2011: International Year of Forests
Zones of Life in a Rainforest
Tropical rainforests are usually divided into five distinct layers. Beginning at the top is the Emergent Layer, which is not continuous like the other layers. It consists of a scattering of tall trees that protrude far higher than the others, ranging from 100 to 250 feet overhead. This level has the most variable conditions since it is more exposed to the elements and gets the full force of the sun, wind and rain.
Ivory our Great White Hawk
Birds of prey like the harpy eagle, native to South America, hunt from the high treetops of this layer. At the World Bird Sanctuary you can see another species that visits the emergent layer in their native range of Central and South American rainforests—a White Hawk named Ivory.
Some monkeys, bats, snakes, butterflies and other insects also inhabit or visit the emergent layer. Butterflies go from flower to flower in the high treetops. The male Blue Morpho butterflies M. peleides are a brilliant blue and will often assemble in the emergent layer to attract a mate. A Morpho butterfly may be one of over 80 species of butterflies in the genus Morpho. They are Neotropical butterflies found mostly in South America as well as Mexico and Central America. Morphos range in wingspan from the 7.5 cm (3 inch) M. rhodopteron to the imposing 20 cm (8 inch) Sunset Morpho, M. hecuba.
Rio, a red and green macaw
Many animals climb or fly between the emergent layer and the next layer down, the Canopy Layer--for example, Macaws, which live on the nuts, fruits and seeds found in these layers. You may see several examples of these beautiful birds in the World Bird Sanctuary’s Nature Center.
More species live in the canopy layer than anyplace else in the rainforest. Sloths (only found in South America), monkeys and other climbing mammals are common here. This layer can be about 20 feet thick, and is formed by the next tallest trees. It acts like a roof over the rest of the rainforest and deflects most of the sun, rain and wind. The air is very still within the canopy, so most plants here rely on animals, not wind, to disperse their seeds. Therefore, many fruits are abundant here.
Moving on downward, the next layer is the Understory. This layer is about 20 to 40 feet above the ground. It is made up of young trees, short species of trees and some taller shrubs. It is darker, there is less wind and it is more humid than the canopy above it. Understory plants have flowers that are large and pale to be easily seen in the dim light. They also have strong odors to help attract pollinators. The humidity is perfect for a variety of amphibians, such as salamanders and frogs. Predators like Jaguars and Ocelots sit up in this layer scanning the ground for prey. Many small birds feed here and at lower levels.
Next is the Shrub Layer, which extends from about 2 to 20 feet above the ground and consists of woody plants and bushes. Although this layer has relatively sparse growth, you may find cauliflorous trees and vines here. These plants have flowers that grow out directly from the bark and some resemble cauliflowers. When not feeding or seeking a mate, the beautiful Blue Morpho butterfly can usually be found resting in this layer with it’s wings folded and looking for all the world like a leaf with large eyespots. This beautiful butterfly, whose topwings are a striking iridescent blue, has brown underwings with large eyespots.
Lastly, at ground level is the Herb Layer which contains saplings, small leafy plants, ferns, fungi, fallen trees and other fallen dead plant material. Less than one percent of sunlight reaches this level. Here giant anteaters, peccaries, tapirs and other large mammals dig up invertebrates, roots and tubers to eat. The previously mentioned Blue Morpho butterfly can be found here, dining on rotten and decomposing fruit. The decomposing litter is a source of food for a variety of small invertebrates like termites, millipedes and earthworms. A myriad of centipedes, scorpions, slugs, beetles and cockroaches live here under stones, leaves and logs.
For more information about the ecology of the rainforests visit the Smithsonian Tropical Research Institute’s website at http://www.stri.si.edu/
Here at the World Bird Sanctuary in Missouri we don’t have a rainforest. However, we do have trails that lead visitors through an old growth Oak/Hickory forest. If you don’t feel comfortable exploring our forest on your own, call 636-225-4390 XT. 0 to learn about one of our newest programs, “Hey, There’s Nature in my Woods”, which is led by one of our knowledgeable naturalists. You may be surprised at what you discover right here in your own backyard.
Submitted by Sara Oliver, World Bird Sanctuary Naturalist
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