This Guayana Highlands ecoregion in northern South America is host to an archipelago of isolated sandstone plateaus and dramatic summits atop nearly vertical escarpments. The tepuis are the remains of the ancient sandstone tableland overlying the even more ancient granitic Guayana Shield.
This Guayana Highlands ecoregion in northern South America is host to an archipelago of isolated sandstone plateaus and dramatic summits atop nearly vertical escarpments.
More than 50 of the highest tabletop mountains are the remains of the ancient sandstone tableland overlying the even more ancient granitic Guayana Shield. They range from 1,000 to 3,000 m in elevation. And they are called tepuis (singular: tepui), a word from the Pemón Amerindians. Many tepuis are graced with dramatic waterfalls, the tallest of which (in fact, the tallest in the world) is Angel Falls dropping 979 meters.
These dramatic features in the landscape perforate an extensive matrix of highland savannas and rain forests across southern Venezuela mostly, with a few outliers in western Guayana, Surinam, and northern most Brazil. Hundreds of smaller sandstone mountains exist in the ecoregion as well.
The Tepuis are characteristically flat-topped steep, nearly vertical escarpments interrupted by terraced talus slopes. Some mountains present more undulating irregular summit contours. Each mountain displays its own spectacular characteristics of shape, biodiversity or elevation.
The highest peaks are Pico da Neblina in Brazil at 3,014 m, the adjacent Pico Phelps (2,992 m) in Venezuela, followed by Roraima-tepui (2,810 m) and Cerro Marahuaka (2,800 m), both in Venezuela. Cerro Ichún, close to the Brazil-Venezuela border, has the largest surface area of all the sandstone tabletop mountains with a total area of 3,260 km2 at an elevation of 1,400 m.
On the highest summits, the temperature can drop to an extreme of 0° C, but generally the temperatures on the summits range from 8° to 20° C on average over the year, depending on elevation. The Tepuis are constantly humid and receive from 2,000 to 4,000 mm of rain per year with a subtle dry season. Soils are generally oligotrophic (low nutrient).
The vegetation on the Tepui Mountains is distinct from the surrounding Amazonian humid forest vegetation and forms a biogeographic complex. A representative tepui hosts four distinct vegetation zones starting at the base, proceeding to the talus slope, on to the base of the escarpment (cliff), and finally the mountain summit.
The vegetation on the Tepuis shows very high endemism (33%). The summit vegetation is of particular interest, and it is here that the high endemism characteristic of the Tepui floristic province is found.
Five vegetation types are found on the summits:
- forests of tall or dwarfed trees, including riverine forests
- epiphytes in forest associations
- shaded crevices of rocks, bluffs and ledges
- wet or dry open savanna without rock outcrops
- exposed rock outcrops, open sandy or rocky areas
The Tepuis ecoregion hosts 186 mammal species, mostly located on the lower slopes of the mountains. This number includes 9 primates that live here including howler monkeys(Alouatta seniculus), night monkeys (Aotus trivirgatus), titi monkeys (Callicebus torquatus), black uakari (Cacajao melanocephalus), weeper capuchins (Cebus olivaceus), and white-faced sakis (Pithecia pithecia). Five cats live here, including jaguars (Panthera onca) and pumas (Puma concolor). Some mammals are restricted to this region of Amazonia; these include an endemic opossum (Marmosa tyleriana) and white-eared opossum (Didelphis albiventris), long-tailed weasels, pale-throated sloths and a great variety of bats (Diclidurus isabellus, Pteronotus personatus, Phyllostomus latifolius, Anoura geoffroyi, Glossophaga longirostris), an endemic rodent (Podoxymys roraimae), three climbing rats in the genus Rhipidomys, and two guinea pigs (Cavia).
A large number of birds are found in the Tepuis ecoregion (628 species) with 41 endemics including tepui tinamous (Crypturellus ptaritepui), fiery-shouldered parakeet (Pyrrhura egregia), tepui parrotlets (Nannopsittaca panychlora), roraiman nightjars (Caprimulgus whitelyi), tepui swifts (Cypseloides phelpsi), rufous-breasted sabrewings (Campylopterus hyperythrus), buff-breasted sabrewings (C. duidae), peacock coquettes (Lophornis pavoninus), tepui goldenthroats (Polytmus milleri), velvet-browed brilliants (Heliodoxa xanthogonys), white-throated foliage-gleaners (Automolus roraimae), tepui antpittas (Myrmothera simplex), red-banded fruiteaters (Pipreola whitelyi), three manakins (Pipra cornutai, P. pipra, and Chloropipo uniformis), among many others.
Reptiles and amphibians are abundant on the summits and slopes of the Tepuis. The more ferocious snakes that occur here include fer-de-lance (Bothrops asper), coral snakes (Micrurus spp.), boa constrictors (Boa constrictor), and bushmasters (Lachesis muta). Iguanas (Iguana iguana) are ubiquitous and tegus lizards (Tupinambis spp.) common.