0:00:45 > 0:00:50Monkeys, together with apes, are our closest relatives.
0:00:50 > 0:00:53They have the richest social life of all mammals,
0:00:53 > 0:00:56and much of their time is spent establishing relationships
0:00:56 > 0:01:00and climbing the social ladder.
0:01:00 > 0:01:04And that has had some remarkable consequences.
0:01:26 > 0:01:28South America,
0:01:28 > 0:01:32and a few capuchin monkeys are having a morning get-together.
0:01:32 > 0:01:38Capuchins are very like the earliest of all monkeys, judging from fossils.
0:01:38 > 0:01:40The basic pattern, you might say.
0:01:43 > 0:01:47With grasping hands and gripping tails, they race through the forest
0:01:47 > 0:01:50with astonishing speed and agility.
0:01:52 > 0:01:56But it's their big brains that really give them an edge.
0:01:56 > 0:02:01If there is one thing that is characteristic of monkeys,
0:02:01 > 0:02:05it is their ability to spot an opportunity and then exploit it.
0:02:05 > 0:02:09That's especially true of capuchins.
0:02:09 > 0:02:12Of course, they'll grab a ripe fruit,
0:02:12 > 0:02:18but they investigate everything in their path. Little escapes them.
0:02:21 > 0:02:23But it's their inquisitiveness that really impresses you
0:02:23 > 0:02:25when you follow them.
0:02:27 > 0:02:30They look for food everywhere.
0:02:34 > 0:02:37Their colour vision is excellent.
0:02:37 > 0:02:40Their sense of smell, however, is no better than ours,
0:02:40 > 0:02:45so to find food that is hidden from view, they use brains - not noses.
0:02:52 > 0:02:57They can, clearly, imagine what might be lurking beneath dry leaves.
0:02:57 > 0:03:01Out of sight is by no means out of mind.
0:03:01 > 0:03:03A good memory must also help.
0:03:03 > 0:03:05Recalling a previous experience
0:03:05 > 0:03:10could make the difference between getting stung and getting honey.
0:03:25 > 0:03:29The troop is just entering these mangroves.
0:03:29 > 0:03:33Most mammals wouldn't find much to eat here,
0:03:33 > 0:03:38but monkeys' big brains enable them to find things that others miss.
0:03:46 > 0:03:51Only the bolder ones chance their hand with crabs.
0:03:55 > 0:03:59It's quite brave to tackle sharp claws with delicate fingers.
0:04:02 > 0:04:06A retreating tide exposes shellfish.
0:04:06 > 0:04:08But eating those poses more problems.
0:04:13 > 0:04:18The clams are full of meat, but it's all locked up behind closed doors.
0:04:22 > 0:04:27However, grasping hands guided by a big brain can deal with that problem.
0:04:36 > 0:04:39These clams are very tough.
0:04:39 > 0:04:42I would have a lot of difficulty in opening them myself,
0:04:42 > 0:04:46but these monkeys have learned that if you hit them hard enough,
0:04:46 > 0:04:49the clam relaxes, the shells can be opened,
0:04:49 > 0:04:52and they can get at the juicy meat inside.
0:04:59 > 0:05:03The whole troop is in on the trick,
0:05:03 > 0:05:07and now at least 20 of them are busy giving the clams the treatment.
0:05:20 > 0:05:25Ten minutes on, and the shells of the clams are still tightly clenched.
0:05:25 > 0:05:28This is hardly fast food.
0:05:31 > 0:05:34The young watch attentively.
0:05:34 > 0:05:38Most will eventually learn how to do it,
0:05:38 > 0:05:41so the clam-cracking technique will pass to the next generation.
0:05:41 > 0:05:46But it takes years for a young monkey to get it absolutely right.
0:05:49 > 0:05:55Patience is important. Unfortunately, so is technique.
0:05:57 > 0:05:59Capuchins, just like us,
0:05:59 > 0:06:03have varied personalities and abilities,
0:06:03 > 0:06:06and some never really get to grips with clam-cracking.
0:06:19 > 0:06:22Those with a good technique AND perseverance
0:06:22 > 0:06:25are now beginning to collect their rewards.
0:06:29 > 0:06:34Although some aren't exactly thrilled by what they find.
0:06:44 > 0:06:48It's not just food that monkeys collect from the forest.
0:06:48 > 0:06:52The two bunches of leaves may look very much the same,
0:06:52 > 0:06:56but this kind is used by the local people
0:06:56 > 0:06:59as an antiseptic and insect repellent,
0:06:59 > 0:07:04whereas this one has no medicinal qualities at all.
0:07:04 > 0:07:09If I put them both down, I think I know which the monkeys will choose.
0:07:29 > 0:07:34Those are pipa leaves - the ones with the insect-repelling sap.
0:07:34 > 0:07:39Pipa is hard to find, so this big bunch will cause a lot of excitement.
0:07:48 > 0:07:51Like many things in monkey life,
0:07:51 > 0:07:54pipa rubbing is a major social event.
0:07:54 > 0:07:57Those taking part disregard the differences
0:07:57 > 0:08:01they might have had at other times and everyone joins in.
0:08:38 > 0:08:42Do these capuchin really know that this behaviour
0:08:42 > 0:08:45protects them against skin infections and mosquitoes?
0:08:45 > 0:08:48Well, of course, it's impossible to say.
0:08:48 > 0:08:52But they do it more frequently during the rainy season
0:08:52 > 0:08:56when there are more skin infections and mosquitoes around
0:08:56 > 0:08:58than at any other time during the year.
0:08:59 > 0:09:05Not all capuchins use pipa. But once one discovers the plant's properties,
0:09:05 > 0:09:06the knowledge quickly spreads,
0:09:06 > 0:09:10so pipa-leaf rubbing becomes a group tradition.
0:09:14 > 0:09:17Capuchins eat most things.
0:09:17 > 0:09:20Some monkeys, however, have particular specialities.
0:09:20 > 0:09:25These are uakaris, and they will eat fruit of an unusual kind.
0:09:27 > 0:09:31The colour of their faces indicates their social position.
0:09:31 > 0:09:34The brighter the scarlet, the more senior the animal.
0:09:34 > 0:09:39The good colour vision that enables them to tell where they are socially,
0:09:39 > 0:09:41also helps them to select fruit.
0:09:43 > 0:09:49Unusually, they will eat fruits that are a vivid green and not yet ripe.
0:09:50 > 0:09:53The monkeys in this forest can all eat slightly different foods,
0:09:53 > 0:09:57allowing many species to live together side by side.
0:09:58 > 0:10:01The saki has special teeth
0:10:01 > 0:10:05which enable it to eat nuts that no other monkey can crack.
0:10:09 > 0:10:14The spider monkey has long limbs and a grasping tail
0:10:14 > 0:10:17which enable it to collect the very ripest fruit.
0:10:19 > 0:10:21But there are foods in this forest
0:10:21 > 0:10:24that not even a spider monkey can get to.
0:10:49 > 0:10:54There is food for monkeys in every part of the rainforest,
0:10:54 > 0:10:57but some of it is very difficult to reach.
0:10:57 > 0:11:00I have only got up here into the canopy in a special crane,
0:11:00 > 0:11:03and I am 120 feet above the ground.
0:11:03 > 0:11:06And here, on the outermost twigs of the trees,
0:11:06 > 0:11:11the stems are too thin to support a normal-sized monkey.
0:11:11 > 0:11:14And yet, there is a lot of food up here.
0:11:14 > 0:11:16Underneath these leaves -
0:11:16 > 0:11:21a cocoon, a caterpillar, another leaf-eating insect.
0:11:21 > 0:11:27But there is one kind of monkey that can get up here and eat these things.
0:11:27 > 0:11:33It's a pygmy marmoset - the smallest monkey in the world,
0:11:33 > 0:11:35no bigger than my hand.
0:11:42 > 0:11:48Its feet are too small to grasp anything but the thinnest twigs.
0:11:48 > 0:11:51Their needle-sharp claws prevent them from slipping.
0:12:00 > 0:12:05As it stalks its insects it has to move with great stealth,
0:12:05 > 0:12:08lest any vibration should scare them off.
0:12:08 > 0:12:11But these hunters are so small
0:12:11 > 0:12:14that not even the thinnest branches tremble under their weight.
0:12:29 > 0:12:34All monkeys have forward-pointing eyes so that they can judge distance.
0:12:34 > 0:12:37That's invaluable when moving around in the trees.
0:12:37 > 0:12:42But this tiny little hunter uses that ability also to pounce.
0:12:50 > 0:12:55But their staple diet is altogether more extraordinary.
0:12:55 > 0:13:00You might think that the lumps on this tree are a natural feature,
0:13:00 > 0:13:04but, in fact, they are wounds inflicted by pygmy marmosets
0:13:04 > 0:13:07that come to this tree trunk every day.
0:13:16 > 0:13:18It's eating gum,
0:13:18 > 0:13:23which it has forced the tree to produce by gnawing its bark.
0:13:23 > 0:13:29And what's more, it is making sure that there will be gum tomorrow,
0:13:29 > 0:13:35because it is also re-opening the wounds that the tree has healed up.
0:13:35 > 0:13:39The marmosets keep opening these wounds
0:13:39 > 0:13:41and the tree keeps closing them
0:13:41 > 0:13:46until so much scar tissue builds up that circular mounds appear.
0:13:46 > 0:13:52Generations of pygmy marmosets have done that on this particular tree,
0:13:52 > 0:13:58resulting in these huge columns of lumps running right up the trunk.
0:13:59 > 0:14:03A well-managed gum tree is an asset for a group of marmosets,
0:14:03 > 0:14:06making it a tempting target for thieves.
0:14:09 > 0:14:12And a rival group is preparing to invade.
0:14:16 > 0:14:20The intruders charge and the owners flee,
0:14:20 > 0:14:23leaving their precious gum undefended.
0:14:27 > 0:14:30While the invaders steal the gum,
0:14:30 > 0:14:35the displaced residents start scent-marking in the trees nearby.
0:14:35 > 0:14:37This seems to reinforce the bonds between them
0:14:37 > 0:14:41and stiffen their resolve to mount a counter-attack.
0:14:46 > 0:14:49It works. The home team are back on their tree.
0:14:59 > 0:15:03But you can share a food resource that is cropped by others
0:15:03 > 0:15:06without having a face-to-face confrontation.
0:15:09 > 0:15:11You might think that when the sun goes down,
0:15:11 > 0:15:14all monkeys would be settling down to sleep.
0:15:14 > 0:15:17That's almost true, but not quite.
0:15:21 > 0:15:25There's only one monkey in the world that collects its food at night.
0:15:25 > 0:15:28And precisely because it IS nocturnal,
0:15:28 > 0:15:31it is very seldom seen and still little known.
0:15:31 > 0:15:35But there is a family of them living in this tree behind me.
0:15:35 > 0:15:36They are douroucoulis.
0:15:40 > 0:15:44They are also known, for obvious reasons, as owl monkeys.
0:15:48 > 0:15:50Their eyes may be huge,
0:15:50 > 0:15:53but, in fact, their night vision is not particularly good,
0:15:53 > 0:15:56suggesting that their ancestors lived by day
0:15:56 > 0:16:01and that douroucoulis became nocturnal relatively recently.
0:16:06 > 0:16:10During the day, the nectar-rich flowers on which they feed
0:16:10 > 0:16:13are guarded aggressively by other monkeys.
0:16:13 > 0:16:15By coming out only at night,
0:16:15 > 0:16:18douroucoulis avoid having to fight for a share and can feed in peace.
0:16:41 > 0:16:42Day breaks.
0:16:44 > 0:16:46The douroucoulis retire
0:16:46 > 0:16:49and a new set of fruit- and nectar-feeding monkeys awake.
0:16:52 > 0:16:55Tamarins set off to collect their share.
0:16:55 > 0:16:58But this forest is not rich in such food,
0:16:58 > 0:17:03and though they live in small groups, finding all they need takes time.
0:17:04 > 0:17:09The female always produces twins, which travel with the family.
0:17:12 > 0:17:17But she has two male partners and she uses her tongue to signal
0:17:17 > 0:17:20that it's time that one of them took over the twins.
0:17:30 > 0:17:34Both are eager to do so, for both mated with her
0:17:34 > 0:17:37and so each has cause to regard the babies as his.
0:17:45 > 0:17:49But the twins have other ideas. They want to stay with Mum.
0:18:00 > 0:18:04She gets rid of them at last, and it is important that she does so.
0:18:04 > 0:18:09She has to provide them with milk, so she must eat much more than usual
0:18:09 > 0:18:11and she would find that difficult
0:18:11 > 0:18:13if she were burdened by her babies all the time.
0:18:20 > 0:18:23The situation is made harder,
0:18:23 > 0:18:26because there are other kinds of tamarins here as well.
0:18:26 > 0:18:30This is one of them - a saddleback tamarin.
0:18:30 > 0:18:33Monkeys usually guard their food ferociously,
0:18:33 > 0:18:38but these two kinds of tamarin often feed side by side.
0:18:39 > 0:18:42And when one leaves, the other follows.
0:18:49 > 0:18:52The emperors go first, and the saddlebacks -
0:18:52 > 0:18:56with their shorter, stumpier legs - try hard to keep up.
0:19:01 > 0:19:04The travelling party shares a quick refuel.
0:19:04 > 0:19:09Both kinds of tamarin, being small and energetic, need frequent snacks.
0:19:10 > 0:19:14They share another thing, too. They have a common enemy.
0:19:14 > 0:19:18They give alarm calls that both species understand.
0:19:18 > 0:19:20TAMARIN SHRIEKS
0:19:20 > 0:19:23A tayra - a kind of giant weasel.
0:19:23 > 0:19:27Not the most dangerous predator in this forest,
0:19:27 > 0:19:29but deadly to a bite-sized monkey.
0:19:40 > 0:19:44It's certainly safer to travel in groups, but having to share food
0:19:44 > 0:19:48is a high price to pay for a warning system.
0:19:48 > 0:19:53There is, however, another rather more subtle advantage.
0:19:56 > 0:20:01Each flower needs time to refill its reservoir of nectar
0:20:01 > 0:20:04after a visitor has drunk from it.
0:20:04 > 0:20:08If either kind of tamarin foraged separately,
0:20:08 > 0:20:10they might make a hazardous journey,
0:20:10 > 0:20:14only to reach a tree that had recently been emptied by the other.
0:20:14 > 0:20:19That would be disastrous for an animal that has to feed so regularly.
0:20:20 > 0:20:23It's far better for tamarins to travel together
0:20:23 > 0:20:26and then share the food when they arrive.
0:20:37 > 0:20:41Howler monkeys - ten times the size of a tamarin.
0:20:43 > 0:20:47They also eat flowers, given the chance,
0:20:47 > 0:20:49but these are not always available.
0:20:49 > 0:20:55In tropical forest, at least leaves can be found all year round.
0:20:55 > 0:20:58Howler monkeys specialise on these.
0:21:00 > 0:21:03The best leaves are up in the canopy,
0:21:03 > 0:21:07so that's the best place to go if you want to watch howlers close-up.
0:21:16 > 0:21:18Leaves are not all the same.
0:21:18 > 0:21:22Some are poisonous, even to a howler monkey.
0:21:22 > 0:21:26Of those that are edible, some are nicer than others.
0:21:26 > 0:21:31But, once again, that monkey ability to see in colour is a great help.
0:21:36 > 0:21:40These red ones are young and succulent,
0:21:40 > 0:21:45and would be very good to eat, if they weren't protected by poisons.
0:21:45 > 0:21:50These mature ones are green and the poison in them has faded,
0:21:50 > 0:21:54but they're fibrous and woody and NOT very good to eat.
0:21:54 > 0:21:59A leaf-eater wants something in between, like this.
0:22:01 > 0:22:06Imagine how difficult it would be to pick the right one
0:22:06 > 0:22:09if you didn't have colour vision.
0:22:17 > 0:22:21Even the best leaves are not easy to digest,
0:22:21 > 0:22:24so, although howlers spend a short time collecting food,
0:22:24 > 0:22:27they spend a long time digesting it.
0:22:27 > 0:22:32In fact, they spend half of every day just lying around,
0:22:32 > 0:22:34like cows, chewing the cud.
0:22:50 > 0:22:55Even after all that digestion, leaves are not very nutritious,
0:22:55 > 0:23:00so howlers can't waste energy chasing rivals through the treetops.
0:23:00 > 0:23:04They use a rather more labour-saving way of doing that.
0:23:09 > 0:23:12GRUNTING
0:23:22 > 0:23:27Howlers have a specially enlarged bone in the throat, the hyoid,
0:23:27 > 0:23:31that enables them to make this extraordinary song.
0:23:31 > 0:23:35It's one of the loudest noises made by any animal
0:23:35 > 0:23:40and the whole family joins in almost every evening.
0:23:40 > 0:23:43They work themselves into a frenzy,
0:23:43 > 0:23:47but since neither they, nor their rivals actually move anywhere,
0:23:47 > 0:23:51it's very hard to say who's winning.
0:23:59 > 0:24:03It may be that this howling serves to strengthen family solidarity
0:24:03 > 0:24:05and deter intruders.
0:24:22 > 0:24:25RASPING GRUNTS
0:24:32 > 0:24:35That may sound a bit like a howler monkey,
0:24:35 > 0:24:38but I've left South America and I'm in Africa.
0:24:38 > 0:24:43The howler's African equivalent is the black and white colobus.
0:24:45 > 0:24:50Many different kinds of monkeys are able to share the same forest,
0:24:50 > 0:24:53because they find their food in different ways.
0:24:54 > 0:25:00Red colobus' stomachs allows them to eat unripe fruit and leaves,
0:25:00 > 0:25:03whereas sooty mangabeys, like saki monkeys,
0:25:03 > 0:25:07have powerful jaws that can break open really tough foods.
0:25:11 > 0:25:15The rest of the monkeys have a more general diet, like capuchins,
0:25:15 > 0:25:18and belong to a group called the guenons.
0:25:18 > 0:25:22All guenons eat fruit and insects,
0:25:22 > 0:25:26but each looks for them at its own level in the forest.
0:25:26 > 0:25:30There are 17 different kinds of guenon in Africa.
0:25:30 > 0:25:33They all have similar-shaped bodies,
0:25:33 > 0:25:36but each has its own colours and patterns
0:25:36 > 0:25:42that serve as signals allowing them to recognise friends and rivals.
0:25:42 > 0:25:45They are the most colourful group of monkeys in the world.
0:25:51 > 0:25:55But colour signals are not a good way of sending urgent messages
0:25:55 > 0:25:57in places where the visibility is poor,
0:25:57 > 0:26:02and that's certainly the case here in the Tai Forest in West Africa.
0:26:03 > 0:26:07Failing to spot another monkey is one thing, but if you miss a warning,
0:26:07 > 0:26:09the consequences could be fatal.
0:26:19 > 0:26:23So how do monkeys keep out of harm's way?
0:26:25 > 0:26:29I'm travelling with one of the most extraordinary
0:26:29 > 0:26:31anti-predator alliances in the world.
0:26:32 > 0:26:38Around me is a troop of sooty mangabeys and mongooses.
0:26:38 > 0:26:42They're keeping an eye out for danger on the ground.
0:26:46 > 0:26:52In the branches above me, there are at least five species of monkey,
0:26:52 > 0:26:57all ready to detect a threat from the sky or from within the canopy.
0:26:58 > 0:27:03In this alliance, monkeys of many kinds travel side by side.
0:27:04 > 0:27:06It's a huge safety network
0:27:06 > 0:27:10that extends from the canopy right down to the forest floor.
0:27:12 > 0:27:16With so many pairs of eyes at every level,
0:27:16 > 0:27:20someone is sure to spot a threat, no matter where it comes from.
0:27:26 > 0:27:30There's little squabbling over food between different species
0:27:30 > 0:27:32because each finds it in a different way.
0:27:37 > 0:27:42Visibility is so poor here that they communicate almost entirely by sound.
0:27:42 > 0:27:47Unlike visual signs, a sound reaches every monkey in a split second.
0:27:47 > 0:27:52It's the best means of staying in contact or warning of danger.
0:27:53 > 0:27:57Diana monkeys forage near the top of the canopy,
0:27:57 > 0:28:00so they're usually first to spot danger from the air.
0:28:04 > 0:28:09Crowned eagles are never far away here, but if one comes too close,
0:28:09 > 0:28:14a specific alarm will be sounded, telling monkeys to drop for cover.
0:28:26 > 0:28:31Danger above! Monkeys plummet down without even looking up.
0:28:34 > 0:28:36The alliance has saved another member.
0:28:38 > 0:28:43All these monkeys have different alarm calls for different predators.
0:28:43 > 0:28:45Watch this!
0:29:11 > 0:29:13SQUEALING
0:29:17 > 0:29:19GRUNTING
0:29:25 > 0:29:29That's the leopard alarm call of the Diana monkey.
0:29:29 > 0:29:34GRUNTING That different one is the spot-nose.
0:29:34 > 0:29:39But the important point is that all species of monkey in the alliance
0:29:39 > 0:29:43recognise one another's call and know the nature of the enemy.
0:29:43 > 0:29:45That's important
0:29:45 > 0:29:50because each predator requires its own particular response.
0:29:52 > 0:29:56All these monkeys know there's a leopard around
0:29:56 > 0:29:59and you might think, therefore, that they would flee,
0:29:59 > 0:30:02but they don't - they're advancing towards it,
0:30:02 > 0:30:06and that's because the leopard is an ambush predator.
0:30:06 > 0:30:10Once it's spotted, it usually gives up and goes away.
0:30:12 > 0:30:15Monkeys are drawn by the call from a large area.
0:30:15 > 0:30:19They even drop lower, so they can keep the cat in full view.
0:30:23 > 0:30:26And here they will stay, on maximum alert,
0:30:26 > 0:30:30until the leopard finally gives up and leaves them in peace.
0:30:44 > 0:30:48The ancient city of Polonnaruwa in Sri Lanka.
0:30:48 > 0:30:53The civilisation that built it 1,000 years ago has long since crumbled,
0:30:53 > 0:30:58but one society that lived here then is still here now and thriving.
0:31:02 > 0:31:07Toque macaques have walked these walls for centuries,
0:31:07 > 0:31:09but only in the last few decades
0:31:09 > 0:31:12have we started to understand their complex society.
0:31:23 > 0:31:27This is one of the most studied monkey groups of all time.
0:31:27 > 0:31:32For 30 years, their daily existence has been recorded in detail.
0:31:32 > 0:31:37That has given us great insight into their private lives.
0:31:39 > 0:31:42These youngsters are playing as equals,
0:31:42 > 0:31:45but they have very different futures ahead of them.
0:31:45 > 0:31:48There's a ruthless class system in monkey society.
0:31:48 > 0:31:53Those born in high-ranking families have a massive head-start in life.
0:31:56 > 0:32:00Emelda is one of them. She is highborn.
0:32:00 > 0:32:05Others have been feasting on berries, but she's come too late to get any.
0:32:05 > 0:32:09The berries are stashed in the cheek-pouches of others.
0:32:09 > 0:32:15Emelda spots Poppin. She is far larger and older than Emelda,
0:32:15 > 0:32:18but she is from a lower-ranking family,
0:32:18 > 0:32:22entitling Emelda to take anything of Poppin's that she wants,
0:32:22 > 0:32:26including the food right out of her mouth.
0:32:33 > 0:32:36Poppin makes it as hard for Emelda as she dare,
0:32:36 > 0:32:42but if she resists too strongly, she risks a beating from the rest.
0:32:54 > 0:32:58In monkey society, it helps to be highborn.
0:32:58 > 0:33:00It also helps to be intelligent,
0:33:00 > 0:33:04and that is particularly apparent during the mating season.
0:33:06 > 0:33:09Toque macaques try to attract one another's attention
0:33:09 > 0:33:14by fluttering their mauve eyelids and flashing their teeth.
0:33:18 > 0:33:23But although there are willing males everywhere you look,
0:33:23 > 0:33:27there is a shortage of females ready to mate.
0:33:31 > 0:33:35Females are only fertile for a few weeks in the year.
0:33:35 > 0:33:39During this short period, lots of males want to mate with them,
0:33:39 > 0:33:42but hierarchy does not allow that.
0:33:42 > 0:33:44This male in front of me,
0:33:44 > 0:33:48after years of political manoeuvring and a good deal of muscle,
0:33:48 > 0:33:53has become alpha male, and he has first pick,
0:33:53 > 0:33:59but there are always some young males who try to beat the system.
0:33:59 > 0:34:01Booster has a lesser rank
0:34:01 > 0:34:05and that prevents him from openly mating with a fertile female.
0:34:05 > 0:34:08His best chance is a secret liaison,
0:34:08 > 0:34:11but the alpha male has recruited many allies,
0:34:11 > 0:34:16and these males will stop any female who tries to sneak away
0:34:16 > 0:34:19and reprimand her, if necessary.
0:34:24 > 0:34:28This security team allows the alpha to concentrate
0:34:28 > 0:34:31on the privileges of his position.
0:34:36 > 0:34:39But Booster's chance has come.
0:34:39 > 0:34:44The alpha male's allies don't have eyes in the backs of their heads,
0:34:44 > 0:34:49and females, like Shanti here, see Booster as a future alpha.
0:34:51 > 0:34:54Allowing him to father their young could be a shrewd investment.
0:34:56 > 0:35:00First, she needs to attract Booster's attention.
0:35:02 > 0:35:05Shanti is flirting.
0:35:05 > 0:35:10Her glances are subtle, because she doesn't want to get caught,
0:35:10 > 0:35:13but they're unmistakable, if you know what you're looking for,
0:35:13 > 0:35:16and Booster certainly does.
0:35:18 > 0:35:21He needs to signal his intentions to Shanti,
0:35:21 > 0:35:25but feign disinterest should the alpha male look in his direction.
0:35:30 > 0:35:34But the alpha has other females to attend to
0:35:34 > 0:35:38and his allies are nowhere to be seen.
0:35:38 > 0:35:40Shanti gives Booster the eye.
0:35:50 > 0:35:55They must be discreet and quick. Shanti's absence may be noticed.
0:36:05 > 0:36:11If Booster DOES take over, he may look favourably on Shanti's young.
0:36:11 > 0:36:14They might, after all, be his.
0:36:21 > 0:36:26A big brain certainly helps you to take advantage of others,
0:36:26 > 0:36:31and the larger the group you live in, the bigger your brain needs to be.
0:36:34 > 0:36:39But it was a dramatic change to the Earth itself
0:36:39 > 0:36:44that allowed monkeys to climb up to the next rung of the social ladder.
0:36:47 > 0:36:5210 million years ago, the climate of the world changed.
0:36:52 > 0:36:54Many places became much drier.
0:36:54 > 0:36:57The rainforests shrank
0:36:57 > 0:37:01and were replaced by scrub and open grassland.
0:37:01 > 0:37:05But there was a lot to eat in this new terrain.
0:37:05 > 0:37:09Some of the monkeys came down from the branches
0:37:09 > 0:37:12and went out to find it in the open.
0:37:14 > 0:37:18The first monkeys to walk out here would have found some familiar foods,
0:37:18 > 0:37:21flowers and seasonal berries,
0:37:21 > 0:37:25but today baboons collect all kinds of other things -
0:37:25 > 0:37:27bulbs, cactus,
0:37:27 > 0:37:29even rabbits.
0:37:32 > 0:37:35The grasslands are a great place for an opportunist.
0:37:35 > 0:37:38Baboons use their fingers and brains
0:37:38 > 0:37:42to collect an extraordinary variety of foods.
0:37:42 > 0:37:45Insect grubs can be picked up
0:37:45 > 0:37:49from the edge of a soda lake in Kenya's Rift Valley.
0:37:49 > 0:37:54Flamingos gather in vast numbers and generate a rich layer of compost
0:37:54 > 0:37:57that contains plenty of food for those patient enough
0:37:57 > 0:37:59to pick through it.
0:37:59 > 0:38:02But a few baboons have become more ambitious.
0:39:23 > 0:39:26Only this troop of baboons catch flamingos.
0:39:26 > 0:39:30It's just five years since the first of them discovered this new food
0:39:30 > 0:39:33and worked out how to get it,
0:39:33 > 0:39:35but the skill has spread quickly
0:39:35 > 0:39:38and now the whole troop are dedicated flamingo hunters.
0:39:44 > 0:39:48Life in the open has its disadvantages, too.
0:39:48 > 0:39:50There are more big predators around,
0:39:50 > 0:39:54so baboons protect themselves by assembling in large groups.
0:39:56 > 0:40:01As among macaques, living in big groups causes social problems.
0:40:01 > 0:40:04And here there's an even more complex social structure,
0:40:04 > 0:40:06within which males compete for females.
0:40:09 > 0:40:12When a female becomes sexually available,
0:40:12 > 0:40:15her bottom swells and turns bright pink.
0:40:15 > 0:40:18All the males can read the message, but she only offers herself
0:40:18 > 0:40:22to males that have looked after her during the rest of the year.
0:40:25 > 0:40:29This male is attempting to join the troop,
0:40:29 > 0:40:33but it may be some time before he can father any offspring.
0:40:33 > 0:40:37First, he has to learn the social order in this complex community
0:40:37 > 0:40:41and a good way to start is to befriend one of the senior females.
0:40:43 > 0:40:46The ledge can get very crowded,
0:40:46 > 0:40:50and the presence of the alpha male is intimidating.
0:40:50 > 0:40:55Even deciding where to sit is a political decision.
0:40:55 > 0:40:59The new male inevitably invades the personal space of others.
0:40:59 > 0:41:01Tempers flare.
0:41:01 > 0:41:04SHRIEKING AND CHATTERING
0:41:16 > 0:41:19Life for a new arrival can be very stressful.
0:41:22 > 0:41:27Established males rely on a network of allies for support.
0:41:27 > 0:41:31The most successful of them invested heavily in such social relationships.
0:41:31 > 0:41:35But knowing who to build them with takes intelligence.
0:41:36 > 0:41:40Grooming is a good way to maintain friendships.
0:41:40 > 0:41:43Looking after babies will also score you points.
0:41:45 > 0:41:48Child-caring brings another benefit.
0:41:48 > 0:41:52Babies are protected in baboon society,
0:41:52 > 0:41:54so no-one will hit you if you're carrying one.
0:41:54 > 0:41:59That allows smart baboons to use infants like shields
0:41:59 > 0:42:01when they feel threatened.
0:42:01 > 0:42:05It takes time and brain power
0:42:05 > 0:42:08to rise to the top in a large group.
0:42:26 > 0:42:31It's easy to imagine how a big brain could help you in baboon society.
0:42:31 > 0:42:35But if social complexity IS the driving force
0:42:35 > 0:42:38behind the growth of the primate brain,
0:42:38 > 0:42:41then it SHOULD be that brain size in primates
0:42:41 > 0:42:44corresponds closely to group size.
0:42:48 > 0:42:51This is the skull of a baboon
0:42:51 > 0:42:54and this lump of Plasticine
0:42:54 > 0:42:58represents the brain which the skull once contained.
0:42:58 > 0:43:02This represents the brain of a bush baby.
0:43:02 > 0:43:05It's essentially a solitary animal,
0:43:05 > 0:43:10but even allowing for its small body size, its brain is tiny.
0:43:10 > 0:43:15This, slightly larger, is the brain of a colobus - group size 15.
0:43:15 > 0:43:21This, bigger still, a guenon - group size 25.
0:43:21 > 0:43:26And back to our baboon - group size 50.
0:43:26 > 0:43:29The relationship is so close,
0:43:29 > 0:43:33that were you to give a skull to a researcher who works with monkeys
0:43:33 > 0:43:37even though they didn't know what kind of monkey it belonged to,
0:43:37 > 0:43:41they could accurately predict the size of group in which it lived.
0:43:46 > 0:43:50500 miles away in the highlands of Ethiopia
0:43:50 > 0:43:54live the largest monkey groups of all.
0:44:02 > 0:44:07Geladas - the world's only grazing monkeys.
0:44:07 > 0:44:10There's a lot of grass up here
0:44:10 > 0:44:14so geladas flourish and gather into enormous herds.
0:44:14 > 0:44:18They don't have nipping teeth like sheep or rabbits
0:44:18 > 0:44:22so they have to collect their grass by hand.
0:44:22 > 0:44:25This is done best by sitting down
0:44:25 > 0:44:30and they spend much of their lives shuffling along on their backsides.
0:44:35 > 0:44:38Because they sit down so much,
0:44:38 > 0:44:41their sexual displays have moved to their chests,
0:44:41 > 0:44:44where other geladas can see them.
0:44:44 > 0:44:48These indicate strength and virility
0:44:48 > 0:44:52and allow individuals to assess each other's status at a glance,
0:44:52 > 0:44:56so avoiding unnecessary confrontations.
0:44:57 > 0:44:59Within these herds are smaller groups,
0:44:59 > 0:45:02like those formed by other monkeys.
0:45:02 > 0:45:08Related females are the core and a male harem leader watches over them.
0:45:08 > 0:45:11And he has to be very vigilant.
0:45:16 > 0:45:21A pack of bachelor males with one goal in mind -
0:45:21 > 0:45:24to displace the holder of a harem.
0:45:28 > 0:45:31The bachelors avoid males with the brightest chests -
0:45:31 > 0:45:34they are in their prime and will have the full support of their family.
0:45:41 > 0:45:46But less impressive males will have to prove their worth in battle.
0:45:49 > 0:45:53A lip-flip from one of the bachelors is a threat. Flip answers flip.
0:45:53 > 0:45:56There's going to be trouble.
0:46:33 > 0:46:38These fights are largely for show and rarely result in injury,
0:46:38 > 0:46:42but they do waste valuable grazing time.
0:46:42 > 0:46:46Eating grass is time-consuming and also occupies your hands,
0:46:46 > 0:46:49so it's hard to find time for grooming.
0:46:49 > 0:46:54So geladas maintain their friendships in another way -
0:46:54 > 0:46:57they chatter to one another.
0:46:57 > 0:47:00CHIRPS AND MURMURS
0:47:02 > 0:47:06These noises are, in effect, VOCAL grooming
0:47:06 > 0:47:12and enable geladas to communicate with many individuals at once.
0:47:12 > 0:47:16And this is the secret of their ability to live in huge groups.
0:47:19 > 0:47:23Their continuous chatter SOUNDS like a language,
0:47:23 > 0:47:26but we have no idea what sort of information they are exchanging.
0:47:28 > 0:47:31One thing, however, IS likely -
0:47:31 > 0:47:36it was the need to communicate detailed social information
0:47:36 > 0:47:39between many individuals
0:47:39 > 0:47:42that led to the evolution of language in our own species.
0:47:45 > 0:47:50So although monkeys living in the tree tops have rich and varied lives,
0:47:50 > 0:47:55it's the ones that came down to the ground and formed large groups
0:47:55 > 0:48:00that have the most complex and communicative societies of all -
0:48:00 > 0:48:04a fact not without significance for our own ancestry.
0:48:23 > 0:48:26Those monkeys cracking shellfish and anointing themselves
0:48:26 > 0:48:29with a natural insecticide
0:48:29 > 0:48:32were showing a kind of behaviour that, not so long ago,
0:48:32 > 0:48:35was thought to be exclusively human.
0:48:35 > 0:48:37But over the past 40 years,
0:48:37 > 0:48:42intensive studies have shown that monkeys have a surprising complexity
0:48:42 > 0:48:46in their tool use, in their language, and in their societies.
0:48:47 > 0:48:50Primatologist Jane Goodall
0:48:50 > 0:48:54is famous for her ground-breaking studies of wild chimpanzees,
0:48:54 > 0:48:59but in 1960, she also began one of the first field studies of monkeys -
0:48:59 > 0:49:04the olive baboons of Tanzania's Gombe Stream National Park.
0:49:06 > 0:49:09Many monkey species have large, heavily armed males.
0:49:09 > 0:49:12They seem to be constantly fighting
0:49:12 > 0:49:15and soon the researchers identified the rank of different males
0:49:15 > 0:49:19in a turbulent hierarchy of threats and challenges.
0:49:23 > 0:49:26It is the young, prime male, entering a new troop
0:49:26 > 0:49:29and eventually confronting the existing leader
0:49:29 > 0:49:34who becomes the new, undisputed ruler of a troop.
0:49:36 > 0:49:39Here, a male's rank depends on his dominance,
0:49:39 > 0:49:42with the alpha male at the top.
0:49:42 > 0:49:46Across Africa, biologists revealed baboon troops as complex,
0:49:46 > 0:49:51highly-ordered and stable societies, containing long-term relationships.
0:49:55 > 0:49:59This includes a key role for the females in the species
0:49:59 > 0:50:01studied by Chadden Hunter -
0:50:01 > 0:50:03the gelada baboon.
0:50:03 > 0:50:07We have about 600 here filling up this valley,
0:50:07 > 0:50:09so just this ocean of fur.
0:50:09 > 0:50:15It's really hard to see just how many monkeys are here in one place.
0:50:15 > 0:50:19Family groups are basically sisters who stick together -
0:50:19 > 0:50:21say, four or five sisters.
0:50:21 > 0:50:25They'll pick a male, he comes into the family,
0:50:25 > 0:50:27has to toe the line with them -
0:50:27 > 0:50:32basically protect them, protect the kids whenever they want him to.
0:50:32 > 0:50:35On the side of the group
0:50:35 > 0:50:40is this tight-knit kind of street gang of mean-looking bachelors
0:50:40 > 0:50:44and if the sisters aren't happy with their male
0:50:44 > 0:50:48then they'll chuck him out and get a new guy.
0:50:48 > 0:50:52Even when there's relative stability,
0:50:52 > 0:50:54males are constantly under pressure.
0:50:54 > 0:50:57The alpha male can never relax.
0:50:58 > 0:51:02By measuring hormone levels,
0:51:02 > 0:51:05Professor Bob Sapolsky has shown that, just like humans,
0:51:05 > 0:51:10baboons suffer from stress and stress-related diseases.
0:51:10 > 0:51:12Baboons and us are very similar.
0:51:12 > 0:51:19WE don't get ulcers cos we have to wrestle somebody for a parking spot.
0:51:19 > 0:51:22We don't have the physical stressors most animals do.
0:51:22 > 0:51:25We're psychologically sophisticated enough
0:51:25 > 0:51:28to invent nonsense in our heads and we get sick with it.
0:51:28 > 0:51:32And largely that's what baboon society is about.
0:51:32 > 0:51:35They've got enough free time and enough food
0:51:35 > 0:51:39that they can spend a lot of time making each other miserable
0:51:39 > 0:51:41with social stress.
0:51:41 > 0:51:47Here's one really stressful thing you can do if you're dominant -
0:51:47 > 0:51:51some lower-ranking guy is in a sexual consortship with a female.
0:51:51 > 0:51:55She's in heat, she's reproductively accessible, they're hanging out.
0:51:55 > 0:51:58What does the dominant guy do?
0:51:58 > 0:52:00He doesn't attack. He's just AROUND.
0:52:00 > 0:52:05He's six feet away, just being on the scene harassing the pair.
0:52:05 > 0:52:07No fights, no threats, no nothing.
0:52:07 > 0:52:11The guy who's being harassed picks up and walks away voluntarily.
0:52:11 > 0:52:14This is psychological stress, straight out of the dictionary.
0:52:15 > 0:52:22So we know that monkeys live complex, even stressful, social lives.
0:52:22 > 0:52:26To maintain cohesion, they constantly send and receive messages.
0:52:30 > 0:52:33Monkeys are excellent communicators.
0:52:33 > 0:52:37If it is possible to get inside the mind of a monkey,
0:52:37 > 0:52:42then the squeals and chatters that accompany almost everything they do
0:52:42 > 0:52:44perhaps hold the key.
0:52:44 > 0:52:47Right from the beginning of these studies,
0:52:47 > 0:52:51it was clear monkeys had something important to say to one another.
0:52:52 > 0:52:57These vervet monkeys are warning each other of a snake.
0:52:57 > 0:53:00RAPID CLICKING
0:53:00 > 0:53:03The first detailed study of primate communication,
0:53:03 > 0:53:06by Robert Seyfarth and Barbara Cheney,
0:53:06 > 0:53:10revealed the true meaning of vervet alarm calls.
0:53:10 > 0:53:15We did a series of experiments in 1977 and '78
0:53:15 > 0:53:19where we'd wait until the monkeys were foraging in a certain area
0:53:19 > 0:53:23and then we would hide a loudspeaker in a bush nearby.
0:53:23 > 0:53:27We'd recorded the alarm calls in natural encounters.
0:53:27 > 0:53:32We took one of these alarm calls and played it from the loudspeaker
0:53:32 > 0:53:35when there were no predators around.
0:53:35 > 0:53:40The monkeys responded by running up into the trees at a leopard alarm,
0:53:40 > 0:53:44looking up or running into bushes at an eagle alarm,
0:53:44 > 0:53:49or looking on the ground around them in the case of a snake alarm.
0:53:49 > 0:53:54This means that the alarm call almost functions like a word.
0:53:56 > 0:53:59Vervet infants have to learn these words.
0:53:59 > 0:54:01They start with broad classes of danger.
0:54:01 > 0:54:06The eagle alarm covers all birds and flying objects.
0:54:08 > 0:54:12As they grow, they become more precise
0:54:12 > 0:54:15and, quite simply, those that can't learn don't survive.
0:54:19 > 0:54:23So we now know that vervet monkeys use words
0:54:23 > 0:54:26and have the rudiments of language.
0:54:26 > 0:54:29Different vocalisations mean different things
0:54:29 > 0:54:33and must be learned by the young members of the troop.
0:54:33 > 0:54:36Recent studies have shown that that applies
0:54:36 > 0:54:39to other species of monkeys as well.
0:54:40 > 0:54:43And monkeys don't just call out warnings of danger.
0:54:43 > 0:54:47Professor Mark Hauser's experiments with these rhesus macaques
0:54:47 > 0:54:52show that they're constantly discussing food.
0:54:52 > 0:54:54COUGH-LIKE GRUNTS
0:54:54 > 0:54:58They tell each other about mundane food items
0:54:58 > 0:55:03using a grunt that Mark refers to as "the boiled-potato call".
0:55:08 > 0:55:12But they use "the caviar call" when the food is more interesting.
0:55:12 > 0:55:15WHISTLES
0:55:15 > 0:55:20Experiments show some monkeys even recognise the calls of other species.
0:55:20 > 0:55:23They've become bilingual.
0:55:30 > 0:55:35The monkeys of the Tai forest are hunted by eagles and leopards,
0:55:35 > 0:55:40but in the wet season the greatest threat is a primate - the chimpanzee.
0:55:40 > 0:55:44They are expert climbers that can follow monkeys into the trees
0:55:44 > 0:55:46and they hunt cooperatively.
0:55:48 > 0:55:50So their prey - red colobus monkeys -
0:55:50 > 0:55:54form a partnership with Diana monkeys.
0:55:56 > 0:55:59Klaus Zuberbuhler plays chimp calls
0:55:59 > 0:56:03and the red colobus immediately look for Diana monkeys.
0:56:03 > 0:56:07THEY are the most likely to spot the chimps and raise the alarm.
0:56:07 > 0:56:12What is interesting when looking at inter-species communication,
0:56:12 > 0:56:16between one monkey species to the next,
0:56:16 > 0:56:21you find that each species possesses their own repertoires.
0:56:21 > 0:56:26A Campbell's monkey has a particular alarm call for a leopard
0:56:26 > 0:56:30which is completely different from the leopard alarm call of, say,
0:56:30 > 0:56:32a Diana monkey
0:56:32 > 0:56:39and it's quite obvious they do understand each other's alarm calls.
0:56:39 > 0:56:42That tells us they must learn it at some point.
0:56:42 > 0:56:47They aren't born with the knowledge of all these other species' calls.
0:56:48 > 0:56:53So as it grows up, a young monkey learns the calls of other species.
0:56:53 > 0:56:56It's a bit like learning a second language.
0:56:57 > 0:57:00It also seems that GROUPS of calls
0:57:00 > 0:57:03may carry a greater meaning than single ones
0:57:03 > 0:57:08with call-groups that are equivalent to adding an adjective to a noun.
0:57:08 > 0:57:13For example, Campbell's monkeys also have multifier calls
0:57:13 > 0:57:18that seem to affect subsequent meaning of alarm calls
0:57:18 > 0:57:23and it's this way of combining calls that has caught our attention.
0:57:25 > 0:57:27And that's an important step.
0:57:27 > 0:57:31If adding one call to another creates a new meaning,
0:57:31 > 0:57:34there's a fascinating parallel with human language.
0:57:34 > 0:57:38One thing is for sure - the more we listen to monkeys,
0:57:38 > 0:57:43the more they'll tell us about their complex, highly social lives.
0:58:16 > 0:58:19Subtitles by Red Bee Media Ltd