"Every year, during Antarctica's short summer" "Adelie penguins perform a surprisingly athletic feat." "Despite their short legs, they go on a route march, or rather in a route wobble." "They're heading for their breeding grounds, where over 300,000 birds will cram together to raise their chicks." "Baby penguins make an easy snack." "So, these birds have made a special journey to be here, too." "But the good times don't last long." "After only a few weeks, the bad weather's back and the penguins must leave before winter closes in." "But down in the bay, a leopard seal waits for that special day." "The day when thousands of young penguins will jump over the edge and take their first ever swim." "All they've ever known is the safety of the massive crowd." "But from now on, it's every penguin for itself." "They each have to take their chances but perhaps some of these young penguins have more than just luck on their side." "At this moment the penguin's life hangs in the balance." "Can it do anything to determine its own fate or is that firmly in the grasp of the leopard seal ?" "To find out, we'll go back in time to see how the penguin's future depends on its past." "7 months earlier the penguin breeding colony is deserted." "Nothing survives mid-winter temperatures as low as -30 degrees centigrade." "It's so cold, that even the sea freezes creating a solid ice sheet, stretching for miles into the ocean." "At this time of year, the adult Adelies are a long way from land." "amongst the loose pack ice, way up to sea." "This remote and empty place is where they spend most of their lives." "Either resting on the ice flows or getting together in small groups, to feed." "And they're not alone" "Leopard seals also live here." "On ice, these killers aren't much of a threat but under water, in their element, they're the penguin's nightmare." "These seals spend the winter lurking under the ice flows stalking any penguins they can." "But in spring as the temperatures rise and the sea ice starts to melt it's a sign of better times ahead." "The leopard seals need do nothing, but wait." "The big penguin hunt of the season is only 5 months away." "The lengthening days are a cue for the Adelie penguins to change their way of life." "To live the ocean and begin a marathon journey." "They're going to march across the frozen sea, towards land." "They're heading for the place where they first hatched, to bring up their own chicks." "Being only one foot tall, they cannot see far, but they navigate by using the sound as their compass." "The weather is critical to the timing of their journey." "The parents that get it right, will be at a huge advantage." "Their chicks will flourish." "That's what drives them on tramping for days without food, living on their body fat." "The penguin parents only have a few months in summer to raise their chicks" "That's why they're rushing across the ice now, to reach the colony early so that their chicks have time to hatch and grow up before bad weather returns." "The skewers have traveled for thousands of miles timing their arrival to be in sync with the penguins." "The skewers will breed here, too and their success depends on a certain amount of pengui failure." "The penguin parents have a tough job ahead." "They've got less than 4 months to bring up their chicks and prepare them for that terrifying first swim." "Everything the adults do from now on could affect their chicks fate on that critical day." "But since eggs come before the chicks first the penguins need to pair up." "They often mate with previous partners, but if the one bird's late, the other won't wait." "The clock's ticking, and the most important thing is to hatch the chicks fast." "As more and more penguins arrive the best nest sites are quickly snapped up." "Small stones are used to build up nests, to keep the chicks dry, when the snow mounts." "High, wind-swept ground is the preferred location." "And it's good to steer clear of too many struggling neighbors picking fights by avoiding the center of the colony." "Forget the stressful inner city the suburbs are much better." "Being on time and getting the right nest can really benefit the chicks." "Being late, or building your nest in the wrong spot could spell disaster in a few months time." "Across the colony, chicks hatch in unison" "Timing is crucial" "They must be ready to leave at the same time, if they're going to survive." "So, does a fledgling's fate depend on its parents ?" "Was it destined to become a seal snack even before it hatched ?" "Adelie penguin chicks are born hungry." "Their parents spend their whole time rushing back and forth to the sea to hunt food for their demanding offspring." "By now, the sea ice is melted so it's a long swim to the feeding grounds, rather than a march." "In the first week or two, chicks still need an adult's body heat to keep them warm so the parents take turns to baby sit." "Not a simple job, as it sounds." "In the overcrowded colony, scuffles break out regularly" "During fights, a chick can easily get pushed out of the nest" "If it's less than 2 weeks old, it's parents won't recognize it so makes no effort to help it back into the warmth." "While dad's battling with the neighbors, mom's far away, hunting for food." "But sadly, now there's one less mouth to feed." "The skewers are here to scavenge." "They'll eagerly pick off small penguin chicks, dead or alive." "Because now they've got their own chicks to feed." "The skewers time their breeding to match the clot of easy prey." "But the plentiful food won't last long." "The parents must put in the effort now, if the chicks are going to thrive because the hunting, soon, gets harder." "Over the next few weeks, the penguin chicks will grow fast and quickly become too big for skewer to tackle." "Only six weeks of summer left." "Strange sounds echo around the ocean." "A leopard seal is using icebergs to amplify its calls." "Solitary by nature, leopard seals use this ice sound system to broadcast their desires." "It's a long distance lonely heart's caller." "Leopard seal seeks partner for brief commitment, and occasional penguin meals." "As it gets warmer, any remaining pack ice floats further out to sea." "And as the sun rises higher in the sky things start to change" "Something's about to happen, that both the penguins and the leopard seals have been waiting for." "The increased sunlight on the water fuels the growth of microscopic algae witch feed shrimp-like animals called krill" "They now grow rapidly, and with much of the ice gone, the krill can swarm in open water where the penguins can easily hunt them down." "So this is boom time" "Fine dining for the penguins, enough for themselves, and their chicks." "The Adelies work hard for their food" "On one lung full of air, they can dive for up to 3 minutes, to depths of 450 feet." "The dive repeatedly to fill their stomachs, and make sure they can bring back plenty for their chicks." "If they get back safely, that is." "A leopard seal is lurking." "It's here to eat krill, too, but fat little penguin would make a juicy addition to the menu." "After 3 weeks, the chicks have grown thick, fluffy plummage so they can be left alone, while both parents go off to hunt for food." "The chicks gather in a crèche they might have to wait days for a meal." "The skewers are on the lookout for any opportunity." "Now the penguin chicks are bigger, they're harder to catch." "But , if a chick is separated from the crèche it's an easier target" "The skewers can gang together, and have a better chance." "But at this age, a strong chick can hold its own." "A week later it's getting warmer." "Antarctic penguins have the densest plumage of any birds." "So the chicks suffer in the heat." "Some are really struggling." "These are the ones most at risk." "The skewers know a potential victim, when they see one." "But there's no need to rush." "This chick will only get hungrier and weaker when its parents are away." "Even if they make it back soon, it looks like the penguin parents won't see their chick alive again." "Now long now until these chicks face their first swim." "for witch they'll need a new set of water-proof feathers." "These grow under the old feathers, and push them out leaving strange tufts of fluff over bits of their body." "They'll soon be fully fledged divers but little do they realize how traumatic their first dip is going to be." "The parent penguins are heading back to the colony, stuffed full of krill." "But the sea is a dangerous place." "A leopard seal has blocked their way." "With perfectly streamlined bodies the penguins swim at high speed, with virtually no drag." "They make a bee line for the shore and slip safely onto dry land." "But it won't be long before the leopard seal has much easier prey to chase." "Now they face an uphill struggle up to the colony." "They're really bloated with food." "In the summer their elastic stomachs can swell to 5 times their winter size." "They each make this arduous journey more than 10 times every breeding season." "The chicks have been waiting calmly in the crèche." "But as soon as the parent returns, things change." "A frenzied chase begins, because the parents won't stand still." "This supposedly happens in families with 2 chicks and there are reasons for the run." "The parent is trying to find out witch chick is the hungriest and feed that one first." "And when the food is short, it's best to invest in the older, stronger chick." "Because that's the one that's likely to survive." "Will its place in the family affect the chances of a young penguin when it faces the leopard seal ?" "This moment is only days away." "A blizzard is a hint that summer's over." "The penguin's time on land is almost up." "The adults are restless, they know it's nearly time to go." "Any late hatching chicks, still not fledged would be in trouble." "As the temperatures drop even further, the sea begins to freeze." "The breeding colony is the only home these fledglings have ever know." "But they can't stay here." "It's time to head down, to the water's edge, and face their future." "With only a few hours until the penguin's mass exodus the leopard seal knows what's coming." "It gets into position, ready for the feeding feast to begin." "If the loose ice in the bay freezes solid the young penguins will be trapped." "But they're ready to go now" "Quite how they know the exact moment to go together, is a mystery." "It's not hunger that drives them because parents often feed their chicks just before they leave." "The mass departure is essential, because if the stay on land they'll die." "The only way out is across the bay running a gauntlet of a killer seal many times their size." "They teeter on the edge, waiting to see who will jump first." "Is it best to forge out in front, or hang at the back ?" "Instinct tells them to stick together so, after one takes the plunge, other quickly follow." "Their timing is critical." "The seal flings the body in the air and breaks its neck." "The hunter then carries its prey away from the shore to begin the bloody task of ripping flesh from bone." "It's trying to avoid contaminating it's hunting ground with gore to hide the horror from the next wave of penguins, and keep them coming." "The leopard seal can't be hungry but it still has an appetite for another kill, and another." "And another." "How many more penguins will die today ?" "For these chicks, there's no turning back now." "One has got separated from the crowd." "Has the seal noticed ?" "Perhaps it's taking a break." "But hunting fledglings here is easier that in the open ocean." "So the seal should carry on while the going's good." "So, what is this penguin's future ?" "Is its destiny just a lottery, or has it somehow sealed its own fate by the actions of its short life ?" "Its struggles are over." "It's free." "The leopard seal seems to have lost that killer instinct, for now." "So, why did this chick have such a close shave, and managed to survive ?" "Was it due to specific events in its short life ?" "Or perhaps because of what happened even before it hatched ?" "If its parents cross the ice at exactly the right time they would have found the best place to nest." "Central enough in the colony, to be well away from skewers but close enough to the edge, to make plenty of foraging trips, and fatten up the chick, fast." "If it was the biggest chick of two, it would have demanded the most food." "and quickly develop the strength needed for its later ordeal." "By timing it right, the parents hatch their chick in sync with the others." "So, it stayed safe, by joining the crèche." "And then fledged, in time to leave with the crowd, in their big exit day." "Perhaps the chicks only mistake, is to mistime its first swim." "It somehow got left behind the main group, and become an easy target." "But being late, also saved its life." "by letting other chicks go ahead, it unwittingly gave the leopard seal the chance to fill its stomach" "At this time of year, leopard seals can easily over eat hunting down 10 or 20 penguins in the morning." "After that, the young seals especially, begin playing with their food." "That was what happened with this chick." "It was lucky enough to be picked on by a leopard seal that wasn't even trying." "Most of the Adelie fledglings do get away safely to sea." "When so many penguins leave the colony at once leopard seals only catch a tiny fraction of the total." "For the next 9 months, the penguins will spread out amongst the pack ice of the Antarctic Ocean" "But every year, when summer comes they'll gather again in massive numbers back to face the huge challenge of another breeding season, all over again." "And the leopard seals are never far away."