveys (Ferreira et al. 2015), from local fishermen and in incidental fishery bycatch reports. The most recent record was in 2020, when one was captured with two adult Olive Ridley Turtles, in a bottom gill net around the coast of Príncipe.

Main Threats for the Survival of Sea Turtles

Sea turtles were once very abundant, but today all seven sea turtle species are threatened at a global scale (IUCN 2021). Unquestionably, human interference throughout the past centuries is the cause of their decline (Lutcavage et al. 1997). Today most of the threats affecting sea turtles in the oceanic islands of the Gulf of Guinea are not exclusive to this part of the world, although cumulative impacts make their conservation particularly challenging.

Historical records reveal that sea turtles were once abundant in São Tomé and Príncipe (Matos 1916) and might have been heavily exploited for their meat and shells since the sixteenth century, when São Tomé and Príncipe were first inhabited (Greeff 1884; Parsons 1962; Parsons 1972). The Portuguese transported hundreds of sea turtles on caravels to feed their crews (Fretey et al. 2000; Loureiro and Torrão 2008) and carapaces and scales were delivered to royal and noble families that collected tortoiseshell jewelry and art objects (Orey 1995). Parsons (1962) indicated that a tortoiseshell industry existed on the islands and supported a domestic trade. Later on, there was also a trading network with Angola, where tortoiseshell products were made into souvenirs (Brongersma 1982; Stuart and Adams 1990; Carr and Carr 1991). The Convention on International Trade in Endangered Species (CITES) came into effect in 1975, to protect plant and animal species from unsustainable levels of international commercial trade, but it was only ratified by São Tomé and Príncipe in 2001 (de Lima et al. 2022). Angola ratified CITES only in 2013, and local artisans of São Tomé and Príncipe report that the occasional clandestine trading of turtle shells still persists.

In the 1990s, 43 artisans working with turtle scutes, known as “tartarugueiros,” were identified (35 in São Tomé and 8 in Príncipe), and an inventory of the scutes and manufactured objects that they possessed weighed 225 kg and 45 kg, respectively, for an estimated value of around 30,000 Euros (Fretey et al. 2000). In 2002/2003, with funds from European Union, all stocks of scutes and manufactured objects were bought from the artisans and donated to the National Museum of São Tomé and Príncipe, and recently destroyed. Until this period, the use of the Hawksbill Turtle shell for the manufacture of handicrafts and jewelry was the greatest driver of the indiscriminate harvest and decline of this species. Today it is still common to find turtle jewelry being sold in some shops in São Tomé, mostly to uninformed tourists.

In the 1990s, almost every sea turtle found at the beach or sea was killed for its meat or shell (Fretey 1998), and despite many conservation efforts over the past few decades, turtles are still killed for their meat and eggs in São Tomé and Príncipe. At sea, adult sea turtles were indiscriminately captured using hooks, harpoons, and gillnets set in front of the main nesting beaches (Castroviejo et al. 1994). Fresh or salted turtle meat was until very recently part of certain traditional menus in São Tomé and Príncipe, and the shell was very often used in the preparation of these dishes as well as for traditional medicinal or as an aphrodisiac (Fretey 1998). However, the use of these animals in traditional ceremonies is not as common as in other West African countries (Barbosa and Regalla 2016). Up until 2016, it was still possible to buy sea turtle meat in the local markets. The most expensive was Green Turtle meat, which sold for 50–100 dobras (2–4 euros) for approximately 300 g, while the least expensive was the Olive Ridley, which sold for around 300 dobras (12 euros) per turtle. Although these practices have decreased drastically in both islands, they still represent a threat to sea turtles in some communities. Finally, a variety of domestic animals and natural predators, including crabs, rats, dogs, and pigs, also depredate sea turtle eggs and hatchlings. Approximately 60% of the sea turtle nests in São Tomé must be transferred to protected hatcheries to prevent nest predation.

In addition to direct exploitation, sea turtles are affected by several indirect threats in São Tomé and Príncipe. Commercial fisheries (many from east Asian countries) operating in the Gulf of Guinea are thought to incidentally capture many sea turtles, mainly Olive Ridley and Leatherback Turtles (Huang 2015). Small-scale fishing activity in both São Tomé and Príncipe represents a major source of income for coastal communities who have few economic resources and opportunities, and the unintentional take in a major threat to sea turtles, particularly longline (vertical and horizontal), demersal gillnet, surface driftnet and purse seine (pers. obs.). However, little is known about the impacts of these artisanal fisheries on sea turtles and other marine resources in São Tomé and Príncipe. The Gulf of Guinea is also the focus of extensive and rapidly increasing oil exploitation activities. Vast oil reserves have been discovered in the last decade, in areas that host important sea turtle habitats. Drilling activities by large international oil corporations, associated with pollution and habitat destruction, are threats that have been increasing and are expected to continue increasing in the region, soon expanding to São Tomé and Príncipe (de Lima et al. 2022).

With a human population estimated to have just surpassed the 200,000 mark, and to be growing at 1.5% each year (Central Intelligence Agency 2021), construction around São Tomé is increasing fast, namely for the tourism sector. The increase in tourism will bring, along with its benefits, some environmental challenges, such as the increase in disturbance of nesting beaches, the need of sand for construction, and the increase in artificial lights by the coast. Despite a national ban of sand mining activities on beaches since 1999 (Decreto-Lei n°35/99) and recently updated (Law n.°9/2020, from 22 of September), sand continues to be extracted, namely from sea turtle nesting beaches, where the effects of sand removal is accelerating erosion, causing the disappearance of several nesting beaches, and exacerbating the consequences of sea level rise due to climate change.

Around urban areas on both islands, most sewage is discharged untreated into the sea. The most extreme national example may be seen in São Tomé city, where the Água Grande river regularly pumps a combination of untreated sewage and petrochemical waste (from the city’s electric generators) directly into the sea at Ana Chaves Bay. In Príncipe, dead stranded turtles found on the beach have been analyzed by Fundação Príncipe to understand whether there is a relationship with the increased presence of waste in the sea and these events. Preliminary analyses show that young and adult turtles (mostly Green Turtles) feed on various solid residues, mostly plastic. In addition to the increasingly presence of this type of waste in the intestinal tract of these animals, it is common to see immature Green Turtles with fibropapillomatosis, a disease that results in the production of tumors, both external and internal, which are benign but may obstruct crucial functions, such as swimming, feeding, sight, and buoyancy, and may lead to death (Herbst 1994). A strong link between this disease and the environmental health of the coastal habitats is already known (Santos et al. 2010; Santos et al. 2011). The first records of this disease in turtles in Príncipe date from 2009 (Loureiro and Matos 2009). Turtles are also particularly vulnerable to a variety of environmental conditions, such as higher water temperature, pollutants, and marine biotoxins, all of which can weaken their immune functions, making them more susceptible to a wide range of pathogens. Sea turtles are often considered sentinels of ecosystem health and in fact, it has been suggested that fibropapillomatosis could serve as an effective tool to monitor ecosystem health in near-shore marine habitats (Aguirre and Lutz 2004).

Conservation

Since the initiation of conservation activities in the country in 1998, one of the first strategies was to work with the government to implement a National Law to protect these threatened species in São Tomé and Príncipe. In 2001, the first draft of the decree was proposed to the national government, but it was only in 2014 that the national law protecting sea turtles and criminalizing the consumptive use of sea turtles and their by-products was adopted in São Tomé and Príncipe (Decreto-Lei n° 8/2014). Remarkably, 5 years before the national law was officialized, the regional government of Príncipe, which has administrative autonomy, implemented a law to protect sea turtles on the island (Decreto-Lei n° 03/2009), which may have encouraged the national government to take action. However, as in many developing nations around the world, enforcement of environmental laws is still challenging, since relevant institutions often lack the technical capability and means to effectively implement the legislation. Since the adoption of the sea turtle national law in 2014, there have been virtually no penalties or sanctions against sea turtle hunters or traders in São Tomé. As for Príncipe, only two cases were penalized with the payment of a fine and some other cases were included in the social assistance program. In this social assistance program, violators of the sea turtle protection law are required to perform social services for the regional government and for the Fundação Príncipe sea turtle conservation program, including a mandatory participation in awareness-raising activities in their own community. This initiative has been an opportunity to involve and promote a change in the mentality of those who violate the law protecting sea turtles.

Before the creation of these domestic laws, São Tomé and Príncipe ratified several international conventions that support in-situ conservation actions (de Lima et al. 2022). The Convention on Biological Diversity (CBD) was ratified in 1999, followed by the Convention on the Conservation of Migratory Species of Wild Animals and CITES in 2001, and by the Abidjan Convention (United Nations Environment Program) in 2002. Although these laws were approved and several conventions were ratified, legal protection of sea turtles does not automatically translate into realistic changes felt on a daily basis. In fact, one of the biggest challenges to sea turtle conservation in developing countries, such as São Tomé and Príncipe, is changing the habits of coastal communities for whom sea turtles are an important source of subsistence and income and are essential for survival. So, as with many other conservation programs worldwide (e.g., Marcovaldi et al. 2005), a consistent and long-lasting conservation program that integrates and generates direct and indirect socio-economic benefits for local communities is essential to prevent sea turtle extinction.

Today, Programa Tatô in São Tomé, and Fundação Príncipe in Príncipe are the key drivers of sea turtle conservation and research in the country. Both conservation programs are based on the key principle that the participation and engagement of local communities are essential for a successful conservation program. On São Tomé, more than 80 people are involved in the conservation activities of Programa Tatô (90% of whom are nationals) and include members from the local communities, young professionals, and 51 rangers responsible for monitoring and protecting foraging grounds and 77 out of the 107 breeding beaches. On Príncipe, Fundação Príncipe, has a team of around 62 people (91% of whom are nationals) developing marine and terrestrial conservation projects, including 32 rangers, who monitor and protect foraging grounds and 36 out of the 50 beaches.

On São Tomé, Programa Tatô initiated a conversion process in 2016, to identify and develop alternative livelihoods for the women who were trading sea turtle products at the main national market, giving rise to a productive group of 17 women willing to transition towards a new livelihood, independent of the sale of sea turtle meat and eggs. Currently, these women produce handicrafts, including school uniforms, reusable masks, and menstrual pads. The program includes continuous follow-up, ensuring the consolidation of this group and their economic sustainability, thus promoting a long-term behavioral change and the recovery of sea turtle populations in São Tomé and Príncipe (Vieira et al. 2017).

We note, however, that the monitoring of beaches and foraging grounds and the direct involvement of a small percentage of the country’s inhabitants is not enough to improve the conservation status of sea turtles. Besides direct employment by creating new jobs for research, internships, ecotourism guides and production of handicrafts, both organizations also develop active and innovative environmental education and public awareness campaigns. In São Tomé, these campaigns were developed after a study to estimate the prevalence of consumption, preference, and availability of sea turtle meat and eggs, and make use of trusted influencers and communication channels. This study helped develop a structured and rigorous approach using behavioral insights to guide behavior change efforts (Veríssimo et al. 2020; Thomas-Walters et al. 2020). Communication, education, and awareness proved to be fundamental strategies not only because they create a better relationship and trust between conservation organizations and communities, but also because they contribute to the development of environmental awareness about the ecological and socio-economic value of sea turtles and about the benefits of their conservation. Awareness efforts involve a variety of initiatives, including educational school programs, sports activities, theater, radio and TV programs and soap operas, beach and ocean clean-ups, and fishing sector awareness activities, among others.

Considering the challenges that sea turtle conservation faces nowadays, both Programa Tatô and Fundação Príncipe have adopted an integrated approach, which is essential to improve the protection and sustainable management of key sea turtle habitats, while developing a community-based marine conservation program that combines research, ecological monitoring, protection of critical sites, environmental education, advocacy, community-based ecotourism, reconversion of former poachers and traders, and development of alternative livelihoods. Thus, these programs have been addressing the diverse and complex challenges of sea turtle conservation, increasing our knowledge of all the sea turtle species that occur on and around both islands, and improving the relationship between sea turtles and diverse stakeholders from small-scale fishing communities to national politicians. Although human threats are still a reality, levels of sea turtle harvest have decreased considerably, and the number of sea turtles recorded on the nesting beaches appears to be increasing (Thomas-Walters et al. 2020). Today sea turtle conservation in São Tomé and Príncipe has an increasing and wider public appreciation, support, and understanding, which provide an opportunity for local stewardship, changing attitudes towards sea turtles and other living marine resources, and preparing future generation to be more aware of environmental topics.

Although research is underway on both islands to better understand the reproductive ecology, spatial and temporal movements, the foraging grounds, and the impacts of anthropogenic threats, it is essential to increase our scientific knowledge for adequate and effective sea turtle conservation guidance, so that critical habitats may be protected using evidence-based conservation priorities and strategies. Major challenges for the future include obtaining resources to maintain the levels of operation developed to date, to continue to support and improve the self-sufficiency of former sea turtle hunters and traders, and to promote greater self-sufficiency of both conservation programs. Nevertheless, the commitment of Programa Tatô and Fundação Príncipe will remain focused on the coastal communities, who are the true motivation for and the main component of any marine conservation program.