The tepuis (or table-mountains) are scattered throughout Bolívar and Amazonas states of southern Venezuela (south of the Orinoco river), penetrating as far as west-central Guyana and northern Brazil, although the main centre is the Gran Sabana in south-east Bolívar. They are the relics of a vast sandstone plateau, whose erosion (other than in the Gran Sabana area) cut right through to the ancient Guiana shield below. For the main part they are surrounded by lowland tropical forest which covers most of the states of Bolívar and Amazonas (this being one of the largest remaining tracts of tropical forest in the world), although in eastern Bolívar, on the Gran Sabana, they rise instead out of the surrounding savannas.

The tepuis rise to heights of 1,500-2,800 m above sea-level, often with vertical cliffs of up to 1,000 m. At the base of these cliffs are talus (scree) slopes consisting of rock debris from above, and these are covered in wet tropical and subtropical forest fed by moisture from clouds that form on a daily basis around the cliffs. The plateau summits are often strongly dissected by canyons and gorges due directly to differential weathering, and some of the larger tepuis have permanent streams or rivers which often result in dramatic waterfalls (e.g. Angel Falls on Auyán-tepui). The vegetation of the summits and higher-elevation slopes is a diverse mixture of elfin forest (rich in mosses, lichens, bromeliads and orchids), scrub, savanna and bogs-and is still essentially untouched (Mayr and Phelps 1967, Maguire 1970). With the extreme conditions of intense light, low temperatures, strong winds, etc., the endemic flora tends to have xeromorphic adaptations (in spite of the heavy rainfall) resulting in unusual growth forms giving the landscape a characteristic appearance (Steyermark 1979).

The tepuis are famous for their high numbers of relict endemics, even within single plateaus. The Guiana floristic province comprises more than 8,000 species of which c.4,000 are endemic to the tepuis; there are 79 plant genera (17% of the province's total) endemic to the tepui summits, vertical bluffs and talus slopes, and 39 (8.5%) are endemic to the summits alone (Steyermark 1979). The fauna of the tepuis, despite being highly endemic, is quite limited in its diversity, with the avifauna being the most conspicuous component (and the most commonly observed plant pollinators) (Wege 1989).

The restricted-range species in this EBA are primarily montane birds occurring in the subtropical and temperate zones from c.600 m upwards (the boundary of the subtropical zone in the tepuis is anywhere from 600 to 1,000 m depending on the region), and principally inhabiting humid forest. Various other habitats are utilized to a lesser extent, although Cypseloides phelpsi, Heliodoxa xanthogonys, Troglodytes rufulus and Emberizoides duidae rely mostly on non-forest situations. Percnostola caurensis is restricted to the tropical zone (occasionally as low as 100 m), but is directly associated with the lower slopes of the tepuis, whereas Spot-backed Antwren Herpsilochmus dorsimaculatus is found in the lowlands around the tepuis, but is apparently not dependent on them, so is considered to be confined to the Orinoco–Negro white-sand forests (EBA 065).

At least seven restricted-range bird species are confined to the Gran Sabana, and this area of tepuis forms the EBA's centre in terms of the abundance of restricted-range species (Wege 1989). However, a number of species are endemic to single tepuis away from this region, e.g. Emberizoides duidae on Cerro Duida, and Myioborus cardonai on Cerro Guaiquinima. The two species present also in other EBAs are worthy of mention: Nannopsittaca panychlora is found north of the Orinoco only on Cerro Papelón and the Paria peninsula (in EBA 032); and Cypseloides phelpsi is known away from the tepuis by just one record (possibly of a vagrant) at Rancho Grande in Aragua state (in EBA 033) (Meyer de Schauensee and Phelps 1978).

Due to the largely inaccessible nature of this isolated region, the tepuis have not yet been seriously affected by human intervention, and at present remain relatively undisturbed (Huber and Alarcón 1988). However, the highland ecosystems are very fragile and highly vulnerable to disturbance. The effects of fire (which is frequently man-induced) can be dramatic, especially as the endemic plants of the tepuis often harbour flammable secondary compounds such as resins and oils, and the results of such destruction can be seen on many of the tepuis, as the vegetation is replaced by bracken Pteridium (Wege 1989).

Currently, other than burning, the primary threats to certain tepui mountain-tops are high-impact adventure tourism and pseudo-scientific exploration (A. Grajal in litt. 1993). The uncontrolled invasion of illegal gold-miners from Venezuela and Brazil has also caused grave problems, especially in La Neblina National Park (M. L. Goodwin in litt. 1993), but also in Jaua-Sarisariñama and (parts of) Canaima National Parks (C. J. Sharpe in litt. 1997). Changes in rainfall patterns from lowland deforestation have the potential to degrade sensitive tepui ecosystems in the future (Dinerstein et al. 1995).

Two of the tepui endemics, are due to their very small ranges, considered to be Vulnerable. Crypturellus ptaritepui is a species known only from Cerro Ptari-tepui and Cerro Sororopán-tepui in south-east Bolívar, where it inhabits cloud forest between 1,350 and 1,800 m. The combined area of the summit and talus at these two sites is only 28 km²; fire has been shown to be a threat to the slope vegetation in the past, and the forest is beginning to be cleared for subsistence agriculture. Myioborus cardonai occupies cloud forest between 1,200 and 1,600 m on Cerro Guaiquinima in west-central Bolívar; the mountain, which rises to 1,800 m, has a talus-slope area of only 110 km², and is being affected by mining activities (Mayr and Phelps 1967, Meyer de Schauensee and Phelps 1978, Ridgely and Tudor 1989, C. J. Sharpe . 1997).

A number of parks protect (though to varying degrees) large parts of the Tepuis EBA (e.g. Alto Orinoco-Casiquiare Biosphere Reserve, Canaima, Jaua-Sarisariñama and Duida National Parks), and recently all lands over 800 m and south of the Orinoco were declared national monuments, thus effectively putting all the tepuis within the protected-area system (A. Grajal in litt. 1993).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Tepuis. Downloaded from https://datazone.birdlife.org/eba/factsheet/31 on 22/11/2024.