0:00:03 > 0:00:05Planet Earth.
0:00:06 > 0:00:08Millions of different species.
0:00:11 > 0:00:13But a few are special.
0:00:16 > 0:00:18Thriving.
0:00:20 > 0:00:21Dominating.
0:00:24 > 0:00:29The key to their success lies in their opportunism.
0:00:30 > 0:00:34For others, it's down to their ability to collaborate.
0:00:35 > 0:00:40And for some, it's all about surviving where others can't.
0:00:41 > 0:00:43So, what is their secret?
0:00:45 > 0:00:47By delving deep beneath the skin,
0:00:47 > 0:00:52we'll reveal the unique features that set some species apart.
0:00:59 > 0:01:01In this series, new behaviour
0:01:01 > 0:01:04and the very latest scientific research
0:01:04 > 0:01:09will throw fresh insight into The Wonder of Animals.
0:01:31 > 0:01:33The African elephant.
0:01:33 > 0:01:36The largest land animal on the planet.
0:01:41 > 0:01:44Colossal, lumbering and ponderous.
0:01:47 > 0:01:50Their astonishing body has always fascinated us.
0:01:52 > 0:01:55Their sheer size seems ill-suited to surviving
0:01:55 > 0:01:59in some of the most challenging habitats on Earth.
0:02:03 > 0:02:05But the inner workings of these giants
0:02:05 > 0:02:09is highly sophisticated and intricate.
0:02:09 > 0:02:14Allowing them to defy the extreme heat of the desert.
0:02:16 > 0:02:21To find food and water in a sparse and barren landscape.
0:02:23 > 0:02:27And to repel predators, both animal...
0:02:29 > 0:02:31..and human.
0:02:32 > 0:02:36In this episode, we are going to explore each element
0:02:36 > 0:02:38of the elephant's remarkable body.
0:02:44 > 0:02:46We're going to unlock the secrets
0:02:46 > 0:02:49of how its extraordinary anatomy and surprising physiology
0:02:49 > 0:02:53have enabled it to become one of the greatest survivors
0:02:53 > 0:02:54in the natural world.
0:03:09 > 0:03:11The Namib Desert, southern Africa.
0:03:13 > 0:03:17Temperatures here can exceed 45 degrees Centigrade.
0:03:21 > 0:03:22There's very little shelter.
0:03:28 > 0:03:32So the first survival challenge facing the elephant here
0:03:32 > 0:03:34is to avoid overheating.
0:03:41 > 0:03:44And various parts of their anatomy help out.
0:03:45 > 0:03:50The African elephant has the largest ears of any animal,
0:03:50 > 0:03:55accounting for 20% of their overall surface area.
0:03:56 > 0:03:59Although they make useful fans,
0:03:59 > 0:04:03they also help cool the elephant down in another, more subtle way.
0:04:05 > 0:04:08These thin flaps dissipate heat fast
0:04:08 > 0:04:11and are therefore cooler than other parts of the body.
0:04:15 > 0:04:17The hotter, red areas are blood vessels
0:04:17 > 0:04:20which can be expanded when required,
0:04:20 > 0:04:23allowing more blood to flow through them.
0:04:24 > 0:04:29When needed, they can pump up to 12 litres every minute.
0:04:32 > 0:04:35Working in a similar way to a car radiator,
0:04:35 > 0:04:39as the blood passes through, it's cooled by the air,
0:04:39 > 0:04:41helping the elephant to lose heat quickly.
0:04:45 > 0:04:47But a recent scientific study has discovered
0:04:47 > 0:04:51that it's not just in the ears that this technique is used.
0:04:54 > 0:04:57Researchers at the University of Veterinary Medicine in Vienna
0:04:57 > 0:05:00noticed that as elephants warm up,
0:05:00 > 0:05:04certain parts of their body appear hotter than others.
0:05:06 > 0:05:08The study found that these hotspots
0:05:08 > 0:05:12have a particularly high concentration of blood vessels
0:05:12 > 0:05:16located just beneath the surface of the skin.
0:05:21 > 0:05:24By allowing more blood flow through these areas,
0:05:24 > 0:05:29the elephant is able to fine-tune its cooling process,
0:05:29 > 0:05:32helping to maintain a perfect temperature.
0:05:36 > 0:05:39And the skin itself is special, too.
0:05:41 > 0:05:44Unlike most mammals, elephants don't sweat.
0:05:48 > 0:05:53They simply can't afford the loss of water in this parched wilderness.
0:05:56 > 0:06:00Instead, their skin has evolved a very different way
0:06:00 > 0:06:02to help them battle the heat.
0:06:07 > 0:06:11Every inch of an elephant's body is covered with wrinkles.
0:06:21 > 0:06:25These help keep an elephant cool by trapping mud and dust.
0:06:37 > 0:06:40This then acts as a sunscreen.
0:06:43 > 0:06:47And it's been calculated that wrinkly skin
0:06:47 > 0:06:51can hold 10 times more muddy water than smooth skin.
0:07:06 > 0:07:11But there's one more cooling element their skin has to offer,
0:07:11 > 0:07:13and it may not seem obvious.
0:07:16 > 0:07:20The elephant is covered in long, wiry hairs.
0:07:26 > 0:07:29In all other mammals, hair is used to provide insulation.
0:07:32 > 0:07:36But in 2012, research from Princeton University
0:07:36 > 0:07:40revealed that they actually help cool the elephant down.
0:07:43 > 0:07:48They act as conductors, drawing heat away from the body.
0:07:52 > 0:07:56This is the first time that any mammal's hairs
0:07:56 > 0:08:03have been found to help lose, rather than retain body heat.
0:08:06 > 0:08:09Elephants have been able to withstand the extreme heat,
0:08:09 > 0:08:12and it's all down to their surprising body.
0:08:13 > 0:08:17But they still need food and a regular supply of water.
0:08:17 > 0:08:21And here in Africa, these are often in short supply.
0:08:29 > 0:08:33Elephants need to drink every two to three days.
0:08:38 > 0:08:41So finding water is a relentless task.
0:08:46 > 0:08:47At the height of the dry season,
0:08:47 > 0:08:51the plains are parched and water is scarce.
0:08:56 > 0:09:02But elephants can locate rain even when it's hundreds of miles away.
0:09:05 > 0:09:07THUNDERCLAP
0:09:08 > 0:09:11By using their feet.
0:09:13 > 0:09:18Research suggests they can pick up a storm's infrasound.
0:09:21 > 0:09:25The low frequencies undetectable to the human ear.
0:09:25 > 0:09:26THUNDERCLAP
0:09:33 > 0:09:37One theory is that the highly-sensitive soles of their feet
0:09:37 > 0:09:41can detect minute seismic vibrations.
0:09:47 > 0:09:50To determine the locality of a faraway storm.
0:10:09 > 0:10:12This incredibly subtle adaptation
0:10:12 > 0:10:15may explain how, even on a clear day,
0:10:15 > 0:10:21elephants seem to know exactly where to go to find rain.
0:10:25 > 0:10:27THUNDERCLAP
0:10:35 > 0:10:39Many different herds will travel vast distances
0:10:39 > 0:10:41to get to the same supply of fresh water.
0:10:46 > 0:10:48TRUMPETING
0:11:04 > 0:11:08And this is much more than just a chance to rehydrate.
0:11:10 > 0:11:14It's also an important occasion for socialising and playing.
0:11:20 > 0:11:22Here, the young must learn from the adults
0:11:22 > 0:11:24how to use their trunks to drink.
0:11:32 > 0:11:35And how to clean themselves.
0:11:50 > 0:11:53At an abundant water source like this,
0:11:53 > 0:11:58elephants can consume up to 220 litres in a single day.
0:12:18 > 0:12:22But how do they cope when they're nowhere near water?
0:12:26 > 0:12:29After just three days without drinking...
0:12:31 > 0:12:34..elephants begin to succumb to dehydration.
0:12:41 > 0:12:46But to survive for an extra few hours, they've evolved a neat trick.
0:12:58 > 0:12:59At the back of their tongue,
0:12:59 > 0:13:04they have a reservoir called the pharyngeal pouch...
0:13:04 > 0:13:09which can store up to five litres of water.
0:13:09 > 0:13:13As a last resort, they can access this emergency supply
0:13:13 > 0:13:17by putting their trunk down their throat and into the pouch.
0:13:20 > 0:13:23They can then drink it, or spray it over themselves
0:13:23 > 0:13:26to cool down the blood vessels in their ears.
0:13:28 > 0:13:33And this anatomical adaptation is unique to elephants.
0:13:33 > 0:13:37It could mean the difference between life and death.
0:13:41 > 0:13:43In the arid regions of Africa,
0:13:43 > 0:13:46there's not only a shortage of water.
0:13:46 > 0:13:50For herbivores, there's also a lack of high-quality food.
0:13:55 > 0:13:57Tree bark...
0:14:03 > 0:14:04..branches...
0:14:08 > 0:14:11..and grass...
0:14:11 > 0:14:14are all difficult to digest
0:14:14 > 0:14:17and can have little nutritional reward.
0:14:18 > 0:14:21In fact, relative to its size,
0:14:21 > 0:14:24the elephant diet contains fewer calories
0:14:24 > 0:14:29and less protein than that of any other mammal.
0:14:31 > 0:14:38So they need to consume vast amounts just to stay alive.
0:14:42 > 0:14:44Grazing up to 19 hours
0:14:44 > 0:14:48and eating up to 300 kilograms every day.
0:14:50 > 0:14:53None of which would be possible without their trunk.
0:14:56 > 0:14:58A fusion of their nose and upper lip.
0:15:00 > 0:15:03It's immensely powerful.
0:15:03 > 0:15:06Capable of lifting up to 350 kilograms.
0:15:08 > 0:15:09But it's flexible, too.
0:15:10 > 0:15:15Allowing them to reach seven metres high up into the trees.
0:15:19 > 0:15:22And it's also highly sensitive.
0:15:30 > 0:15:33On the tip of an African elephant's trunk
0:15:33 > 0:15:35are two finger-like extensions
0:15:35 > 0:15:40that can be pinched together to grasp even the tiniest morsel.
0:15:44 > 0:15:48And inside, it's even more intricate.
0:15:54 > 0:16:00The elephant's trunk contains more than 100,000 muscle units.
0:16:08 > 0:16:13Fluid within the muscle cells becomes firm when compressed,
0:16:13 > 0:16:15working like a hydraulic system,
0:16:15 > 0:16:19offering superb flexibility and rigidity.
0:16:25 > 0:16:29Different sections of the trunk can work independently
0:16:29 > 0:16:34and can bend or twist, lengthen and shorten.
0:16:36 > 0:16:40It's one of THE most versatile tools in the animal kingdom.
0:16:43 > 0:16:45And when combined with their tusks,
0:16:45 > 0:16:48the elephant is formidable.
0:16:56 > 0:17:00Elephants' tusks occur in both males and females
0:17:00 > 0:17:03and they're actually modified teeth.
0:17:03 > 0:17:07Incisors that develop in the upper jaw
0:17:07 > 0:17:11and replace milk teeth around six months after birth.
0:17:11 > 0:17:14They can keep growing as much as 17 centimetres a year
0:17:14 > 0:17:18and can reach three metres in length.
0:17:18 > 0:17:21And because elephants favour one tusk over another,
0:17:21 > 0:17:24they tend to be worn down at different rates.
0:17:30 > 0:17:32Working in tandem with their trunk,
0:17:32 > 0:17:37an elephant's tusks are an invaluable tool for moving trees,
0:17:37 > 0:17:40stripping branches and foraging for food.
0:17:47 > 0:17:50And once they've harnessed that food,
0:17:50 > 0:17:53it's the teeth inside their mouth that take over.
0:17:53 > 0:17:57Elephants have four huge molars.
0:17:57 > 0:18:01The largest of any mammal alive today.
0:18:01 > 0:18:04Each one grows up to 30 centimetres high
0:18:04 > 0:18:07and can weigh as much as five kilograms.
0:18:10 > 0:18:12Their size and shape is crucial
0:18:12 > 0:18:15when it comes to eating such a tough diet.
0:18:17 > 0:18:21But these teeth are not permanent.
0:18:21 > 0:18:26If they were, once worn down, the elephant would starve to death.
0:18:27 > 0:18:30Instead, they've evolved an ingenious solution.
0:18:33 > 0:18:35Unlike most mammals,
0:18:35 > 0:18:40elephants' teeth grow in cycles throughout their lives.
0:18:40 > 0:18:42The molars start at the back of their mouth
0:18:42 > 0:18:45and gradually move forward,
0:18:45 > 0:18:49pushing out the older ones which are worn down.
0:18:49 > 0:18:51It's like a conveyer belt.
0:18:54 > 0:18:58And these teeth can be replaced up to six times
0:18:58 > 0:19:00during the elephant's life.
0:19:02 > 0:19:07But vegetation alone can't supply all of the elephant's needs.
0:19:16 > 0:19:21And their quest for a balanced diet leads them to some unusual places.
0:19:31 > 0:19:36This cave in Kenya is deep inside an extinct volcano.
0:19:38 > 0:19:42The walls are covered with thousands of scratch marks.
0:19:44 > 0:19:48Some are 150 metres down in the darkness.
0:19:59 > 0:20:03In the middle of the night, elephant families visit the cave.
0:20:10 > 0:20:14They come here to mine the salt from the cave walls.
0:20:15 > 0:20:18All mammals need salt.
0:20:21 > 0:20:25But there simply isn't enough sodium in the elephant's herbivorous diet
0:20:25 > 0:20:29to sustain such a huge animal.
0:20:30 > 0:20:34So elephants are constantly on the hunt for it.
0:20:40 > 0:20:44They use their tusks to scour the walls.
0:20:47 > 0:20:48Scratching away the salt...
0:20:51 > 0:20:52..to supplement their diet.
0:21:07 > 0:21:10They've been coming here for generations.
0:21:19 > 0:21:23Able to return to the same location year on year,
0:21:23 > 0:21:28thanks to an astonishing long-term memory.
0:21:37 > 0:21:41Elephants have the biggest brain of any land mammal.
0:21:44 > 0:21:48But there are two parts of it that are particularly enlarged.
0:21:48 > 0:21:50The cerebral cortex...
0:21:53 > 0:21:54..and the olfactory system.
0:21:54 > 0:21:57These areas are fundamental
0:21:57 > 0:22:02to complex learning and, crucially, memory.
0:22:02 > 0:22:05Allowing elephants to store and process information
0:22:05 > 0:22:08that's vital to their survival.
0:22:12 > 0:22:16And this capacity to learn and remember
0:22:16 > 0:22:17has helped them to survive
0:22:17 > 0:22:20some of the worst that nature can throw at them.
0:22:22 > 0:22:26One study found that in a severe drought,
0:22:26 > 0:22:29the older females led the herd to a waterhole
0:22:29 > 0:22:32hundreds of miles from their home territory.
0:22:41 > 0:22:45They can even recall the exact location of water sources
0:22:45 > 0:22:48last visited over 30 years before.
0:23:04 > 0:23:07Elephants have an incredible long-term memory.
0:23:07 > 0:23:11This doesn't only help them find food and water,
0:23:11 > 0:23:14it also helps them avoid predators.
0:23:24 > 0:23:28Although huge, elephants are hunted by lions.
0:23:34 > 0:23:37The big cats target younger elephants
0:23:37 > 0:23:40if they become separated from their herd.
0:23:40 > 0:23:41TRUMPETING
0:23:41 > 0:23:43SNARLING
0:23:54 > 0:23:57So when the two are forced to share a waterhole,
0:23:57 > 0:24:01elephants must know exactly how to protect their young.
0:24:03 > 0:24:05TRUMPETING
0:24:16 > 0:24:19And for this, they rely on
0:24:19 > 0:24:22the memories of the older members of the herd.
0:24:24 > 0:24:27A recent study suggests that the older matriarchs
0:24:27 > 0:24:30with a greater accumulated knowledge
0:24:30 > 0:24:33make better decisions than younger ones
0:24:33 > 0:24:36when they're faced with a predatory threat from lions.
0:24:41 > 0:24:46So herds with older individuals are less susceptible to attack.
0:24:51 > 0:24:54They keep the young at the centre of the group,
0:24:54 > 0:24:58forming a defensive cordon to hold the lions at bay.
0:25:01 > 0:25:04Each encounter reinforces their memory
0:25:04 > 0:25:08and helps keep the herd safe for generations to come.
0:25:14 > 0:25:19But perhaps the elephant's greatest feat of memory
0:25:19 > 0:25:23is in defence of the biggest of all threats to their survival.
0:25:29 > 0:25:33Humans have been killing elephants for thousands of years.
0:25:35 > 0:25:37But it's not just for their tusks.
0:25:40 > 0:25:44The Maasai tribe in Kenya are cattle herders.
0:25:44 > 0:25:47And as a result, frequently come into conflict
0:25:47 > 0:25:50with elephants over precious resources.
0:25:50 > 0:25:53These animals are often killed as a result.
0:26:00 > 0:26:02But they use their memory
0:26:02 > 0:26:05to protect themselves in a remarkable way.
0:26:07 > 0:26:09A brand-new scientific study
0:26:09 > 0:26:12has discovered that elephants can recognise
0:26:12 > 0:26:16and remember the dialects of those tribes
0:26:16 > 0:26:18that have threatened them in the past.
0:26:23 > 0:26:25The researchers played audio recordings
0:26:25 > 0:26:29of two different local tribes to a group of elephants.
0:26:30 > 0:26:33Firstly, the Kamba people,
0:26:33 > 0:26:36who rarely come into contact with elephants.
0:26:36 > 0:26:38KAMBA DIALECT
0:26:42 > 0:26:45The herd appear relaxed throughout.
0:26:47 > 0:26:49But this is what happened when the same herd
0:26:49 > 0:26:52were played a recording from the Maasai tribe.
0:26:52 > 0:26:54MAASAI DIALECT
0:27:00 > 0:27:01TRUMPETING
0:27:08 > 0:27:13What's more, the research found that it's not just separate tribes
0:27:13 > 0:27:16that elephants can differentiate between.
0:27:16 > 0:27:18They appear to be able to distinguish
0:27:18 > 0:27:21between gender and even age.
0:27:21 > 0:27:26Correctly sensing the threat of older male Maasai,
0:27:26 > 0:27:31but not reacting to recordings of the unthreatening women
0:27:31 > 0:27:34and young adults from the same tribe.
0:27:35 > 0:27:38It's the elephant's capacity to learn and remember
0:27:38 > 0:27:41that has increased their chances of survival
0:27:41 > 0:27:45in an ongoing battle for scant resources.
0:27:53 > 0:27:58Within their huge frame, the most surprising adaptations
0:27:58 > 0:28:02enable elephants to stay cool in extreme heat.
0:28:07 > 0:28:11To find food and water in barren landscapes.
0:28:15 > 0:28:17TRUMPETING
0:28:17 > 0:28:22And to learn how to avoid their single greatest threat, humans.
0:28:27 > 0:28:29This has allowed them to become
0:28:29 > 0:28:33one of the great survivors of the natural world.
0:28:33 > 0:28:36And that is The Wonder of Elephants.