Guide of Amphibians and Reptiles of São Tomé and Príncipe

By César J. Pollo

The Gulf of Guinea oceanic islands (Príncipe, São Tomé and Annobón) are the result of volcanic activity of the Cameroon Volcanic Line that occurred along this fracture in the earth’s crust during the lower Tertiary and early Quaternary and that continues inland as the Cameroon/Nigerian mountains.
They are located between 220 and 350 kilometers from the western coast of Central Africa and have never been in contact with the mainland. The three islands are separated from each other and from the West African coastlines by ocean depths in excess of 3000 m.
São Tomé is geologically younger than Príncipe and considerably larger, at 836 km2, is situated 280 km off the mainland and 180 km northeast of the southern-most of the oceanics. Príncipe has only about 136 km2 in area, but it is well-watered and has significant relief provided by a central volcanic peak, it is about 146 km northeast of São Tomé, 220 km from de African mainland and 220 km southwest of Bioko (known in colonial times as Fernando Poo and now part of the Republic of Equatorial Guinea).
The herpetofauna of these islands includes 27 species of reptiles, 18 of which are currently considered to be endemic and eight species of endemic amphibians of five families. The cryptic diversity within the islands populations only recently began to be addressed. Due to this, several new species have been described in recent years, while others are currently on the process of being described, as well as it undermines efforts to apply successful and appropriated conservation strategies.
These islands harbour a diverse amphibian fauna, seven frogs and one caecilian, the rate of endemism of amphibians in São Tomé e Príncipe is 100%. Amphibian's endemism on the islands are: Leptopelis palmatus, considered a classic example of island gigantism, that lives in the lowland forests and Phrynobatrachus dispar and Hyperolius drewesi only found on Príncipe. Hyperolius thomensis, Phrynobatrachus leveleve, Ptychadena newtoni and Schistometopum thomense have only been found on São Tomé. The genus Hyperolius is endemic to the two islands.
For reptiles, aside from Hemidactylus longicephalus and Pelusios castaneus on São Tomé, Trachylepis cf. affinis in Príncipe, and Hemidactylus mabouia and Boaedon cf. fuliginosus on both islands, all other reptile species appear to be endemics, Hemidactylus and Lygodactylus geckos, Panaspis skinks and various snakes, Philothamnus thomensis, Philothamnus girardi (Annobón), Hapsidophrys principis, etc.
The reptiles and amphibians of the Gulf of Guinea islands pose some of the most difficult questions with respect to colonization. Some genetic analysis indicates that some of these species appear to have their closest relatives in East Africa.
São Tomé and Príncipe is a breeding place for five of the seven known species of marine turtles in the world, has one of the 11 populations with maximum risk of extincion worldwide, turtle population of the critically endangered Hawksbill (Eretmochelys imbricata), the only viable nesting population in the Eastern Atlantic. Príncipe Island possesses one of the last sea turtle aggregations in West Africa. Despite its high conservation value, local and regional information on their numbers and habitats remains scarce.

• Language: English
• Publisher: César J. Pollo
• Release date: Feb 23, 2018
• ISBN: 9781370487394

César J. Pollo

Más de 25 años de experiencia en diferentes sectores del medio ambiente y desde distintos ámbitos de trabajo, consultoría, administración pública y organizaciones no gubernamentales.He desarrollado y desarrollo mi trabajo profesional en temas relacionadas con el medio natural, proyectos LIFE, planes de recuperación y estrategias de especies amenazadas, daños de fauna, etc., y en la redacción y propuesta de medidas correctoras y compensatorias a proyectos de infraestructuras y de explotación de recursos naturales, para su incorporación en declaraciones de impacto ambiental e informes ambientales.En la actualidad interesado por la sostenibilidad ambiental, los objetivos de desarrollo sostenible, los bancos de conservación o de hábitats, la conectividad, las medidas compensatorias, la gestión de especies amenazadas, el comercio internacional de especies, el turismo de naturaleza y la custodia del territorio. Y aficionado a la historia.Aunque por mi edad soy un inmigrante digital, también estoy interesado en el desarrollo de proyectos de empresas sociales, culturales y medioambientales con una base digital y en Responsabilidad Social Empresarial.Experiencia en el diseño y ejecución de iniciativas de apoyo a la realización de proyectos que impulsen el progreso sostenible y el bienestar de comunidades locales en países en vías de desarrollo, mediante el uso racional, viable, sano, justo y ético de los recursos naturales.Conocimiento y formación en seguridad operativa sobre el terreno para ONGs, planificación y prevención, diferentes situaciones de riesgo y peligro, análisis de riesgos, estrategias de seguridad, niveles de alerta, seguridad personal individual y colectiva, seguridad en inmuebles, gestión de la información, uso y desplazamiento de vehículos, aplicación de SIG a gestión de riesgos naturales, etc.

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Introduction

The Gulf of Guinea oceanic islands *

The Gulf of Guinea oceanic islands (Príncipe, São Tomé and Annobón) are the result of volcanic activity of the Cameroon Volcanic Line that occurred along this fracture in the earth’s crust during the lower Tertiary and early Quaternary and that continues inland as the Cameroon/Nigerian mountains.

They are located between 220 and 350 kilometers from the western coast of Central Africa and have never been in contact with the mainland. The three islands are separated from each other and from the West African coastlines by ocean depths in excess of 3000 m.

The Cameroon Volcanic Line extends across the ocean-continent transition and magmatic extrusions (occurred at various times from over 60 million years ago to the very recent Holocene continental island of Bioko) up through it have given rise to major oceanic and continental topographic relief extending from southwest to northeast including the oceanic islands of Annobón (4.9 million years), São Tomé (13+ my) and Príncipe (31+ my).

São Tomé is geologically younger than Príncipe and considerably larger, at 836 km², is situated 280 km off the mainland and 180 km northeast of the southern-most of the oceanics, Annobón (or Pagalu) (17 km²) which is part of the Republic of Equatorial Guinea. Príncipe has only about 136 km² in area, but it is well-watered and has significant relief provided by a central volcanic peak, it is about 146 km northeast of São Tomé, 220 km from de African mainland and 220 km southwest of Bioko (known in colonial times as Fernando Poo and now part of the Republic of Equatorial Guinea), the only continental and most northerly island of the volcanic line.

The islands are within the wet tropical belt and have an oceanic equatorial climate with mean annual temperatures range from a maximum of 30 to 33 ºC (near sea level) to a minimum of 18 ° to 21 °C. At higher altitudes, the temperature often drops to 9 ºC or lower. Annual rainfall varies dramatically depending on elevation. The mountainous parts of the centres of the islands act as barriers to the prevailing southwesterly wind, causing heavy rainfall in the south-west and south, where annual averages are 7,000 mm on São Tomé and 5,000 mm on Príncipe, whereas on the island of Annobon rainfall is somewhat less. The main dry season on São Tomé and Príncipe occurs from June to September and is called the gravana, is more marked in the north and east of the islands and, in some years, may be non-existent in the south-west. A smaller dry season called the gravanito lasts from December to February. The seasons on São Tomé and Príncipe are affected by the inter-tropical front.

The islands are generally mountainous in the interior, sloping sharply down to the coasts. In São Tomé, one major mountain chain runs north to south while a second runs northwest to southwest. Príncipe has two chains as well, both running east to west. The highest peak on São Tomé is 2,024 m asl (Pico São Tomé), on Príncipe is 948 m (Pico Príncipe) and 598 m (Quioveo) on Annobon, they host a wide range of natural and anthropogenic gradients, from very densely populated landscapes to some of the most pristine tropical island ecosystems of the planet and home to hundreds of species of flora and fauna found nowhere else in the world.

An area of low land at the base of the volcanoes is the only relatively flat land on the islands. The volcanic soils of basalts and phonolites, which are more than 3 million years old, are relatively fertile and have been used for plantation crops.

Tropical and subtropical coastal rivers flow swiftly and are marked by waterfalls and rapids. Drain from the central highlands interiors radiating towards the coasts and flow to the Gulf of Guinea. Rivers are surrounded by lowland forest, montane rainforest and mangrove forest. The largest river of São Tomé is the Io Grande, which drains the southeastern portion of the island. Other large rivers on São Tomé include the Abade, the Manuel Jorge and the Rio d'Ouro and the Rio Papagaio is the longest river on Príncipe. Most rivers are perennial and experience seasonal fluctuations.

The islands were uninhabited in 1470-71 when the Portuguese discovered them. Colonization began in the early sixteenth century when São Tomé became the world's largest sugar producer and, after this crop's decline, the island grew to be an important slave trading post. Annobon became a Spanish colony in the eighteenth century. In the nineteenth century, coffee and cocoa plantations were established on São Tomé and Príncipe and africans were moved to the islands to work on the estates.

* Annobón is often described as being in the Gulf of Guinea, like the neighboring islands of São Tomé and Príncipe, but the formal boundary line for the Gulf of Guinea established by the International Hydrographic Organization actually runs north of it.

Oceanic and continental islands of the volcanic line of the Gulf of Guinea.

Map under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

Island biogeography

The Gulf of Guinea oceanic islands belong biogeographically to the West African rainforest zone. They are situated between two large regions (the Guinea forests and the Congo basin) that have recently received increased attention due to their exceptional biodiversity.

São Tomé and Príncipe with Annobón form the boundaries of the habitat type (bioma) Tropical and Subtropical Moist Broadleaf Forests (São Tomé, Principe and Annobón moist lowland forests ecoregion).

The forests of West Africa, including the islands of the Gulf of Guinea, form one of the world’s biodiversity hotspots. The Guinean Forests of West Africa support impressive levels of biodiversity, having high levels of species richness and endemism. In terms of plants, approximately 9,000 species of vascular plant are believed to occur in the hotspot, including 1,800 endemic species. The hotspot also supports an exceptional diversity of other terrestrial species. There are 416 mammal species, 917 bird species, 107 reptile species and 269 amphibian species within the hotspot boundary. Of these species, 65 mammals, 48 birds, 20 reptiles and 118 amphibians are thought to be endemic.

In addition to their biological richness, a number of ongoing threats to biodiversity in the Guinean Forests have resulted in the loss of more than 85 percent of the native vegetation cover. The main threat to the ecoregion is the removal of primary forest, which is driven by land privatization.

Map showing Guinean Forests of West Africa Biodiversity hotspot in red.

Source: Critical Ecosystem Partnership Fund.

http://www.cepf.net/where_we_work/regions/africa/guinean_forests/Pages/default.aspx

Classified as Globally Outstanding, São Tomé, Príncipe and Annobón Moist Lowland Forests terrestrial ecoregion (Threat status: Vulnerable) supports exceptionally high levels of endemism (particularly relative to its size) at the generic, specific and subspecific levels.

Concerning terrestrial habitats, around 37 endemic angiosperm plant species are found on Príncipe, 97 on São Tomé and 20 on Annobón. Only 16 of the region's endemic plants are shared by more than one island. This emphasizes the high degree of isolation under which their floras evolved and it indicates that each island received its flora separately from the mainland. The Rubiaceae, Orchidaceae, and Euphorbiaceae are characteristic of the islands' flora having high generic diversity. Significant endemic radiations between some genera (e.g. Begonia and Calvoa) are also found.

The Pteridophyte flora of the islands is also considered particularly rich. São Tomé is known to support 13 endemic bryophytes, one endemic gymnosperm and 10 endemic ferns and lycophytes, while Príncipe is known to support two endemic bryophytes and three endemic ferns and lycophytes. The islands are distinguished as Centers of Plant Diversity.

Based on their isolation and geographical characteristics, the islands have given origin to rapid speciation processes in its fauna, which are reflected in its high number of endemic species (centre of endemism) with no parallel worldwide, a unique and excepcional biota of global conservation significance. Many of species typically do not cross saltwater barriers and are absent from most oceanic islands.

The Gulf of Guinea islands centre of endemism is particularly striking in birds, shrews, reef fishes, burrowing reptiles and amphibians. Many of the species on these islands have small populations and feature in the world list of species threatened with extinction.

Many species of animals occur on only a single island, the oceanic islands are small, some lineages may have diversified rapidly within a single island to fill divergent ecological niches. Like the Macaronesian archipelagos, the Gulf of Guinea islands share a number of sister species across taxonomic groups, indicating that interisland dispersal within the island chain also may have been an important mechanism generating diversity.

Twenty one of the 30 reptiles found on the islands of São Tomé, Príncipe and Annobón are Endemic. Four of the most severely threatened reptile species in the hotspot are marine turtles.

Sao Tomé, the largest island, is notable for its high endemism in fauna, including approximately 18 butterflies, 21 birds, 9 reptiles and 5 amphibians.

Annobón Island is an important breeding site for a number of seabirds and at least two threatened species of marine turtle: hawksbill turtle; and leatherback. Also includes the Critically Endangered Annobón lidless skink (Panaspis annobonensis), species Priority 1 on the Basis of Relative Biological Importance, where it is threatened by habitat loss and, potentially, predation by introduced species.

The São Tomé and Príncipe Biodiversity Activity Education Poster.

The California Academy of Sciences Gulf of Guinea expedition V.

The three oceanic islands, with an area of c. 1000 km², hold 29 endemic bird species (the highest density of bird endemism by area in the world), with up to four endemic genera on São Tomé and another on Príncipe. The non-pelagic bird fauna includes 28 unique