Monday, September 23 -- Film: The Baboons of Gombe

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Film about a troop of baboons who live on the shores of lake Tanzanyka, narrated by Jane Goodall and featuring her, her husband, and their child, endearingly nicknamed "Grub." Showed such behaviors as male-male competition, males befriending females and h elping protect their young, males using their friends' young to protect themselves from attacks by other males, the insinuation of a new male into a troop, young being carried underneath their mother's bellies and then learning to ride on top of them as t hey age, childless females showing an extreme interest in newborns, and so on.

Wednesday, September 25 -- Old World Monkeys

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Infraorder Catarrhini (Old World Monkeys)

Geographic Distribution of the Catarrhines

Old world monkeys are found throughout tropical Africa and Asia. The only exceptions are the macaques- some species live in Japan and others in northern Africa.

Differences between Platyrrhines and Catarrhines

Remember that these classifications represent two different evolutionary branches, so they are actually pretty distinct.
€ The most obvious difference is the shape of the nose: platyrrhine means flat-nosed, whilecatarrhine means hook-nosed. In platyrrhines, the nostrils are farther apart and they point outward, while in the catarrhines, they're closer together and they point down.
€ The number of teeth in each type is distinct, but we don't have to memorize their dental formulas for a test. The old world monkeys have big, sharp canines with a diastema (gap between canines and incisors), and the upper canines are kept sharp by being honed against the first premolar on the bottom.
€ Old world monkeys are larger on average than the new world monkeys. Baboons are the biggest of the old world monkeys, especially the males.
€ The Catarrhine family includes more folivores. Among the new world monkeys, the howlers are exceptions cause they're folivores, too.
€ Catarrhines are also more terrestrial.
€ Catarrhines tend to have a narrower range of niches. They share their habitats with prosimians and apes, so there're a lot of niches lying around which aren't filled by the old world monkeys since some other primate filled it first.

Taxonomy of the Infraorder Catarrhini

There are two superfamilies; Cercopithecoidea (old world monkeys) and Hominoidea (apes)
Today we will cover the old world monkeys, and next time we'll do the apes.

The Differences between Cercopithecoids and Hominoids

These aren't phyletic groups; apes are just a subset of the old world monkeys in terms of evolution. However, they're traditionally classified as a parallel family.
€ Cercopithecoids have a narrow nose and palate, and smaller brains relative to body size than Hominoids.
€ Cercopithecoids' molars are bilophodont (two cusps) but Hominoids' have several cusps.
€ Cercopithecoids have tails (often long), while Hominoids have no tails.
€ Cercopithecoids are laterally compressed, with a narrower thorax and pelvis, and a longer trunk. Compare this to hominoids like the gorillas, who are pretty wide in the chest.
€ Cercopithecoids' back legs are at least as long as or longer than their front legs, while Hominoids tend to have longer arms than legs.

In Cercopithecoidea superfamily we have only 1 family, Cercopithecidae.
It has 2 subfamilies:
Cercopithecinae, also called cheek-pouch monkeys, and
Colobinae, also called leaf-eating monkeys.

The Differences between Cercopithecines and Colobines

€ Colobines have more space between the eyes, and their incisors are narrower than in the cercopithecines.
€ Colobines have a deeper jaw which extends father below the joint. Colobines' molars have high sharp cusps, while cercopithecines' have lower, more rounded cusps.
€ Colobines have a complex stomach, which is atypical for primates. It is divided into four chambers kind of like a cow's stomach, and it works the same way too; The first chambers are less acidic fermentation chambers. Full of bacteria, they break d own the leaves, digest the cellulose, and make it available for absorption.
€ Cercopithecines, on the other hand, have a simple stomach with no chambers but they do have cheek pouches (and thus their name). These pouches open inside the cheek at the base of the teeth and extend down into the neck. Also called buccal pouches, they are used to stuff food into for storage. The two pouches together can hold about a stomachfull. The pouches are good for grabbing food quickly and then getting out of there. Then the monkey can eat it somewhere safe. Also, since they live in groups, there's competition over food so if you can grab a whole meal and get away you won't have to share it.
€ Colobines have long tails, while cercopithecines' tails are variable but often short.
€ Colobines have longer hind legs, related to being more arboreal; They do more leaping and climbing. This is also probably the reason for the long tail. Cercopithecines have similar arm and leg lengths.
€ Colobines have short thumbs. (Brachiators generally have short or no thumbs, probably since they tend to get caught when swinging through foliage at great rates of speed.)

Superfamily Cercopithecoidea - The Facts

Subfamily Cercopithecinae

1. African cercopithecines

a. Cercopithecus: Numerous arboreal species, and one (C. Aethiops) that is highly terrestrial. Dispersed widely throughout Africa. This genus includes the red forest monkey, the blue monkey, and the vervet monkey (aethiop s). They play a lot since that teaches them about social interactions and they need to exercise their brains. As a secondary sexual characteristic, the males have blue testes and red penises. They live in grassy savannah, and to look for predators the y'll stand on their hind legs to see over the brush.
b. Erythrocebus: This genus is the Patas monkey, a specialized running monkey found in W and N central African savannahs. Their societies are made up of one male with several females. Living in the savannah as they do, they can't c limb trees to escape. They can run at speeds up to 35 mph.
c. Papio (baboons): Savannah dweller, but found also in forests and in arid land, throughout West East Central and Southern Africa, as well as the southern tip of the Arabian peninsula. We will say there are 5 species, but this is subject to debate. Some characteristic species are the yellow baboon and hamadryas baboon. Baboons form 'friends;' male-female long term social relationships which do not imply exclusive breeding. Papio also includes the drill and mandrill, who hav e a distinctive face. This is a mixture of pigment and structural colors.
d. Cercocebus: (mangabeys): Arboreal. 4 species, but again subject to debate. They are found variably throughout Africa. Their society varies from one-male groups to mutimale-multifemale groups.
e. Theropithecus (geladas): Arid high country dwellers, mostly in Ethiopia and in arid parts of E Africa. They form hierarchical groups with troops, clans, and and one-male units like the hamadryas baboons. They have manes and red eyes.
f. Macaca: There are several species; 12 according to Smuts et al. Macaques have a wide distribution and a wide range of habitats. Some are arboreal, others terrestrial. They are used in biomedical research a lot. They can be seen mostly in S and SE Asia, but there's one in Japan and one in N Africa (Barbary macaques). They live in large multimale-multifemale groups. As in many old world monkeys, females get genital swellings when they're in estrus. This occurs especially often in multimale groups. This way, all the males are aware she's ready so they'll compete and she'll get the stronger ones' sperm.

2. Asian cercopithecines

a. Macaca: Many species spread across Asia, including the north Japanese islands. As we saw happen in the baboon film, other females often want to pet babies. Also, males want to see newborns sometimes. Macaques are omnivorous or frugivorous, and their societal structure is variable. Rhesus macaque has been used the most in biomedical. We might also see radiata, called the bonnet macaque, or the pigtail macaque which is solidly built.

Subfamily Colobinae

1. African Colobines

a. Colobus: Found in African forests, there are six species (subject to debate). They are mostly folivorous but some eat seeds too. Colobus monkeys live mostly in one-male groups, but some form multimale groups. Examples are the re d colobus and the black and white colobus who has a spectacular long white tail.

2. Asian colobines

a. Presbytis (langurs or leaf monkeys): This genus includes numerous species dispersed widely through forested areas in South and Southeast Asia. Their society is variable, with one-male or multimale groups. Langurs are known for t heir practice of infanticide.P. entellus, the hanuman langur, is atypical in several respects. Some examples of this genus are the grey langur, the banded leaf monkey, and the silver leaf monkey which has a long tail!

b. Nasalis (proboscis monkeys): Limited to coastal areas of Borneo and the Mentawai islands west of Sumatra, there is just one species. The big nose is a secondary sex characteristic of males. In females, the nose is just a little pinocchio nose. In males, the bigger the nose is, the sexier the monkey is. This is an example of the effects of sexual selection which we'll speak more of later. Proboscis monkeys are folivorous seed predators. Nasalis has multilevel groups.

c. Rhinopithecus (golden monkeys): Three species who all live in the forests of China, with some species in the mountains. They even get some snow sometimes. Golden monkeys live in large groups up into the hundreds. They seem to ha ve a hierarchical society like baboons. They're rare and obscure and they're just beginning to be studied. Golden monkeys are highly endangered so it's a race to study them before they disappear.

Friday, September 27 -- Apes

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At 10 million years ago, our ancestral species split into 3. At 5 million the first branch split into the gibbon and the siamang (which used to be a different genus but is now recognized as a gibbon). The second branch split into chimps/bonobos (who split apart at 2mya), humans, and gorillas. This branch is known as the African apes). The third branch split into orangutans. Thus, biologically speaking, humans should be in the same family as gorillas, but when the current taxonomic system was set up, they wanted humans to be in a separate group.

The way we actually do it is: hominoidea has hominidae (Homo), hylobatidae (Hylobates), and pongidae (Pongo, Pan, Gorilla)

There's more info about apes than prosimians. This is partly because they're more interesting to us since they're more closely related, and partly because nocturnal, arboreal little beings are really hard to study but land-living big creatures are easier.

Taxonomy of the Hominidae

Two families for us to study: Hylobatidae and Pongidae

Some characteristics which distinguishHominoidea from Cercopithecoidea

Many of their differences in anatomy are related to differences in locomotion- apes brachiate. Gibbons and orangutans brachiate the most, but the other apes also show adaptations for it.
Long arms
Apes have long arms relative to their leg length.
Broad pelvis and thorax
Apes tend to be compressed front-to-back instead of side-to-side like the monkeys.
Short lumbar segment
Apes have short lumbar segment (the spine from ribs to pelvis.)
High limb mobility
They have a reduced ulnar styloid, a short olecranon process, and spool-shaped trochlea. These all mean a greater surface area in the joints so that they have a wider range of movement. Compare your arm to a dog' s forelegs which really don't have such a broad range of movement.
No external tails
No explanation necessary!
Distribution of body sizes
Apes as a group are the largest primates. The exception is the gibbon, who is not quite so large.
Large brains relative to body size
This is a general trend, not an absolute difference.
Sexual dimorphism
Most marked in orangutans and gorillas. Some difference in chimps and bonobos, less in gibbons and siamangs.

Species Male: Female
Size Ratio
Gibbon 1.07
Siamang 1.09
Orangutan 2.21
Bonobo 1.36
Chimpanzee 1.2
Gorilla 2.36

Geographic Distribution

In Africa, the chimp is distributed widely, the bonobo is found only in Zaire south of the Zaire river, and the gorilla has widely-scattered patches. In Asia, gibbons are widely spread while the orangutan has patches in Borneo and Sumatra. Mostly they liv e in rainforests but chimps are in savannah sometimes and gorillas are up in mountains usually. Apes are mostly frugivorous. The exceptions are gorillas who eat more leaves and stems, and chimps who eat lots of things besides fruit, but still eat a fair a mount of fruit too. Almost every social variation that we have seen so far exists in the apes.

And now, may I present the Apes...

Family Hylobatidae (gibbons)

This family includes only one genus, Hylobates, with 9 species distributed through the forests of South and SE Asia. Besides man, gibbons are the most successful apes measured in abundance and diversity of species. They're all pretty much the same size, about 5 kg, except the siamang, who is about 10kg. Highly adapted for brachiation, gibbons have extremely long arms and fingers. Their fingers are like hooks. They can move really, really fast by swinging through the branches by their arms.
Most gibbons are frugivorous. They like small amounts of fruit scattered around in trees, even though there are some trees which will produce a lot of fruit at once. By looking for the trees with smaller harvests, they compete more with birds and small ma mmals for food rather than with other primates.
Examples from this family include the siamang, the lar gibbon, and the silvery gibbon. Gibbons show a lot of variation in coat color but that's not good for distinguishing between species; some species have different coat colors for each sex, while others just have two different color coats distributed randomly. It is easier to distinguish gibbon species by their song because their songs are more distinctive.
Most of the species don't overlap. They're found in S India, down the Malay peninsula, in Borneo, and in Sumatra. They do not live outside of tropical rainforests. It is surmised that they were originally one species which radiated out from a single area. As sea level went down, different groups got isolated and then became separate species and now they don't interbreed any more.
Gibbons form small, monogamous groups, more like birds than typical primate. A family is usually 5-6 individuals because the kids stay until they're about 5 or 6 but the parents have another kid every year. A couple cooperates in defending their territory , and males cooperate in parental care. Indeed, in the siamang, the males do most of the parental work after the first year. This is unusual for primates. When they reach maturity, juveniles of both sexes go off and find a mate and establish their own territories. Usually they develop a new territory, but sometimes they just establish theirs on one of their parents' property. Although they have direct encounters from time to time, gibbons mostly defend their territories by going around the boundaries and singing often. They have throat pouches that inflate which helps the sounds resonate better. (We listened to tapes of these calls in class.)

Family Pongidae (the great apes)

Genus pongo (orangutans)

Orangutans are highly arboreal. This is shown anatomically in the structure of their hips and shoulders. Although they have really mobile joints, they don't really swing like the gibbons. It's more like they climb around with four hands. They just hang out because they're too heavy to fling themselves around like gibbons. Adult males get so big they sometimes have to get down and walk from one tree to the next! Orangutans also exhibit size dimorphism. When they reach adulthood, males get throat sacs and face flanges filled with fat.
Orangutans are found a little bit on Sumatra and a little on Borneo. They're really endangered, and found strictly in the rainforest. Being fruit eaters, they need to move around a bit to find their food. They don't move too quickly, so they rely on knowi ng a lot about where and when fruit can be found. They know when which trees are ripe, etc. They may only move a few hundred meters in a day, but they cover a lot of territory in a year. They'll do things like watch the birds and other animals to figure o ut where food is good. Orangutans have little social organization- the maximum group size is mom with baby. A couple may have brief associations while the female is in estrus, and maybe a few orangutans will congregate at a good fruit tree, but they tend to ignore each other when they're eating together. However, there's evidence that they recognize people whose ranges are near theirs. Females have smaller rages than males. Their ranges overlap extensively but they don't defend boundaries.
Sometimes females will copulate with young males who don't have secondary sex characteristics yet. Also, young males will sometimes rape females which is unusual in primates other than humans. Males probably move house more than females; Females come into estrus only every several years since they keep their young around for so long, so if all of the females in a male's range have babies, he may move on to better pickings.

Genus Pan (bonobos)

Bonobos are a recent find. They were only first described in 1929 from specimens in museums. Not studied much in the wild until recently, they are similar to chimpanzees in a lot of anatomy and habits. Bonobos are more slender and lighter in build, but th ey're actually not much smaller, even though they're also called pygmy chimpanzees. Pretty terrestrial, bonobos live in Zaire in a small patch of the rainforest south of the Zaire river. Less carnivorous than chimps, they eat more leaves and stems. Like c himps, they have a fission-fusion type of society, but bonobos form larger groups than chimps. Bonobos are also less violent; no one has seen organized aggression between communities like you see in chimps.
What is also unusual is that there's a lot of sexual activity among all individuals, of any age and of any gender combination. Females remain sexually active even when they're lactating or pregnant. Sex seems to have become more a social activity and less a reproductive one. Bonobos copulate missionary style, whereas most primates do it doggie style. Females will engage in genital-genital rubbing, and even look like they've climaxed. This behavior is involved in reducing tension, and mediating social rela tionships. For instance, a group will come upon a tree with lmited amounts of food left, and you know that there's going to be some competition for food resources. Two females will suddenly turn to each other and do some g-g rubbing until everyone is happ y and mellow again. (New idea for world peace?)

Genus Pan (chimpanzees)

Chimps are knuckle-walkers, and are terrestrial. Most primates walk on the flats of their hands, but chimps walk on their knuckles with their hand turned over. Chimps exhibit less size dimorphism than other apes, but both chimp and bonobo females have pro minent genital swellings when they are in estrus. (Why do some females advertise it and other don't? Answers later.) Chimps have quite big testicles relative to body size, especially compared to gorillas, for example.
Chimps are found a little in western Africa and across the equatorial belt in mid-Africa. They've only been closely studied in their eastern ranges - in Kibale forest and in Mahale mountains in Tanzanyka. So how much variation there is across the populati on, we don't really know.
Although they're mostly frugivorous, chimps eat termites and ants too. Chimps exhibit tool use for gathering ant and termintes, especially the females. The males tend to hunt more. They'll eat monkeys, antelope, pigs, anything young and easily catchable. They're pretty opportunistic about it- they won't chase things who are likely to escape easily, but if they happen across some noctural animal who is asleep, they'll start right in on it. They do hunt in groups but there doesn't seem to be extensive coope ration about it.
Socially speaking, they have a fission-fusion society; there'll be 20-100 chimps who defend a common territory, but within this group they're broken up into smaller-sized groups. The female tends to be more solitary, with a range where she spends most of her time, while the male is more sociable and tends to go around with other guys. Females usually leave their natal territory when they reach sexual maturity, so they end up living with non-relatives. Males stay, so they've got their brothers and uncles e tc. around them. Females do, however, maintain close relationships with their offspring, even after they're grown. If they're in the same community, they'll spend time together. Males do social grooming with a wider range of individuals than females do. M ales hanging out together and associating together is also a good thing because there is a lot of hostilities between communities. If a male were wandering around alone, he'd probably get attacked because males from one community will attack if given the chance. Males will patrol the border together, and they'll even go on a raid. Researchers will see them all getting excited, riling each other up, and gathering together. Suddenly, they'll get quiet, sneak to the neighboring territory, and invade! If the y encounter a lone male, they'll gang up in a frighteningly organized way; some will hold him down while others hit him. Chimps are the most violent primates besides us humans!

Genus Gorilla (gorillas)

This family has 1 genus, gorilla, and one species, g. gorilla. Gorillas are the largest primate. They exhibit extreme sexual dimorphism, males being more than twice the size of females. Mostly terrestrial, gorillas are knucklewalkers. Their distribution is limited; they're found only in tropica Africa. The eastern mountain gorillas are high enough that the climate isn't really tropical, but geographcially it is tropical. Gorillas live in open canopy places 'cause they eat vegetation that grows on the gound. They also like it in wet places. Gorillas have been studied mostly in the Bururi forest.
Gorillas eat mostly terrestrial vegetation such as leaves and stems. This is not high quality food compared to fruit, insects, or meat, since there's not a lot of calories in the food. There's no competition for food, but you have to eat a lot to get your daily requirements.
The gorilla's social system is usually composed of a single adult male with multiple females. There are usually about 5-10 animals in a group. All of the social organization centers around the male; the females aren't generally related to each other and their only link is that they like the same guy.

Discussion --

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Today I wasn't in class but I heard that we played a sort of quiz game with teams, testing our knowledge of primates.

Let me know your thoughts:
Last modified: October 6, 1996