Keywords

Introduction

Across the world, islands harbor a rich diversity of reptile species, many of them endemic. In contrast to other groups of non-volant terrestrial vertebrates such as small mammals and amphibians, reptiles are successful dispersers across marine barriers due to their ecology and physiology, which enable them to endure long-distance rafting events (Vitt and Caldwell 2004). Some island reptiles, such as the Galapagos tortoises and marine iguanas, rank amongst the most iconic species in the world. These species are especially famous for providing Charles Darwin (1809–1882) with the inspiration for his theory of evolution by natural selection. Island reptiles have since become important models for the study of evolution and adaptation in insular environments. For instance, the anoles (Squamata: Dactyloidea) of the West Indies and lacertids (Squamata: Lacertidae) of the Mediterranean islands are now classic systems for evolutionary and ecological studies (e.g., Corti et al. 2006; Losos 2009). In the eastern Atlantic, reptiles of the Madeira, Cabo Verde and the Gulf of Guinea oceanic archipelagos have been the subject of phylogenetic and biogeographic studies (e.g., Jesus et al. 2003, 2005a–c, 2006, 2007, 2009; Vasconcelos et al. 2010), recent descriptions of cryptic diversity (e.g., Miller et al. 2012; Ceríaco 2015; Ceríaco et al. 2016, 2017, 2021a; Soares et al. 2018), as well as ecological studies (e.g., Lopes et al. 2019).

With approximately 30 species and exceptional endemism, the Gulf of Guinea archipelago is a hotspot for reptile diversity, especially when considering the small land area of the islands. Here we present an updated taxonomic overview of the terrestrial reptiles of these islands and surrounding islets, highlighting diversity, endemism, biogeographic patterns and conservation. Marine turtles are the only non-terrestrial reptiles occurring in these islands and are covered in Ferreira-Airaud et al. (2022). We also provide a brief history of the research on reptiles in the archipelago and highlight important avenues for future work.

History of Reptile Research

The first record of a reptile from the Gulf of Guinea oceanic islands was the description of Mocoa (currently Panaspis) africana by Gray (1845). There are no data regarding the collector or precise locality of collection, but the type locality has since been restricted to Príncipe Island (Soares et al. 2018). Some decades later, the curator of the Zoological Museum of Berlin, Wilhelm Peters (1815–1883), described Typhlops (Ophthamidion) [currently Afrotyphlops] elegans based on specimens collected by the German explorer Heinrich Wolfgang Ludwig Dhorn (1838–1913) on Príncipe (Peters 1868). Subsequently, the German zoologist Richard Greeff (1829–1892) explored São Tomé and Rolas islet from 1879 to 1880 and provided one of the first reports of their herpetofauna (Greeff 1884). Based on specimens collected by Greeff, two species of reptile were described: Scalabotes (now Lygodactylus) thomensis by Peters (1881) and Hemidactylus greeffii by Bocage (1886a). Some of Greeff’s specimens are still extant in the collections of the Museum für Naturkunde Berlin (ZMB) and Zoologisches Museum Hamburg (ZMH).

Following Greeff’s surveys, two Portuguese museums funded expeditions to the Gulf of Guinea oceanic islands. In 1885, the Botanical Gardens of the University of Coimbra sent their chief gardener Adolfo Frederico Möller (1842–1920) to São Tomé to explore and collect natural history specimens for the Botanical Gardens and the university museum. Most of the zoological specimens collected by Möller were sent to the Zoological Museum of the University of Coimbra (ZMUC, now part of the Museu da Ciência da Universidade de Coimbra—MCUC), and a brief inventory of these specimens was published by Vieira (1886). Almost all of this material was examined and identified by the Portuguese zoologist José Vicente Barbosa du Bocage (1823–1907) and is still extant in the collections of MCUC (Themido 1941; LMPC pers. obs.). Some amphibian and reptile specimens, however, were likely sent by Möller to the Russian zoologist Jacques von Bedriaga (1854–1906) who was a correspondent scholar with the University of Coimbra. Bedriaga published a thorough revision of the amphibians and reptiles of São Tomé and described a new subspecies of gecko, Hemidactylus mabouia var. molleri (currently a synonym of H. longicephalus, see below), in honor of Adolfo Möller and provided a detailed description of a specimen of Dendroaspis jamesonii from the island (Bedriaga 1892, 1893a–c). Bedriaga’s publications triggered criticism from Bocage (1892a–c, 1893), who cast doubts on the identity of Hemidactylus mabouia var. molleri (Bocage 1892a) and the Dendroaspis (Bocage 1892c). These disagreements have since been addressed in Ceríaco and Marques (2012) and Ceríaco et al. (2018). There are no further records of the specimens sent by Möller to Bedriaga and they are presumably lost.

Also in 1885, Francisco Xavier Oakley de Aguiar Newton (1864–1909), commonly known as Francisco Newton, was hired by the National Museum of Lisbon to conduct zoological surveys in the Gulf of Guinea. From 1885 to 1895, Newton explored all the Gulf of Guinea islands, as well as Benin, and his specimens were ultimately deposited in the Zoological Section of the National Museum of Lisbon. This material was studied by Barbosa du Bocage, director of the museum, and Júlio Guilherme Bethencourt Ferreira (1866–1948), Bocage’s pupil. Based on Newton’s collections Bocage described four species of reptile from the Gulf of Guinea oceanic islands: Feylinia polylepis, Mabuia [= currently Trachylepis] ozorii, Typhlops [= currently Letheobia] newtoni, and Philothamnus girardi. Also based on these collections, Bocage provided important revisionary works on the fauna of these islands (Bocage 1886a–c, 1873, 1887, 1890, 1892a–c, 1893, 1895, 1903, 1905), and Ferreira (1897) described Hemidactylus newtoni from Annobón. The entirety of Newton’s collections was unfortunately lost in the fire that destroyed the Museu Bocage, Lisbon, in 1978.

Following Newton’s steps, the Italian explorer Leonardo Fea (1852–1903) explored the four principal islands of the Gulf of Guinea from 1901 to 1902 under the sponsorship of the Museo Civico di Storia Naturale of Genoa, Italy (currently known as Museo Civico di Storia Naturale “Giacomo Doria;” MSNG). Fea’s collections, which are still extant in the MSNG with a small subset in the Natural History Museum of London (BMNH), were initially studied by George Albert Boulenger (1858–1937). Based on these collections, Boulenger (1906) described four new taxa: Hemidactylus aporus from Annobón, Typhlops [currently Letheobia] feae from São Tomé, Boodon [=Boaedon] bedriagae, from both São Tomé and Príncipe, and Gastropyxis [currently Hapsidophrys] principis from Príncipe. Some of these specimens were revisited by Lilia Capocaccia in a revision of certain snake genera (Capocaccia 1961a) and the type catalog of the MSNG (Capocaccia 1961b).

A small collection of reptiles from São Tomé and Príncipe, collected by Henri Navel (1878–1963) in 1920, was subsequently studied by the French herpetologist Fernand Angel (1881–1950), who described Typhlops naveli (currently considered as a junior synonym of Letheobia newtoni; fide Roux-Estève 1974) from Príncipe (Angel 1920). An additional contribution to the knowledge of São Tomé snakes was provided by the curator of the American Museum of Natural History, Charles M. Bogert (1908–1992), who used specimens collected by the Portuguese explorer José G. Correia (1881–1954) to review the identity of the São Tomé Jitas (Boaedon; Bogert 1940).

During the 1950s and 1960s the Portuguese Centro de Zoologia da Junta de Investigações do Ultramar (CZL) conducted zoological surveys on São Tomé and Príncipe. The first mission, conducted by the Portuguese zoologist Fernando Frade Viegas da Costa (1898–1983; commonly referred to simply as Fernando Frade), lasted from September 10 to December 26, 1954. Between 1966 and 1967, several herpetological specimens were collected by different researchers associated with the colonial enterprise over the course of multiple scientific surveys. The material collected during these surveys was studied by the Portuguese herpetologist Sara Maria Bárbara Marques Manaças (1896–death date unknown), resulting in two publications (Manaças 1958, 1973). Most of the specimens were housed in the collections of the Instituto de Investigação Científica Tropical (IICT), in Lisbon, Portugal, but in 2016 they were incorporated into the collections of the Museu Nacional de História Natural e da Ciência (MUHNAC), of the University of Lisbon, Lisbon, Portugal. A total of 157 reptile specimens from these expeditions are still extant in these collections (Ceríaco and Marques 2018; Ceríaco et al. 2021b).

Throughout the 1960s and 1970s, several authors used existing specimens in various collections for taxonomic revisions of different genera, resulting in important contributions to the knowledge of the Gulf of Guinea oceanic islands taxa. For instance, the French herpetologist Georges Pasteur (1930–2015) used specimens of the Fea collections in the BMNH to revise the Lygodactylus of these islands (Pasteur 1962), leading to the description of two subspecies of L. thomensis: L. thomensis delicatus from Príncipe, and L. thomensis wermuthi from Annobón. The Swiss herpetologist Jean-Luc Perret (1925–) used specimens from the CZL and Fea collections in the BMNH for his major revision of the genus Panaspis (Perret 1972). Subsequently, the Romanian herpetologist Ion Eduard Fuhn (1916–1987) used specimens from Fea collections housed in the BMNH to describe Panaspis annobonensis from Annobón and review the Panaspis of São Tomé and Príncipe, at the time both considered P. africana (Fuhn 1972).

Following the independence of Equatorial Guinea (from Spain in 1968) and São Tomé and Príncipe (from Portugal in 1975), several teams undertook expeditions to the islands to further expand knowledge on their herpetological diversity. In 1984 a team from the zoology and anthropology department of the Faculty of Sciences of the University of Lisbon and the Museu Nacional de História Natural (Museu Bocage), Lisbon, led by Luis Mendes (1946–), conducted a 1 month (June 13 to July 7) zoological expedition to São Tomé (Mendes et al. 1988). Although the expedition did not have a dedicated herpetologist, some reptile specimens were collected, and these are still extant in MUHNAC collections (Ceríaco and Marques 2019).

Ronald Nussbaum (1942–) from the University of Michigan and Michael Prfender (1960–) visited the islands of São Tomé and Príncipe in June and July of 1988. While mainly focused on the study of amphibians, especially the São Tomé endemic caecilian Schistometopum thomense (Bocage, 1873), Nussbaum and Pfrender also collected several reptile specimens, of which 333 are still in the collections of the University of Michigan Museum of Zoology (UMMZ; see University of Michigan Museum of Zoology 2020). These specimens have not been included in any publication or study, although they represent the third largest reptile collection from São Tomé and Príncipe in any museum and are an important source of data on the geographical distributions of many species. From 1989 to 1991 expeditions to São Tomé and Príncipe led by Catherine Loumont (1942–), Tillman Nill (date of birth unknown), Jakob Fahr (1966–) and Jan Haft (1967–), resulted in reviews of the herpetofauna of these islands (Schätti and Loumont 1992; Nill 1993; Haft 1993). Some of these specimens are housed in the ZMB and the collections of the Muséum d’Histoire Naturelle de la Ville de Genève, Geneva, Switzerland (Andreas Schmitz pers. comm.)

A major contribution to our understanding of the herpetofauna of the three oceanic islands of the Gulf of Guinea was provided by José Jesus (1967–) from the University of Madeira, Funchal, Portugal, who dedicated part of his Ph.D. thesis to study the phylogeny and phylogeography of the islands’ reptiles, providing molecular data for many of the taxa. Jesus and his team visited Príncipe, São Tomé and Annobón in the summer of 2002, and based on the specimens and tissues collected, provided the first molecular phylogenetic and phylogeographic context for the species of the genus Trachylepis (Jesus et al. 2005a, b), Hemidactylus (Jesus et al. 2005c), Lygodactylus (Jesus et al. 2006), Panaspis (Jesus et al. 2007) and Philothamnus (Jesus et al. 2009) occurring in these islands. Jesus et al. (2003) also provided an updated checklist of the reptiles of Annobón, in which they noted the first records of Tropical House Gecko, Hemidactylus mabouia, and the invasive Flowerpot snake, Indotyphlops braminus on the island. The specimens collected by Jesus and his team were primarily deposited in the collections of the University of Madeira, with smaller subsets in MUHNAC and the California Academy of Sciences (CAS), San Francisco.

At about the same time, in 2001, the CAS led by herpetology curator Robert “Bob” C. Drewes (1942–), began what would become known as the CAS Gulf of Guinea Expeditions. This project, which has made a total of 12 expeditions to the islands as of 2020, is still ongoing and has been one of the most comprehensive efforts to study the biodiversity of São Tomé and Príncipe islands since Francisco Newton’s expedition in the nineteenth century. Due to Drewes’ herpetological background, the project has always had a strong emphasis on the study of the amphibians and reptiles of these islands (see Bell et al. 2022). The reptile collections resulting from these expeditions are currently the largest in the world (Table 19.1), with a total of 449 specimens (Scheinberg and Fong 2019). One important taxonomic contribution from these expeditions was the description of the Príncipe Gecko, Hemidactylus principensis Miller, Sellas and Drewes, 2012, the first endemic reptile described from the Gulf of Guinea oceanic islands since 1972 (Miller et al. 2012).

Table 19.1 Main natural history institutions housing reptile specimens from the Gulf of Guinea oceanic islands. Acronyms follow Sabaj (2020)
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Finally, since 2013, a team from MUHNAC led by Luis M. P. Ceríaco (1987–) started herpetological surveys in São Tomé and Príncipe. A total of four expeditions (two in 2013, one in 2015, one in 2016) to Príncipe and São Tomé islands, as well as to Tinhosa Grande islet, were conducted by the team, which resulted in the collection of 155 reptile specimens, currently housed in MUHNAC collections (Ceríaco and Marques 2019). Combined with the specimens collected by Mendes et al. (1988) and those originally from IICT (Ceríaco and Marques 2018), MUHNAC collections hold a total of 354 specimens of São Tomé and Príncipe reptiles and are the second largest in the world. Building on the knowledge amassed through newly collected specimens, the available Portuguese and North American collections, as well as the molecular baseline provided by the Jesus et al. studies, Ceríaco and team have contributed to the taxonomic revision of most of the reptile groups occurring on the islands. This led to the description of: three species of skinks of the genus Trachylepis (Ceríaco 2015; Ceríaco et al. 2016)—Trachyelpis adamastor Ceríaco, 2015, Trachylepis thomensis Ceríaco, Marques and Bauer, 2016, and Trachylepis principensis Ceríaco, Marques and Bauer, 2016, endemic to Tinhosa Grande islet, São Tomé, and Príncipe, respectively; a new species of Cobra (Ceríaco et al. 2017)—Naja (Boulengerina) peroescobari Ceríaco, Marques, Schmitz and Bauer, 2017; a new species of the genus Panaspis, endemic to São Tomé (Soares et al. 2018)—Panaspis thomensis Ceríaco, Soares, Marques et al., 2018; and a new species of lamprophid snake of the genus Boaedon (Ceríaco et al. 2021a)—Boaedon mendesi Ceríaco, Arellano, Jadin et al., 2021. In 2018 Ceríaco’s team moved to the Museu de História Natural e da Ciência of the University of Porto (MHNCUP) and new field work has been carried out since then.

Diversity and Endemism

At present, a total of 29 reptile species have been reported as resident from the oceanic islands of the Gulf of Guinea (Table 19.2). Of these, 22 are endemic to one or two islands, three are presumed invasive/introduced species, and one corresponds to questionable records of a putative species of mamba. An additional species is considered vagrant to São Tomé. We discuss the taxonomic status and biology of each species in more detail below.

Table 19.2 List of terrestrial reptiles from Príncipe (P), São Tomé (ST) and Annobón (A) islands
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Crocodilians

There are currently no established crocodilian populations inhabiting the Gulf of Guinea oceanic islands. Historical records dating back to the first decades of Portuguese presence suggest that a species of Crocodylus occurred on São Tomé. A report from the Portuguese navigator Gonçalo Pires (birth and death dates unknown), transcribed by Valentim Fernandes (ca. 1450–1519) and subsequently published by several authors (Henriques 1917; Baião 1940; Ceríaco et al. 2018) mentions the following:

There were many lizards of about twelve cubits [approximately 540 cm], but now there are few. They eat men and women, cows and bulls and all types of animals. These lizards don’t exit the water, as their tails stay always inside freshwater, and any animal that he captures he takes into the water and in the water he kills it, and it rears up on his tail achieving the size of a man. The current captain, Fernã do Mello, has a very big and fearful lizard contained in a pond, and above this pond he mounted a scaffold to allow its observation. This lizard used to move from the river to the pond several times a month. And he caused a lot of damage to the men and animals, and 1 day, a small and despicable man who observed the lizard for some time, once he found it in the pond and with his hoe he cut the lizard’s limbs and closed the pond so he couldn’t ever escape and went to tell this to the captain.

[LMP Ceríaco’s translation from the archaic Portuguese original]

In a subsequent passage of the text, the authors refer to the “very big lizards, that now fear the men.” [author’s translation from the archaic Portuguese original]. Due to the perceived danger that the São Tomé crocodiles posed to the Portuguese settlers, it is fair to assume that the population was completely extirpated. As no archeological remains of these animals are known, the taxonomic identity of this historical São Tomé crocodilian cannot be determined but is likely that they were either an insular population of Crocodylus niloticus Laurenti, 1768, or C. suchus Geoffroy Saint-Hilaire, 1807.

However, the presence of crocodiles in the islands may be more common than the available data suggest. In early April 2021, a live crocodile appeared on Roça Colónia Açoreana beach, in the southeastern part of São Tomé Island (Fig. 19.1, 1). Other records of a large lizard seen in the Angra Toldo region, and said to be a crocodile, had previously surfaced on social media, but these records have never been confirmed. The animal from Colónia Açoreana was a female Crocodylus niloticus, of approximately two meters total length, which was observed and photographed for several weeks on the beach. Due to the safety concerns it presented, the animal was killed by the authorities at the end of the month (Fig. 19.1, 3–4). The specimen’s head and skin were prepared by two of the authors (LMPC and MPM) and deposited in the biology laboratory of the Portuguese School of São Tomé and Príncipe (Fig. 19.1, 2). Molecular studies are underway to identify the source population of the animal in continental Africa. At about the same time of the appearance of the crocodile in Colónia Açoreana, two Angolan fishermen in a castaway boat that had drifted from the Angolan coast near the mouth of Congo River were rescued near São Tomé by the local authorities. The Gulf of Guinea sea currents and the considerable flow of the Congo River at that time due to heavy rains on the continent may help to explain both of these arrivals.

Fig. 19.1
Five images of crocodiles from Sao Tomé Island. It includes a crocodile swimming in a body of water, the skin of the crocodile on a table in a laboratory and a crocodile lying on the ground with open mouth.

Crocodile from Colónia Açoreana beach, São Tomé Island: (1) Live photo of the animal on 4 April 2021; (2) Skin of the specimen in the biology laboratory of the Portuguese School of São Tomé; (3, 4) Specimen after being shot. Photo credits: (1) Maria Branco, (2) Luis M. P. Ceríaco, (3, 4) Unknown

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Terrapins

Family Pelomedusidae

Only one species of terrapin occurs in the Gulf of Guinea oceanic islands, the West Africa mud turtle, Pelusios castaneus (Schweigger, 1812) (Fig. 19.2, 1). The species has mostly been recorded from São Tomé, where it is locally known as “Bencú” and is used by Santomeans in the local gastronomy. Recent sightings in Príncipe suggest that the species also occurs on the island, but currently, there are still no available specimens in public collections to permit a clearer and detailed assessment of its taxonomic status. The species has a considerable distribution through West and Central Africa, extending from Senegal to northern Angola (Bour et al. 2016; Rhodin et al. 2017). Fritz et al. (2010) presented evidence from three mitochondrial and three nuclear loci that the population from São Tomé is closely related to populations from Ivory Coast and represents a recent colonization. A subsequent study by Kindler et al. (2016) using the same loci but with additional geographic sampling uncovered several geographically distinct clades across the distribution of P. castaneus, with the São Tomé population nested within a West African clade along with specimens from Ivory Coast and Nigeria. Despite not being a common species, P. castaneus has been reported from the island since the 1880s (Greeff 1884; Bocage 1886a, 1889) and was more recently found in Oque d’el Rei, Água Grande District (February 2013, specimens deposited in the collections of MUHNAC). Data on the distribution, abundance, ecology, and natural history of this species in São Tomé are still very limited, although it is expected that the species inhabits rivers, streams and temporary water bodies as it does throughout its range in continental Africa (Bour et al. 2016). As the phylogenetic studies indicate, a possible human-mediated introduction of P. castaneus to São Tomé cannot be rejected, but further research is needed to clarify the evolutionary history of this population.

Fig. 19.2
Eight images of different reptiles in the Gulf of Guinea oceanic island. It includes Pelusios castaneus,Hemidactylus principensis,Feylinia polylepis,Trachylepis thomensis,Afrotyphlops elegans,Boaedon mendesi, Hapsidophrys principis, and Naja peroescobari.

Gulf of Guinea oceanic island reptiles: (1) West African mud turtle, Pelusios castaneus, from São Tomé Island; (2) Príncipe Gecko, Hemidactylus principensis, from Príncipe Island; (3) Manyscale Feylinia, Feylinia polylepis, from Príncipe Island; (4) Adamastor Skink, Trachylepis thomensis, from São Tomé Island; (5) Elegant Worm Snake, locally known as Cobra-bobô, Afrotyphlops elegans, from Príncipe Island; (6) Mendes’ House Snake, locally known as Jita, Boaedon mendesi, from Príncipe Island; (7) Príncipe Emerald Snake, locally known as Suá-suá, Hapsidophrys principis, from Príncipe Island; (8) São Tomé Cobra, locally known as Cobra-preta, Naja peroescobari, from São Tomé Island. Photo credits: (1–8) Luis M. P. Ceríaco

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Squamata

Squamate diversity in the Gulf of Guinea oceanic islands includes 28 species from two families of lizards—Gekkonidae, Scincidae—and four families of snakes—Typholpidae, Lamprophiidae, Colubridae and Elapidae. All species are endemic to the islands, except for one native skink (family Scincidae), two introduced geckos (family Gekkonidae), one introduced snake (family Typholopidae), and one gecko (family Gekkonidae) and one snake (family Elapidae) that are based on doubtful or problematic records that require further investigation.

Family Gekkonidae

The geckos of the Gulf of Guinea oceanic islands belong to two different genera: the Dwarf Geckos of the genus Lygodactylus Gray, 1864, and the Tropical House Geckos of the genus Hemidactylus Goldfuss, 1820. Each island is represented by its own endemic form of Lygodactylus: the Príncipe Dwarf Gecko, L. delicatus Pasteur, 1962, the São Tomé Dwarf Gecko, L. thomensis (Peters, 1881), and the Annobón Dwarf Gecko, L. wermuthi Pasteur, 1962. Following the initial description of L. thomensis by Peters (1881), several authors considered the populations on all three islands as conspecific (e.g., Bocage 1886a, 1892b, 1893, 1903, 1905; Boulenger 1885, 1906; Sternfeld 1917; Loveridge 1947). Pasteur (1962) reviewed the group and described delicatus and wermuthi as subspecies of thomensis based on morphological and coloration differences. With the exception of Manaças (1958), subsequent authors followed the Pasteur (1962) taxonomy (Schätti and Loumont 1992; Haft 1993). Jesus et al. (2006) were the first to provide molecular data for these island taxa and found the level of divergence in 12S and 16S mitochondrial genes was within the level of divergence observed between other species within the genus. With this combination of phenotypic and genetic distinctiveness, and their allopatric distributions, Ceríaco et al. (2018) considered each island population as a valid species. Data on the distribution, abundance, ecology, and natural history of the three species are limited. Lygodactylus thomensis and L. delicatus are commonly observed in human settlements, especially on walls, fences and other structures (Manaças 1958, LMPC pers. obs.); however, Jesus et al. (2003) noted that L. wermuthi has only been found in forested areas. Manaças (1958) recorded specimens of flies (Diptera) in the stomach contents of L. delicatus.

The taxonomy of the genus Hemidactylus is considerably more complex. A total of six species are currently recorded for the islands. Four of these are endemic to the islands: the Príncipe Gecko, Hemidactylus principensis Miller, Sellas and Drewes, 2012, endemic to Príncipe and Tinhosa Grande islet (Fig. 19.2, 2); Greeff’s Gecko, H. greeffii Bocage, 1866, endemic to São Tomé and Rolas islet; Newton’s Gecko, H. newtoni Ferreira, 1897, endemic to Annobón; and the Annobón Gecko, H. aporus Boulenger, 1906. The remaining two species are most likely human introductions—the Long-Headed Tropical Gecko, H. longicephalus, Bocage, 1873, occurring on São Tomé and Príncipe, the Tropical House Gecko, H. mabouia (Moreau de Jonnès, 1818), occurring on all three islands and Rolas.

Príncipe and São Tomé islands, as well as the surrounding islets of Tinhosa Grande and Rolas, respectively, host an endemic lineage of the genus Hemidactylus comprising H. principensis and H. greeffii (Bauer et al. 2010; Miller et al. 2012; Ceríaco et al. 2020a). These two species exhibit a clear synapomorphic character that differentiates them from all other African species of Hemidactylus: the absence of the terminal phalanx and claw of the first digit (thumb) of the manus (Bocage 1886a, 1905; Boulenger 1906; Loveridge 1947; Haft 1993; Miller et al. 2012). Both species are members of the African-Atlantic clade, a group mainly comprising Angolan and Western African species that are closely related to Brazilian species such as H. brasilianus Amaral, 1935 (Ceríaco et al. 2020a). While H. greeffii was described in the 1880s by Bocage (1886a), H. principensis was only recently described by Miller et al. (2012) on the basis of genetic divergence and several morphological differences, including iris coloration and body size. The unidentified Hemidactylus from Tinhosa Grande reported by Ceríaco (2015) was shown, through the use of molecular data, to be conspecific with H. principensis from Príncipe Island (Ceríaco et al. 2020b). The known distribution of both species is very limited (Greeff 1884; Bocage 1886a, 1905; Boulenger 1906; Manaças 1958; Schätti and Loumont 1992; Haft 1993; Miller et al. 2012). Both species appear to be less abundant in more developed areas and preferring less disturbed habitats (LMPC pers. obs.); however, they are able to colonize and thrive in both forested and more xeric areas, as in the case of the Tinhosa Grande islet population.

The Annobón endemics, H. newtoni and H. aporus, have a more convoluted taxonomic history. H. newtoni was described by Ferreira (1897) based on a series of seven specimens collected by Francisco Newton in 1893: one adult male, five adult females and one juvenile. These same specimens were previously examined by Bocage (1893), who tentatively identified them as H. mabouia, noting, however, that they differed from H. mabouia in being “smaller and having relatively larger and closer dorsal tubercles.” Ferreira (1897) considered the dorsal patterns of transverse “W” shaped markings extending from the neck to the insertion of the tail, the number and disposition of the dorsal tubercles, and the “very long and flattened digits, with strong claws and enlarged proximally, with larger and more numerous number of subdigital lamellae [7–8 in the first finger, 11–12 in the fourth toe]” as diagnostic characters for H. newtoni. Bocage (1903) provided a French translation of the original Ferreira (1897) description in Portuguese. Surprisingly, neither Ferreira (1897) nor Bocage (1903) provided data on the number of preanal or femoral pores of the male specimen. Loveridge (1947) interpreted this omission as a complete lack of preanal or femoral pores in the male syntype, which would thus resemble the other putative endemic species, H. aporus (see below). Loveridge noted that “if correctly counted, the greater number of subdigital scansors of H. newtoni, approaching those of H. echinus O’Shaughnessy, 1875, afford good grounds for separation.” The type series of H. newtoni was lost in the fire that destroyed the collections of Museu Bocage (Lisbon) in 1978. Jesus collected new material in the early 2000s and provided the first molecular data for H. newtoni (Jesus et al. 2005c), noting that it was sister to “an individual from an undescribed form from São Tomé,” recently identified as H. longicephalus by LMPC (pers. obs.). Further studies are needed to better understand the phylogenetic placement of H. newtoni among its African congeners and begin to understand its evolutionary history, as well as its natural history, distribution and ecology.

The second Annobón endemic, H. aporus, was described by Boulenger (1906) based on several specimens, including males and females, collected by Fea. According to the author, the species is very similar to H. bocagii [=H. longicephalus], but differs by having the dorsal tubercles “larger, closer together, forming 16–20 more regular longitudinal series” and lacking precloacal or femoral pores in males (present in H. longicephalus; see Ceríaco et al. 2020a, b). The species differs from H. newtoni in the number of subdigital lamellae (“5 lamellae under the inner digit, 7 under the third and fourth” in H. aporus fide Boulenger (1906) versus “7–8 in the first finger, 11–12 in the fourth toe” in H. newtoni fide Ferreira (1897)). Loveridge (1947) considered the species valid, noting that the absence of pores in the males distinguishes aporus from all other West African species with the exception of sympatric H. newtoni [if this is indeed true], from which it differs in “possessing fewer subdigital scansors, 7 (instead of 11–12) under the fourth toe, and 16–20 (instead of irregularly disposed) dorsal tubercles.” The species has not been collected since its original description over a century ago, and our current knowledge is limited to the very brief, original description (Meiri et al. 2017). The type series is still extant in the Museo Civico di Storia Naturale “Giacomo Doria,” Genoa, Italy (Giulliano Doria pers. comm.). While the available evidence supports the identity of H. newtoni as a valid species, the status of H. aporus requires further research.

The presence of Hemidactylus longicephalus, a coastal species endemic to western Angola and southwestern Democratic Republic of the Congo, was first noted in São Tomé when Bedriaga (1892) misidentified the specimens at his disposal as a new subspecies of H. mabouia, which he named as H. mabouia var. molleri. The convoluted history of this putative taxon was briefly discussed by Ceríaco and Marques (2012) and Ceríaco et al. (2018). Ceríaco et al. (2020a) definitively synonymized molleri with longicephalus, a hypothesis already put forward by Loveridge (1947). In addition to the records from São Tomé provided by Bedriaga (1892), Bocage (1903; as H. bocagii, a junior synonym of longicephalus) and Manaças (1958) provided records from Príncipe, and Carranza and Arnold (2006) and Ceríaco et al. (2020a) provided additional records of the species for São Tomé. Jesus et al. (2005c) noted the presence of a putative new species of Hemidactylus from São Tomé, which was later confirmed to be conspecific with longicephalus (LMPC pers. obs.) Both morphological and molecular data provided by Ceríaco et al. (2020a), unambiguously identify the São Tomé and Príncipe populations as conspecific with the Angolan form. Consequently, the authors concluded that the species naturally colonized the islands relatively recently or were introduced to the islands through human activities, as São Tomé, Príncipe and Angola were Portuguese colonies, and the islands were an important stopover for ships departing from Angola to the Americas and Europe (Ceríaco et al. 2020a). Due to the limited number of collected specimens, not much is known about the ecology and distribution of this species on the islands, but in Angola, it tends to be found in coastal lowland areas or in human settlements (Ceríaco et al. 2020a).

Finally, H. mabouia is one of the most widespread and ubiquitous species of gecko in the world, native to Central and Western Africa but introduced to North, Central and South America, as well as the Caribbean (Kraus 2009; Agarwal et al. 2021). There are historical and modern records of this species on the three islands (e.g., Greeff 1884; Bocage 1886c, 1889, 1892a, 1905; Vieira 1886; Bedriaga 1892; Boulenger 1906; Manaças 1958, 1973; Schätti and Loumont 1992; Haft 1993; Hofer 2002; Jesus et al. 2003, 2005c; Miller et al. 2012; Ceríaco et al. 2018, 2020a). Jesus et al. (2005c) and Ceríaco et al. (2020a) provided molecular evidence indicating that the Gulf of Guinea oceanic islands populations are almost indistinguishable from the continental populations of the species, suggesting a recent arrival/introduction to the archipelago. The species is very common in human settlements and is often observed on houses and other buildings at night.

Family Scincidae

The skinks occurring on the Gulf of Guinea oceanic islands belong to three different genera: the feylinias of the genus Feylinia Gray, 1845, leaf-litter skinks (also known as snake-eyed skinks) of the genus Panaspis Cope, 1868, and the common skinks of the genus Trachylepis Fitzinger, 1843. The fossorial and limbless Many-scaled Feylinia, Feylinia polylepis Bocage, 1887 is endemic to Príncipe (Fig. 19.2, 3). Described by Bocage (1887) as a subspecies of Feylinia currori Gray, 1845, the species has been recorded on the island by several authors (Bocage 1903; Boulenger 1906; Angel 1920; Manaças 1958, 1973; Brygoo and Roux-Estève 1983; Hofer 2002; Ceríaco et al. 2018; Soares et al. 2018). Due to its secretive lifestyle, this species is still poorly known in terms of its ecology, natural history, and phylogenetic position, although, as noted by Brygoo and Roux-Estève (1983), its taxonomic validity is unquestionable. The species is morphologically most similar to Feylinia currori, but the lack of molecular data for most of the representatives of the genus limits any attempt to understand its phylogenetic placement. The feylinia is very common and is found under leaf-litter, logs, or rocks.

The taxonomic history of leaf-litter skinks, genus Panaspis, of the Gulf of Guinea oceanic islands is quite complex. All authors who have dealt with this species during the nineteenth and the first half of the twentieth century considered that populations on the three islands were conspecific (e.g., Greeff 1884; Bocage 1886a, 1889, 1903, 1905; Bedriaga 1892; Boulenger 1906; Manaças 1958), bearing the specific epithet africana (or aftricanum, depending on the genus they were placed in by the different authors—see Soares et al. 2018). The species was originally described as Mocoa africana by Gray (1845). Although Gray (1845) did not provide a precise type locality, the type specimen is unambiguously identifiable as originating from Príncipe (Soares et al. 2018). Subsequently, Fuhn (1972) revised the Gulf of Guinea Panaspis, leading to the description of the Annobón population as P. africana annobonensis. Perret (1973) considered annobonensis as a full species, a decision that would later be supported using molecular data (three mitochondrial and one nuclear locus) by Jesus et al. (2007) and Medina et al. (2016). A more recent taxonomic revision by Soares et al. (2018) led to the description of a third species—Panaspis thomensis Ceríaco, Soares, Marques et al., 2018, endemic to São Tomé. The three species form a clade within the genus Panaspis along with P. cabindae (Bocage, 1866) from Angola (Medina et al. 2016; Soares et al. 2018). Panaspis africana, P. annobonensis, and P. thomensis are some of the most conspicuous reptiles on their respective islands. They are typically encountered in forested areas in leaf-litter, and even in gardens in more urban areas (Jesus et al. 2003; Soares et al. 2018).

Similar to the Leaf-litter skinks, the common skinks of the genus Trachylepis are also among the most conspicuous lizards on these islands. Four species occur in the Gulf of Guinea oceanic islands: Trachylepis adamastor Ceríaco, 2015, endemic to Príncipe and Tinhosa Grande islet; T. thomensis Ceríaco, Marques and Bauer, 2016, endemic to São Tomé and surrounding islets (Fig. 19.2, 4); T. ozorii (Bocage, 1893), endemic to Annobón; and T. affinis (Gray, 1838) on Príncipe. Originally described in the late nineteenth century by Bocage (1893), the taxonomy and nomenclatural history of T. ozorii have always been stable (see Ceríaco et al. 2016). Based on mitochondrial sequence data, Jesus et al. (2005a) concluded that T. ozorii was not closely related to any of the Gulf of Guinea oceanic island Trachylepis. This result was confirmed by Ceríaco et al. (2016) and Weinell et al. (2019), the latter demonstrating that T. ozorii is sister to the Western African species Trachylepis polytropis (Boulenger, 1903) and represents a distinct dispersal event to the archipelago. Jesus et al. (2003) noted that the species was widespread across the island, but was not usually found in wet or shaded areas.

The taxonomy of T. adamastor and T. thomensis is somewhat more muddled than that of the Annobón congener. For a long time, both the Príncipe and São Tomé populations were considered conspecific to the T. maculilabris (Gray, 1845) species complex (see Ceríaco et al. 2016), a widespread species in West and Central Africa, long known to harbor cryptic diversity (Mausfeld-Lafdhiya et al. 2004). Jesus et al. (2005a) were the first to show, based on molecular data (three mitochondrial loci), that the populations from Príncipe and São Tomé were not conspecific. As a first step to clarify the taxonomy of the group, Ceríaco (2015) described T. adamastor from Tinhosa Grand islet. The available specimens had been preserved in formalin, and therefore, no molecular data were available for comparison with the other island populations. Consequently, the species was described solely based on its striking size and coloration differences relative to the other island’s specimens. Ceríaco et al. (2016) later described two additional species based on a combination of morphological and genetic data: T. principensis from Príncipe and T. thomensis from São Tomé. In a species-level phylogeny of the genus, Weinell et al. (2019) confirmed the distinctiveness of the Príncipe and São Tomé populations and noted that the species were not each other’s closest relatives—the Príncipe lineage (incorrectly labeled by Weinell et al. (2019) as T. thomensis) is sister to T. maculilabris, while the São Tomé population (incorrectly labeled by Weinell et al. (2019) as T. principensis) is sister to the Indian Ocean endemic Trachylepis comorensis (Peters, 1854), which occurs in Comoros, Madagascar and coastal Mozambique. Both Ceríaco et al. (2016) and Weinell et al. (2019) lacked molecular data for T. adamastor and were unable to assess its taxonomic position in the context of a molecular phylogeny. Ceríaco et al. (2020b) provided the first molecular data for T. adamastor, showing that it is actually conspecific to T. principensis, rendering T. principensis as a junior synonym of T. adamastor. Trachylepis thomensis is commonly found in forested areas and in human settlements, showing an almost exclusively terrestrial lifestyle. By contrast, T. adamastor is more abundant in less populated areas, ranging from forested habitats to the open, rocky habitats of the Tinhosa Grande islet. Trachylepis adamastor is commonly found basking on trees (Ceríaco et al. 2016). More recently the population size and diet of the Tinhosa Grande population of T. adamastor was reviewed by Sousa et al. (2022).

The presence of T. affinis, a complex of species occurring from Senegal to Angola, on São Tomé and Príncipe has been interpreted differently by several authors. In particular, Fischer (1886) described Euprepes cupreus from São Tomé, and this taxon is currently considered a junior synonym of T. affinis (Ceríaco et al. 2016, 2018). To date, Fischer’s (1886) record remains the only available record of this species on São Tomé. By contrast, several authors reported the species from Príncipe under a variety of names—Mabuya raddoni (Angel 1920; Manaças 1958, Hofer 2002), Mabuya blanlingii [sic] (Manaças 1958) and Mabuya/Trachylepis affinis (Hallermann 1998; Jesus et al. 2005a; Ceríaco et al. 2016, 2018). These are all currently synonyms of T. affinis, according to Ceríaco et al. (2016), based on the molecular similarity between Principe and other continental populations. The species likely represents a recent arrival to the island, and further data are needed to assess if a São Tomé population is extant. In Príncipe, the species is mostly found in the vicinity of human settlements, especially around Santo António city.

Family Typhlopidae

Considering the diminutive size and isolation of the Gulf of Guinea oceanic islands, the diversity of typhlopid snakes is remarkable. At least four species from three different genera—Afrotyphlops Broadley and Wallach, 2009, Letheobia Cope, 1868, and Indotyphlops Hedges, Marion, Lipp, Marin and Vidal, 2014—occur on the islands. The genus Afrotyphlops is represented by the Príncipe endemic Afrotyphlops elegans (Peters, 1868), locally known as “Cobra-bobô” (Fig. 19.2, 5), which is the same name used on São Tomé to refer to the endemic caecilians of the genus Schistometopum Parker, 1941 (Bell et al. 2022). Not much is known about the ecology of this fossorial species, however, in multi-locus and morphological phylogenetic analyses of typhlopid snakes, Kornilios et al. (2013) and Hedges et al. (2014) showed that it is closely related to the Central African Afrotyphlops angolensis (Bocage, 1866).

Two species of Letheobia are currently recognized and both occur on Príncipe and São Tomé: Letheobia newtoni (Bocage, 1890) and Letheobia feae (Boulenger, 1906). Both species were originally described from São Tomé (Bocage 1890; Boulenger 1906), and recent molecular data indicate the species are distinct and form a monophyletic group with Letheobia simoni (Boettger, 1879) and L. episcopus (Frazen and Wallach, 2002), from Israel and Turkey, respectively (Kornilios et al. 2013; Hedges et al. 2014). This intriguing biogeographic pattern may be an artifact of our current poor knowledge of the taxonomic diversity and distribution of the species of genus Letheobia. Two other forms were described from Príncipe: Boulenger (1906) described Typhlops [=Letheobia] principis and Angel (1920) described Typhlops [=Letheobia] naveli. Both of these species were later synonymized with L. feae and L. newtoni, respectively, by Roux-Estève (1974). No molecular data exist for the Príncipe populations, and thus their taxonomic relationships with the São Tomé forms have not been fully ascertained. Given the patterns of speciation in the archipelago and the morphological conservatism of these snakes, the possibility that the Príncipe forms represent valid species should be investigated. Due to their mostly fossorial lifestyles, almost nothing is known about the ecology and distribution of either species.

Finally, Jesus et al. (2003) reported the presence of Indotyphlops (as Ramphotyphlops) braminus (Daudin, 1802) on Annobón. These small, fossorial snakes are an invasive species originally from Southern Asia and have been introduced to islands across the globe (Wallach 2009).

Family Lamprophiidae

Two species of lamprophid snakes occur in the Gulf of Guinea oceanic islands: Boaedon bedriagae Boulenger, 1906, endemic to São Tomé, and B. mendesi, endemic to Príncipe (Fig. 19.2, 6). The two taxa were considered conspecific by most authors over the last century but were recently split into distinct species by Ceríaco et al. (2021a). The species are sister taxa and are closely related to the southern African B. capensis Duméril, Bibron & Duméril, 1854 species complex, contrary to the historical assignment to either the Boaedon lineatus Duméril, Bibron & Duméril, 1854 or Boaedon fuliginosus (Boie, 1827) species complexes from Western and Central Africa (Ceríaco et al. 2021a). Locally known as “Jita,” these species rank amongst the most well-known species on the islands, where the locals recognize them as harmless. Both species are quite common and are often found in both pristine habitats and agricultural areas (Ceríaco et al. 2021a). Both species can be observed perched in trees or in vegetation and are often observed at reed frog (Hyperolius spp.) breeding sites, suggesting anurans may be an important part of their diet (RCB, LMPC pers. obs.).

Family Colubridae

The colubrids of the Gulf of Guinea oceanic islands belong to two different genera: the arboreal emerald snakes, genus Hapsidophrys Fischer, 1856, represented by the Príncipe endemic Hapsidophrys principis (Boulenger, 1906), locally known as Suá-suá (Fig. 19.2, 7), and the arboreal green snakes of the genus Philothamnus (Smith, 1847), represented by the São Tomé endemic, Philothamnus thomensis Bocage, 1882, also locally known as Suá-suá, and the Annobón endemic Philothamnus girardi Bocage, 1893.

The Príncipe Suá-suá, H. principis was described in the early twentieth century by Boulenger (1906), although older records exist from the late nineteenth century, as Gastropyxis (= Hapsidophrys) smaragdina (Bocage 1887, 1903). The species is relatively poorly studied, but Jesus et al. (2009) provided a phylogeny based on two mtDNA loci supporting H. principis as a distinct evolutionary lineage sister to H. smaragdina from Gabon. Hapsidophrys principis is an arboreal species, mostly found in forested areas (LMPC pers. obs.).

Regarding the two species of Philothamnus, recent molecular revisions by Engelbrecht et al. (2019) provided some insights regarding their taxonomic validity and placement within the genus. With a molecular dataset of three mtDNA and two nuDNA loci, Engelbrecht et al. (2019) found that the island species form a strongly supported clade with West-Central African congener P. dorsalis (Bocage, 1866). Species delimitation analyses with this same dataset found moderate support for P. thomensis as a distinct evolutionary lineage but no support for P. girardi as a distinct lineage (Engelbrecht et al. 2019). Given the geographic isolation of P. girardi on Annobón, morphological differences noted by Bocage (1893), and the relatively modest molecular dataset and geographic sampling in Engelbrecht et al. (2019), we conservatively maintain P. girardi as a valid species. Philothamnus thomensis is considered a forest specialist but can also be found in shade-plantation habitats and gardens (RCB, pers. obs.), while Jesus et al. (2003) noted that P. girardi is widespread on Annobón, mainly in large open spaces with shrubs and grasses, outside of the main village.

Family Elapidae

Only one species of elapid snake is confirmed for the Gulf of Guinea oceanic islands: the São Tomé endemic Naja (Boulengerina) peroescobari Ceríaco, Marques, Schmitz and Bauer, 2017, locally known as “Cobra-preta” (Fig. 19.2, 8). It is the only venomous species of snake in the Gulf of Guinea oceanic islands, and human fatalities can occur even if rare (Ceríaco et al. 2017). As a large and conspicuous snake, it was one of the first reported species of reptiles for São Tomé. The species was historically identified as Naja melanoleuca Matschie, 1893, a widely distributed Central African species (Ceríaco et al. 2016). Until recently, it was assumed that Portuguese settlers introduced Cobra-preta to control rodent pests that afflicted agricultural crops. However, historical, morphological and molecular evidence reject this hypothesis (Ceríaco et al. 2017; Wüster et al. 2018) and instead indicate that the Cobra-preta is distinct from N. melanoleuca and is endemic to São Tomé. The Cobra-preta is classified as Endangered by the International Union for the Conservation of Nature (IUCN 2021), and is the only threatened terrestrial reptile from the Gulf of Guinea oceanic islands. The Cobra-preta is mostly seen in forested and shady habitats across the southern half of the island and is apparently absent in the northeast regions. It is commonly seen basking on roads during the day (Ceríaco et al. 2017). The invasive Least weasel, Mustela nivalis Linnaeus, 1766, and Black rat, Rattus rattus Linnaeus, 1758, have been reported as prey items of the species (Ceríaco et al. 2017).

There are unconfirmed records of a second species of elapid snake on São Tomé: a green Mamba of the genus Dendroaspis. The evidence regarding the presence of this snake on São Tomé was summarized in Ceríaco et al. (2018). Three experienced herpetologists reported a species of mamba from the island: Dendroaspis jamesoni by Jan (1857, 1858, 1859, 1863), Jan and Sordelli (1870) and Fischer (1856, 1885) and Dendroaspis angusticeps by Bedriaga (1893a). Fischer (1856) even provided a drawing of the specimen from “Insel St. Thomé (West-Africa)” (Fig. 19.3). Unfortunately, none of the specimens examined by the three different authors is still extant. The specimen examined by Jan (1857, 1858, 1859, 1863) was destroyed during the Allied bombing of Milan, Italy, during the World War II. Fischer’s (1885) specimen likely suffered the same fate when the ZMH collections were damaged during WWII. The specimens sent by Adolfo Möller to Bedriaga and used by the latter to describe his specimen of Dendroaspis angusticeps (Bedriaga 1893a) are also currently unaccounted for. Lacking the original specimens and without any recent record of the species, there are significant doubts regarding these accounts, and several authors have recognized this mystery (Schätti and Loumont 1992; Nill 1993; Ceríaco et al. 2018). Either the historical records are simply cases of mistaken identity and/or poor locality data, or there is an elusive species of green Mamba on São Tomé that has evaded researchers for more than a century.

Fig. 19.3
A diagram of a green mamba with both the ventral and dorsal views of the head, as well as the cloacal area.

Fischer’s (1856) plate of “Dendroaspis Jamesonii Schlegel” from “Insel St. Thomé (West-Africa)”

Full size image

Conservation

Although no studies have yet been conducted to specifically assess the threats faced by the reptiles of the Gulf of Guinea oceanic islands, it is likely that these are similar to the threats faced by their continental African counterparts. Habitat degradation and destruction caused by land-use change, climate change, non-native species, and direct persecution (especially in the case of snakes) can have seriously detrimental effects on local populations of reptiles. Given their abundance and mostly generalist ecology, as well protected habitats in the Obô Natural Parks on São Tomé and Príncipe, most species of reptiles from the Gulf of Guinea oceanic islands are not currently considered threatened (IUCN 2021; Table 19.2). The endemic geckos H. greeffii and H. principensis, however, are considered Near Threatened, and their apparently low abundance and the potential for competition with introduced congeners H. mabouia and H. longicephalus may have negative impacts on their populations. Many species, including Hemidactylus aporus, H. newtoni, Panaspis annobonensis, Letheobia newtoni and L. feae are classified as Data Deficient due to insufficient population and distribution data and lingering taxonomic uncertainty. Currently, only Naja (Boulengerina) peroescobari is considered threatened, as Endangered. This classification is due to its endemic status and threats associated with both direct persecution and indirect death by car traffic. More detailed studies are needed to uncover potential risks caused by land-use change, one of the main and more prevalent threats to reptiles of the Gulf of Guinea oceanic islands, as well as local strategies to mitigate persecution, especially in the case of the Cobra-preta.

In recent years several reports on social media have depicted non-native species occurring on São Tomé Island. For instance, a dead specimen of an adult Orton’s Boa Constrictor (Boa constrictor ortonii Cope, 1877), a subspecies endemic to Peru, South America, was found in the vicinity of São Tomé airport in August 2018. These animals are not easily transported by accident, and its presence on the island is likely due to intentional importation. Boas are listed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), and thus importation to the country should be registered. Consulting the CITES Trade Database (UNEP–WCMC and CITES 2021), there are no records of any live specimen of reptile being legally imported to the country since 1975. Thus, illegal trade may be operational in the country, which could constitute a major threat to the native biodiversity. In March 2020, an adult female of agama, Agama sp. was found basking on the walls of a building in downtown Santo António city, Príncipe. The specimen was collected and euthanized and deposited at the facilities of Príncipe Trust Foundation in Santo António (Frazer Sinclair, pers. comm.). The specimen was collected at a construction site with raw materials imported from the African mainland, suggesting this individual was a stowaway. To our knowledge, no other specimens have been observed on the island. Some species of the genus Agama are usually human commensals and have already been introduced to the Cape Verde islands (Vasconcelos et al. 2014). Research is underway to identify the source population of this sole agama female specimen.

Future Research

Despite over a century of research, the taxonomy and diversity of terrestrial reptiles from the Gulf of Guinea oceanic islands are still incompletely documented. Taxonomic revisionary studies are sorely needed for some groups (as noted above), and the presence of the São Tomé Green Mamba remains an intriguing mystery. In addition, the biogeographic history of most lineages is poorly understood in part because the taxonomy of continental species is still in flux. Other than some anecdotal data presented in taxonomic reviews (e.g., Ceríaco et al. 2016, 2017), there are few studies focused on the ecology, natural history, and conservation of species. Furthermore, in contrast to the comprehensive assessments that have been conducted for other groups, notably birds (Melo et al. 2022), no studies exist on the impacts of invasive species or land use for terrestrial reptiles (Soares et al. 2022). Another important topic that needs further attention is the venom composition, medical significance and social impact of N. peroescobari snakebite. Finally, Pacheco et al. (2020) report considerable Haemocystidium parasite diversity in reptiles, and although this study did not include samples from any Gulf of Guinea oceanic islands taxa, the topic presents an exciting opportunity to investigate parasite-host interactions in an insular community.