0:00:27 > 0:00:30A three-ton hippo at 30km per hour...
0:00:31 > 0:00:34..the most dangerous animal in Africa.
0:00:37 > 0:00:41Hippos are full of surprises!
0:00:42 > 0:00:47Hippos spend most of their lives in water - but they can't actually swim.
0:00:56 > 0:01:00Behind that cuddly exterior lurks a mean streak.
0:01:03 > 0:01:08Hippo bulls are violently territorial - armed with foot-long tusks.
0:01:12 > 0:01:17For a hippo bull, success is measured in real estate.
0:01:17 > 0:01:19ANGRY GROWLING
0:01:19 > 0:01:24Life is a beach - but keeping it that way is no picnic.
0:01:33 > 0:01:36Hippopotamus means "river horse".
0:01:36 > 0:01:41The river is the one place hippos feel secure and confident.
0:01:41 > 0:01:46Although they breathe air, they look far more relaxed underwater,
0:01:46 > 0:01:51and can hold their breath for up to six minutes at a time.
0:01:51 > 0:01:55Their feet have nails, not hooves, and are partly webbed.
0:01:58 > 0:02:03Because they can't swim, hippos don't like being out of their depth.
0:02:03 > 0:02:07They prefer to keep their feet firmly on the bottom.
0:02:16 > 0:02:24But being a non-swimmer isn't the disadvantage it seems. Hippos are virtually weightless underwater.
0:02:24 > 0:02:31It's easier to use a kind of space-walk than to swim against the current.
0:02:33 > 0:02:38The big shock is how fast these beach boys move on land.
0:02:38 > 0:02:40They're not distance runners,
0:02:40 > 0:02:45but they can cut quite a dash in the hundred metres.
0:02:51 > 0:02:58As a hippo submerges, special valves automatically seal its ears and nostrils.
0:02:58 > 0:03:02But that doesn't stop it hearing or communicating underwater.
0:03:02 > 0:03:11Buzzy, clicky sounds are made inside the hippo's closed-off airways - they sound like the dolphins' clicks,
0:03:11 > 0:03:14and that's no coincidence.
0:03:14 > 0:03:21Recent research shows hippos are related to dolphins and whales and share a common ancestor.
0:03:46 > 0:03:50Unlike their dolphin relatives, hippos don't eat fish.
0:03:50 > 0:03:54In fact, it's more the other way around.
0:03:54 > 0:03:58Even the very young are mobbed by dung-feeders.
0:04:08 > 0:04:13Other scroungers hoover up dead skin cells from the hippo's hide
0:04:13 > 0:04:16or pick food from its fearsome teeth.
0:04:29 > 0:04:32Hippos live in many parts of Africa.
0:04:32 > 0:04:39This is one of their most popular stamping grounds - the Luangwa River in Zambia.
0:04:40 > 0:04:48Meandering waterways and sandy beaches provide an ideal home for several hundred hippo groups or pods.
0:04:53 > 0:04:57This is the Beachmaster - a 3-ton bull in his prime.
0:04:57 > 0:05:02He's ruled his stretch of beach and river for several years.
0:05:04 > 0:05:08His empire may be just a few hundred metres,
0:05:08 > 0:05:11but he's master of all he surveys.
0:05:17 > 0:05:21Right now, his pod includes around 40 other hippos,
0:05:21 > 0:05:24all of whom must dance to his tune.
0:05:28 > 0:05:33Females are always welcome, but so are other males,
0:05:33 > 0:05:35provided they know their place.
0:05:35 > 0:05:40The Beachmaster is an absolute dictator
0:05:40 > 0:05:45and an early morning show of sabre-rattling helps preserve the status quo.
0:06:02 > 0:06:08But the latest tenant has the cheek to answer back. He hasn't yet learnt the house rules.
0:06:08 > 0:06:12The boss will have to bring him down a peg or two.
0:06:37 > 0:06:42Job done! The Beachmaster has made his point.
0:06:48 > 0:06:53It's the end of the rainy season, and the river is running high.
0:06:53 > 0:06:56Several females on Hippo Beach have given birth.
0:07:08 > 0:07:12Luckily, the baby's quite at home underwater.
0:07:14 > 0:07:19It's normal for a dad to be curious about his offspring,
0:07:19 > 0:07:23but stepping on a new mother's toes is foolhardy.
0:07:30 > 0:07:35Females are fearless in defending their young.
0:07:35 > 0:07:40The Beachmaster may lord it over the boys, but not her!
0:07:58 > 0:08:03There has to be room in this river for bulls...
0:08:03 > 0:08:05AND for babies.
0:08:12 > 0:08:17At this time of year, there should be plenty of space for everyone.
0:08:17 > 0:08:22The Luangwa floodplain is awash from the rains, creating peaceful lagoons.
0:08:23 > 0:08:28The hippos spread out wherever the water is deep enough to cover them.
0:08:33 > 0:08:39Females in particular prefer these tranquil backwaters
0:08:39 > 0:08:42to life in the river's fast lane.
0:08:47 > 0:08:52Because there's no current, it's a safer playground for the babies -
0:08:52 > 0:08:54and easier to keep an eye on them.
0:08:59 > 0:09:05Though the lagoon is full of crocodiles, they tend to give hippos a wide berth.
0:09:05 > 0:09:12The babies may look tempting, but the crocs don't want to tangle with their formidable mothers.
0:09:14 > 0:09:18As usual, the biggest danger comes from sparring males.
0:09:19 > 0:09:24They don't attack babies deliberately but the youngsters can get caught in the crossfire.
0:09:41 > 0:09:46A boundary dispute like this may last for a couple of days.
0:09:52 > 0:09:57This mother and baby are caught between crocs on the bank
0:09:57 > 0:09:59and belligerent bulls in the water.
0:10:03 > 0:10:09But the infant is just a few hours old, and still too weak to walk.
0:10:18 > 0:10:22Out of water, the baby could easily overheat.
0:10:23 > 0:10:26AND it attracts too much attention.
0:10:34 > 0:10:39So far, no-one wants to mess with mother. But she's not invincible.
0:10:47 > 0:10:51All she can do is wait until the baby is mobile.
0:11:18 > 0:11:22A few hours later, the youngster is able to walk,
0:11:22 > 0:11:26and can be shepherded to a quieter spot.
0:11:30 > 0:11:33After the rains, the grass is lush -
0:11:33 > 0:11:38a time of plenty for all Luangwa's inhabitants - including the baboons.
0:11:45 > 0:11:51While there's grass in the swamp, the hippos can eat all day without overheating.
0:12:02 > 0:12:07A hippo plucks vegetation with enormous muscular lips
0:12:07 > 0:12:10and grinds it with cow-like teeth.
0:12:10 > 0:12:15It also digests its food like a cow, in a four-chambered stomach
0:12:15 > 0:12:20where grass is fermented gradually to extract the maximum nutrition.
0:12:20 > 0:12:25It can put away 50 kilos of fodder at a sitting.
0:12:25 > 0:12:30But this bean-feast doesn't last long.
0:12:31 > 0:12:37Within weeks of the last rain, some lagoons are already drying out.
0:12:51 > 0:12:57By now, most of the hippos are long gone back to the main river.
0:12:57 > 0:13:00Only the ruling bulls remain.
0:13:06 > 0:13:11For the yellow-billed storks, however, less water means more food
0:13:11 > 0:13:15as they dredge the slime for trapped fish.
0:13:23 > 0:13:28Mud may be glorious, but it's no substitute for water.
0:13:31 > 0:13:36For a bull, territory is next to life itself, and hard to give up,
0:13:37 > 0:13:40even when it has turned to porridge.
0:13:40 > 0:13:45But as the dry season bites, the only alternative
0:13:45 > 0:13:48is to leave or be baked alive.
0:13:49 > 0:13:52The exit begins.
0:14:07 > 0:14:12In the withered grasslands, flocks of quelea are also on the move.
0:14:12 > 0:14:17Over the next few weeks, their numbers will swell to plague proportions,
0:14:17 > 0:14:20as the dry season tightens its grip.
0:14:56 > 0:15:03By now, the Luangwa river has shrunk to a shallow channel among the white sands of Hippo Beach.
0:15:09 > 0:15:14As more and more bulls are forced back to the river,
0:15:14 > 0:15:18each new arrival is checked out by the Beachmaster.
0:15:18 > 0:15:22He knows that first impressions are everything,
0:15:22 > 0:15:24and he's got to make his count.
0:15:29 > 0:15:35Some of the incomers are powerful specimens, used to running their own show.
0:15:35 > 0:15:38Each one must be faced down from the start.
0:15:41 > 0:15:43But this male seems unfazed.
0:15:43 > 0:15:47Perhaps he fancies his chances against the boss.
0:15:55 > 0:15:59The two bulls square up in a ritual confrontation,
0:15:59 > 0:16:04both spinning their tails to shower each other with water and dung.
0:16:18 > 0:16:24But if the challenger doesn't back down, the Beachmaster will have to put his money where his mouth is.
0:16:36 > 0:16:39The boss may have met his match.
0:16:39 > 0:16:42But the new guy celebrates too soon.
0:17:15 > 0:17:21The stab wounds inflicted during these clashes don't normally result in death,
0:17:21 > 0:17:25but if enough blood is shed, it's always a possibility.
0:17:25 > 0:17:29This time, order is restored - the newcomer retreats.
0:17:37 > 0:17:44Females don't have the same obsession with social standing. Their priority is to run the nursery.
0:17:54 > 0:18:00This stretch of river is ideal for babies, with water deep enough to offer shelter,
0:18:00 > 0:18:05and a gently-sloping, family-friendly beach.
0:18:08 > 0:18:11In parts of Africa and ancient Greece,
0:18:11 > 0:18:17hippo goddesses were thought to protect human babies and pregnant women.
0:18:49 > 0:18:53Young hippos have a longer childhood than most mammals.
0:18:56 > 0:19:01It's six or seven years before they reach sexual maturity
0:19:01 > 0:19:03and this turns into...
0:19:03 > 0:19:05this.
0:19:19 > 0:19:23Even as adults, hippos have plenty of leisure time.
0:19:24 > 0:19:30Every few days, they haul out of the water and into the sun. The warmth aids digestion.
0:19:34 > 0:19:39But they usually wait for the big boss to make the first move.
0:19:43 > 0:19:48Fresh from his recent triumph, the veteran's street cred is intact.
0:19:51 > 0:19:55If he's lucky, he could stay in power for a decade or more.
0:19:55 > 0:19:59He's an impressive sight, and he knows it!
0:20:04 > 0:20:08As soon as the boss has shown the way,
0:20:08 > 0:20:12the rest of the hippos set off up the beach -
0:20:12 > 0:20:18the bulls in a strict pecking order according to size and rank.
0:20:20 > 0:20:25Once ashore, there are other customs to observe.
0:20:29 > 0:20:34Muck-spreading is the hippo equivalent of presenting your business card.
0:20:34 > 0:20:38Bulls recognise each other mostly by smell,
0:20:38 > 0:20:44and pick up subtle signals about each other's place in the hierarchy.
0:20:44 > 0:20:47Hippos are sticklers for etiquette
0:20:47 > 0:20:51and it isn't until the Beachmaster has parked his chin,
0:20:51 > 0:20:56that everyone else seems able to fully relax.
0:21:17 > 0:21:22Once the sunbathers are settled, they attract various hangers-on.
0:21:22 > 0:21:26Red-billed oxpeckers dine on skin parasites.
0:21:31 > 0:21:33And other beachcombers home in too.
0:21:34 > 0:21:37Baboons.
0:21:44 > 0:21:49They've come to collect a few of the hippos' business cards.
0:21:55 > 0:22:01Hippo or elephant dung is a treasure trove of seeds and insects -
0:22:01 > 0:22:03always worth a rummage.
0:22:08 > 0:22:13Guinea fowl come to the beach to sand bathe and squabble.
0:22:22 > 0:22:26But their rowdy behaviour can cause trouble.
0:22:27 > 0:22:30Hippos aren't as brave as they look.
0:23:11 > 0:23:17Back in their element, the panic subsides. The hippos feel safe again.
0:23:26 > 0:23:30But Hippo Beach doesn't just belong to the hippos.
0:23:30 > 0:23:34Carmine bee-eaters fly in from further south to breed.
0:23:34 > 0:23:36Elephants come to drink and bathe.
0:23:44 > 0:23:48The bee eaters lay their eggs in holes in the riverbank.
0:23:48 > 0:23:55High-rise nests are packed tightly together in a commune used for generations.
0:23:55 > 0:23:58The hippos don't bother the birds.
0:24:05 > 0:24:08But other locals do.
0:24:10 > 0:24:16The monitor lizard is an expert climber and isn't put off by being outnumbered.
0:24:30 > 0:24:35He's got a nose for which holes contain eggs or chicks
0:24:35 > 0:24:40and there's little the frantic parents can do to stop him.
0:24:58 > 0:25:05Further down the beach, an African fish-eagle spots the commotion caused by the lizard's attack.
0:25:09 > 0:25:12It's too good a chance to miss.
0:25:35 > 0:25:42It seems the fish eagle doesn't live on fish alone. Safety in numbers has its limits.
0:25:50 > 0:25:54That's one more vacancy at Bee-eater Towers!
0:26:12 > 0:26:17The head of Hippo Beach is feeling under pressure too.
0:26:18 > 0:26:24On the run from a fight upstream, this bull is still testosterone-charged.
0:26:27 > 0:26:33Again the Beachmaster is forced to rise to the challenge.
0:26:37 > 0:26:42Maybe this chap's bitten off more than he can chew.
0:26:48 > 0:26:53When it comes to the crunch, he's all talk and no trousers!
0:26:59 > 0:27:03For a lone bull, finding a home isn't easy.
0:27:12 > 0:27:16In the dry season, food can be hard to find too.
0:27:16 > 0:27:20But now the sausage trees are flowering.
0:27:23 > 0:27:28Birds aren't the only nectar drinkers. Baboons like it too.
0:27:31 > 0:27:37The sausage tree is one of the most common along the Luangwa river - and one of the most popular.
0:27:37 > 0:27:40The flowers develop into tasty fruit...
0:27:43 > 0:27:46..for anyone who can reach them!
0:27:50 > 0:27:56By now, last year's sausages have become giant salami two feet long and ten pounds in weight.
0:28:00 > 0:28:05These monsters are too much of a mouthful for a giraffe.
0:28:05 > 0:28:07But the night is young.
0:28:39 > 0:28:46Night on Hippo Beach - and there's a rush of activity. Well...a sluggish ramble, anyway.
0:28:46 > 0:28:51Most of the herd is heading away from the beach to seek out food.
0:29:08 > 0:29:11And tonight's special is...
0:29:11 > 0:29:13sausages.
0:29:16 > 0:29:23This is the gastronomic highlight of a hippo's year. A moment to be savoured, not rushed.
0:29:25 > 0:29:31As the sausages tumble from the trees, the hippos sniff them out one by one.
0:29:57 > 0:30:02The relationship between sausage tree and hippo isn't all one way.
0:30:03 > 0:30:05First, the sausage feeds the hippo.
0:30:05 > 0:30:09And in return, the hippo distributes its seeds.
0:30:16 > 0:30:20But hippos can't live on sausages alone.
0:30:20 > 0:30:23They need bangers AND grass.
0:30:26 > 0:30:33Well-worn trails, flattened by generations of hippo feet, lead to the traditional grazing areas.
0:30:35 > 0:30:39As drought kicks in, reaching the remaining grass
0:30:39 > 0:30:44may mean a 10km round trip, over dangerous ground.
0:30:51 > 0:30:56Most of the hippos make it safely back to Hippo Beach,
0:30:56 > 0:31:00but every so often there's bound to be a casualty.
0:31:06 > 0:31:10A dead hippo in the river attracts a crowd of mourners...
0:31:13 > 0:31:15..and the resident crocs.
0:31:18 > 0:31:25The hippos sniff and lick the carcass in what seems to be a kind of last rites.
0:31:37 > 0:31:40The crocs have a different agenda.
0:31:45 > 0:31:49And here's another opportunist, the hyena.
0:31:54 > 0:31:59But the hippos seem keen to chase it away.
0:32:04 > 0:32:07As the scavengers gather, however,
0:32:07 > 0:32:10there's nothing the hippos can do.
0:33:08 > 0:33:11Next morning, the feast continues,
0:33:11 > 0:33:15but this grisly spectacle serves an important purpose.
0:33:17 > 0:33:23The crocs help keep the river clean and healthy for all its inhabitants.
0:33:23 > 0:33:27By tidying up the dead, they protect the living.
0:33:27 > 0:33:30Including the Beachmaster.
0:33:30 > 0:33:36Once again, he leads the way out of the water and the social shuffle begins.
0:34:10 > 0:34:15Sunbathing may aid digestion, but there is a catch.
0:34:15 > 0:34:17Hippos have very sensitive skin.
0:34:18 > 0:34:23But they have evolved a special form of sun protection.
0:34:23 > 0:34:30Modified sweat glands round the face and other burn-points produce a thick pink substance like nail varnish.
0:34:33 > 0:34:38Gradually, the beach bums turn bright pink. But it isn't sunburn...
0:34:40 > 0:34:43..it's sunscreen.
0:34:50 > 0:34:54By the end of the day, they're done to a turn.
0:34:55 > 0:35:00Time to follow the beachmaster back to the river.
0:35:19 > 0:35:22In the cool of the evening,
0:35:22 > 0:35:25quelea come by to drink,
0:35:25 > 0:35:29each bird hopping politely forward to take its turn.
0:35:37 > 0:35:39Buffalo head for the water too.
0:35:39 > 0:35:43After a day in temperatures of 40 degrees Celsius or more,
0:35:43 > 0:35:45they're parched.
0:35:46 > 0:35:49But there's a welcome committee.
0:36:01 > 0:36:03Round here, the price of a drink can be high.
0:36:09 > 0:36:12It's best to swig and run.
0:36:16 > 0:36:19Danger is often hard to see,
0:36:19 > 0:36:23so no-one can afford to drop their guard.
0:36:33 > 0:36:38But thirst can be a killer too, so it's a calculated risk.
0:36:45 > 0:36:48With crocodiles on the prowl,
0:36:49 > 0:36:51everyone's on edge.
0:36:51 > 0:36:54Only the hippos can afford to relax.
0:37:21 > 0:37:25You need to have eyes in the back of your head.
0:37:25 > 0:37:28Lions hang out at the beach club too.
0:37:38 > 0:37:43This seems a dicey moment for the Beachmaster to leave the safety of the water...
0:37:45 > 0:37:50..but another disturbance has caught his eye.
0:38:17 > 0:38:21The Beachmaster's goal - a dead buffalo.
0:38:36 > 0:38:42Hippos rarely eat meat, but every so often they're tempted to steal from the lions' larder.
0:39:07 > 0:39:16Territorial bulls can be so busy warding off contenders, they have no time to forage properly at night.
0:39:20 > 0:39:25Maybe simple hunger drove the Beachmaster to brave the lions.
0:39:35 > 0:39:39The boss is safely back in the bosom of his pod,
0:39:39 > 0:39:43but as the sun goes down on Hippo Beach,
0:39:43 > 0:39:48his neighbours get restless. Something is spooking them.
0:39:55 > 0:40:00Hyenas are back, drawn by the smell of carrion...
0:40:02 > 0:40:04..another dead hippo.
0:40:28 > 0:40:32Once again, the hippos appear to be trying to ward them off.
0:40:32 > 0:40:36They don't seem to want to let the body go.
0:40:37 > 0:40:41The carcass has become a bone of contention.
0:40:41 > 0:40:45but why the hippos are so flustered is a mystery.
0:41:28 > 0:41:34After several hours of this peculiar stand-off, the hippos concede and are driven back into the water.
0:41:48 > 0:41:51The hyenas have the last laugh.
0:42:33 > 0:42:36By October, the height of the dry season,
0:42:36 > 0:42:39Hippo Beach looks more like a can of sardines.
0:42:41 > 0:42:47It's one of the few bits of river still deep enough for hippos to submerge,
0:42:47 > 0:42:51and there are now around 800 animals living cheek-by-jowl.
0:43:01 > 0:43:06The Beachmaster struggles to keep a lid on things.
0:43:46 > 0:43:52One troublemaker just won't let it drop. He's cruising for a bruising.
0:44:36 > 0:44:41Ears cocked, head high, the boss bull is a terrifying sight.
0:44:42 > 0:44:45But is his rival convinced?
0:44:53 > 0:44:57Maybe the Beachmaster's days are numbered.
0:45:13 > 0:45:19But now the opponent's on the run again, and on dry land there's nowhere to hide.
0:45:20 > 0:45:25As the other bulls settle back in their seats,
0:45:25 > 0:45:29the Beachmaster prepares for round two.
0:45:35 > 0:45:43The contenders square up for a real showdown, dribbling with anticipation at the front,
0:45:43 > 0:45:46and more dung flying from the back.
0:46:09 > 0:46:12The new boy makes the first move.
0:46:12 > 0:46:16But he keeps his head down and doesn't look too confident.
0:46:23 > 0:46:29The Beachmaster holds his ground. It's time to show that no-one kicks sand in HIS face!
0:47:04 > 0:47:07A victor emerges.
0:47:07 > 0:47:10The Beachmaster has won the day.
0:47:23 > 0:47:28It's time for the Beachmaster to claim the perks of his position -
0:47:28 > 0:47:31first pick of the hundreds of females.
0:47:34 > 0:47:36This river horse is riding high!
0:47:44 > 0:47:47He's made it through another year
0:47:47 > 0:47:51and now he'll get the chance to father many more babies.
0:47:54 > 0:47:57This is still his place in the sun -
0:47:57 > 0:48:00he's the master...
0:48:00 > 0:48:02of Hippo Beach!
0:48:39 > 0:48:43Subtitles by Anne Morgan BBC Scotland 2001
0:48:43 > 0:48:46E-mail us at subtitling@bbc.co.uk