The Rainforest Canopy

RAINFOREST PRIMATES

Primates (pictures | news) are characteristic of every continental rainforest realm, except for the Australasian realm, and are made up of nearly 200 living species in more than 50 genera. Primates are thought to have originated from their insectivore-like ancestors between 100 million and 65 million years ago. The ancient primates most resembled lemurs and the tarsier of today, and upper primates did not appear until 37 to 23 million years ago. Upper primates include monkeys, apes, chimps, and humans, and the non-human species are generally divided into Old World monkeys and New World monkeys.

Old World and New World monkeys are thought to have diverged from a common ancestor about 55-60 million years ago. Since that time, the two groups have been evolving separately and today have notable differences. For example, Old World monkeys have nostrils that are close together and open downward, while New World monkeys have nostrils that are wide apart and open toward the sides. Old World monkeys sleep in a sitting position, while New World monkeys tend to sleep lying down. While Old World monkeys live in a variety of habitats, all New World monkeys are arboreal. As for body structure, many New World monkeys are equipped with a prehensile tail, a feature that Old World monkeys lack. However, Old World monkeys make up for the absence of a prehensile tail by having fully opposable first digits (thumbs and big toes), meaning that this digit is apart from the others, as in humans. Among New World monkeys, only a few species have partially opposable first digits, while the rest totally lack opposability. Since Old World monkeys lack prehensile tails, some species rely on brachiation for locomotion through the treetops. In addition, Old World monkeys generally tend to show more pronounced sexual differences than New World monkeys.

AFRICA

The African continent is known for its arboreal primates including chimps and Colobus monkeys. However, Africa has some lesser known primates like the insectivorous Pygmy Bushbaby with its large radio-dish-like ears used to pick up insect movement and huge eyes for nocturnal action. Its niche is filled by lorises in Asia and related (same sub-order) lemurs of Madagascar

Madagascar [learn more at WildMadagascar.org]

Madagascar lacks the dominant form of primate distributed worldwide, those of the suborder Haplorhini (monkeys, chimps, gorillas, and Homo sapiens). Instead, their niche has been filled by a more primitive (read as older) group of primates, the lemurs. Lemurs belong to the sub-order Strepsirhini together with bushbabies, lorises, and pottos which, like the original lemurs, are nocturnal, insectivorous primates characterized by a small body, a long nose, and large eyes. Lemurs have an interesting evolutionary history and the only reason they still exist today is because of Madagascar's isolation (actually one species, believed to be introduced, is shared with the Comoros, a set of small islands off the northwestern coast of Madagascar).

Back in the days of the super continent Gondwanaland (formed of Africa, South America, Australia, Antarctica, India, and Madagascar), Madagascar was still part of the African mainland. About 160 million years ago, when Madagascar separated from the African continent, it had no primate life. The first lemur-like primates on the fossil record appeared roughly 60 million years ago, about which time the gap between Madagascar and Africa was still narrow. By rafting or walking during low ocean levels, lemur-like primates reached Madagascar. The island continued to drift eastward and by the time monkeys evolved 23-17 million years ago, the gap was too wide to be bridged and Madagascar missed the arrival of the more competitive, more intelligent primates that descended from the same ancestors as the lemurs. The mainland lemur lineage in Africa, Europe, and North America, which was not isolated from the evolutionary changes of the world, was quickly out-competed by the monkeys and driven to extinction. Only the enclave of lemurs on Madagascar survived, although some Strepsirhines (Bushbabies, lorises, and pottos) managed to pull though by retaining their nocturnal, solitary, and insectivorous traits. Since their arrival, the lemurs of Madagascar have been free to radiate into the large island's many niches without much competition or predation, and some have developed adaptations similar to those of monkeys, including forming social groups, being herbivorous, and being active by day. Today lemurs can be found in virtually all of Madagascar's ecosystems, from the tropical rainforest to the unique spiny desert to the deciduous woodlands. Upper primates did not reach Madagascar until about the time they learned to sail on the high seas. Two thousand years ago man invaded and began to threaten lemurs by destroying their environment. At one time, more than 48 lemur species existed, including giant gorilla-sized species, but today the number has been reduced to about 32 species.

The poster species for lemurs is not a rainforest dweller, but exists in the dry and deciduous parts of Southwestern Madagascar. The ring-tailed Lemur is recognizable by its black-and-white-banded tail much like that of a raccoon. Unlike other lemurs, the ring-tailed lemur spends a good portion of its time on the ground.

The aye-aye is one of the world's most bizarre creatures. This lemur, first classified as a rodent, is superbly adapted to its specific niche as evidenced by its long twig-like middle finger, huge eyes, rat-like teeth, and large bat-like ears. The nocturnal aye-aye uses its long middle finger as a tool for finding insects. After tapping the tree bark, it uses its sensitive hearing to detect the movement of insect larvae. Studies have found that the aye-aye is capable of sensing insect movement at a depth of 12 feet. Sadly this odd creature is endangered by both habitat destruction in northeastern Madagascar and widespread persecution by native Malagasy who consider it a harbinger of bad luck.

The largest living lemur is the Indri (Indri indri) of the montane forests of eastern Madagascar. In coloration, it resembles a giant panda with its black and white fur, but in body shape it is more anthropomorphic with its long neck and arms, and small ears. The Indri feeds on canopy fruits and leaves and is best known for its eerie yet beautiful song, which can carry for more than 1.2 miles (2 km). This diurnal lemur will bark when confronted with danger, and make kissing sounds when affectionate. Despite its large size, the Indri refuses to move along the ground, and will negotiate gaps by leaping, often more than 33 feet (10 m), between tree trunks. Naturally rare due to its low birth rate (one birth every three years) and small population density, today the Indri's numbers are small and dwindling due to habitat loss and hunting. A good portion of the world's remaining Indri population is in the Analamazaotra (Perinet) reserve and surrounding forest, due east of Madagascar's capital, Antananarivo. The Indri will not survive in captivity, a trait that is a major hurdle to possible rehabilitation projects and conservation.

One of the most recently discovered (by Western science) large mammal species is the golden bamboo lemur (Hapalemur aureus), which was found by an expedition searching for the greater bamboo lemur (H. simius), which was believed to be extinct. The last known (at the time) greater bamboo lemur specimen died in captivity in the mid 1970s, and in 1986 an expedition was organized to confirm that the species was extinct. The expedition found a previously undescribed bamboo-eating lemur with reddish gold fur, which was later named the golden bamboo lemur. Interestingly, Madagascar's forests support a third species of bamboo-eating lemur, the gentle bamboo lemur (H. griseus). These three species coexist by having specialized bamboo-feeding habits. The golden bamboo lemur, apparently tolerant of high concentrations of cyanide, eats the cyanide-containing leaf bases, shoots, and piths of new growth giant bamboo. The amount of cyanide consumed daily by this species is enough to kill three men. The greater bamboo lemur eats the mature pith of the same bamboo, while the gentle bamboo lemur eats the leaves of another bamboo species.

Today virtually all lemurs are threatened by habitat destruction. Unfortunately, natives are increasingly turning to lemurs as a source of meat. Many lemurs are particularly easy targets for hunting because evolution has rendered them ecologically naive (a term coined by Quammen in 1996) in that without natural predators over the majority of their existence, evolution has left them without fear of man. Similar behavior has been observed throughout the world in ecosystems (especially islands like the Galapagos) where predators have been historically non-existent.

ASIA

Asia has more arboreal primate diversity than Africa, but still far less than the New World. One of the best known Asian primates are the Gibbons of Southeast Asia which represent about seven species characterized by long arms (armspan may reach 7 feet—2.1 m) and no tail. These arboreal apes are considered acrobats of the trees for their prowess and agility in the high canopy where their diet includes fruits and leaves, supplemented with eggs and small birds. Gibbons are strongly territorial, but defend only an area large enough to provide food for family sustenance. Gibbons live in family groups of three to six individuals; usually one male, one female, and young. Other Asiatic primates include macaques, langurs, leaf monkeys, and Proboscis monkeys.

SOUTH AMERICA

South and Central America have the greatest arboreal primate diversity, probably because they evolved as forest dwellers and never descended to fill the terrestrial niches occupied by their Old World counterparts. South America is home to some of the world's smallest monkeys, the marmosets and tamarins, which average between the size of a rat and a squirrel. The largest species reaches 21 ounces (600 g), while the pygmy marmoset reaches its maximum at six inches (15 cm.) and three ounces (80 g). The pygmy marmoset, the smallest monkey in world, has a unique nocturnal feeding habit. It has chisel-like incisor teeth which allow it to gouge holes in bark to start the flow of tree fluids on which it feeds. Interestingly, both human rubber tappers and marmosets must be careful not to over-tap the trees, which would have the effect of killing the trees and destroying a source of sustenance. Other marmosets and tamarins feed on insects, eggs, fruits, and berries and are characterized by a long, bushy, non-prehensile tail. The exceedingly rare gold lion tamarin of the Poco das Anas Biological Reserve in Brazil is famous for its beautiful, long, golden fur and serves as a flagship species for the conservation of Brazil's endangered Atlantic forest. This small tamarin has recently been threatened by fires which burned nearly 1/3 of its reserve.

South America's wide primate diversity also includes: the world's only nocturnal monkey, the douroucouli; the intelligent capuchin monkeys, named for the resemblance of their crown hair to the capuche of French friars; the saki or sloth monkeys, known as flying monkeys for their ability to leap over 30 feet between trees; the variable uakari monkeys including the bald Uakari, a favorite of many tourists with its bald head and bright glowing red face; and many other species.

Review questions:

• What are lemurs and where are they found?
• Generally, how are New World monkeys different from Old World monkeys?

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Continued / Next: Other canopy mammals