Geoscience Reference
In-Depth Information
Plants throughout the tropics have developed similar adaptive strategies. The
structure and characteristics discussed above are evident in each of the regional
expressions of the Tropical Rainforest Biome.
Animals
Studies of tropical rainforest animals reveal an overwhelming diversity of species
compared with other terrestrial biomes. As many as 450 bird, 93 reptile, 37 am-
phibian, and 70 mammal species have been recorded on less than 247 ac (1 km
2
)in
the Guyanan rainforest in South America. Other tropical regions of the world
show similar diversity. Isolated tropical rainforests and those of more recent origin,
such as those of the Hawaiian and Pacific Islands, Australia, and New Guinea,
reveal less variety. Studies on butterflies have reported species counts as high as
300-500 in a given study area of tropical rainforests of Africa and South America.
Termites and beetles show even higher numbers.
The tropical rainforest landscape is varied in structure, growthforms, and spe-
cies. This diversity of habitats, along with diverse survival strategies in the use of
those habitats, provides opportunities for many more animals than the homogene-
ous habitats of more simply structured biomes, such as grasslands. Partitioning of
space, food resources, and timing of activity expand the species capacity of the for-
est. Diurnal and nocturnal behaviors allow different animals to use the same habi-
tat at different times. Using different layers of the canopy as habitat further
separates resources and increases capacity. Selection of varied food choices, such
as leaves, gums, bark, fruits, nuts, seeds, and other organisms, within the same
environment, allows for the survival of many species without direct competition.
Even the location of food sources can be partitioned to provide diversification. For
example, on the island of Trinidad in the Caribbean Sea, three species of tanagers
have been found to extract insects from different microhabitats off the same tree
without directly competing. One species of bird feeds on insects from the underside
of leaves, another from small vines, twigs, and leaf petioles, and the third takes
insects from the main branches. This allows all three species to utilize the same
food source without the need to compete.
Common characteristics found among mammals, birds, reptiles, and amphib-
ians include various adaptations to an arboreal life. For example, arboreal anteat-
ers, pangolins, some rodents, and many monkeys and possums in the rainforest
have developed prehensile tails. A prehensile tail allows the animal to hang on to a
tree branch while using its other limbs for catching prey, eating, or grooming.
Another adaptation to arboreal life is the evolution of opposable digits that aid in
climbing. Many arboreal species also have sharp claws to hang on to trees and
branches. Additional adaptations include binocular vision to aid in accurately see-
ing distances and dimensions. This is particularly helpful when leaping between
trees within the dimly lit forest.
