Biotope of dendrobates ventrimaculatus at the Inselberg at French Gyana for www.poison-frogs.com

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Poison Frogs - Biotopes - Inselberg, Fr. Gyana

Inselberg biotope in French Guyana

by Erik Poelman


Poison frogs are commonly believed to be abundant in primary and secondary forest only. Yes, you will find several species in primary forest living on the forest floor between the fallen leaves. These are most commonly Epipedobates, Phyllobates and Colostethus species. However the true Dendrobates species often inhabit very different habitats, where you would not really expect the presence of frogs in the first place. One of these habitats is an Inselberg in the Nouragues reserve of French Guyana. Inselbergs are rocky outcrops of several hundred meters high and reach out over the canopy of the primary forest. The mountain consists of pure granite rock on which cyanobactery are growing, which gives it a brown appearance. Plain rock with harsh weather conditions, influence of wind, lightning, heavy rain and sunshine, that are constantly changing stress the environment and make it hard for plants to grow on these rocks.
The cyanobactery and carpet of algae make it possible for some pioneer plants to get their grip on the rocks. One of these plants is the bromeliad Pitcarnia geykesii. It can grow quite large, forms several leaves with very small thorns and like all bromeliads is able to keep some water inside its leaf axils. They flower in beautiful red flowers that are visited by several species of hummingbirds, which collect its nectar. Other plants profit from the carpets these bromeliads form.
The most common tree you will find on such a mountain is a Clusia. They can grow high, but because of the influence of the wind will not grow taller than 5 meters high. These Clusia trees are again colonised by several Orchid species, but also on this particular mountain by the bromeliad Catopsis berteroniana. This epiphytic (growing on other trees) bromeliad has much larger water bodies formed by its leaves and traps insects as nutrient source. The Clusia trees form small enclaves of low forest on the rocks and underneath them a thick layer of leaves will form. Larger terrestrial (rooting on the ground) bromeliads of the genus Aechmea can root here. They have even larger water bodies. The abundance of these bromeliads with their water bodies are again colonised by poison frogs. On this particular mountain the Amazonian poison frog (Dendrobates ventrimaculatus) is abundant. Early morning and during or just after rains you can find them foraging on the stones, where they hunt small ants and termites. When the sun is shining they retreat in the Catopsis and Aechmea bromeliads, which they also use for breeding. They share the patches of forest formed by Clusia trees with Dendrobates tinctorius (French Guyana morph). These large dendrobatid frogs use the small water pools on the rocks for tadpole deposition and lay their eggs in the thick leaf litter under the Clusia trees. Again early morning you can find them hopping over the stones to other patches of low forest. Much less abundant, but present, are Epipedobates femoralis, Epipedobates hahneli and Colostethus baeobatrachus (French Guyana populations of C. brunneus). They live in the larger more humid Clusia patches and deposit their tadpoles in small streams and pools that are formed on the rocks during rainy season. Keep in mind where your frogs are originally coming from when you want to keep them successfully and even get them breeding. The larger Dendrobates (tinctorius, azureus) are often found in far more open places than you might expect!

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