Geoscience Reference
In-Depth Information
Other animals, such as ground birds, tapirs, anteaters, some snakes, and inver-
tebrates spend their entire life on the forest floor. Larger animals, particularly herbi-
vores, are rare because of limited food available on the forest floor, due to the rapid
decomposition of fruits and restricted number of plants able to survival under the
deep shade of the forest canopy. The fauna of the Neotropical rainforest today is
the accumulative result of millions of years of geologic, climatic, and biological
events.
Mammals
More mammals inhabit tropical rainforests than any other biome. Of the 500 spe-
cies of mammals that have been identified in the Neotropics, 60 percent are
endemic to the rainforests of South America. These include all platyrrhine mon-
keys, anteaters, opossums, echimyid rodents, and all living sloths. Some are highly
specialized and adapted to life in the trees with prehensile tails, sharp claws, dis-
tinctive communication, and great leaping abilities. Others are generalists, feeding
on a variety of food items and foraging in the trees, on the ground, and in the
waterways.
Many of the mammals of the Neotropical forest have adapted to arboreal life
by evolving prehensile tails and long limbs that allow them to swing from branch
to branch and tree to tree within the forest. In addition, primates, porcupines, and
sloths, among others, have opposable digits and long claws to hang on branches
and trees. Binocular vision allows many to see clearly in the dense forest cover and
have accurate depth perception, a clear asset when leaping from branch to branch.
Other adaptations include varied feeding strategies or modifications in body parts
to facilitate the use of the different resources available in the rainforest. For exam-
ple, anteaters have developed long tongues that allow them to gather insects often
hidden within logs. Sloths have jaws and teeth that allow them to chew leaves,
their primary food sources. Porcupines in the tropical forest have jaws and teeth
that allow them to consume tree bark.
The distribution of mammals is a combined result of geologic and biological his-
tory and evolution. By the late Cretaceous, early Paleocene (65 mya), South America
along with Antarctica and Australia broke from Africa. As Antarctica continued to
drift south and Australia drifted east, South America became isolated and remained
that way for the next 50 million years. During this isolation, several endemic orders
of mammals appeared on the South American continent, most of which are now
extinct. Only the order Xenarthra (or Edentata), which contains anteaters, sloths,
and armadillos, survives. Other Neotropical mammals—including the primates,
marsupials, and rodents—have relatives on distant continents.
The uplift of the Andes Range was another significant event in the geologic his-
tory of the Neotropical rainforest. The rise of the mountains affected temperature,
climate, and moisture regimes in high elevations, and presented an effective cli-
matic as well as biological barrier to lowland forests. Another important event in
Neotropical biogeography took place around 7 mya, when the Isthmus of Panama
