Film: The Primates: Life in the Trees

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 the 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 the macaques on Koshima- it's an offshore island, so they're isolated and are therefore 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.