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TROPICAL RAINFORESTS:
The Canopy
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About this site
Providing tropical forest news, statistics, photos, and information, rainforests.mongabay.com is the world's most popular rainforest site. [more] |
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Uroplatus fimbriatus gecko in Madagascar. (Photo by R. Butler)
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AMPHIBIANS AND REPTILES
AMPHIBIANS
Frogs are overwhelmingly the most abundant amphibians in the rainforest. Unlike temperate frogs which are mostly
limited to habitats near water, tropical frogs are most abundant in the trees and relatively few are found near
bodies of water on the forest floor. The reason for this occurrence is quite simple: frogs must always keep their
skin moist since almost half of their respiration in carried out through their skin. The high humidity of the rainforest
and frequent rainstorms gives tropical frogs infinitely more freedom to move into the trees and escape the many
predators of rainforest waters. The differences between temperate and tropical frogs extend beyond their habitat.
Whereas nearly all temperate frogs lay their eggs in water, the majority of rainforest species place eggs in vegetation
or lay them in the ground. By leaving the water, frogs avoid egg-predators like fish, shrimp, aquatic insects,
and insect larvae. Several species of frogs, including the American glass frogs, lay their eggs on vegetation that
overhangs water. The humid climate keeps the eggs moist and when the tadpoles hatch they drop into the water below.
Glass frogs are also interesting because they are transparent except for their visible organs and faint yellow
spots that some species possess. The yellow spots resemble a cluster of the frog's eggs, enough to fool predators.
Other frog species develop fully into froglets within their eggs, and emerge as fully formed frogs, thus by-passing
the tadpole stage all together.
REPTILES
When many people think of the "jungle," they think of huge deadly snakes; but this is not the case in
the canopy where very few species pose any threat to humans. The majority of canopy snakes are constrictors or
mildly venomous species and are rarely encountered by humans. Even in the canopy, chances are you will not see
many snakes since numerous species camouflage themselves like leaves and vines.
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Boa Constrictor, Costa Rica 2001
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The best known venomous canopy-dwelling snake is the eye-lash viper of the New World which exists in several different
color forms including yellow, green, olive, and orange. The eyelash viper is so named for the presence of small
horned scales above the eye. Also found in the canopy are various constrictors of the Boa family which use their
strong muscles to constrict their prey to death.
In addition to snakes, the forest canopy contains lizards. Iguanas are large greenish lizards of the New World
- which have the unique ability to fall over 60 feet (18 m) from canopy trees unharmed. Their strong tail is used
for balance during the fall and catching branches during the ascent to break the impact of the fall. Iguanas often
habit limbs that overhang rivers so they are able to escape predators by dropping into the river and waiting submerged
for over 30 minutes. Iguanas may attain a length of 6 feet (1.8 m), though are generally smaller. Iguanas have
the ability to undergo a small color change to better blend in to their
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Male Green Iguana, Costa Rica 2001
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surrounding environment. But the true color-change artists of the forest are the chameleons - of which every forested
continent has its own. Chameleon are lizards that have the ability to rapidly change their colors to match their
surroundings, although tend to change more in accordance to their emotions. The Old World, or True chameleons of
Africa and Madagascar have the best color change ability and will often assume bright orange, purple, and blue
coloring to reflect their mood. South America has the anole, a much less spectacular chameleon, while Asia has
the Agamas.
INVERTEBRATES
Insects are the most successful rainforest animals as demonstrated by their tremendous diversity. Insects are so
ubiquitous that they have filled many niches usually occupied by other animals. For example, some postulate that
in South America the role of the forest elephant in the forest is filled by army ants. In the rainforest canopy,
insects abound: a study of rainforest canopy in Peru with 500 cubic meters of foliage (about the size of a two
car garage) found more than 50 species of ants, 1000 beetle species, 1700 arthropod species, and more than 100,000
individuals. A rainforest tree alone can have some 1200 species of beetle, while a single hectare of rich forest
canopy is projected to have 12,448 beetle species.
There are many insects and other invertebrates that would not usually be considered arboreal but exist in the rainforest
canopy. For example, several species of crabs have been found hundreds of feet above the ground in tank bromeliads
of Neotropical forests. Similarly, earthworms and giant planarians (flatworms) are also part of the canopy system,
with earthworms playing an important role in the processing of canopy soils and mulch that supports epiphytic growth.
Even leaches are found in the canopy where they may surprise first time visitors to the Asian forest canopy. Mosquitoes
too, are abundant in the canopy, though on the ground there are generally few puddles for breeding and no pronounced
seasonal changes to stimulate massive mosquito breeding frenzy. In the canopy, mosquitoes lay their eggs in the
up-turned leaves of epiphytes like tank bromeliads. Therefore, you may be more likely to get mosquito bites in
the canopy than on the forest floor.
Many insects like stick insects, katydids, leaf hoppers, and mantids have developed incredible behavior, body structure,
and color to mimic their surroundings. These insects, which mimic dead and living leaves, half-eaten leaves, sticks,
bark, bird droppings, and flower parts, avoid detection by predators and prey as they hunt and rest.
Review questions:
- What are three types of mimicry?
- Why is completely important?
[print version]
Continued: Forest floor
Unless otherwise specified, this article was written by Rhett A. Butler [Bibliographic citation for this page]
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