0:01:01 > 0:01:08Summer in Antarctica - and the seas around the outer islands are teeming with life.
0:01:17 > 0:01:23Fur-seals are streaming in their thousands to their traditional breeding beaches
0:01:23 > 0:01:26on the island of South Georgia.
0:01:33 > 0:01:38It's November and the race to breed has started.
0:01:38 > 0:01:45Some bull-seals have claimed territories on the beach and will defend them against all comers.
0:01:45 > 0:01:51You have to be fairly cautious how you approach... Now, now, now!
0:01:51 > 0:01:59..how you approach these big bulls because they've got very sharp teeth and can be extremely aggressive.
0:01:59 > 0:02:02At the moment, it's not too bad,
0:02:02 > 0:02:07but in two weeks, all the females will have come ashore too
0:02:07 > 0:02:12and there will be over 100,000 fur-seals on this one beach.
0:02:13 > 0:02:19Each dominant bull in this dense and seemingly structureless crowd
0:02:19 > 0:02:27rules over a territory of about thirty square metres which will accommodate about a dozen females.
0:02:27 > 0:02:34The frontiers between these territories are invisible to us, but very clear to the bulls.
0:02:34 > 0:02:41When neighbours meet face-to-face across a boundary, they put on a display of force,
0:02:41 > 0:02:47but they won't fight if each stays on his own side of the frontier.
0:02:47 > 0:02:52The heavily pregnant females arrive two or three weeks after the males
0:02:52 > 0:02:57and head for the prime territories near the high-water mark.
0:02:57 > 0:03:01Only if these are full will they go lower down.
0:03:01 > 0:03:08By December, over a million Antarctic fur-seals, 95% of the world's population,
0:03:08 > 0:03:11have landed here on South Georgia.
0:03:11 > 0:03:15One or two days after their arrival, the cows give birth.
0:03:17 > 0:03:26Each baby is greeted by a flock of hungry skuas, keen to feast on the afterbirth that comes with it.
0:03:44 > 0:03:52A mother will refuse to be parted from her vulnerable pup for the next seven days.
0:03:55 > 0:04:03The pups grow rapidly on the rich, fatty milk and double their weight in 60 days.
0:04:13 > 0:04:19It will be eight years before they have to fight for territory.
0:04:19 > 0:04:22This is just play.
0:04:28 > 0:04:36The bulls must now be on their guard, for the females are becoming sexually available
0:04:36 > 0:04:42and, offshore, males without territories are hanging around.
0:04:47 > 0:04:52They keep watch for a weakened bull or an abandoned territory
0:04:52 > 0:04:57and will dash ashore to claim it if they see a chance.
0:04:57 > 0:05:02Once they've got a territory, they can mate with its females.
0:05:02 > 0:05:07Lots of these young hopefuls wait in the shallows.
0:05:13 > 0:05:17One of them thinks he sees an opportunity.
0:05:41 > 0:05:45No luck. He's not big enough...yet.
0:06:09 > 0:06:16The urge to breed is so strong that there is always some youngster prepared to try his luck.
0:06:16 > 0:06:21Three or four times a day, there are major battles on the beach.
0:06:51 > 0:06:54These fights can be really damaging.
0:06:54 > 0:07:02Most territory-owning bulls carry severe wounds. Their flippers get split, their necks badly gouged.
0:07:14 > 0:07:19Mothers try to keep their pups out of harm's way.
0:07:21 > 0:07:24Another challenger concedes,
0:07:24 > 0:07:32but he's still in trouble for he'll have to dodge other outraged bulls on his way back to the sea.
0:07:32 > 0:07:39Although few are killed during these fights, many will die later from their wounds or from exhaustion.
0:07:51 > 0:07:58By Christmas, in the middle of the Antarctic summer, breeding is over, as are the battles on the beaches,
0:07:58 > 0:08:05but further south the race to breed, having started later, is still in full swing.
0:08:26 > 0:08:34Chinstrap penguins are returning from their feeding grounds 20 miles offshore to feed their chicks.
0:08:43 > 0:08:48Now, in midsummer, there is almost 24 hours of daylight.
0:08:48 > 0:08:53Here, on Deception Island, there is continuous traffic from the beach
0:08:53 > 0:08:59up a two-lane highway to the nesting sites high in the hills.
0:08:59 > 0:09:06Each day, 100,000 commuters make the trip. It's nature's greatest rush-hour.
0:09:22 > 0:09:26The trek takes the chinstraps over an hour.
0:09:26 > 0:09:33The first obstacles they must cross are the torrential streams pouring from a melting glacier.
0:09:59 > 0:10:04Chinstraps, like all penguins, are both tough and persistent.
0:10:04 > 0:10:09A rough-and-tumble in the white water doesn't deter them.
0:10:13 > 0:10:21Accomplished mountaineers, they have elected to nest high up on the steep exposed slopes of volcanic ash.
0:10:26 > 0:10:34The stiff quills of their tails provide support, preventing them from slipping backwards.
0:10:40 > 0:10:47Exposed ridges are the first suitable nesting grounds to be free of snow,
0:10:47 > 0:10:52and to make the best use of the short Antarctic breeding season,
0:10:52 > 0:10:56penguins will make immensely long climbs to reach them.
0:11:04 > 0:11:08There are over 200,000 birds on Deception Island,
0:11:08 > 0:11:15each pair with its own tiny nesting territory, evenly spaced from its neighbours.
0:11:15 > 0:11:18PENGUINS ARE IN FULL VOICE
0:11:22 > 0:11:25In spite of the din and confusion,
0:11:25 > 0:11:32returning birds are able to find their nest and partners without any difficulty.
0:11:32 > 0:11:37The reunion is always marked with a jubilant display.
0:11:49 > 0:11:52The parents will now swap duties.
0:11:52 > 0:11:57The one just arrived will feed the chicks and guard them,
0:11:57 > 0:12:02while the other, having fasted for a couple of days,
0:12:02 > 0:12:07will go down to the sea to feed and collect more food for the young.
0:12:17 > 0:12:22Those that are nesting on the lower slopes are lucky.
0:12:22 > 0:12:29Others have to climb so high that their nests are up in the clouds for much of the time.
0:12:39 > 0:12:47The trek down from the nest can take another hour, but it has to be done if the chick is to be fed.
0:12:50 > 0:12:57When at last they reach the sea, their journey that, so far, has been merely arduous
0:12:57 > 0:13:00becomes very dangerous indeed.
0:13:10 > 0:13:13A leopard-seal.
0:13:15 > 0:13:20A single leopard-seal may catch up to six penguins an hour.
0:13:20 > 0:13:24During the season, it will kill hundreds.
0:13:33 > 0:13:41A wounded bird, having escaped almost miraculously from the seal, must now face the merciless skuas.
0:13:51 > 0:13:57In spite of its injury, it still struggles upwards towards its nest.
0:14:21 > 0:14:28The chinstraps only nest on islands that are released by the sea-ice early in the season.
0:14:28 > 0:14:33As the summer advances, the ice continues to retreat
0:14:33 > 0:14:37until even the edge of the continent becomes free.
0:14:39 > 0:14:45By January, at the height of summer, there is almost continuous daylight
0:14:45 > 0:14:52and along the Antarctic peninsula temperatures regularly rise above freezing.
0:14:52 > 0:14:59Fjords that were locked in ice for the last eight months are now littered with ice-floes.
0:14:59 > 0:15:04Leopard-seals haul out to bask in the sun.
0:15:08 > 0:15:13Now, for a short time, Antarctica's wildlife can afford to relax.
0:16:33 > 0:16:41With temperatures climbing, snow and ice turns into Antarctica's most precious commodity - fresh water.
0:16:41 > 0:16:48And that makes it possible for the continent's sparse vegetation to resume its growth.
0:16:49 > 0:16:55Banks of moss are the home of a whole population of tiny animals.
0:16:58 > 0:17:06Deep within the crevices, ice still remains, imprisoning some of the hardiest creatures on earth -
0:17:06 > 0:17:11the only land animals that can survive the Antarctic winter.
0:17:11 > 0:17:18Barely larger than a pinhead, these tiny mites contain a natural antifreeze
0:17:18 > 0:17:23that allows them to supercool to minus thirty degrees centigrade.
0:17:38 > 0:17:42As the ice disappears, they come to life.
0:17:45 > 0:17:50These minute creatures have no fixed breeding season.
0:17:50 > 0:17:58They're opportunists and reproduce whenever temperatures creep above freezing.
0:17:58 > 0:18:01Often thousands cluster together.
0:18:01 > 0:18:05Most are herbivores that feed on the moss and dead vegetation,
0:18:05 > 0:18:10but they themselves are food for a few tiny carnivores.
0:18:10 > 0:18:16Hunters and hunted - this is Antarctica's own miniature Serengeti.
0:18:18 > 0:18:26In just a few places, there is enough melt-water to create freshwater ponds.
0:18:26 > 0:18:33They are havens for another range of invertebrates - little crustaceans and insect larvae.
0:18:51 > 0:18:56Green is a rare colour on the Antarctic continent,
0:18:56 > 0:19:01for moss can only grow where there is both freshwater and soil.
0:19:01 > 0:19:08But one kind of vegetation manages to survive on bare rock alone - lichens.
0:19:08 > 0:19:13They can dissolve rock and extract nutrients from it,
0:19:13 > 0:19:18but that takes a very long time, especially at these low temperatures.
0:19:18 > 0:19:23This miniscule forest may have taken centuries to reach this size.
0:19:27 > 0:19:32I am now 1,000 miles further south still.
0:19:32 > 0:19:36The south pole lies about 800 miles over there.
0:19:36 > 0:19:41If I was that distance from the north pole,
0:19:41 > 0:19:48I would expect to find among these rocks at least 100 species of flowering plants.
0:19:48 > 0:19:55In the whole of Antarctica, only two species of flowering plants have been found.
0:19:55 > 0:20:02Neither of them grows this far south. All that grows on these rocks are tiny lichens like this.
0:20:02 > 0:20:10One or two species of moss occur in these latitudes but, otherwise, only lichens grow farther south than this.
0:20:10 > 0:20:15Some of them get to within 200 miles of the pole.
0:20:17 > 0:20:22Antarctica's commonest organism is not a lichen but a plant - an alga.
0:20:22 > 0:20:28It lives in the snow and paints great areas of it bright pink.
0:20:29 > 0:20:35In summer, the melting snow releases the algae into the sea.
0:20:35 > 0:20:42Just offshore, icebergs moving back and forth with the tide are also disintegrating.
0:20:42 > 0:20:47All these changes release minerals and nutrients.
0:20:47 > 0:20:51Suddenly the inland waters become very rich,
0:20:51 > 0:20:56and floating algae - phytoplankton - bloom in vast clouds.
0:21:00 > 0:21:07Icebergs scouring the sea-floor make things difficult for life of any kind,
0:21:07 > 0:21:14but in sheltered areas and deeper water, there is a large and varied community of sea creatures.
0:21:26 > 0:21:31Life here, in temperatures close to freezing, is very slow.
0:21:31 > 0:21:36A sponge or starfish may live for over 40 years.
0:21:46 > 0:21:49There are fish here too.
0:21:49 > 0:21:55Blue-eyed shag dive down to depths of over 100 metres in search of them.
0:21:59 > 0:22:05The shags' feeding grounds are never far away from their colonies
0:22:05 > 0:22:09on the few rocky crags that are free of snow.
0:22:15 > 0:22:20Uniquely among Antarctic birds, their chicks hatch without down
0:22:20 > 0:22:25and at first rely totally on their parents for warmth.
0:22:38 > 0:22:45Many chicks may die if the summer storms are severe, but shags, like most Antarctic birds, are long-lived
0:22:45 > 0:22:50and a pair will produce many young during their lifetime.
0:22:50 > 0:22:57Blue-eyed shags don't nest along the southern part of the Antarctic peninsula
0:22:57 > 0:23:02because there is very little open water there.
0:23:02 > 0:23:04But one bird is not daunted by that.
0:23:04 > 0:23:11Antarctic terns patrol the bays in search of small crustaceans and fish.
0:23:11 > 0:23:19Their breeding season is long and even in the late summer, chicks are still hatching.
0:23:27 > 0:23:34In some years, bad weather and predatory skuas cause heavy losses of eggs and chicks,
0:23:34 > 0:23:41but Antarctic terns have the rare ability to lay two or three times in a season.
0:23:46 > 0:23:51Not until February, the very height of summer,
0:23:51 > 0:23:56does the winter sea-ice finally retreat to its minimum extent
0:23:56 > 0:24:01and release isolated outcrops of rock in the deep south.
0:24:03 > 0:24:10This is the Scullin Monolith, one of the few areas of bare rock for many miles.
0:24:10 > 0:24:15Here, 300,000 Antarctic petrels come to breed.
0:24:43 > 0:24:51Adelie penguin colonies that, in the spring, were cut off from the sea by miles of winter sea-ice
0:24:51 > 0:24:55are now directly accessible to open water.
0:24:55 > 0:25:02The adults, with hungry chicks to feed, can swim directly back to the beaches,
0:25:02 > 0:25:09although some, rather optimistically, decide to stop for a rest on the way.
0:25:36 > 0:25:43There is now constant activity on the beaches as both adults must collect food
0:25:43 > 0:25:48to satisfy the demands of their well-grown and ever-hungry chicks.
0:25:53 > 0:26:01Returning adults have to find their chicks amongst hundreds of others that wait patiently in creches.
0:26:01 > 0:26:06But a chick can instantly recognise the call of its parent.
0:26:06 > 0:26:13A mad steeplechase that can last several minutes helps to separate the rightful chick from imposters.
0:26:13 > 0:26:18The strongest chick of a pair is always fed first.
0:26:21 > 0:26:26In years when food is scarce, younger chicks are rarely fed
0:26:26 > 0:26:33and skuas are constantly on the look-out for such weakened birds.
0:26:39 > 0:26:44Repeated harrying from above sends panic through the colony.
0:26:51 > 0:26:59Many penguins are forced to regurgitate their meals and the skuas feast on the spilt krill.
0:27:02 > 0:27:09Small, unattended chicks that stray from the creche are quickly attacked.
0:27:30 > 0:27:38As the pressure to complete breeding increases, there is a constant battle between penguins and skuas.
0:27:43 > 0:27:46This time the chick is lucky.
0:27:47 > 0:27:52Attacks by skuas are very nasty and brutal,
0:27:52 > 0:27:56but they are not the main danger to the colony.
0:27:56 > 0:27:59Adelies choose windy nest sites.
0:27:59 > 0:28:05Breeding so early in the season, they rely on the wind to clear away the snow
0:28:05 > 0:28:13as they can only lay their eggs on bare rock, but now, at the end of the season, they pay the price.
0:28:13 > 0:28:18Soon the sea will freeze and autumn storms will cover the rock with snow.