Monday, September 16 -- Film: The Primates: A Life in the Trees

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From the series "Life on Earth" With David Attenborough
A general survey of the primates, from the more primitive to the more developed.

Our first group are the prosimians. They're quite primitive and look like squirrels or something, but they have what no other mammal besides primates does; opposable thumbs.
The indri looks sort of like a koala and it calls a lot 'cause it's in canopy and you can't see very far. So, to let its neighbors know where it is, it uses sound.
The sifaka is a vertical leaper; it uses its opposable thumbs to grasp branches and it leaps from trunk to trunk. When it's on the ground, the way its skeleton and musculature have developed, it can't walk normally on all fours or on twos, so it kind of does a side-ways skip and hop like an excited four-year-old.
The loris is nocturnal, and communicates by smell. Prosimians have a pretty good sense of smell for a primate.

The next advanced set of primates are the monkeys.
The most primitive monkey is the marmoset. It is diurnal. They look like squirrels and use visual signals. Socially, they're monogamous. Their diet is mostly fruit and insects. By fruit we mean gum. Since it is scarce, when they find a good gum tree, they defend it. They mark their trees with urine. When another group seems too close, first they use shrieks to defend, then genital display.

Developmentally,they're like between lemurs and other monkeys like...
The howling monkeys defend territory by low guttural calls that can be heard up to 5 km away! Biggest monkeys in S America. Since they're kinda big, howlers use prehensile tail to keep from falling. They're reddish brown, with a not so great sense of smell. To smell a piece of fruit, they have to get it right up to their nose. They also select food by color. The howler can see color, as all monkeys do. Prosimians like the lemurs can't see color.

Those were South American monkeys. Now we'll see monkeys from the rest of the world. In Africa, many of the primate species came down from trees. No African monkey has a prehensile tail, so they don't do so well in trees.
For example, baboons- when threatened, they seek safety on ground, not in the trees. While young, they cling to mom. Baboons eat not only leaves, but also insects, roots, rodents, lizards, even other monkeys if available. There is increased predation on ground, so their eyesight is a little better. Males use visual signals to keep order. Often, when someone is misbehaving, a simple eyebrow flash is enough to intimidate them into obedience.
Some other ground dwellers left Africa for Europe's rock of Gibraltar. May have been originally brought by roman soldiers as pets? These are the Barbary macaques. Macaques live in many places in Africa and Asia.
The Japanese macaque has dense fur to get through Japan's harsh winters. They don't hibernate, so need food every day. Sometimes the only thing to do is to burrow through snow to get to it. One group uses volcanic hot springs to keep warm.
Macaques live all over Japan. Take Koshima- an offshore island, they're isolated and so are different than the mainland macaques. Scientists wanted to study them. To entice them out, the scientists began offering them sweet potatoes. One female began to take them to a pool and wash them. Then her close family began doing it, and now all the monkeys on the island wash their sweet potatoes. Then they all began to wash them in the sea, even when they were already clean. Only the old didn't do this new behavior; The young learned from their mothers while clinging to their backs, but the old didn't pick it up. The scientists really wanted to study the monkeys, but every time they gave them sweet potatoes, the monkeys ran off to wash them. So, they offered rice, figuring the monkeys would take a while to pick it up off the sand, but the same girl grabbed big handfuls of rice and sand and took it down to the water. When she threw it in the water, the rice floated and the sand sank, and she skimmed the rice off the surface of the water. Soon all the other ones began to do it too. Although usually a term reserved for human societies, this is a shared culture.

You will have noticed that monkeys are pretty much four-footed.
One group of monkeys is two-footed. To see them, we'll go back to the rain forests of the old world.

The silver leaf monkey lives in the forests of the far east. The young are pink, but the adults are black and silver. They're the biggest tree monkey in Asia. They do big jumps from tree to tree.

Primates tend to grow bigger through the generations, but this makes things difficult for tree-dwellers, because pretty soon it becomes difficult to find a branch that they can sit on. The apes solve these size problems by swinging below the branches, instead of balancing atop them.
Look at the orangutan. They have lost their tails completely. They rarely let go with more than two hands/limbs. Some males grow so big they have to walk on ground, not brachiating at all.
Gibbons solved the size problem by becoming smaller again, with long arms and fingers. It is the best acrobat in the woods 'cause it swings so well but is so small. Such acrobatics has its risks, however; branches that you land on might break. One third of all gibbon skeletons examined show signs of fractures.

Now we move to central Africa in the mountains to see the biggest, rarest, shyest ape- the gorilla. The gorilla has the same sense abilities that we do; same degree of smell, sight, hearing etc. The gorilla is quite peaceful: violence within the group is very rare. Violence against an invading male, maybe. Their fingers have sensitive pads in end, with ridges to enhance touch sense. All gorillas have unique fingerprints like humans. They spend the day grazing and playing. Juvenile males have wrestling matches regularly. Because food is so plentiful and their only predators are men with guns, the gorilla has no need to be agile in body or mind.

However, another ape lives in these forests. It has a widely varied and scattered diet. It eats fruits, flowers, termites, ants honey, eggs, birds, and even mammals. This is the chimpanzee. To find all this food you need a nimble mind. Although they spend a lot of time on the ground, they haven't lost the grasping foot the way the gorillas have. Chimps make a bed every night and spend the night in trees. They also go up in them to find food. They may have up to 50 in group. Just as lemurs use scent to distinguish each other, chimps use sight to tell each other apart. For this reason, they have very distinct faces. Chimps have strong social ties. Mothers and young will stay together for like 5 years. Much social bonding is done by grooming. A male who has been gone a few days is greeted by an ecstatic bout of grooming by his friends. Also chimps fingers are very agile; they even use tools. They will prepare a stick and use it to fish out termites. Chimps have the most extensive vocabulary sounds. Being curious, chimps are always testing their environment.
Although they live in the scrublands, chimps have also gone out into the open country, where they found meat. The eyes which were developed to see branches also let it see a long way away. The hands that can use tools also can use weapons. This group left the other 15 million years ago and became us. Although we're 15 millions years apart, the chimps are our cousins.

Wednesday, September 18 -- The Prosimians

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Taxonomic Hierarchies

The current taxonomic system that we use these days was thought up by Carl Linnaeus who loved to name everything in Latin. Here is a mnemonic to remember the taxonomic levels;

King Philip can order five great specimens

This stands for Kingdom Phylum Class Order Family Genus Species.

People also insert super-families, sub-orders, sub-families etc. for further classifications.

The taxonomy of the common chimp:

Kingdom Animalia
Phylum Chordata (things with backbones)
Class Mammalia
Order Primates
suborder Anthropoidea (prosimian would be the other option)
infraorder Catarrhini (old world monkeys)
superfamily Hominoidea (includes apes and humans)
Family Pongidea
Subfamily Ponginae
Genus Pan (chimps)
Species Troglodytes (common chimps)

To help in recognizing what level a taxonomic name is, remember this:

Superfamilies always end in -oidea
Families always end in -dae
Subfamilies always end in -nae

If two animals are of a different species, they won't interbreed naturally. In captivity, they're not always so picky. But anyway the species classification is based on a characteristic that's really in nature. The other levels of taxonomy are just for our convenience, and there's always lots of disagreement about how things should be classified.

The Difference between Prosimians and Anthropoids

People used to classify things together if they looked similar. Recently they've gotten better at reconstructing the tree of life. It has thus become more possible to group beings together because they have a common ancestor rather than because they look similar to a scientist. This is better cause it's based on fact, not on an opinion of how they look or behave. This is called a phyletic classification; to classify things by their real ancestors. Using this newer-type classification, we would divide the primates into two groups:
Strepsirrhines are the lemurs and the lorises.
Haplorrhines are the tarsiers, monkeys, apes, and humans.
But the traditional way of doing it is prosimians vs. anthropoids, based on how anthropoids all have similar adaptation developments. Prosimians are the Lemurs, Lorises, and Tarsiers in this classification. This traditional classification system is what we'll use since that's how our text divides things, but we should be aware that the scientific community will most likely be moving toward the phyletic classification system.

Characteristics that differentiate the prosimians from the anthropoids

Prosimians are pretty small relative to the Anthropoids. Anthropoids have fused skulls while the prosimians do not. The orbit (eye socket) is open in the prosimians, closed in anthropoids. Anthropoids have nails, while the prosimians have a grooming claw on the index finger of the hind foot. (The rest of the digits have nails.) The prosimians' teeth are also different; The incisors are almost horizontal in prosimians, and this is called the grooming comb because they use it to groom. Some species also use it for feeding; gouging into trees to get gum or insects.

...and the strepsirrhines from the haplorrhines

In strepsirrhines, the upper lip is divided, only attached inside. Strepsirrhines have a moist naked nose, unlike haplorrhines but like other mammals. Strepsirrhines' eyes have a reflecting tapetum like cats or deer. It is right behind retina and it makes the eyes more sensitive so that they're better at picking up low levels of light. Note that strepsirrhines are mostly nocturnal, so they need to be able to see in low light levels. Typical prosimian behavior patterns; nocturnal, insectivorous, solitary.

Lorises and galagos are in Africa and Asia
Lemurs are just on madagascar
Tarsiers are just in SE asia

A Catalogue of the Prosimians

Seven families, subdivided into 3 groups: Lemuriformes and Lorisiformes which are the prosimians even if you classify by ancestry, and the Tarsiformes who are developmentally like the prosimians but are actually more closely related to the anthropoids.

1. Lemuriformes (All found only in Madagascar)
Lemurs used to be all over the world, but they got outcompeted by the more advanced anthropoids. The anthropoids never got to Madagascar, so the lemurs were able to stick around there. The Lemuriformes includes five families:

a. cheirogaleidae (dwarf lemurs)
This family includes dwarf lemurs and mouse lemurs.
Taxonomy: Four genera e.g. microcebus (mouse lemur)
Biogeography: The perimeters of Madagascar in the forests
Body size: Very small- all less than a pound
Activity pattern: All nocturnal
Locomotion: Quadrupedal, climbers
Diet: Fruit, leaves, gum, insects
Society: Usually solitary. cheirogaleidae are interesting because for primates they are very seasonal (Season=rainy season as opposed to cold season); They accumulate fat seasonally, breed seasonally, and they hibernate through dry season.

b. lemuridae (true lemurs)
Taxonomy: 2 genera- The ring-tailed lemur is genus lemur. The other genus is verecia- variegated lemur.
Biogeography: Throughout Madagascar
Body size: Larger than the dwarf lemurs; 1-4 kg
Activity pattern: Diurnal, esp. lemur catta (ring-tailed)
Locomotion: Quadrupedal, climbers
Diet: Fruit, leaves, not too many insects
Society: Group living, but mating patterns vary. They use scent for marking territory, fighting, or any other communications

c. lepilemuridae
Taxonomy: 2 genera; lepilemur and hapalemur
Biogeography: Only Madagascar
Body size: Less than 1 kg
Activity pattern: Crepuscular or nocturnal
Locomotion: Quadrupedal. lepi is a leaper, hapa is a climber
Diet: Bamboo
Society: lepi asocial, hapa forms small groups with 3-6 individuals

d. indridae (indris and sifakas)
These are the biggest leumuridae. Specialized leapers, they have long powerful hind legs, long slender front legs. In the genus indri, who did loud calls in Monday's film, the females are dominant over the males. Sifakas have a lot of white on them and tend to be diurnal.
Taxonomy: 3 genera- Indri (indris), propithicus (sifakas), and avahi (wooly indris)
Biogeography: The coasts of Madagascar
Body size: Avahi smaller than 1 kg. Indri and propithicus, 3-10 kg
Activity pattern: Diurnal, but avahi are nocturnal
Locomotion: Leapers
Diet: Folivorous. They have an appropriate morphology which includes hypertrophied salivary glands, long hindgut, huge caecum
Society: Indri and avahi monogamous, but propithicus has unusual social mating patterns.

e. daubentonidae (aye-aye)
This family is the weird one. One of the most specialized primates. They build nests of leaves. They have an elongated middle finger which is used for getting insects. At night, insects are burrowing and hiding. The aye-aye taps on wood with its finger, listens to the insects be disturbed, then uses finger to get into the crevices to get insects. They also have weird teeth; elongated incisors, like rodents, used to get at insects in the wood. You may not know this, but there are no woodpeckers in madagascar. Instead, the aye-aye has filled that niche.
Taxonomy: 1 genera 1 species
Biogeography: NE and central-NW tropical forests of madagascar
Body size: Large- 3 kg body.
Activity pattern: Nocturnal
Locomotion: Quadrupedal climbers
Diet: Mostly insects
Society: Solitary? They're not studied too much since they're so rare.

2. Lorisiformes: Family Lorisidae
Divided into two subfamilies: Lorisinae, or the Lorises (Found in Asia and Africa) and Galaginae, the galagos better known as bushbabies (Found in Africa). These will be treated separately. Lorises are very slow creepers, while galagos are jumpers and leapers. They both have a reduced second digit (index finger). Just a nub, it's almost gone.

Taxonomy: 4 genera- 2 in Asia, 2 in Africa. The genus in India is loris, or the slender loris, while the genus in far eastern Asia is nycticebus, called the slow loris. Considered a defense from predation, they move so slowly they're simply not noticed. The two African genera are arctocebus (called angwatibo) and perodicticus (called potto).
Biogeography: Loris is found in India, while nycticebus is found in far eastern Asia. The arctocebus is found in western Africa from Niger to the Congo.
Body size: Slow loris & potto are large: 1 kg. Slender loris & angwatibo are small: 250 g
Activity pattern: All are nocturnal
Locomotion: Quadrupedal
Diet: Large species eat fruits and gums while the small eat insects
Society: Solitary?

galaginae (bushbabies)
They have big ears and long fluffy tails.
Taxonomy: 1 genus
Biogeography: All in Africa
Activity pattern: Nocturnal
Locomotion: Quadrupedal, leapers
Body size: Less than 1 kg
Diet: Insects, fruits, gums
Society: Solitary with nested ranges. They also have neighborhoods.

3. Tarsiformes
The family Tarsidae, or the tarsiers. Found in SE Asia, they're anatomically similar to anthropoids.Their evolutionary affinity lies with the anthropoids; They have a complete lip, not a split lip, and their placenta is hemichorial. This means that the mother's blood supply is interlinked with the fetus', letting them transfer nutrients more efficiently. They have no reflective tapetum, and they have a globular brain instead of an elongated one like the prosimians. However, their behavior is more like the prosimians; they're nocturnal and insectivorous.
Taxonomy: 1 genus, tarsius, with 3 species: syrichta, spectrum, and bacanus.
Biogeography: Syrichta is found in the Phillipines, spectrum in Sulawesi (The Celibes), and bacanus in Borneo and Sumatra. The 3 species don't overlap.
Body size: Small- 150 grams
Activity pattern: Nocturnal
Locomotion: Vertical clingers and leapers
Diet: Insectivorous, faunivorous. They will sit listening, and then pluck insects from the air and eat them. Alternatively, they'll leap into the air, holding onto a branch with their tail, and grab insects to eat.
Society: Monogamous or solitary with nested ranges.

Friday, September 20 -- New World Monkeys

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The order primates is divided into prosimians and anthropoids, like we said yesterday.

Differences between Prosimians and Anthropoids: A Review

Anthropoids have fused mandibles while prosimians' can move independently.

Brain size:
Anthropoids have larger brains relative to their body weight.

Nails vs. claws:
Anthropoids have nails vs. claws. (one exception: we'll see today.)

Visual system:
Anthropoids have binocular and color vision. Prosimians don't have either one but they can smell better than anthropoids.

Body size:
Anthropoids tend to be larger.

Ecological diversity:
Anthropoids fill more niches than Prosimians- places which are drier, colder, sparser etc. Anthropoids also exploit more food sources than Prosimians. Anthropoids are all diurnal. (one exception: we'll see today.)

The Anthropoids are divided into two infraorders. These represent two different lines of descent, which are also divided geographically:
Catarrhines are the old world monkeys, which we'll cover next Wednesday.
Platyrrhines are new world monkeys, which we'll cover today.

Geographic Distribution of the Platyrrhines (New World Monkeys)

They're only found in South America. Fossils go all the way south but species living currently only go a little out of the tropics. They maybe arrived 30 million years ago over the sea somehow- but it was not by a land bridge. Maybe they floated over on something?? Consider the great coincidence of it all- that a mating pair would both end up floating over the ocean at close enough to the same time so they could mate, they found each other, they found a land that was ecologically suited to them but had no other primates on it. This type of immigration is called an adaptive radiation- one species arrives somewhere and then diversifies into many.

Taxonomy of the New World Monkeys

Infraorder Platyrrhini: 3 families, 16 genera
Common features:
Platyrrhini means flat-nosed. New world monkeys' nostrils have a wide septum and they face outward. Old world monkeys have a narrow septum and their nostrils face forwards. New world monkeys are small-to-medium, up to 10 kg. They have 3 premolars while the old world monkeys have 2 premolars. The new world monkeys have a diversity of diets, habits, and social systems.

Family Callitrichidae (marmosets & tamarins)
Taxonomy: 4 genera. The genus saguinus includes the cotton-topped tamarin, the emperor tamarin(named for the emperor of Austria), the jeffries tamarin, the silvery tamarin, and the black-chested mustache tamarin. There's only one species in the genus leontopithicus, and that's the golden lion tamarin. The genus callatric is the common marmoset. The last genus, cebuella, is the pygmy marmoset. They're cute!
Biogeography: Amazon basin, Colombia, Panama
Body size & Anatomy: Small, 'squirrel-like' with long prehensile tails. They're all under 1k. They also redeveloped claws on their fingers except for the hallux. Unusual for primates, they typically have twins. Also, they're decorative; usually colorful and tufty.
Diet: Fruit, insects, gums. Marmosets can be very specialized in eating certain gums.
Society: Facultatively polyandrous or monogamous. They're flexible. Males do a lot of infant care, as well as older siblings. Males in some species carry the young most of the time.

Family Callimiconidae (Goeldi's marmoset)
Taxonomy: A single species, callimico
Biogeography: Amazonia
Body size & Anatomy: Small- less than 1 kg
Diet: Fruit, insects, gums
Society: Apparently polygynous

Family Cebidae
Body size & Anatomy: Generally larger than callitrichids and callimico. They have nails on all digits. They also have long hairy tails, except cacajo, the uakari, which is bald and tail-less.
Subfamily Cebinae
Taxonomy: 2 genera: Cebus (organ-grinder or capuchin monkeys) and saimiri (squirrel monkeys)
Biogeography: Widely distributed in neotropical forests
Body size & anatomy: Small (saimiri = 1 kg) to medium (cebus = 4 kg). Cebus has the largest brain compared to its body size for any new world monkey.
Diet: Frugivore-insectivores, but some will eat anything available.
Society: Multimale-multifemale societies. Squirrel monkeys have a short breeding system and females are dominant.

Subfamily Pithecinae
This is the grab-bag subfamily- has a lot of odds and ends.
Taxonomy: 5 genera: Aotus (night monkey), callicebus (titi), pithecia, chiropotes, and cacajao (uakari), which may be the ugliest new world monkey. They have bright red faces, and are bald.
Biogeography: Pithecia, cacajao (who like to live in flooded forests so haven't been studied too much since they're hard to get to), and chiropotes restricted to Amazonia; Aotus distributed widely; Callicebus dispersed patchily.
Body size & Anatomy: Medium size, 2-4 kg, but aotus and callicebus about 1 kg
Diet: Frugivores, 'seed predators;' uakari eats unripe fruit- really just opens it to get the seeds
Society: Pithecia, cacajao and chiropotes variable; aotus and callicebus monogamous. Aotus (night monkey) is the only nocturnal monkey.

Subfamily Alouttinae

Taxonomy: A single genus alouatta. There are lots of species. These are the howler monkeys. They're pretty common. More often heard than seen.
Biogeography: Found in all regions, they're the most widely dispersed of all the platyrrinni.
Body size & Anatomy: Large (7-8 kg), with an enlarged hyoid bone (in throat) and very deep mandible (related to howling). Long hind gut (related to folivory) because leaves take a long time to digest. Howlers are the analogues of colobinae in old world. Prehensile tails, used for support during feeding.
Diet: Folivorous
Society: Social organization variable, multi-male to single-male groups. Unusual to have such variation within a subfamily. Since they're so common and are easy to identify and slow-moving, they're often studied.

Subfamily Atelinae (wooly monkeys and spider monkeys)
Taxonomy: 3 genera: Ateles (spider monkey), brachyteles (wooly spider monkey aka mariki), and lagothrix (wooly monkey). An interesting physiological fact about these guys: the female's clitoris is bigger than the male's penis! This makes them hard to sex.
Biogeography: Ateles: all areas except SE brazil. Brachyteles: endangered and rare; a few hundred individuals only SE Brazil. Lagothrix: limited to upper Amazon.
Body size & Anatomy: Large; up to 9.5 kg. They are long-limbed, with prehensile tails used in feeding and locomotion (rapid brachiation).
Diet: Frugivorous, but brachyteles folivorous
Society: Ateles has a fission-fusion social system; A group shares a boundary and defends it but they don't usually hang out together. Brachyteles has multimale groups but not much overcompetition, so the females mate with lots of guys. For a male to beat out the others, he just needs to put in more sperm per session, so they have ended up with really big testes. Also there are multifemale groups.

Discussion --

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We discussed requirements for the impending paper on natural selection, and then brainstormed together on ways to describe and explain how it works.
Let me know your thoughts:
Last modified: Thursday, September 26, 1996