MONKEY TYPES: OLD AND NEW WORLD, LEAF- AND FRUIT-EATING

MONKEYS


leaf-eating monkey

The range of many monkey species is determined by rivers. Since most monkey species don't swim, they generally don't cross large rivers except under extraordinary circumstances. Some large rivers have completely different monkey species on each side of their banks. Sometimes the species are similar enough that it seems conceivable that as a breeding couple of one species floated on logs across the river a hundreds of thousands of years ago and over time established a new species.

Primates generally use their incisors, canines, lips and fingers when they eat. How they use them depends on what they eat. Almost all primates eat fruit, seed and leaves. Many eat small prey, mostly insects, other arthropods, small animals and birds’ eggs. Even so there is some specialization.

In the wild monkeys are very finicky eaters. They sniff, feel and nibble what they eat and often spit out what they don’t want, leaving behind a trail of half eaten fruit and leaves on the forest floor. Sometimes this because they eat fruits that have worms and insects in them while leaving undisturbed fruit alone. For many monkey species worms and insects are their primary source of protein.

The predators that monkeys have to worry about most are eagles and humans. Snakes and cats are largely terrestrial animals who are no match for agile monkeys in the trees.

Websites and Resources: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org

Fruit-Eating Monkeys

Monkeys are also divided into fruit-eating monkeys and leaf-eating monkeys. Fruit and nut eating primates generally have a larger brain than leaf-eating apes and monkeys because they need more sophisticated reasoning, scientists suggest, to find food which is only found in some areas at certain times of the year while leaves are generally available everywhere throughout the year. The brain of the leaf-spider monkey, for instance, is only half the size of the fruit-eating howler monkey, even though occupy roughly the same terrain.


Ice-cream-eating monkey

Fruit-eating monkey have a higher rate of metabolism than leaf-eating monkeys. This allows them to move more quickly and dexterously through the large area of forest to seek out of fruiting trees. To keep going they need high energy-rich food such as fruit. Fleshy fruits are easy to digest. Food passes through their bodies quicker and they defecate frequently.

Fruit-eating monkeys can get to widely scattered sources of food more quickly and efficiently than leaf-eating monkeys. They endure a kind of feast and famine existence in which they go long periods without food were no fruits are available and travel a long distance to find it. But once a food source is found they gorge themselves until it is depleted.

Different fruit eating monkeys, such as spider monkeys, capuchin and titis, often compete for the same fruits trees. The largest monkeys or the one in the largest group usually win out. ruit trees only fruit at certain times and sometimes these times are unpredictable Fruits are generally low in protein. Small primates often supplement their diets with small animal or insect prey or nectar-filled flowers. Large ones eat leaves.

Fruit eating monkeys generally have long arms and tails which allows them to swing through the trees like acrobats. They generally have oversize large intestines, which help them digest fruit. Their incisor teeth tend to act like scoops and are broader and larger that those of leaf-eating monkeys.

Leaf-Eating Monkeys

Leaf-eating monkeys generally much more slowly and deliberately through the trees. They tend to stick around one place, constantly munching on leaves they choose rather moving around a lot and picking and choosing.

Leaf-eating monkeys defecate less than fruit-eating monkeys, often when after waking up in the morning and tight after nightfall. Moreover, they have to be carful about what they eat because their slow metabolism absorbs toxins earlier than the quicker metabolism of fruit-eating monkeys.


primate global distribution

Leaf-eating monkeys generally have a low metabolism which allows them to survive on large quantities of low-energy but ubiquitous food like leaves. They have developed jaws and chewing muscles and sharp crested molars that allow them break through the tough cell walls of leaves to get at the nutrients inside and make them easier to digest.

Leaf eating monkeys have chambered stomachs like ruminants such as cows. They eat large quantities of leaves and rely on bacteria in their stomachs to break down the cellulose in the leaves. These monkeys often spend several hours eating and several hours relaxing while food in their stomachs digest.

Leaf-eating monkeys have longer intestines for their body size than fruit-eating monkeys to allow for more time to absorb nutrients. Their digestive system is dominated by their small intestine, which absorbs the nutrients. Some have large stomachs or colons, which act as fermentation chambers to breakdown the cellulose and lignin in the leaves to make them digestible. They also have efficient kidneys and livers to filter out toxins and other chemicals the plant produce as a defense.

Leaf eating monkeys often do better in second growth forest than virgin ones because the monkeys sometimes eat so much fruit and vegetation from certain kinds of trees that overdose on toxic chemicals. In young forests the trees are not large, and do not bare as much of fruit and leaves, consequently they are less likely to provide chemicals in quantities that would cause the monkey to OD.

Old and New World Monkeys

Scientists divide monkeys into Old World monkeys — those from Asia, Africa and Europe — and New World monkeys — those from North and South America. There are no monkeys in Australia, New Zealand or islands in the major seas unless they have been introduced there.

The main difference between Old World and New World monkeys is their tails. Old World monkeys never developed their tails into a adaptable, prehensile, fifth limb as New World monkeys did. They use their tails for balance when they scamper along branches and to help control their jumps and landings.


an Old World monkey

Scientists distinguish between Old World and New World monkeys based on their noses. The noses of New World monkeys are flat and broad with widely-spaced nostrils that are pointed towards the side of the face whereas the noses of Old World monkeys are thinner and straighter and the nostrils are narrower and point forward. The scientific name of New World monkeys from South America is platyrrhines — flat-noses — while the scientific name of Old World monkeys is catarrhines — hooked noses.

Some scientists speculate that because many species of African monkeys spend a lot of time on the ground developing an agile tail was not a priority. In the Old World there are many species of monkeys who spend a lot of time on the ground while in the New World there are none.

Old World monkeys also have calloused patches on their rump, longer hind limbs than forelimbs, two pre-molar teeth and flattened nails on their digits. All are diurnal and most are at least partly terrestrial. David Attenborough wrote: “Old World monkeys have ear drums, which like our own, lie deep in the head, at the bottom of a tube. New World monkeys have eardrums so close to the ear surface of the head that they can easily be seen within the ear.”

Old World Monkeys

Old World monkeys (Scientific name: Cercopithecidae) and baboons, includes macaques, rhesus monkeys , mangabeys, mandrills, guenons, patas monkeys, langurs, proboscis monkeys, colubus, and many others There are 22 genera and about 1 species of Old World monkeys. These monkeys are widely distributed in the Old World from southern Spain and Gibraltar into northwest Africa; throughout sub-Sahara Africa; parts of the Arabian peninsula, and throughout central and South Asia, including southern China and most of Japan.

Some Old World monkeys have a greater tolerance for cold than any other non-human primates. One species of macaque lives in the cold and snowy regions of northern Japan. The earliest evidence of cercopithecids comes from Oligocene Period (33 million to 23.9 million years ago) fossils from Egypt. Fossil records from the Old World, matching the distribution of modern species. Some extinct species almost the size of gorillas. [Source: Phil Myers, Animal Diversity Web (ADW) /=] /=\


noses of New and Old World monkeys

There are two ecologically and morphologically distinct subfamiliesof Old World monkeys, based largely on dietary adaptions: 1) the cercopithecines, who are omnivorous and have cheek pouches and simple stomachs; and 2) the colobines, are folivorous (leaf-eating), lack cheek pouches, and have complex stomachs. /=\

Cercopithecines are mostly fruit-eating monkeys. They have rounded molars, cheek pouches used to store food, a short tail, well-developed thumbs and arms and legs of similar size which are useful in walking with all fours. They include macaques, baboons, some mangabeys, and guenons.

Colobines are mostly leaf-eating monkeys. They have high-cusped, shearing molars, no cheek pouches, multi-chambered stomachs for fermenting fibrous leaves, long legs for leaping, short or absent thumbs and very long tails. They include langurs and colobus monkeys.

Old World Monkey Characteristics

Phil Myers wrote in Animal Diversity Web: Cercopithecids (Old World monkeys) are medium to large size, ranging from around 1.5 kilograms to over 50 kilograms. Many have a stocky build. Their nostrils are close together and face downward, a condition known as catarrhine. The forelimbs generally are shorter than the hindlimbs. All digits have nails; these are flat, not curved as in cebids (New World monkeys). The thumb and big toe are opposable except the genus Colobus, in which the thumb is nearly absent. The palms and soles are naked. A tail is present and may be long or vestigial, but it is never fully prehensile as in many cebids (New World monkeys). Many cercopithecids have ischial callosities, brightly colored patches of skin on their rumps. These are used in dominance and sexual displays. The facial muscles or cercopithecids are well developed, and facial expressions play an important role in social behavior. The fur of these monkeys is usually gray or brown, but some are brightly marked. The fur is never wooly and rarely silky. [Source:Phil Myers, Animal Diversity Web (ADW) /=]

Cranially, cercopithecids have a robust and heavily ridged skull compared to cebids (New World monkeys), and the rostrum (hard, beak-like structures projecting out from the head or mouth) of some species (baboons) is rather long. The palate is long and concave, extending beyond the last molar. The bullae are small but a bony eustachian tube is present (formed from the ectotympanic). The dental formula is 2/2, 1/1, 2/2, 3/3 = 32. The medial incisors are often broad and spoon-shaped; the upper canines are usually large and separated from incisors by a small diastema; the first lower premolar is enlarged and its edge shears against the sharp posterior edge of upper canine; the molars quadrate and bilophodont. On the lower molars, a hypoconulid is present. /=\

Cercopithecids are almost exclusively diurnal (active mainly during the daytime). They exhibit a great variety of social behavior. Most can be found in groups of varying size, and interactions among individuals may be complex. The basic unit seems to be a family group, but sometimes much larger bands form. Most cercopithecids are arboreal (live mainly in trees), but baboons are primarily terrestrial. /=\

Many cercopithecids show pronounced sexual dimorphism (differences between males and females). This may be in body size (males are up to twice the weight of females in some species), color, or in the degree of development of the canines. /=\

New World Monkeys


New World monkeys

New World monkeys (scientific name: platyrrhines) refers to the five families of primates that are found in the tropical regions of Mexico, Central and South America: 1) Callitrichidae (marmosets and tamarins), 2) Cebidae (many New World monkeys, including capuchin and squirrel monkeys), 3) Aotidae (night monkeys, also known as owl monkeys), 4) Pitheciidae (titis, saki monkeys and uakaris), and 5) Atelidae (larger Latin American monkeys such as howler, spider, woolly, and woolly spider monkeys). [Source: Wikipedia]

The five aforementioned families are grouped together as the Ceboidea, the only extant superfamily in the parvorder Platyrrhini. Platyrrhini is derived from the Greek for "broad nosed". Their noses are flatter than those of other monkeys. Monkeys in Atelidae family, such as spider monkeys, are the only primates that have prehensile tails (tails that can grasp and hold objects such as tree branches).

New World monkeys descend from African simians that colonized South America. About 40 million years ago, the Simiiformes infraorder split into the parvorders Platyrrhini (New World monkeys) and Catarrhini (apes and Old World monkeys) somewhere in Africa. Platyrrhini are currently conjectured to have dispersed to South America on a raft of vegetation across the Atlantic Ocean during the Eocene epoch, possibly via several intermediate now submerged islands (See Below).

New World Monkey Characteristics

New World monkeys are small to mid-sized primates, ranging from the pygmy marmoset (the world's smallest monkey), at 14 to 16 centimeters (5.5 to 6.5 inches) and a weight of 120 to 190 grams (4.2 to 6.7 ounces), to the southern muriqui, at 55 to 70 centimeters (22 to 28 inches) and a weight of 12 to 15 kg (26 to 33 pounds). [Source: Wikipedia]

New World monkeys differ slightly from Old World monkeys in several aspects. The most prominent phenotypic distinction is the nose. The clade for New World monkeys, Platyrrhini, means "flat nosed". The noses of New World monkeys are flatter than the narrow noses of Old World monkeys, and have side-facing nostrils.

New World monkeys are the only monkeys with prehensile tails. The tails of Old World monkeys are shorter and can’t grasp. Prehensility has evolved at least two distinct times in platyrrhines: 1) in the Atelidae family (spider monkeys, woolly spider monkeys, howler monkeys, and woolly monkeys), and 2) in capuchin monkeys (Cebus). Although prehensility is present in all of these primate species, skeletal and muscular-based morphological differences between these two groups indicate that the trait evolved separately through convergent evolution. The fully prehensile tails that have evolved in Atelidae allow them to suspend their entire body weight by only their tails, with arms and legs free for other foraging and locomotive activities. Semi-prehensile tails in Cebus can be used for balance by wrapping the tail around branches and supporting a large portion of their weight.


Geoffroy's spider monkey using is prehensile tail

New World monkeys (except for the howler monkeys of genus Alouatta) also typically lack the trichromatic vision of Old World monkeys. Colour vision in New World primates relies on a single gene on the X-chromosome to produce pigments that absorb medium and long wavelength light, which contrasts with short wavelength light. New World monkeys also differ from Old World monkeys in that they have twelve premolars instead of eight, with a dental formula of 2.1.3.3 or 2.1.3.2, (consisting of 2 incisors, 1 canine, 3 premolars, and 2 or 3 molars). This contrasts with Old World Anthropoids, including gorillas, chimpanzees, bonobos, siamangs, gibbons, orangutans, and most humans, which share a dental formula of 2.1.2.3

Many New World monkeys are small and almost all are arboreal, so knowledge of them is less comprehensive than that of the more easily observed Old World monkeys. Unlike most Old World monkeys, many New World monkeys form monogamous pair bonds, and show substantial paternal care of young. They eat fruits, nuts, insects, flowers, bird eggs, spiders, and small mammals. Unlike humans and most Old World monkeys, their thumbs are not opposable (except for some cebids).

New World Monkeys Evolved From Monkeys That Floated from Africa?

Evidence published in the early 2020s suggests that New World monkeys evolved from primates that traveled across the Atlantic Ocean from Africa to South America on a raft of vegetation — a seemingly improbable scenario that appears to have happened more than once. Riley Black wrote in National Geographic: For decades, paleontologists have wondered exactly how primates made it to South America. The continent’s spider monkeys, capuchins, and marmosets form their own primate group, separate from those in Africa and Asia. The leading theory is the ancestors of these monkeys somehow rafted across the Atlantic Ocean between 40 and 32 million years ago. [Source: Riley Black, National Geographic, July 19, 2023]

As new fossils have been discovered, however, the story’s become much more complex. South America was home to a broader array of primates than previously known, hinting at a key prehistoric time when rafts of vegetation ripped up by intense storms swept ancient monkeys across the sea. This appears to have happened at least twice — and perhaps more.

The latest evidence of these ancient transatlantic excursions is a tiny fossil tooth uncovered from rocks in the Brazilian Amazon. “Immediately, when one of my Brazilian colleagues showed me this tiny tooth emerging, my heart began to beat very fast,” says Laurent Marivaux, a paleontologist at the University of Montpellier in France. The 34-million-year-old tooth, described by Marivaux and colleagues in the journal PNAS, doesn’t look like it came from a South American monkey, instead resembling the teeth of early monkeys called eosimiids found in South Asia.

The new species is not the first strange animal to show up in South America’s prehistory. In 2020 paleontologist Erik Seiffert and colleagues announced the discovery of a monkey in Peru called Ucayalipithecus that had ancestral ties to ancient Africa, rather than being part of the modern South American lineage. Primates must have made the journey from Africa to South America at least twice, then, and the new tooth might indicate that a third group also journeyed across the ancient ocean.

Ashaninkacebus — an Early New World Monkey with Old World Links


Ashaninkacebus

Riley Black wrote in National Geographic: Named Ashaninkacebus simpsoni by Marivaux and colleagues, the new fossil primate is known only from a single upper molar found along Brazil’s Juruá River. The arrangements of cusps on the tooth identify it as both a primate and possibly an eosimiid. Based on fossils of eosimiids found elsewhere, Marivaux and colleagues expect Ashaninkacebus was a small species, about the size of a common marmoset at roughly half a pound, that primarily dined on insects and fruit. [Source: Riley Black, National Geographic, July 19, 2023]

While the molar is certainly that of a primate, other experts are not entirely sure of its relationships. Eosimiids were present in Africa as well as Asia. “As such, this becomes another example of a primitive lineage from Africa turning up in South America,” says University of Toronto paleontologist Mary Silcox, who was not involved in the new study.

If Ashaninkacebus is an eosimiid, then it would represent a third, distinct primate group that rafted between the continents. But there is another possibility, one that connects the new find to the monkeys living in South America today, known as platyrrhines. “My suspicion is that Ashaninkacebus could be a stem platyrrhine,” says University of Southern California paleontologist Erik Seiffert, who was not involved in the new study. Rather than representing a group of primates that arrived in South America only to became extinct, he says, the molar might document when the earliest ancestors of the continent’s monkeys arrived. “If this turns out to be the case, then there would only be evidence of two dispersals,” Seiffert says.

Regardless of whether Ashaninkacebus is an early platyrrhine or represents a distinct group, there is still the question of how the primates hopped between continents multiple times. “All our assumptions and scenarios are based on our knowledge of the fossil record,” Marivaux says. Since the 1970s, paleontologists have pondered whether primates might have traveled across the ancient Atlantic on rafts of floating vegetation. No other explanation seemed to fit. There were no land bridges connecting South America and Africa during the relevant time, nor was there any evidence that the primates took a circuitous overland route.

How Could Animals Cross a Huge Sea

Riley Black wrote in National Geographic: Monkeys were not the only animals to make the trip. Paleontologists have also found that the ancestors of capybaras and other rodents, called hystricognaths, likely rafted from Africa to South America as well. Surviving a cross-continent journey on a mass of vegetation seems like a one-in-a-million chance. So scientists have tried to determine whether there was one rafting event with rodents and monkeys together on a bed of entangled plants, or several. [Source: Riley Black, National Geographic, July 19, 2023]

The puzzle is almost impossible to resolve via direct fossil evidence. But from piecing together what the world’s continents, currents, and climates were like at the time of primates’ arrival in South America, Marivaux and colleagues propose that there was a brief window when conditions were just right for the mammals to “unwillingly embark” to a different continent.

South America’s earliest primates were small, fruit-eating species, hinting that their ancestors lived in humid forests along the western coast of Africa around 40.5 million years ago. The animals near deltas and river systems had a greater chance of being swept up in floods, holding on tight as parts of trees were broken off and washed out to sea.

This speculative scenario is not just conjecture, nor unique to South America’s monkeys. The lemurs and tenrecs of Madagascar arrived on that island from mainland Africa on rafts, and small lizards have island hopped around the Bahamas on natural rafts, as well. “A whole ecosystem can move along these shreds of riverbank,” Marivaux says. Modern rafts of vegetation can be very large, some of them with upright trees still holding fruit, and many primates and rodents along prehistoric Africa’s coast lived in places where rafts capable of carrying them may have been made during surging storms.

Paleontologists are still working out exactly when these crossings occurred. The new study suggests that the voyages took place about 40.5 million years ago, when South America and Africa were only about 1,000 kilometers (600 miles) apart — much closer than the present gulf of over 3,000 kilometer (1,840 miles). At the time the New World monkeys dispersed to South America, the Isthmus of Panama had not yet formed and ocean currents, unlike today, favoured westward dispersal. Seiffert, however, favors a later time. Around 33 million years ago sea levels dropped, closing the oceanic distance in a different way. “A significant amount of erosion in near-shore environments might have led to the calving of large rafts,” he notes.

Future fossil finds will help inform the story, though they may be difficult to uncover. “The fossils that have been recovered from this part of Amazonia are largely isolated teeth because of the way they have to be collected,” Seiffert says. Researchers often take shovelfuls of sediment from the inclined riverbanks to screen wash in water, a process that sifts tooth and bone from the dirt and rock. Unfortunately, sometimes small bones are destroyed and only the harder teeth remain. Nevertheless, the discovery of three early South American primates since 2015 indicates that there are likely more out there, and the future may reveal new details of how primates arrived and flourished in South America. “Ten years ago,” Marivaux says, “this would have been unbelievable.”

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated December 2024


This site contains copyrighted material the use of which has not always been authorized by the copyright owner. Such material is made available in an effort to advance understanding of country or topic discussed in the article. This constitutes 'fair use' of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this site is distributed without profit. If you wish to use copyrighted material from this site for purposes of your own that go beyond 'fair use', you must obtain permission from the copyright owner. If you are the copyright owner and would like this content removed from factsanddetails.com, please contact me.