"DAVID TENNANT:" "The islands of Svalbard in Arctic Norway are home to around 3,000 polar bears." "(MECHANICAL WHIRRING)" "In the last programme, we saw how spy cameras were keeping them under surveillance." "Snow-cam moves over both ice and land using four-wheel drive and tundra wheels." "Blizzard-cam travels at up to 60 kilometres an hour powered by propellers." "(WHIRRING)" "Snowball-cam moves with no visible moving parts and its lens has a self-righting mechanism to film the bears." "(GROWLING)" "Last time, the spy cameras captured the first few moments as a mother left her den, followed by her new cub." "The mother created her own home movie." "There was not a single person around." "And the bears proved obliging subjects, showing us their lives in intimate detail." "Drift-cam caught a second family as it emerged from the dens." "This time, a mother with two cubs." "The families embarked on two very different adventures." "A roaming male forced the mother with one cub" "to stay on higher ground." "(CUB SQUEALING)" "But the two-cub family reached the frozen sea where the mother could hunt for seals." "The two families became separated as the ice broke up in the spring." "The mother with one cub was marooned on the island with no seals to eat, while iceberg-cam followed the fate of the other family." "They stayed with the retreating ice and spent the summer swimming between the ice floes, following seals." "The landlocked mother scavenged what she could." "She even ate seaweed to fend off hunger pangs while her cub practised his hunting skills." "A tern colony offered the chance of protein but the birds put up an effective defence." "In contrast, the family on the ice were in bear heaven." "As the bears hunted, they showed their intelligence, creating a new plan for every hunt and taking their prey by surprise." "But the intelligence that helped the bears gain a meal was also a challenge for the spy cameras." "Other landlocked bears received a welcome feast when a dead whale washed ashore." "(GROWLING)" "But, elsewhere, the mother and cub struggled to survive." "On the ice, the cubs grew to twice the size of the cub on land." "But scavenging for food had its dangers." "The owner returned to reclaim the carcass." "When we last saw the family, they faced a choice." "To run and risk provoking a reaction, or to stand their ground." "It's a difficult decision for the mother." "The returning male sizes up his uninvited guests." "Standing her ground is a show of strength." "But, still, the male muscles in." "The cubs await their mother's next move." "It's a showdown." "She stands to make herself look bigger." "The cub copies." "But the male won't back off." "Having shown she can't be intimidated, the mother guides her cubs to safety." "And the male regains his meal without a fight." "She takes her cubs north, to where the firmest ice can be found." "Back on Svalbard, it's high summer." "Barnacle geese, that had overwintered in Scotland, have started to breed." "Their calls bring hope to hungry bears." "(GEESE HONKING)" "The cub stays back as his mother explores the possibilities." "Bears have only recently discovered this new source of food, seeking out colonies that nest on the ground rather than on cliffs." "The eggs are a rich source of protein." "Just 250 are as nutritious as one ringed seal." "She carefully picks up an egg in her jaws before swallowing its contents." "But the geese launch an attack." "(HONKING)" "Some have goslings, a bite-sized snack for a bear." "(CRUNCHING)" "In just one day, one bear can devour over 1 ,000 eggs and hatchlings, destroying a whole colony." "But as the threat escalates, so does the defence." "(GEESE CALLING)" "Arctic skuas join the attack." "(CHIRPING)" "A skua lands a direct hit." "She's had enough." "In future, the birds will have to start nesting on cliffs to avoid polar bear attacks." "Skuas may have saved the colony, but they have left the bear still hungry." "Meanwhile, iceberg-cam has found the mother with two cubs." "The family take a break." "Swimming between ice floes is exhausting for the cubs." "(WHIRRING)" "(WHIRRING)" "But she also needs food to fuel their journey." "(GRUNTING)" "Bearded seals, just what they need right now." "Hunting with two cubs in tow is a challenge." "She must work out her best strategy." "Her quarry is close." "She signals the cubs to stay behind." "They are quite a liability for a hunting bear." "They must stay quiet." "But kids will be kids." "(SQUEALING)" "She climbs in backwards, a smart move that avoids making a splash." "This is clever stuff, few bears do this." "Polar bears rarely hunt more than 300 metres away from their cubs." "The seal is at the limit of her range." "As she gets further away, the cubs get restless." "Her stealth is extraordinary." "She flattens her ears to lower her profile as she sizes up her target." "She can surprise the seal by swimming underwater." "She dives." "But the cubs are nervous." "They don't like losing sight of her, and she has a long way to go." "And this isn't helping one little bit." "(GRUNTING)" "Their mother emerges exactly where the seal was sitting." "She seems surprised that it's gone." "This is one lesson that hasn't gone well." "Back on land, glaciers are the only places where bears can still hunt." "It's a natural home for iceberg-cam." "Glacial fjords provide enough ice to attract their favourite prey," "a harp seal." "And where there are seals, there are bears." "Glacial fjords are no substitute for sea ice." "But polar bears find any ice irresistible." "For those trapped on the island, it's as if they are seeking what they have been denied." "But then iceberg-cam spots some familiar figures." "This is not a safe place to be." "The glacier is crisscrossed with ravines, and the leading edge is unstable." "It's too dangerous for the mother and cub to stay." "Out on the sea ice, iceberg-cam negotiates its way around the ice floes." "It often takes days to spot a bear in this ever-changing ice world." "(WHIRRING)" "The vastness of the sea ice can be a lonely place for a bear." "He drinks from pools of melted ice, the only source of fresh water available." "He's picked up a scent." "Another male bear is on the prowl." "In spring, this could provoke a fight, but the bears are now out of the breeding season." "Polar bears are usually thought of as solitary." "They space out across the ice, travelling further than any other land predator, as they follow their prey." "They rarely meet." "But when they have the chance, they make the most of every social opportunity." "And two polar bears can soon become three." "(GRUNTING)" "Despite the distance they travel, they enjoy close friendships and can recognise individuals even after many years." "(GRUNTING)" "Back on Svalbard, the snow's disappearance makes life easier for the reindeer." "But as they tuck into the summer growth of lichen, they need to stay alert." "Polar bears eat reindeer, a fact that makes them understandably nervous." "But this mother must choose her battles wisely." "Reindeer are fast and difficult to catch." "She must conserve her energy and avoid pointless pursuits." "As the bears move up the coast, snow-cam gets ready for action." "But the first bear it finds is an inquisitive young male." "Like so many bears, he finds the spy-cams intriguing." "(WHIRRING)" "(WHIRRING)" "He subjects it to a pressure test, using a technique that works well on seal dens." "Snow-cam is supposed to be indestructible but it's buckling under the pressure." "Snow-cam films its last." "(RATTLING)" "Back on the sea ice, drift-cam takes over filming duties." "The male from the previous gathering is polishing off a bearded seal." "His friends haven't gone far." "(WHIRRING)" "They've shared a meal and have the face paint to prove it." "(GROWLING)" "There is a feeding etiquette around a seal carcass." "Bears that approach correctly are often allowed to share, particularly friends." "As ever, the spy-cams are proving a huge hit." "(SNIFFING)" "With the drift-cams out of action, it's time for reinforcements." "Blizzard-cam returns to frontline duties and deploys backup." "Snowball-cam's arrival fascinates the curious bears, particularly as the steep slope gives it momentum." "(GRUNTING)" "He tries some fancy footwork." "More bears join the team." "(WHIRRING)" "Time for kick-off." "It's polar bear football." "Their ball control needs practice, but they are experts at dribbling." "(GROWLING)" "But the game descends into argument." "They might deserve a red card, but it's just another game." "They're honing their fighting skills for when they really need it." "(GROWLING)" "By sparring, they test each other's strengths and weaknesses." "(GROWLING)" "These training bouts will help them judge their opponents when fighting over females." "(GROWLING)" "A real fight can result in serious injuries and, sometimes, death." "Even play-fighting can get quite heated." "But the bears avoid biting too hard." "(GROWLING)" "But snowball-cam is in the thick of it, as over a tonne of polar bear collide." "(CLATTERING)" "(WHIRRING)" "Snowball-cam returns to the benches." "The bears might be play-fighting, but it's safest to stay out of the ring." "(GROWLING)" "(SQUAWKING)" "On Svalbard, a kittiwake colony brings hope to the hungry mother and cub." "The nests are out of reach, but there is still food to be had." "She does some rock climbing." "A challenge for the cub, he sits this one out." "She is after grass." "Grass flourishes wherever bird droppings provide fertiliser." "But the cub is not so keen." "It provides little real nourishment, but it helps stop hunger pangs." "These are really emergency rations." "If the bears are to survive, they will need protein." "Grazing grass is a hangover from their evolutionary past." "Polar bears evolved from the more omnivorous brown bear only 1 50,000 years ago." "This polar bear has been naturally colour-matched to his nearest relative and shows the physical similarity that still exists between the two species." "(GROWLING)" "He received his makeover lolling around in the muddy debris left by glaciers." "His ancestors exploited the polar north by becoming more carnivorous and aquatic." "They became more curious and intelligent, too." "(SNIFFING)" "They also had to protect themselves from the cold, a fact that creates problems in the Arctic summer when temperatures rise to a sizzling 6°." "Polar bear coats consist of hollow hairs to provide perfect insulation." "They also have an inner lining made of dense under-fur." "Beneath all this, is a 20-centimetre layer of blubber." "As a result, they can suffer heat exhaustion at temperatures that elsewhere would be considered chilly." "He mostly loses heat through his footpads, belly, and nose." "He carefully submerges all three." "Summer bears have a lot of time to kill." "And, with little to eat, they need to conserve energy." "They react by doing very little." "They become experts at just chilling out." "Out on the sea ice, the temperature hovers just above freezing, but it's enough to start a melt." "The ice is breaking beneath his feet." "(GRUNTS)" "Even though polar bears can cope with the cold, theyjust hate falling through the ice." "They pick their way very carefully indeed." "He's tracking bearded seals, an ambitious quarry." "She has battle scars from a previous bear encounter." "It won't be easy." "The bear has two to choose from." "The odds are good." "But he's treading on thin ice." "He spreads his legs to distribute his weight, and progresses carefully." "(GRUNTING)" "But it's not enough." "For a hunting bear, it doesn't get much worse than this." "The seal could hardly fail to notice." "But this battle-hardened seal is in no rush." "(GRUNTING)" "Finally, he gains some purchase." "He's back in the game." "He still believes he's in with a chance." "He can charge at 40 kilometres an hour." "But bears usually wait until they're 30 metres away." "This one started at 300." "She has all the time in the world to escape." "The bear must have been unnerved by his unscheduled dunking to put on such an amateur performance." "The disappearing ice is also troubling the family." "The ice is now so thin, it only supports the weight of the lighter cubs, leaving the mother struggling." "(GRUNTING)" "(GROWLING)" "These are dangerous times." "Negotiating thin ice can quickly lead to exhaustion." "This is a sign that the mother must head north to the more permanent ice cap as quickly as possible." "But a combination of wind and current destroys her best-laid plan." "A sudden swell turns ice into open ocean." "The cubs are too young to swim long distances safely." "(GRUNTING)" "(SQUEALING)" "But going back is not an option." "The cubs' only hope is to keep up." "They paddle for their lives, staying as close to Mum as possible." "She can swim 80 kilometres or more, but the cubs will soon be struggling." "(WINDS HOWLING)" "On the island, months of having to make do are taking their toll." "The cub is half the size of those on the ice." "(GRUNTING)" "A colony of walrus blocks their path." "Just one would make a substantial meal." "(SNORTING)" "But walrus can weigh a tonne and a half, and their tusks can reach a metre in length." "(GRUNTING)" "Hardly a pushover." "Her only hope is to find one that is weak or injured." "She assesses the colony." "With a cub to provide for, she can't take risks." "She provokes the walrus to test their reactions." "(GRUNTING)" "(GROWLING)" "All are healthy." "She won't take the gamble." "But all is not lost." "She has caught a new scent." "The cubs are in trouble." "They are exhausted." "The male cub rests his head on his sister." "They crowd into the mother's slipstream, trying to gain any advantage." "At last, there is hope." "They have finally reached the pack ice that forms the polar ice cap." "It's the ultimate hunting habitat for polar bears." "The ice cap stretches all the way to the North Pole." "Seals are found wherever it meets the sea." "It's been a long journey." "They are 1 60 kilometres from Svalbard and 250 kilometres from the den sites where they were born." "For now, she can relax, having fulfilled her mission." "It's the perfect spot to spend the few months left of summer." "Guided by her sense of smell, the mother discovers what's left of the stranded whale." "But it looks like the remains have been stripped clean by bears." "The massive backbones says it all." "There's not a scrap to be found." "(GRUNTING)" "This was their last hope." "With the carcass gone, the bears search the shore for scraps." "All that remains are some bleached bones." "There is little nutrition here." "But at least the cub has found something to chew on." "Calcium from the bones will help the mother's milk supply but the cub needs meat to survive." "Now, they have another problem." "Other bears can't be trusted with small cubs." "But, for now, they have other things on their mind." "The bears seem more interested in what lies beneath the surface than what's on land." "There is still meat to be found here, partially preserved by the cold water." "Despite her hunger, the mother can't risk joining in." "But the other bears don't stay long." "The mother grasps her opportunity." "Her cub's survival depends on her success." "(GRUNTING)" "The remains lie four metres down." "And, at the deepest point, flesh still clings to the backbone." "She emerges triumphant." "The meat must be rancid, but it's still a lifesaver." "She brings some back to the shore." "This is the moment the cub has been waiting for, but still he has to wait." "However unfair it seems, she must regain her strength or her cub won't survive anyway." "Finally, she leaves him some scraps to chew on." "(WHIRRING)" "Blizzard-cam is on a new mission at the edge of the polar ice cap." "But an inquisitive bear spots the spy-cam first." "(GROWLING)" "(WHIRRING)" "As blizzard-cam awaits the bear, the melt water re-freezes, cold-welding the skis to the ice." "This is a problem." "Blizzard-cam's defence tactic is to retreat from overenthusiastic bears." "But it is literally frozen to the spot." "There is nothing blizzard-cam can do, but film its own fate." "Polar bears will try to eat almost anything, including blizzard-cam's armoured covering." "(SNIFFING)" "Perhaps he thinks blizzard-cam's coating has a soft centre." "(SNIFFING)" "As he tries to fathom it all out, he frees blizzard-cam from the ice." "This is a much better game." "(WHIRRING)" "(GRUNTING)" "(GRUNTING)" "Blizzard-cam makes a break for it." "It deploys snowball-cam as a decoy." "This is the polar bear's favourite spy camera and this young male is no exception." "Never before has it come under so much pressure." "(WHIRRING))" "Valiantly, snowball-cam keeps filming until the very end." "(RATTLING)" "Back at the whale carcass, Glaucous gulls make the most of the free lunch provided by the diving bears." "Their raids drive the bears to distraction." "The gulls keep up the teasing." "It's unusual for any to get caught." "But this polar bear has had enough." "He vents his frustration." "(YELPING)" "This young male bullies a gull into submission." "(SQUEALING)" "He then turns his attention elsewhere, a dangerous situation for the cub." "(GROWLING)" "She growls a warning, but it's not enough." "(ROARING)" "The cub slips." "(GRUNTING)" "(GROWLING)" "The mother must get her cub away from danger as quickly as possible." "They head north." "She knows that this is where the ice and, with it the seals, will first return." "It's now September, but the sea might not freeze again for another two months." "Her cub is unlikely to survive that long." "(PANTING)" "But there is hope on the horizon." "An ice rainbow heralds change." "In the far north, temperatures drop at last and ice sheets start to grow, rather than disappear." "Then a miracle happens." "Building pressure combines with powerful southerly currents to push the drift ice southwards." "The ice gathers near the most northerly islands first." "The landlocked bears are thrown a lifeline by a change in the weather and ocean currents." "It's still a big swim, but the prize will be more than worth it." "It's within reach at last." "And the seals soon notice their arrival." "They tease them, confident that the bears can't catch them in the water." "The first landlocked bears make it to the ice floes." "Others quickly follow." "This is what they've spent the summer waiting for." "It's a gathering of very happy bears." "For the mother and cub, the change is even more significant." "It has saved their life." "It's a huge swim out to the ice floes for the little cub." "He finally makes it to the ice nine months after he was born." "His mother has triumphed against the odds to reach this land of plenty." "(GRUNTING)" "On the way, she taught her cub the survival skills for what could be an increasingly ice-free future." "More than anything, the cub learnt that curiosity is the key to survival." "But there is one more challenge ahead." "A young male has caught a seal." "They can't walk away from the chance of fresh meat." "(GRUNTING)" "(GROWLING)" "He charges." "But she refuses to be intimidated." "She needs a meal far more than he does." "She drives home her determination." "Well-fed bears eat only the blubber, leaving the rest for others." "They waited the whole summer for this moment, their first taste of fresh meat for four months." "They are safe from starvation." "Of all the subjects ever filmed by spy-cams, the polar bear has shown the greatest curiosity and intelligence." "(WHIRRING)" "And none more so than this mother." "Against the odds, she brought her cub up in one of the longest periods without ice in Svalbard's history." "As the spy-cams revealed the challenges the bears faced over the summer, they captured many intimate moments like this." "But iceberg-cam finally found itself trapped between ice floes." "(CREAKING)" "As ever, the mother's curiosity is peaked." "The curiosity that helped the mother and cub survive is now testing iceberg-cam to destruction." "This same curiosity is this cub's and all polar bears' best hope for the future."