Life in the Trees The Life of Mammals

Meerkats in the Kalahari Desert.

They spend the night in burrows.

They find all the food they need on the ground.

They are swift and expert runners.

But oddly enough, they also climb

and they have very good reasons for doing so.

But first of all, they have to warm up in the early morning sun.

And once they are warm, it's time for breakfast.

They find THAT, for the most part, underground.

If you have your head in the sand, you can't see danger approaching.

And since they have many predators, someone must always stand guard.

Sentries aren't very effective if they can't see over the tall grass,

so to get a really good view, they have to climb as high as they can.

They don't have particularly long claws, or any other special climbing adaptations.

Nonetheless, they are surprisingly agile up in the branches.

They'll climb up just about anything if it gives them extra height.

An ability to climb is important for a meerkat on sentry duty,

but for some mammals, it's essential.

They spend nearly all their time up in the branches.

If you do that, you really do need special adaptations.

So, what kind of body does a tree dweller need?

Grasping hands, long arms to reach distant branches, a long tail, perhaps, to help with balance?

So, nothing like this, then!

These are hyrax and, in this safari lodge in Kenya,

they have acquired a taste for sunbathing.

Looking at their general body shape,

you might think they'd be as good in trees as rabbits or guinea pigs.

But they are surprisingly capable at climbing around in the branches

and the reason has to do with their special feet.

Their rubbery soles don't look very special and you can only see how effective they are,

when their owners stop lazing about in the sun and go off to feed.

Hyrax have an extremely flexible spine.

That helps them to scamper up tree trunks with surprising speed.

But it's their feet that help them stay up there.

There are special muscles in the middle of each foot

which pull up the centre of the sole.

The pads are moist, creating a slight suction which improves their grip, though not all that much.

Watching them clamber around makes me feel I ought to be standing underneath with a net,

just in case they fall!

And what is the reward for this high-wire act?

Leaves.

They supply the hyrax with both food and drink.

Succulent leaves are hard to find on the ground,

but up in the branches, hyrax can get all they need for the day in a couple of hours.

So climbing trees is vitally important for a hyrax, even if it does slip every now and then.

Fortunately, these trees are not very high,

but elsewhere in the world, there are trees that are ten times as tall as this,

and there, to be safe, you need something better than rubbery feet.

Claws should be long.

And so should tails.

Tails may not look like climbing aids, but they can be of great help in keeping your balance.

This is tropical America - and these are coati.

Much of their food can be found on the ground.

They climb, primarily, for a different reason...

safety.

At the first sign of danger, up they go.

These days, we too have got specialist tree-climbing gear.

You start by catapulting a fishing line over a bough, and using that to haul up a rope.

Then, with clip-on hand-holds - and the help of a counterweight - you can go up, too.

As in all forests, the trees compete to capture the sunshine.

Here, in the tropics, they grow very tall in the process.

And it is up in the canopy, 100 or more feet above the ground, that the real richness of the forest lies.

A third of the Earth's land is still covered by trees of one kind or another.

So, not unexpectedly, mammals belonging to very different families

have managed to acquire the skills and physical adaptations needed to get up into the trees to feed.

This, I suppose, is what most people would think of as a real forest -

the tropical rainforest.

There's a greater variety of food up here than there is anywhere else in the natural world.

The most obvious source of food up here, of course, are leaves.

There are certainly enough of them.

But leaves aren't really very good food.

They're rather tough, indigestible and don't contain much nutriment.

One mammal solves that problem not by eating more, but by doing less.

The sloth moves as if it's powered by the wrong sort of batteries

and prevents itself from falling off, not by muscle-power, but by hanging from hooks - its claws.

But there's a lot more than leaves to eat up here, as coatis know.

If you are fast and agile enough, you can catch birds up here.

But if you are not, well, some birds make their nests here

and then eggs and chicks make a good and easy meal.

And then there are brightly-coloured fruits with fleshy coverings, which are sufficiently good enough to eat

to persuade animals of all kinds to swallow them and so distribute the seeds.

The coatis need little encouragement to do that.

Fruit makes up most of their diet and it is quite a good plan to grab it before it falls

and comes within reach of other fruit-eaters down on the ground.

If you are going to stay up here for a long time, you will need to drink.

That - perhaps surprisingly - is not necessarily a problem.

Sometimes it's even easier to get a drink up here than it is down below.

These bromeliads - vase plants - are full of water

and sometimes these tiny ponds contain insect larvae or even frogs.

So there's protein as well.

Woolly monkeys regularly drink from them,

so they have no need to go down to the ground and hardly ever do so.

All in all, the larder in the forest canopy is far too rich to ignore

and many mammals come up here and feed up here.

But they have very special climbing skills and they are much more at home up here than I am.

These are proper tree-climbing claws.

They belong to the sun bear of Indonesia.

It is a fruit-eater and spends more of its time up in the trees than any other bear.

Bears don't have tails that might help with their balance.

But balance isn't a problem for the sun bear because it usually embraces branches rather than runs along them

and it has very strong forearms.

And if that's the way you climb, going down is almost as easy as going up.

The South American tamandua is an anteater.

Like all anteaters, it has powerful front legs with which to rip open ants' nests,

and they're a great help in climbing.

It has a tail and that has become an extremely valuable climbing aid.

It's prehensile, it can grip.

It is, in effect, a fifth limb,

so the tamandua can use its front legs in the same way that its ground-living relatives do.

Its tail is so well-muscled, it can support the animal's entire weight...

..which is just as well!

But there are only so many ant and termite nests in any one tree

and, sooner or later, the tamandua has to go and look elsewhere.

That means it has to leave the branches and trundle across the forest floor.

No big mammal can spend its entire life in a single tree.

They all have to move to find new sources of food.

Descending one tree, moving across the ground and climbing up another is one method.

But there is another, more energy-efficient way

to cross from one tree to another up there.

Here in South America, woolly monkeys do that by using their tails

which are even longer and stronger than the tamandua's.

A small gap like that might be crossed with the help of a prehensile tail,

but no tail is going to help with a gap that size.

From up there, they must look like an abyss -

but they are the great challenges for any tree dweller.

Squirrels deal with the problem with dazzling ease.

They are such lightweights

that they can race along the thin twigs at the end of the branches

and they are spectacular jumpers.

Their powerful hind legs provide the thrust.

Their long tail acts as a rudder.

And their shorter front legs serve as shock absorbers to cushion the landing.

Superb sight enables them to judge distance with great accuracy,

an essential ability when racing along this three-dimensional highway.

They are at their most acrobatic during the mating season

when males pursue the females.

One male may begin the chase, but others quickly join in.

Eventually, one wins.

But as soon as he has claimed his prize, the chase will start again

and the female may mate with up to eight different males in a day.

But a gap this size is just too big,

so a grey squirrel, like a tamandua, often has to come to the ground to visit all the trees in its range.

A grey squirrel can leap eight feet.

But there is another tree dweller that can leap much farther than that.

Although it's no bigger than my hand,

it could jump from this tree to that tree over there, more than 50 feet away,

an astonishing distance.

To see how it does it, we'll have to come back at night.

Since they have an acute sense of smell and love seeds and nuts,

maybe these will tempt one down from the tree tops.

They are flying squirrels.

How do they fly?

Just watch.

Maybe "gliding squirrel" would be a more accurate name.

They are, nonetheless, astonishing.

That furry membrane stretching between wrist and ankle makes a most efficient aerofoil.

Flying squirrels are not territorial and half a dozen can be foraging in the same area of woodland.

Although this squirrel may have travelled a very long distance

to get to this valuable source of food,

it's such an expert glider, it has done so with a minimum of effort.

And in forests like this one, where food sources are often very widely dispersed,

the ability to travel fast and far but with very little effort

is a very valuable ability indeed.

There are few gaps in these forests that defeat them,

but to cross really long distances, they do need height.

They steer partly with their tail

and partly by moving their outstretched legs,

so that they vary the tension of their gliding membrane.

And you can see that they CAN steer

when one squirrel uses the same take-off point, but glides away to land on different trees.

Even so, they are not agile enough in the air to escape birds of prey,

so during the day, they sleep in holes and only emerge when it's dark.

Gliding from branch to branch was a comparatively small step for tree-living mammals,

but one group of them made a truly gigantic leap.

Their arms changed into wings.

The shoulders, the elbows, the wrists remained much the same,

but the hand and the fingers changed dramatically.

Flying foxes - fruit bats in Australia.

They and their insect-eating cousins are the only mammals

that have developed true, powered flight.

They are so big that they can't roost in holes.

Instead, they sleep out in the open in colonies that may be hundreds of thousands strong.

The thumb on each hand is free of the wing and has a hooked claw.

Using that - and the claws on the toes -

fruit bats are surprisingly nimble, clambering about in the branches.

Wings may have solved the problem of getting from one tree to another,

but landing is still a challenge.

As a fruit bat approaches its chosen perch, it goes into a glide.

Then it lowers its toes and hooks them onto a branch.

This is a textbook example of how it's supposed to be done.

But some perches are more difficult to reach than others.

Wings need regular grooming.

They are also very delicate, but small tears quickly heal.

The wing membrane is among the fastest growing of mammalian tissues.

They fan their wings to keep cool.

It can be very hot hanging in the baking sun.

Take-off requires a special technique.

Two or three wing beats lift the body to the horizontal, and only then should the feet be unlatched,

so you don't lose too much height.

It's hard work, particularly if you are carrying a baby which is a third of your own weight.

Once in the air, however, fruit bats are extremely strong flyers.

They can travel great distances - as much as 30 miles, 50 kilometres - in a single night,

if that's necessary to find food.

They may have lost a lot of moisture, hanging around in the midday sun,

so their first call is often to a nearby lake to get a drink.

They do this in a rather unusual way.

First, they dip their chests in the water.

Then they return to their roost and lick the moisture from their fur.

But there ARE hazards.

Crocodiles.

The bats only touch the water for less than a second

and usually the crocodiles are just not quick enough to catch them.

But if one miscalculates and comes down on the water, it's a different matter.

They are surprisingly good swimmers. The worst danger comes when they get to land.

Being unable to drop into space, as they can from a perch,

they find it difficult to take off.

Now the crocodiles have the advantage.

But a few individuals lost to crocodiles

makes little impact on the bat colony.

This roost alone contains a staggering five million.

Living together in these vast numbers brings several important advantages.

Flying foxes collect fruit and nectar of many different kinds.

But knowing which species of fruit tree is in season when is not easy, and some are very unpredictable.

If a few individual bats return smelling of a particular fruit,

the news that this food has just come on the market spreads quickly through the whole colony.

Each bat knows where trees of the various species can be found,

so the next night, it will go to its own favourite patch to collect the new fruit.

That is why the whole five million don't follow one another to the same tree.

Huge wings are good for long-distance flying, but not for manoeuvrability in the air.

When the bats return in the dawn, hunters are awaiting them.

Eagles know exactly where a bat's blind spots are and attack from below.

Powerful though eagles are, fruit bats are big animals and a hit isn't necessarily a kill.

Raids like these are another reason why an individual bat finds it an advantage to roost in a colony.

Since it is surrounded by tens of thousands of others,

there is a good chance that an eagle will pounce on someone else.

Most colonies have a resident pair of eagles that nest nearby.

A breeding pair will take about half a dozen bats a day, but that makes little impact on bat numbers.

Skilled though the eagles are in taking bats on the wing,

their most successful strategy is to snatch them as they hang in the branches.

There's another way of getting around in the treetops.

Instead of having fingers that are greatly elongated and form struts for a wing,

they can be very small, muscular and give you an extremely powerful grip.

And the mammals that did that are of particular interest to us

because they contain our earliest ancestors.

Most of them are small and nocturnal, and the best way to find them is with a torch like this.

Highly reflective eyes caught in the torch's beam.

They belong to a slender loris - a primate, related to the monkeys -

and it lives in southern India.

Using a light may be the best way of finding a loris,

but it's certainly not the best way of seeing how they behave naturally.

To do that, you have to turn off your lights.

Infrared cameras give us the rare chance of watching a slender loris

without disturbing it.

It's moving so quietly,

that if it wasn't for this monitor,

I wouldn't even know that it was just over there.

Lorisis have elongated thumbs and have lost their index fingers,

so their grasp is wide enough to encircle quite stout branches.

They can hold on so tightly that it's almost impossible to detach one from a branch against its will.

It's the talent for gripping - and a long reach -

that enables them to deal with that problem of crossing from one tree to another.

That's what it is after - berries.

There is another here.

Lorisis live in small groups of four or five.

Something seems to have caught this one's eye.

Perhaps it's our dim infrared light.

It's frozen, motionless - standard alarm behaviour from a loris.

It can't move fast, so stands little chance of out-running a predator.

Instead, it simply stops and hopes that nobody will notice it.

And now it is off again. It's scent marking.

That drop of urine will tell any others that it is here.

It washes its hands in its urine, to leave a trail of smelly footprints behind it.

Some people think the urine gives the animal a better grip. It's certainly sticky!

Its eyes both face forwards,

giving it the stereoscopic vision to judge distance accurately.

It hunts not by speed, but by stealth.

Silence - acoustic camouflage -

enables it to catch its prey unawares.

Gripping feet - like prehensile tails -

leave hands free for the pounce.

That was a grasshopper!

And now it's found a stick insect.

This is a mantis. Mantises defend themselves in two ways -

either by camouflage or aggressive display, like this.

And neither of them seem much good against a loris!

Only one creature stands a chance of removing something from the grasp of a loris.

And that is another loris!

Africa has got its own similar creature - only a much more lively and athletic one.

The lesser bushbaby.

It's probably the most numerous primate in Africa,

but you seldom see it because it only comes out at night.

They have a regular pathway through these trees

which they mark with their urine,

so you can predict they will go from one tree to the other.

They're related to lorisis and physically similar -

with grasping hands,

stereo vision and large ears.

But their way of getting around is completely different.

They hunt not by stealth,

but by speed.

They jump 30 times their body length.

This one is carrying an infant.

And a leap like that is nothing to a bushbaby!

Before one takes off, it moves its head from side to side, working out the best place to land.

That's important, because these trees are very thorny.

Bushbabies of one species or another have colonised every type of forest in Africa,

and millions of years ago, ancestral bushbabies even spread beyond the continent.

Somehow - perhaps on a floating log - they reached the island of Madagascar.

Here, there were neither predators nor competitors,

and they diversified into an extraordinary range of species

which exploit every environment on the island.

They are the lemurs.

LEMUR CRIES

The most specialised of them is the golden bamboo lemur.

It was discovered only recently,

and it lives on a part of the bamboo

that would be fatal to most animals.

Bamboo pith is full of cyanide.

The golden lemur eats 12 times as much as would normally kill an animal of its size.

Other Madagascan plants defend themselves in a different way.

Didierea is covered with ferocious spines,

yet it is the chosen home and feeding grounds of another lemur - the sifaka.

Clambering about here

requires some very delicate footwork.

Mother's tail clearly makes a better handhold for a youngster -

but even at this age, a young sifaka is able to negotiate the spines.

Collecting didierea leaves and flowers -

the sifaka's main food -

looks more hazardous than travelling through its branches.

But when sifakas decide to move,

they can travel very fast indeed.

They use the same method as bushbabies,

but with such speed and confidence

that they seem to bounce from trunk to trunk.

Only in slow motion can you see how accurately they land,

and how instantaneously they can take off again.

But given the chance,

they assess their jumps with care.

Takeoff starts sideways-on to the line of flight,

so they have to rotate their bodies in midair.

Those hind legs, having kicked off,

have to be swung forward to act as shock absorbers as they make contact.

Their back feet are long and narrow, with an enormous big toe,

so that they can lock on to a trunk as soon as they hit it.

Within seconds, they are off again.

And a female can even do all this while she is carrying a baby.

Down on the ground, the method doesn't work quite so well.

Extremely long legs and very short arms

make it impossible to run on all fours,

so, again, it has to be jumping.

But with no vertical trunk to push away from, the leaps are shorter.

Back in the trees, they can travel at speed again.

And they need to, for they have a savage enemy.

The fossa.

Its speed through the branches rivals that of the sifakas,

but its technique is entirely different. It's not a primate with jumping ancestors,

but a kind of giant mongoose - and it is still a four-footed runner.

Nonetheless, they are a close match for one another.

But when it comes to the long jump,

the sifaka wins.

A four-footed runner can't match that.

But it's caught a scent of something else - a female who is ready to mate.

She has taken up residence in a tree, and there she is holding court.

She will attract several males.

There is going to be strong competition.

An unusually long tail helps in maintaining balance,

and they manage to negotiate surprisingly thin branches.

The female decides who to mate with. She drives off those she's not interested in.

THEY SNARL

Mating itself is a noisy affair.

It's made the more difficult,

by having to balance on a branch while it is going on.

THEY GRUNT

THEY CRY AND HISS

Few animals can match a fossa for speed in the trees,

and few can descend headfirst, like this.

The fossa can do so, because it has very flexible ankles

that allow it to twist its feet to point backwards.

To find the supreme tree-traveller, we have to go to another continent.

We have to climb into the canopy

of the forests of South-East Asia.

BIRDS SING

This forest is home to the fastest of all the flightless inhabitants of the canopy in the world.

It is so swift and so agile,

that it is capable of catching birds in midair.

Gibbons.

Not monkeys, but small apes.

Their long jump record is about the same as a sifaka - around 40ft -

but they can move at even greater speed.

They are such skilled acrobats and can change direction in mid-flow.

We may be distantly related to the lesser apes,

but when you watch gibbons like this,

you realise how ill-equipped we are for a life in the trees.

Our forearms are too short, our thumbs too big, our shoulders and hips too inflexible

and our eye-to-hand co-ordination - compared with gibbons - is poor.

They have one characteristic which we, and all primates, lack -

that is a ball-and-socket joint in their wrists.

THAT allows them to perform these fantastic aerial gymnastics.

Hurtling through the branches hand over hand

is the gibbons' standard way of getting around.

Their unique wrist joint

enables them to rotate the body around the hand and not the shoulder.

That saves a lot of energy!

Moving at this speed can be hazardous. Branches may break.

Jumps may be misjudged.

Researchers estimate that most gibbons fracture bones at least once in their lives.

And fatal falls are certainly not unknown.

Life in the trees is a dangerous business.

One serious mistake is likely to be your last.

Mankind's success started when its feet hit the ground

and it stood up on its hind legs.

But the coati, hyrax, tamandua and the gibbon

are proof that there is a very good living to be had up there.

GIBBONS CRY

Exactly what goes on high in the canopy of the rainforest, 100-200ft above the ground,

was, for a long time, a mystery.

It was so difficult to get up there and move around safely.

But now, we've got ways of doing just that.

And the key to them...is this -

a very, very powerful catapult!

James Aldred is a catapult expert.

The first thing you need to do is find your tree!

'Having found a suitable tree, you need to get the rope up into it.

'You stretch out a bit of tarpaulin

'and lay the line out. Fishing line.

'Play it out there, so it won't snag as it's running,

'connect a fishing weight, stick it in the catapult and go!

'Usually, you hit the trunk first time, or get snagged anyhow.

'Sooner or later, you'll get it.

'Having got that lightweight line over, you pull up the climbing rope.

'Anchor that, and you're ready to go up there.'

The scene is set to get a human up into the rainforest canopy.

My climb to the canopy

was only possible after a great deal of preparation.

James and the team worked in the forest for ten days before the crew and I arrived.

'We went with an assistant producer and climbing colleague, Phil Hurrell.

'One of the main hazards in the rainforest was rain! It rained continually from day one.

'There were storms, winds... Dislodging dead wood from above!

'The next problem was snakes. We actually found a hognose viper in with our kit.

'Once you get up there,'

the last hazard you encounter is primates.

Howler monkeys are getting rather boisterous, hooting and hollering.

They are only about this big. They are quite a small primate.

They are quite intimidating and territorial and did their best to get me out the tree.

They succeeded! Embarrassing to be seen off by a primate this big,

but such is the way of life!

Finding a suitable tree is very time-consuming.

'Phil and I must have climbed 12-15 trees over those first ten days.'

We're about four days into our ten-day set-up period,

but we're having real trouble finding a decent location.

It's got to be a really fantastic shot - something that really knocks off anything that's gone before.

'But the next day, I thought I'd found the perfect tree.'

It's very big, very exposed.

Each branch is the size of a moderate UK oak tree.

Big. It's a big tree!

Having said that, it is an emergent. The view is stunning, but it IS exposed.

It's very exposed -

and not somewhere you want to dangle David Attenborough!

It took us six or seven days to even find a tree.

When you get up there, you're rewarded with a stunning insight

to a world no-one else has ever seen.

You see things which no-one else has seen, or will see. Very privileged.

Those last days were manic. Phil rigged one tree, I rigged the other.

'By the skin of our teeth!

'Once the crew arrives, you get the camera person up first.

'In this case it was Justine.'

Nearly there, Justine.

It looks good from here, actually.

I'll film you there. Suits me!

'So, she ran up there. Got settled.

'Phil was ready to receive David.

'To get David up, we used a counterbalance system -

'a rope going up over a pulley, across to another pulley and back to the ground.

'Someone climbs up one side, with David attached on the other side.

'They jump off a branch, they come down as a sack of spuds and lift David into position.'

'The idea was he could move down that cable, parallel to a branch.

'He could talk about the things you could expect to find in the canopy.

The other shot was a reveal to show David in context. Nerve-racking!

We had 16kg of camera going down on a cable which was 100m -

180ft up - and you've got, you know, David Attenborough at the other end.

However many safeties you do - it WAS bomb-proof - it does make your heart flutter!

Is it quite solid down here now?

David has just been up and down - safely - which is a good thing.

It's good. I'm feeling rather pleased with myself.

In recent years, the abundance of tropical forest species

and the detail of their relationships has been revealed.

First-hand observation has been vital, but simply seeing the animals in the forest

is a challenge in itself.

A colleague, Lesley Ambrose, has studied bushbabies for eight years

and she only sees the eyes in the trees!

Studying the animals in the canopy remains a major problem.

We really know nothing about what they get up to.

Although you can only see the eyes of these animals and you may never get a close-up view,

fortunately nearly all bushbabies give a range of very loud calls.

HIGH-PITCHED CRIES

Some of the calls are like whistles...

Some of them are like screams...

Some of them sound like cross babies crying -

which is why they are called bushbabies.

Once we cottoned on to this idea of the differences in the calls,

we began recording them in earnest.

We now have a huge library of the sounds of all these different species.

By recording these sounds, and then by studying them in the laboratory,

by displaying them on a graph,

you can understand how they communicate with each other.

This provides an enormously complex means of communication,

which we're beginning to unravel.

Some of the calls - particular sounds they communicate over a long distance -

seem to be species-specific.

That's how we recognised the fact that animals that may look the same,

were totally different species!

When I started, there were only six species known to science.

Now, we're approaching 26 species. There's still a few we're not sure about

and others that we just don't know what they are!

All of us students have discovered at least one new species of bushbaby,

during their field work.

If anyone wants to study these animals in the rainforest,

it's actually a good opportunity to find out new things that no-one has ever seen before.

It's surely astonishing that in the 21st century,

we're STILL discovering new species of mammals.

Not just any old mammals - primates. The group to which WE belong!

For, although the tropical forest has been a mammal habitat for many millions of years,

it's only now, in the 21st century,

that we humans are truly equipped to reveal its mysteries.

In the next episode of The Life Of Mammals,

we meet the monkeys - creatures with colourful appearances

and even more colourful social lives.

Subtitles by Dorothy Moore and Susan Mason, BBC Broadcast 2003

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