0:00:06 > 0:00:10Scoured by ice and weathered by storms.
0:00:14 > 0:00:1820,000 square miles of rugged coastline,
0:00:18 > 0:00:21lochs and mountains.
0:00:23 > 0:00:27On the face of it, it looks bleak and lifeless,
0:00:27 > 0:00:31but wildlife is thriving in this unforgiving place -
0:00:31 > 0:00:33if you know where to look.
0:00:37 > 0:00:39The seasons may be harsh...
0:00:41 > 0:00:43..and the opportunities fleeting...
0:00:44 > 0:00:48..but animals and people have found ways to succeed here,
0:00:48 > 0:00:51turning adversity into advantage.
0:00:54 > 0:00:58This is Scotland's wild heart -
0:00:58 > 0:01:00the Highlands.
0:01:45 > 0:01:48It's October in the North West Highlands
0:01:48 > 0:01:51and the forests of Glen Affric are flushed with gold.
0:02:02 > 0:02:04It's a still, crisp, perfect morning.
0:02:14 > 0:02:16But this is a shallow beauty.
0:02:21 > 0:02:24With the brief summer now past,
0:02:24 > 0:02:27the animals of the Highlands are in for the long haul.
0:02:31 > 0:02:35The next few months will see them driven to desperate measures...
0:02:41 > 0:02:44..as they prepare for the lockdown of the Highlands' longest,
0:02:44 > 0:02:47darkest and most overwhelming season.
0:02:51 > 0:02:54It'll be April before the sun rises clear of these peaks again.
0:02:58 > 0:03:03Some take flight, seeking refuge in the warm south,
0:03:03 > 0:03:07but those that remain will need every drop of resilience they can muster.
0:03:11 > 0:03:14Only the toughest will survive what the elements are about to throw
0:03:14 > 0:03:16at the Highlands.
0:03:38 > 0:03:41Here among the mountains you have to be perfectly adapted
0:03:41 > 0:03:43to make it through.
0:03:45 > 0:03:49With four of the five highest peaks in the Highlands,
0:03:49 > 0:03:52this is the most extensive alpine terrain in Scotland.
0:03:56 > 0:04:00At these altitudes, heavy snow can arrive in almost any month,
0:04:00 > 0:04:03and it lies here all year round.
0:04:06 > 0:04:09But one animal has got what it takes to live here.
0:04:15 > 0:04:17Once extinct in these mountains,
0:04:17 > 0:04:19but living and breeding here once again...
0:04:23 > 0:04:25..they're reindeer.
0:04:28 > 0:04:34Reintroduced in the 1950s, after an absence of over 8,000 years,
0:04:34 > 0:04:36they're better adapted to these extreme conditions
0:04:36 > 0:04:38than any other Scottish mammal.
0:04:41 > 0:04:43Like many of the world's reindeer herds,
0:04:43 > 0:04:45people look after these animals.
0:04:50 > 0:04:54But for most of the year they're left to fend for themselves on these wild hills.
0:04:57 > 0:04:59Calves are born in the spring...
0:05:01 > 0:05:05..but reindeer are large animals with an eight-month gestation period.
0:05:06 > 0:05:10So to make the most of the good times, they need to mate now,
0:05:10 > 0:05:12before the winter lockdown takes hold.
0:05:18 > 0:05:22In their short rut, triggered by decreasing day length,
0:05:22 > 0:05:26a dominant male will try to mate with as many females as possible.
0:05:31 > 0:05:34Each will only be receptive for a short time,
0:05:34 > 0:05:36so it's crucial the rut happens now.
0:05:38 > 0:05:41This distinctive dark male has ruled the herd for two years...
0:05:43 > 0:05:46..but this year, he's got competition.
0:05:55 > 0:05:58This paler bull is exactly the same age,
0:05:58 > 0:06:00but he's never beaten the dark male,
0:06:00 > 0:06:03so he's been unable to father even a single calf.
0:06:08 > 0:06:12This year could mark the end of his losing streak,
0:06:12 > 0:06:17but he'll need to pick exactly the right moment for his challenge
0:06:17 > 0:06:20and he's only got a few days to do it.
0:06:35 > 0:06:39The Cairngorms National Park is by far the biggest in the UK.
0:06:43 > 0:06:47Larger than Luxembourg, it contains more native forest
0:06:47 > 0:06:48than any other part of Britain.
0:06:52 > 0:06:54Much of this is evergreen Scots pine...
0:06:58 > 0:07:02..but there are over 10,000 acres of broadleaf woodland here, too.
0:07:12 > 0:07:15In these forests, autumn is a fruitful time,
0:07:15 > 0:07:19with the trees casting berries and nuts on the forest floor.
0:07:22 > 0:07:25They're a critical food source for red squirrels.
0:07:42 > 0:07:47This little female has already seen more than her fair share of winters.
0:07:54 > 0:07:59At six years old, she's already lived double the average for a red squirrel.
0:08:02 > 0:08:05Perhaps it's the richness of this place,
0:08:05 > 0:08:08with its supply of beech and hazelnuts,
0:08:08 > 0:08:10which has sustained her for so long.
0:08:12 > 0:08:15She's not alone here.
0:08:15 > 0:08:18Bearing a distinctive battle-scarred nose,
0:08:18 > 0:08:20her neighbour is almost as old.
0:08:29 > 0:08:35Outside the breeding season, red squirrels are usually tolerant of each other,
0:08:35 > 0:08:39but these two constantly compete over the available resources.
0:08:55 > 0:08:58Tail swishing means keep your distance.
0:09:12 > 0:09:16But all this scrapping is using up valuable energy...
0:09:17 > 0:09:20..and the long haul hasn't even started yet.
0:09:34 > 0:09:38Although the Highlands are known for their clear autumn days,
0:09:38 > 0:09:42October and November are amongst the wettest months of the year,
0:09:42 > 0:09:45with rain falling on two out of three days.
0:09:56 > 0:10:01But this autumn deluge is a critical part of the life cycle of one animal...
0:10:05 > 0:10:07..Atlantic salmon.
0:10:11 > 0:10:14Here at the falls of Shin, 30 miles North of Inverness,
0:10:14 > 0:10:16big numbers are gathering.
0:10:18 > 0:10:21Returning from their 2,000-mile ocean migration,
0:10:21 > 0:10:24they're getting ready to move upriver.
0:10:27 > 0:10:31Their eggs can only survive in the shallow headwaters of Highland rivers,
0:10:31 > 0:10:33high up in the mountains.
0:10:36 > 0:10:40So raised water levels present them with their best chance
0:10:40 > 0:10:42of reaching the spawning grounds.
0:10:47 > 0:10:50They must time it right, if their offspring are to survive
0:10:50 > 0:10:52and make their own journey out to sea.
0:10:54 > 0:10:56But there's a problem.
0:10:59 > 0:11:01The falls are blocking the salmon's path.
0:11:06 > 0:11:09There's only one way to get around them,
0:11:09 > 0:11:11and that is to go over them.
0:11:21 > 0:11:24It's a game of persistence and luck.
0:11:36 > 0:11:38Launching themselves above the sill
0:11:38 > 0:11:40requires formidable acceleration.
0:11:47 > 0:11:51Their muscles are adapted for short, sharp bursts of energy.
0:11:55 > 0:11:58Leaps can cover more than three metres.
0:12:03 > 0:12:06And although they fail time after time,
0:12:06 > 0:12:10their desire to push on is so strong, they never give up.
0:12:30 > 0:12:34But clearing the falls is only the first challenge.
0:12:34 > 0:12:36Ahead of them lies a gruelling journey
0:12:36 > 0:12:40to their spawning grounds on the Western fringes of the Highlands.
0:12:55 > 0:12:59Back on the Cairngorm plateau, the pale reindeer bull
0:12:59 > 0:13:02has made the decision to challenge the dominant male.
0:13:10 > 0:13:12It's a well-timed move.
0:13:12 > 0:13:15The dark bull has been mating and he's tired.
0:13:17 > 0:13:21To win the fight, the pale bull will need to force his way up the hill
0:13:21 > 0:13:24and drive the ruling male down into the valley.
0:13:26 > 0:13:29REINDEER GRUNTS
0:13:40 > 0:13:44But the dark bull takes the initiative and moves down
0:13:44 > 0:13:46to block his rival's advance.
0:13:51 > 0:13:54Grunting and pacing are all part of the build-up.
0:14:05 > 0:14:07Game on.
0:14:17 > 0:14:20Reindeer battles can carry on for many hours...
0:14:23 > 0:14:25..but they rarely fight to the death.
0:14:37 > 0:14:40They're equally matched - it's all about who'll tire first.
0:14:56 > 0:14:59They're close to exhaustion, but neither will back down.
0:15:14 > 0:15:18Little by little, the pale bull pushes his rival up the slope.
0:15:28 > 0:15:29A quick turn...
0:15:40 > 0:15:42..and it's all over.
0:15:47 > 0:15:49They're both completely exhausted.
0:15:51 > 0:15:54The dark male doesn't have the spirit for another round
0:15:54 > 0:15:56and heads for the edge of the herd.
0:15:59 > 0:16:03For the first time, the pale bull will have his chance to breed.
0:16:13 > 0:16:17In the forest, the red squirrels are working frantically.
0:16:20 > 0:16:24Hoarding food is an important way of getting through the coldest months,
0:16:24 > 0:16:28and the old squirrel is burying nuts on the forest floor.
0:16:35 > 0:16:37Before each nut is stored, it's assessed.
0:16:39 > 0:16:43Weight and smell will tell her if it's good or bad.
0:16:45 > 0:16:49And as she handles each one, it's marked with her unique scent.
0:16:51 > 0:16:55A good spatial memory and a highly developed sense of smell
0:16:55 > 0:16:58will allow her to find it later in the winter.
0:17:02 > 0:17:06But the forest floor is a dangerous place for a tree-loving mammal.
0:17:14 > 0:17:16A pheasant is no threat...
0:17:21 > 0:17:25..but birds of prey like buzzards will readily snatch an off-guard squirrel.
0:17:29 > 0:17:32She freezes on the spot with her eyes fixed on the danger.
0:17:50 > 0:17:52She's safe.
0:17:55 > 0:17:58But while she's been sitting tight,
0:17:58 > 0:18:01her neighbour has been helping herself to the cache.
0:18:23 > 0:18:27Remarkably, the old squirrel has a strategy to deal with this
0:18:27 > 0:18:32and confuses her thieving neighbour by pretending to bury a nut
0:18:32 > 0:18:34before moving it elsewhere.
0:18:38 > 0:18:43It looks like a game, but these preparations are urgent and serious.
0:18:46 > 0:18:48A cold front is sweeping in from the East.
0:18:50 > 0:18:54The Highlands are on the cusp of winter.
0:19:13 > 0:19:1880 miles East, on the Aberdeenshire coast, near the loch of Strathbeg,
0:19:18 > 0:19:20visitors are arriving for winter.
0:19:35 > 0:19:37Pink-footed geese.
0:19:42 > 0:19:46They've travelled more than 600 miles nonstop
0:19:46 > 0:19:48from their breeding grounds in Iceland.
0:19:52 > 0:19:54To them, the Highlands offer a sanctuary
0:19:54 > 0:19:57from the unbearable conditions further North.
0:20:02 > 0:20:05Over the next few months, they'll spread out across
0:20:05 > 0:20:08the fertile wetlands on the edges of the Highlands.
0:20:11 > 0:20:13More than 80,000 will arrive on these beaches
0:20:13 > 0:20:15after their marathon journey.
0:20:16 > 0:20:18But they can't rest here long.
0:20:20 > 0:20:23It's 48 hours since they've fed
0:20:23 > 0:20:26and they must head to more fertile grounds.
0:21:00 > 0:21:06It's early November and animals are making their final preparations for winter.
0:21:11 > 0:21:1590 miles north, on Copinsay in the Orkney Islands,
0:21:15 > 0:21:19one of the last and most dramatic events of all is playing out.
0:21:22 > 0:21:27Every other Highland animal completes their breeding cycle in summer,
0:21:27 > 0:21:29but grey seals are an exception to the rule.
0:21:32 > 0:21:36Breeding now, because it takes the whole of summer and early autumn
0:21:36 > 0:21:39to feed themselves into peak condition for pupping.
0:21:42 > 0:21:47Once they're on the beaches, neither females or males will feed...
0:21:50 > 0:21:53..and all births will happen in just a few weeks.
0:21:56 > 0:22:00This pup was born weighing 13 kilos...
0:22:01 > 0:22:06..but because grey seal milk is 50% fat, he'll gain two kilos a day,
0:22:06 > 0:22:09more than trebling his weight in just three weeks.
0:22:12 > 0:22:16Once he's weaned, the mother will turn her attention to the bulls.
0:22:22 > 0:22:28She's looking for one type of bull in particular -
0:22:28 > 0:22:31the biggest and strongest.
0:22:33 > 0:22:37This huge battle-scarred male controls the beach
0:22:37 > 0:22:39and its harem of females.
0:22:43 > 0:22:45The smaller bulls daren't challenge him.
0:23:01 > 0:23:03They sit on the waterline,
0:23:03 > 0:23:06testing each other's strength in the shallows.
0:23:06 > 0:23:09SEALS GROWL AND SNARL
0:23:19 > 0:23:23But the dominant bull doesn't get involved in small skirmishes -
0:23:23 > 0:23:25he doesn't need to.
0:23:27 > 0:23:30The female seals swim straight to him...
0:23:31 > 0:23:34..bypassing the younger, less dominant males.
0:23:40 > 0:23:44Grey seal courtship starts with splashing and scrapping.
0:23:55 > 0:23:59But unusually for a large mammal, it then relaxes into a tender embrace.
0:24:10 > 0:24:13Soon both mating and pupping will have to cease...
0:24:18 > 0:24:21..as the biggest storm of the season is on its way.
0:24:36 > 0:24:39Back on the mainland, the weather is settled...
0:24:44 > 0:24:46..and the salmon are on the move.
0:24:49 > 0:24:53Their journey from coast to spawning grounds can cover many miles...
0:24:56 > 0:24:59..and the complete trip can take more than six months.
0:25:05 > 0:25:08They don't eat anything on their migration,
0:25:08 > 0:25:12so why they strike at an angler's fly is still a complete mystery.
0:25:15 > 0:25:18But the vast majority evade even the most skilled fishermen.
0:25:47 > 0:25:52The fish are driven ever onwards by an ability to sense unique chemicals
0:25:52 > 0:25:54from the remote mountain burns
0:25:54 > 0:25:57where they spent the first few years of their lives.
0:26:02 > 0:26:07After an extraordinary journey, they finally come home.
0:26:12 > 0:26:15And now they're ready to complete their life cycle.
0:26:19 > 0:26:22Females seek out sheltered positions where their eggs
0:26:22 > 0:26:24will have the best chance of survival.
0:26:33 > 0:26:35The males have changed dramatically.
0:26:37 > 0:26:41To show dominance, their jaws have curved upwards,
0:26:41 > 0:26:44exposing rows of ferocious-looking teeth.
0:26:45 > 0:26:48Charged with testosterone,
0:26:48 > 0:26:52this male's intolerant of any impostor,
0:26:52 > 0:26:54even a juvenile salmon.
0:27:01 > 0:27:03He moves in on the female.
0:27:05 > 0:27:09Using her body, she digs a hollow in the riverbed,
0:27:09 > 0:27:11where she'll safely lay her eggs.
0:27:20 > 0:27:22She's ready.
0:27:23 > 0:27:25The male moves in...
0:27:31 > 0:27:33..releasing his sperm as the eggs appear.
0:27:44 > 0:27:47The salmon have completed their breeding cycle.
0:27:56 > 0:27:59Conditions may be calm in the northwest,
0:27:59 > 0:28:02but on Copinsay it couldn't be more different.
0:28:12 > 0:28:14The storm has arrived.
0:28:23 > 0:28:26Wind gusts can exceed 100mph on this exposed coast...
0:28:32 > 0:28:35..and the waves tower to more than 12 feet.
0:28:43 > 0:28:47Climate change may be behind the increase in huge storms like this.
0:28:48 > 0:28:51Potentially disastrous for wildlife.
0:29:12 > 0:29:15The grey seal pups are too young to swim,
0:29:15 > 0:29:19so they're hauling themselves up onto the field beyond the beach.
0:29:24 > 0:29:28This one's become separated from its mother.
0:29:30 > 0:29:33It's tired and hungry.
0:29:33 > 0:29:35SEAL PUP WHIMPERS
0:29:36 > 0:29:41At just a few days old, it needs 2½ litres of milk a day to survive.
0:29:52 > 0:29:55If it can't find its mother quickly,
0:29:55 > 0:29:56it'll die.
0:30:19 > 0:30:24Other females are highly territorial and attack pups in their patch,
0:30:24 > 0:30:26so it must keep moving to stay alive.
0:30:45 > 0:30:50In sheer desperation, it tries to suckle from another pup's flippers.
0:30:51 > 0:30:54It's weakening fast
0:30:54 > 0:30:56and burning precious energy.
0:31:02 > 0:31:06Malnutrition is the most common cause of death in seal pups.
0:31:23 > 0:31:28But astonishingly, the mother has found her way back to the lost pup...
0:31:30 > 0:31:34..and at last, it's safe.
0:31:56 > 0:32:00As the sea calms, something remarkable happens...
0:32:18 > 0:32:21..cannibalism.
0:32:23 > 0:32:26The dominant bull is feasting on the carcass of a pup.
0:32:29 > 0:32:32Possibly one swept into the waves by the power of the storm.
0:32:36 > 0:32:40This strange and disturbing behaviour is a recent discovery.
0:32:49 > 0:32:53Hardly ever seen and never filmed before,
0:32:53 > 0:32:56scientists aren't sure why grey seals have turned cannibal.
0:32:58 > 0:33:03It could be pure hunger, or dwindling fish resources,
0:33:03 > 0:33:07but whatever the reason, the behaviour seems to be on the increase.
0:33:40 > 0:33:42With the breeding cycle completed,
0:33:42 > 0:33:44the male salmon lies exhausted in the water.
0:33:47 > 0:33:50As spawning salmon don't eat once they enter the breeding cycle,
0:33:50 > 0:33:54their muscle fat will only sustain them for a limited period.
0:33:58 > 0:34:02He's a shadow of the powerful fish that leapt the falls back in early October.
0:34:07 > 0:34:09Despite these incredible challenges,
0:34:09 > 0:34:135% of salmon actually make it back to the ocean.
0:34:18 > 0:34:20But not this one.
0:34:40 > 0:34:44His body will now become food, for the same tiny creatures
0:34:44 > 0:34:48that will sustain his own offspring once they hatch.
0:35:09 > 0:35:13It's now mid November and the Highlands are looking straight
0:35:13 > 0:35:15into the jaws of winter.
0:35:17 > 0:35:21For the first time since March, temperatures drop below zero...
0:35:32 > 0:35:34..and it starts to snow.
0:35:52 > 0:35:56A heavy fall like this early in the season is rare...
0:35:59 > 0:36:01..but soon the entire region -
0:36:01 > 0:36:05from Glencoe in the West, to the high tops of the Cairngorms -
0:36:05 > 0:36:07is coated in fresh powder.
0:36:20 > 0:36:23But this is the beginning of the winter lockdown.
0:36:32 > 0:36:35With grass and heather buried beneath the snow,
0:36:35 > 0:36:38the struggle for the animals will inevitably become tougher
0:36:38 > 0:36:39over the next few weeks.
0:36:50 > 0:36:54But these conditions are perfect for one species,
0:36:54 > 0:36:56which is flocking to the mountains in droves.
0:37:01 > 0:37:03Humans.
0:37:07 > 0:37:11With five resorts and up to 100 days of snow a year,
0:37:11 > 0:37:14the Highlands have been an important ski area since the 1950s.
0:37:21 > 0:37:25The ski centre on Cairngorm Mountain is also a magnet for wildlife.
0:37:34 > 0:37:35A ptarmigan.
0:37:40 > 0:37:42This Arctic member of the grouse family
0:37:42 > 0:37:44is at home on the very highest peaks
0:37:44 > 0:37:46of the Cairngorms and Western Highlands.
0:37:50 > 0:37:53Able to survive on a meagre diet of heather,
0:37:53 > 0:37:56they moult into a pure white plumage for the winter.
0:38:07 > 0:38:10There are white mountain hares here, too.
0:38:16 > 0:38:20They can also survive on the withering shoots at the edge of the snowfield.
0:38:27 > 0:38:31There's a reason why the ptarmigan and hares choose to live here.
0:38:35 > 0:38:39As the winter lockdown sets in, predators like golden eagles
0:38:39 > 0:38:41range widely to find food.
0:38:50 > 0:38:54But they're shy birds and will stay away from human activity
0:38:54 > 0:38:56at all costs.
0:39:04 > 0:39:07So, as long as the ptarmigan and hares stay close to the skiers,
0:39:07 > 0:39:09they should remain safe.
0:39:33 > 0:39:34But it's a dangerous game.
0:39:36 > 0:39:39Although the eagles won't venture near people,
0:39:39 > 0:39:42they're less troubled by the lifts and buildings.
0:39:44 > 0:39:47So the ptarmigan and hares need to keep watch at all times.
0:39:59 > 0:40:02By December standards, it's been a huge dump of snow.
0:40:04 > 0:40:09In Abernethy Forest, at the foot of the Cairngorms, the drifts lie deep.
0:40:14 > 0:40:18Small birds like crested tits are now vulnerable.
0:40:22 > 0:40:25In the UK, they're only found in these Highland forests.
0:40:28 > 0:40:31The breeding population is around 2,000 pairs,
0:40:31 > 0:40:34but a harsh winter can decimate their numbers.
0:40:43 > 0:40:45A resident of the canopy in the summer,
0:40:45 > 0:40:48winter brings them down to the forest floor to feed.
0:41:04 > 0:41:08Like red squirrels, crested tits cache food...
0:41:11 > 0:41:15..and it's a matter of urgency to dig up the stash of seeds for fresh energy.
0:41:19 > 0:41:22Small song birds are unable to carry much fat,
0:41:22 > 0:41:24so they need to feed constantly.
0:41:27 > 0:41:29They've got competition.
0:41:32 > 0:41:35Coal tits will raid crested tit caches.
0:42:06 > 0:42:09And even though the crested tits are bigger,
0:42:09 > 0:42:11persistence pays off.
0:42:18 > 0:42:22But squandering energy through fighting would be dangerous now.
0:42:23 > 0:42:27The lockdown has only just arrived and far worse is on the way.
0:42:41 > 0:42:43Pressure is falling...
0:42:48 > 0:42:51..and storm-force winds hammer in from the west.
0:42:54 > 0:42:56It's a blizzard.
0:43:07 > 0:43:09But these are the conditions that make reindeer
0:43:09 > 0:43:11such masters of the Highland winter.
0:43:19 > 0:43:21Reindeer coats are double layered.
0:43:26 > 0:43:29A dense, fuzzy underfur provides a warm base.
0:43:32 > 0:43:36And the long outer hairs are hollow and filled with air
0:43:36 > 0:43:38to provide superb insulation.
0:43:51 > 0:43:53Even feeding is no problem.
0:43:57 > 0:44:00The powerful winds prevent the build-up of snow
0:44:00 > 0:44:04and having huge spade-like feet means that reindeer can easily
0:44:04 > 0:44:06dig up heather and lichens.
0:44:23 > 0:44:26Ptarmigan also take the blizzard in their stride.
0:44:28 > 0:44:31Their thick winter plumage includes feathers around the feet
0:44:31 > 0:44:34that act like snow shoes.
0:44:37 > 0:44:41The snow bunting also has warm feathers around its tiny toes.
0:44:43 > 0:44:47Up to 15,000 of these migrants arrive in the Highlands in winter
0:44:47 > 0:44:51and often follow animals like reindeer to take advantage
0:44:51 > 0:44:54of the food exposed by the scraping and digging.
0:45:06 > 0:45:08The blizzard is easing...
0:45:11 > 0:45:14..but 60% of the Highlands have now been covered by snow
0:45:14 > 0:45:16for the best part of three weeks.
0:45:21 > 0:45:24And the flakes just keep on falling.
0:45:40 > 0:45:45For the red squirrels, food caches are a life-saver.
0:45:46 > 0:45:48But supplies are running desperately short...
0:45:51 > 0:45:54..and now, where there were once two squirrels,
0:45:54 > 0:45:56just one remains.
0:46:03 > 0:46:08Unable to cope with this savage opening to winter,
0:46:08 > 0:46:10the older female has already succumbed.
0:46:24 > 0:46:29The old squirrel's death has thrown a lifeline to her neighbour.
0:46:29 > 0:46:32Able to exploit twice as many food caches,
0:46:32 > 0:46:36her chances of surviving this brutal winter have been significantly raised.
0:46:59 > 0:47:03The Highlands are now approaching the winter solstice -
0:47:03 > 0:47:05the longest night of the year.
0:47:08 > 0:47:12In the Highlands, this means more than 18 hours of darkness.
0:47:15 > 0:47:17But the rule of night is challenged.
0:47:28 > 0:47:30The northern lights.
0:47:36 > 0:47:39Generated by gas in the Earth's atmosphere
0:47:39 > 0:47:42colliding with charged particles from the sun,
0:47:42 > 0:47:44the lights can dance until dawn.
0:47:58 > 0:48:02And now, each day, the sun will rise a few minutes earlier.
0:48:07 > 0:48:09The light is returning.
0:48:15 > 0:48:18The weather is warming, too.
0:48:18 > 0:48:20Although the snow still lies deep
0:48:20 > 0:48:23from the Trossachs to the Cairngorms,
0:48:23 > 0:48:25the thaw has begun.
0:48:47 > 0:48:51The small rise in temperature is triggering new behaviour
0:48:51 > 0:48:53from the ptarmigan and hares.
0:48:56 > 0:48:58The beginnings of courtship.
0:49:04 > 0:49:07Female mountain hares can come into season in the depths of winter
0:49:07 > 0:49:09if temperatures climb above freezing...
0:49:11 > 0:49:15..and males will try and find as many receptive mates as they can.
0:49:18 > 0:49:20But the females are picky.
0:49:26 > 0:49:29They'll outrun, outbox and vault clear of any male
0:49:29 > 0:49:33they don't consider fit and athletic enough to mate with.
0:50:10 > 0:50:13Unlike the hares and most of their grouse relatives,
0:50:13 > 0:50:15ptarmigan will seek out a single mate.
0:50:20 > 0:50:22But at this point in the season,
0:50:22 > 0:50:25it's more about chasing other males around the resort.
0:50:42 > 0:50:45The white creatures will need to be very careful now.
0:50:46 > 0:50:50Their lives depend on their camouflage
0:50:50 > 0:50:53and the thaw has started to expose clear patches of heather.
0:50:58 > 0:51:02If the snow melts early, they'll be an easy target for the eagles.
0:51:19 > 0:51:23Further down the mountain, the hills are now completely clear of snow.
0:51:35 > 0:51:39Black grouse - close relatives of the ptarmigan -
0:51:39 > 0:51:42are also starting their mating displays.
0:51:51 > 0:51:56Although the females won't appear at these courtship sites - called leks - until the spring,
0:51:56 > 0:51:58the males compete year round.
0:52:06 > 0:52:09They're working out who's the dominant bird.
0:52:18 > 0:52:22It's a three-way contest to gain control of the best spot in the lek.
0:52:24 > 0:52:28The wheezing calls and plumped-up feathers are all part of the display.
0:52:42 > 0:52:46But the real clincher is the eyebrows.
0:52:47 > 0:52:51Large eyebrows are a sign of high testosterone,
0:52:51 > 0:52:53and the bigger and brighter the brows,
0:52:53 > 0:52:57the more attractive the male will be to females in the spring.
0:53:08 > 0:53:12As the hours of sunlight increase, the thaw picks up pace.
0:53:15 > 0:53:18Even high on the peaks, the patches of exposed heather are growing.
0:53:21 > 0:53:23Perfect camouflage for red grouse.
0:53:27 > 0:53:30But the hares are now at risk of attack from the eagles.
0:53:57 > 0:54:00Mountain hares always flee uphill.
0:54:00 > 0:54:03Because eagles need height to strike,
0:54:03 > 0:54:06this closes the gap and reduces their ability to manoeuvre.
0:54:12 > 0:54:16The eagle flushes a ptarmigan and switches target.
0:54:19 > 0:54:22But the eagles aren't the only predators here.
0:54:25 > 0:54:27Ravens can also kill a tired hare.
0:54:36 > 0:54:39But hares can run at nearly 45mph.
0:54:40 > 0:54:42So it stays out of reach...
0:54:45 > 0:54:48..and slips into the heather just in time.
0:54:55 > 0:54:57It's unusual for snow to lie in the whole Highland region
0:54:57 > 0:55:00for more than a few weeks.
0:55:07 > 0:55:11Although it's still only January, the temperatures have at last
0:55:11 > 0:55:13started to climb above freezing.
0:55:17 > 0:55:19Rivers and burns now churn with meltwater.
0:55:25 > 0:55:29And the Highland animals are at last granted a brief reprieve
0:55:29 > 0:55:31from the onslaught of winter.
0:55:37 > 0:55:40Even now, there are signs of the season's end.
0:55:44 > 0:55:48New spring salmon have started to enter the river systems,
0:55:48 > 0:55:52embarking on the same epic journey that ended for others
0:55:52 > 0:55:53only two months ago.
0:55:55 > 0:55:59HE PLAYS SCOTLAND THE BRAVE
0:56:07 > 0:56:10These spring salmon are revered by Highlanders.
0:56:12 > 0:56:16On the great rivers like the Dee, Tay and Spey,
0:56:16 > 0:56:19they're given a hero's welcome before the river is opened
0:56:19 > 0:56:20for the fishing season.
0:56:22 > 0:56:24Lord of creation,
0:56:24 > 0:56:29we ask that you will bless this living water of the Spey,
0:56:29 > 0:56:34flow river flow, fill our hearts with joy and gladness
0:56:34 > 0:56:36and thanksgiving always.
0:56:38 > 0:56:39Amen.
0:56:40 > 0:56:42Whisky is poured into the river -
0:56:42 > 0:56:45a gesture to wish the salmon good health.
0:56:55 > 0:56:58And at last, with great anticipation,
0:56:58 > 0:57:00the anglers can cast their lines.
0:57:04 > 0:57:06The seasons have come full circle.
0:57:11 > 0:57:13And spring feels close at last.
0:57:18 > 0:57:22The animals that have survived the challenges of the long haul
0:57:22 > 0:57:25will now face up to the intensity of spring.
0:57:27 > 0:57:30With an uncertain future for our climate,
0:57:30 > 0:57:34living wild in the Highlands looks set to become more extreme than ever.
0:57:38 > 0:57:40But this living landscape has been changing
0:57:40 > 0:57:43and renewing itself for millennia.
0:57:49 > 0:57:51So the Scottish Highlands will always be
0:57:51 > 0:57:55one of the world's most magical, wild places.
0:57:57 > 0:58:00Next time - the people of the Highlands.
0:58:04 > 0:58:08Over the centuries, many of the riches of these wild places have been lost.
0:58:11 > 0:58:15With forests cut down and wild animals driven to extinction.
0:58:16 > 0:58:18But now they're returning.
0:58:21 > 0:58:24Never before have so many people found new and surprising ways
0:58:24 > 0:58:27of putting back what we've lost.