1 00:00:12,946 --> 00:00:16,746 This is a story about one of nature's top predators... 2 00:00:18,985 --> 00:00:23,888 ...and how it uses its stamina, intelligence and tenacity to survive. 3 00:00:26,226 --> 00:00:27,488 For the first time, 4 00:00:27,660 --> 00:00:32,290 you'll have an extraordinary view of the wolf and the wolf's world. 5 00:00:36,002 --> 00:00:39,028 Through the eyes of its leaders and their family - the pack - 6 00:00:39,205 --> 00:00:43,403 you'll witness the stress and success of their life as a team. 7 00:00:48,515 --> 00:00:53,748 And see how the events in the pack's life take place here, in their territory. 8 00:00:54,087 --> 00:00:57,181 A place that's worth protecting in any way they can. 9 00:01:01,428 --> 00:01:03,862 You'll join them in their constant search for food - 10 00:01:04,030 --> 00:01:05,964 food big enough to fight back... 11 00:01:07,600 --> 00:01:10,967 And watch as they battle their bitterest enemies - their neighbours - 12 00:01:11,137 --> 00:01:14,106 and their other fierce rival, the grizzly... 13 00:01:14,374 --> 00:01:17,070 encounters that threaten their future. 14 00:01:21,181 --> 00:01:25,481 This is a story, but everything you're about to see is based on fact. 15 00:01:26,352 --> 00:01:28,217 The strength of the wolf is the pack, 16 00:01:28,388 --> 00:01:33,451 but is this pack up to the challenges of life on the wolf battlefield? 17 00:01:50,543 --> 00:01:54,673 The Rocky mountains of North America... home to hundreds of wolves. 18 00:01:54,848 --> 00:01:58,614 A wilderness that stretches for thousands of square kilometres. 19 00:02:02,188 --> 00:02:04,315 With special technology we can analyse 20 00:02:04,491 --> 00:02:08,393 the wolf's world in a way that ordinary cameras cannot show. 21 00:02:11,231 --> 00:02:13,631 Creating a virtual reality... 22 00:02:15,068 --> 00:02:19,129 From this view, we can focus in on just two hundred square kilometres - 23 00:02:19,372 --> 00:02:21,340 our pack's domain. 24 00:02:21,541 --> 00:02:23,509 Revealing the key zones within it: 25 00:02:25,411 --> 00:02:26,810 Lowland plains... 26 00:02:27,113 --> 00:02:29,775 with ridges above for lookout points... 27 00:02:37,957 --> 00:02:40,517 A river that flows all year round... 28 00:02:50,069 --> 00:02:52,765 Dense, forested slopes for cover... 29 00:03:00,413 --> 00:03:04,474 And all this flanked by towering mountain peaks. 30 00:03:09,856 --> 00:03:15,726 Prime wolf territory, currently occupied by our Battlefield pack - the Jets. 31 00:03:17,397 --> 00:03:21,060 This tightly knit team of seven wolves is led by the alpha pair - 32 00:03:21,367 --> 00:03:25,098 a big, silver male and his smaller, black mate. 33 00:03:26,606 --> 00:03:29,507 The alphas are mother and father to four adolescents - 34 00:03:29,676 --> 00:03:32,144 all born just under two years ago. 35 00:03:35,148 --> 00:03:38,481 The seventh wolf, an adult male, is an outsider - 36 00:03:38,651 --> 00:03:40,482 and pack underdog. 37 00:03:42,555 --> 00:03:46,218 All the wolves are expert hunters. They need to be. 38 00:03:46,392 --> 00:03:51,523 lt's January and on the face of it, the wolf's world looks lifeless... 39 00:03:54,133 --> 00:03:56,397 There's deep snow on the high slopes 40 00:03:56,569 --> 00:03:59,436 and it's minus 2O degrees Celsius. 41 00:04:00,640 --> 00:04:03,768 Most small mammals are hibernating and are off the menu. 42 00:04:06,479 --> 00:04:11,246 Only larger prey, like buffalo and elk, are awake and available. 43 00:04:12,185 --> 00:04:14,653 But they're too big for a single wolf to tackle, 44 00:04:14,821 --> 00:04:17,756 and they're always on the move to find enough to eat. 45 00:04:25,865 --> 00:04:29,232 So, the Jets must stick together, and be nomadic too. 46 00:04:34,407 --> 00:04:36,602 Wolves are built for long-distance travel... 47 00:04:36,776 --> 00:04:38,971 Their long legs, big lungs and hearts 48 00:04:39,145 --> 00:04:41,909 give them a cruising speed of eight miles per hour. 49 00:04:45,385 --> 00:04:47,683 They can average fifty kilometres a day - 50 00:04:48,321 --> 00:04:51,256 and clock up three laps of their territory a week. 51 00:04:56,396 --> 00:04:59,456 But how do they find their way around such a large area - 52 00:04:59,632 --> 00:05:02,692 and where do they start looking for food? 53 00:05:04,437 --> 00:05:08,339 lt's always one of the alpha wolves who leads the way. 54 00:05:15,548 --> 00:05:19,143 The alphas have held this territory for almost three years. 55 00:05:27,427 --> 00:05:31,727 Experience has taught them that the herds don't move randomly. 56 00:05:33,366 --> 00:05:37,097 They visit favourite feeding areas at certain times of year - 57 00:05:37,437 --> 00:05:40,235 and they always follow the same routes. 58 00:05:40,406 --> 00:05:42,431 Wolves don't move randomly either... 59 00:05:44,110 --> 00:05:47,170 ...which suggests they have a mental map of their territory, 60 00:05:47,347 --> 00:05:51,340 an in-built route-planner that helps them visualise where they are, 61 00:05:51,517 --> 00:05:54,247 and which path to take to intercept their prey. 62 00:06:04,697 --> 00:06:07,131 A wolf's brain is thirty per cent bigger than a dog's - 63 00:06:07,300 --> 00:06:11,737 and it's this extra brainpower that helps the wolf navigate so effectively. 64 00:06:20,980 --> 00:06:24,416 The pack's trails make up a closed circuit inside their territory - 65 00:06:24,684 --> 00:06:27,016 but some routes connect with their neighbours' trails, 66 00:06:27,186 --> 00:06:31,919 creating a huge network of wolf highways for thousands of square kilometres. 67 00:06:37,797 --> 00:06:39,958 With so many other wolves in this area, 68 00:06:40,133 --> 00:06:45,036 it's vital our pack has exclusive rights to its territory and food supply. 69 00:06:46,239 --> 00:06:49,208 Somehow, the wolves must protect what's theirs... 70 00:06:51,944 --> 00:06:53,434 ...because next door 71 00:06:54,414 --> 00:06:56,814 they have the neighbours from hell! 72 00:06:58,317 --> 00:07:02,310 ln just four years, this rival pack has grown unusually large. 73 00:07:02,522 --> 00:07:04,080 There are twenty-two of them. 74 00:07:06,325 --> 00:07:09,158 The Big Pack's alpha wolves have raised many youngsters - 75 00:07:09,328 --> 00:07:11,660 and none of them have left home yet. 76 00:07:15,835 --> 00:07:18,133 There are problems with a pack this size. 77 00:07:18,304 --> 00:07:20,329 They can't afford a day without a kill. 78 00:07:20,506 --> 00:07:24,033 And to find enough food, they need a big territory. 79 00:07:29,115 --> 00:07:31,345 This makes the Big Pack dangerous... 80 00:07:31,517 --> 00:07:35,112 sooner or later they could invade the Jets' living space. 81 00:07:45,465 --> 00:07:49,902 Our pack's best defence is to engage in chemical warfare. 82 00:07:52,071 --> 00:07:53,971 The agent they use is scent. 83 00:07:54,140 --> 00:07:56,768 lt's a clear warning to outsiders to keep out - 84 00:07:56,943 --> 00:08:01,141 a signal all wolves recognise and ignore at their peril. 85 00:08:04,817 --> 00:08:07,183 Wolves leave a scent mark every hundred metres 86 00:08:07,353 --> 00:08:10,379 or so along their trails and boundaries. 87 00:08:22,735 --> 00:08:27,035 These signposts are unmissable, and they last for weeks... 88 00:08:27,974 --> 00:08:31,410 ideal for animals constantly on the move. 89 00:08:36,449 --> 00:08:40,044 And the source material is portable and easy to produce. 90 00:08:49,929 --> 00:08:55,026 As the urine spreads and evaporates, it releases the wolf's personal perfume. 91 00:08:59,805 --> 00:09:03,468 Scent marking is the responsibility of the two pack leaders. 92 00:09:03,643 --> 00:09:06,578 All they need to do is refresh each mark as they travel - 93 00:09:06,746 --> 00:09:10,739 leaving a trail of reassuringly familiar, smelly hotspots. 94 00:09:13,419 --> 00:09:17,651 A wolf has more than two hundred million scent receptors in its nose, 95 00:09:17,890 --> 00:09:22,452 making its sense of smell ten thousand times more sensitive than ours. 96 00:09:25,197 --> 00:09:29,395 Along its territorial boundaries, each pack goes into overdrive, 97 00:09:29,569 --> 00:09:32,800 responding to the threatening smell of its neighbours. 98 00:09:35,141 --> 00:09:36,870 The stakes are so high here 99 00:09:37,076 --> 00:09:41,809 that wolves use droppings, as well as urine, as a double deterrent to intruders. 100 00:09:46,619 --> 00:09:51,386 The alphas encounter and produce a scent signal every two minutes. 101 00:09:54,160 --> 00:09:59,359 By doggedly reinforcing their frontline, they try to keep their territory secure... 102 00:10:05,137 --> 00:10:08,766 ...leaving them time to relax and socialise. 103 00:10:13,412 --> 00:10:16,904 The pack's social life revolves around the alpha wolves... 104 00:10:17,817 --> 00:10:22,117 They dominate more by strength of personality than by brute force. 105 00:10:24,957 --> 00:10:28,916 They use facial expressions and body language to keep everyone in line 106 00:10:29,095 --> 00:10:30,926 and show how they feel. 107 00:10:36,802 --> 00:10:39,771 Dominance and submission help keep the peace. 108 00:10:41,507 --> 00:10:43,407 These tussles may look aggressive, 109 00:10:43,576 --> 00:10:46,136 but they can simply be a way of reinforcing bonds 110 00:10:46,312 --> 00:10:49,907 and reassuring each wolf of its place in the pack. 111 00:10:53,719 --> 00:10:55,880 The adolescents are almost full-grown... 112 00:10:56,122 --> 00:10:58,590 but still too young to leave the pack. 113 00:10:59,825 --> 00:11:02,589 For them, free time is playtime. 114 00:11:13,973 --> 00:11:15,907 Company is vital for a wolf... 115 00:11:18,044 --> 00:11:21,172 separation can lead to disaster. 116 00:11:22,114 --> 00:11:25,277 Last spring, the alpha female was left alone... 117 00:11:28,521 --> 00:11:33,390 With prey in very short supply, the pack was forced to split up to search for food, 118 00:11:33,559 --> 00:11:36,756 leaving her at the den to guard her pups. 119 00:11:37,563 --> 00:11:40,430 After a week, she faced a harsh choice - 120 00:11:41,467 --> 00:11:44,402 leave her pups or starve. 121 00:11:46,806 --> 00:11:49,331 Even underground, pups can be vulnerable... 122 00:11:49,508 --> 00:11:53,444 but in the end the mother's hunger drove her to take the risk. 123 00:12:03,889 --> 00:12:07,655 A grizzly's sense of smell is as powerful as a wolf's - 124 00:12:07,827 --> 00:12:12,230 and after a long winter without food, it has a craving for protein. 125 00:12:56,709 --> 00:13:00,008 This time the wolves' attack came too late... 126 00:13:05,084 --> 00:13:10,954 With her pups dead, the female's only chance to breed last year was dashed. 127 00:13:13,859 --> 00:13:16,293 Teamwork is the key to wolf survival. 128 00:13:16,462 --> 00:13:19,761 Even if you're the underdog, it's best to be one of the gang. 129 00:13:22,001 --> 00:13:24,731 Life on his own would be lonely and short. 130 00:13:34,146 --> 00:13:39,311 Operating as a pack is also the only way wolves can hunt big animals effectively. 131 00:13:45,424 --> 00:13:48,916 And it's always the alpha wolves who take the lead. 132 00:14:03,709 --> 00:14:06,007 The Jets haven't eaten for four days 133 00:14:06,178 --> 00:14:09,272 and now they're totally focused on finding food. 134 00:14:15,354 --> 00:14:17,481 Each wolf taps into its mental map, 135 00:14:17,923 --> 00:14:20,517 which isn't just a 3-dimensional route-planner, 136 00:14:20,693 --> 00:14:22,854 it's also a picture catalogue - 137 00:14:23,395 --> 00:14:26,091 a menu of prey animals available. 138 00:14:27,967 --> 00:14:29,958 Any one is an attractive target. 139 00:14:30,135 --> 00:14:35,471 But ranging in size from fifty to a thousand kilos - none is easy meat. 140 00:14:38,911 --> 00:14:41,641 Bighorn sheep are fairly small, but live in groups, 141 00:14:41,814 --> 00:14:45,306 have big attitudes - and serious headgear. 142 00:14:52,858 --> 00:14:57,227 Others, like moose, are solitary and roam territories of their own. 143 00:14:57,396 --> 00:14:58,363 Every few weeks, 144 00:14:58,530 --> 00:15:02,899 the wolves check up on them to see if they've become sick or injured. 145 00:15:12,378 --> 00:15:15,472 Who to hunt and when are key to a successful kill - 146 00:15:15,714 --> 00:15:17,875 and their mental maps help them select animals 147 00:15:18,050 --> 00:15:20,917 that could offer the easiest pickings. 148 00:15:23,255 --> 00:15:25,246 Top of the menu today are elk... 149 00:15:25,424 --> 00:15:29,417 and the wolves must use their mental map to work out how to intercept them. 150 00:15:34,667 --> 00:15:38,433 Years of following migrating herds all through the changing seasons 151 00:15:38,771 --> 00:15:42,036 mean the wolves have memorised the elks' routine. 152 00:15:42,274 --> 00:15:45,903 ln January, they can predict the elk are heading for the valleys to the east, 153 00:15:46,078 --> 00:15:48,410 forty kilometres away. 154 00:16:19,144 --> 00:16:22,170 Just getting here has taken seven hours. 155 00:16:22,448 --> 00:16:26,350 Now they find a vantage point to keep the elk under surveillance. 156 00:16:28,721 --> 00:16:33,454 The best strategy for hunting big animals is to select the most vulnerable. 157 00:16:33,826 --> 00:16:36,522 Usually by midwinter, with food harder to find, 158 00:16:36,795 --> 00:16:39,628 some pregnant females will be struggling... 159 00:16:47,673 --> 00:16:50,107 As well as being almost four months pregnant, 160 00:16:50,309 --> 00:16:53,210 they have their seven month-old calves with them. 161 00:16:54,747 --> 00:16:58,683 The youngsters are weaned, but still stay with their mothers for protection. 162 00:16:58,851 --> 00:17:03,948 Wolves are always interested in calves, as they're more likely to make mistakes. 163 00:17:06,458 --> 00:17:08,983 But so far, this winter's been mild 164 00:17:09,161 --> 00:17:11,891 and food in this valley is still within easy reach. 165 00:17:12,064 --> 00:17:16,194 The females look well fed and healthy - and so do their calves. 166 00:17:19,138 --> 00:17:22,369 Has our pack come all this way for nothing? 167 00:17:23,475 --> 00:17:24,874 And there's another problem - 168 00:17:25,044 --> 00:17:28,480 the Jets are only four kilometers from their northern border. 169 00:17:29,314 --> 00:17:33,307 There's a danger the elk will drift across into Big Pack territory. 170 00:17:37,623 --> 00:17:42,583 From their position above the herd, the wolves may be able to spot a weak animal. 171 00:17:45,764 --> 00:17:50,292 After hours of waiting, it's the alpha male who makes a move... 172 00:17:59,011 --> 00:18:03,948 They've seen no obvious soft target, so it's time to take a closer look. 173 00:18:09,588 --> 00:18:12,455 They make no attempt to hide as they approach... 174 00:18:16,995 --> 00:18:19,987 ...and the elk know they're there. 175 00:18:24,069 --> 00:18:26,264 The wolves split up and assess the herd, 176 00:18:26,438 --> 00:18:28,030 looking for the wounded... 177 00:18:28,440 --> 00:18:29,600 the lame... 178 00:18:30,109 --> 00:18:31,599 the weak. 179 00:18:36,315 --> 00:18:39,011 Weakness is easier to see if the elk are moving; 180 00:18:39,184 --> 00:18:41,778 easier still if they're running. 181 00:18:42,020 --> 00:18:45,046 The alpha female has picked out a nervous calf... 182 00:18:45,557 --> 00:18:48,424 at this age, it's had little experience of wolves 183 00:18:48,594 --> 00:18:51,358 and its confidence can be easily shaken. 184 00:19:00,906 --> 00:19:02,840 Now the elk are forced to run, 185 00:19:03,008 --> 00:19:05,272 but the older animals know what to do. 186 00:19:07,179 --> 00:19:10,114 They run towards the front and in the middle of the herd - 187 00:19:10,449 --> 00:19:12,713 furthest away from the chasing pack - 188 00:19:12,885 --> 00:19:17,015 where they're less likely to be spotted if they are carrying an injury. 189 00:19:19,791 --> 00:19:21,588 The wolves can run as fast as elk, 190 00:19:21,760 --> 00:19:23,853 but after going without food for several days, 191 00:19:24,029 --> 00:19:26,725 will they have the stamina to keep up? 192 00:19:34,139 --> 00:19:35,936 The elk head for a frozen riverbed 193 00:19:36,108 --> 00:19:39,134 where drifting snow is deeper than on the slopes. 194 00:19:48,387 --> 00:19:50,582 lt's not a problem for the long-legged elk, 195 00:19:51,723 --> 00:19:54,954 but it slows the wolves and saps their energy... 196 00:20:02,901 --> 00:20:07,463 The wolves clear the drift and accelerate to forty miles per hour. 197 00:20:14,713 --> 00:20:18,843 The herd tries a different strategy and heads for the woods. 198 00:20:25,624 --> 00:20:28,320 They're much more sure-footed on the uneven surface of roots 199 00:20:28,493 --> 00:20:30,586 and hollows around the trees... 200 00:20:32,164 --> 00:20:34,826 Here, the wolves might find it tough to keep up. 201 00:20:35,000 --> 00:20:38,697 And perhaps among the trees, it's harder for them to single out a target? 202 00:20:45,677 --> 00:20:47,508 But the wolves are still focused... 203 00:20:47,679 --> 00:20:51,479 seeking to match their mental picture with a victim. 204 00:21:01,793 --> 00:21:03,624 The elk now turn for high ground - 205 00:21:03,795 --> 00:21:07,891 and use the slope to pick up speed and shake off the wolves that way. 206 00:21:25,450 --> 00:21:27,714 lnvisible to them, the herd runs straight 207 00:21:27,886 --> 00:21:31,947 through the pack's territorial boundary, marked by their scent. 208 00:21:37,963 --> 00:21:41,455 But will the wolves cross their own frontline? 209 00:21:44,469 --> 00:21:48,530 They don't hesitate... the stakes are just too high. 210 00:21:55,814 --> 00:21:57,441 They're in no-man's land now, 211 00:21:57,616 --> 00:22:02,144 and just a kilometre from the border of the Big Pack's territory. 212 00:22:05,090 --> 00:22:09,356 Even after five kilometres, the wolves still push the elk... 213 00:22:14,833 --> 00:22:17,199 The alpha female's locked onto a target... 214 00:22:17,369 --> 00:22:22,773 But the elk looks young and fit, so what can she see that we can't? 215 00:22:26,478 --> 00:22:28,412 ln fact, the elk's lame - 216 00:22:28,647 --> 00:22:32,708 and by slowing down the action, we can analyse her injury. 217 00:22:33,218 --> 00:22:38,349 Her right hind leg looks deformed and she can't fully extend it as she runs... 218 00:22:46,732 --> 00:22:49,792 Her hock joint appears bigger than it should be... 219 00:22:55,240 --> 00:22:57,800 lnside there's a bony growth over the joint. 220 00:22:57,976 --> 00:23:00,604 lt's like arthritis, but in such a young elk 221 00:23:00,779 --> 00:23:03,475 it's probably been caused by a kick or fracture. 222 00:23:03,682 --> 00:23:06,378 And it's now become a life-threatening handicap... 223 00:23:12,824 --> 00:23:15,850 The younger wolf is lighter and faster than her mother. 224 00:23:16,395 --> 00:23:19,489 But the elk weighs three times their combined weight... 225 00:23:19,798 --> 00:23:22,392 and it will take both of them to bring her down. 226 00:23:25,003 --> 00:23:26,698 Hamstringing is an option - 227 00:23:26,872 --> 00:23:29,033 but it's not the quickest way to kill... 228 00:23:29,207 --> 00:23:32,074 and one kick could be fatal for the wolves. 229 00:23:41,553 --> 00:23:43,612 The elk's almost running on empty, 230 00:23:43,789 --> 00:23:47,953 but a huge dose of adrenalin gives her a burst of incredible strength... 231 00:24:04,743 --> 00:24:08,702 Finally, the elk loses the fight... 232 00:24:15,120 --> 00:24:16,951 But our pack's in alien territory... 233 00:24:17,122 --> 00:24:20,421 and its presence hasn't gone unnoticed... 234 00:24:26,131 --> 00:24:28,656 The Big Pack is just two kilometres away. 235 00:24:28,834 --> 00:24:33,294 lt too was shadowing the herd... and spotted the elk running. 236 00:24:40,045 --> 00:24:41,842 Howling helps them muster... 237 00:24:49,921 --> 00:24:53,948 ...and delivers a spine-chilling warning to the Jets. 238 00:25:08,640 --> 00:25:11,336 No time for squabbling over the best cuts now... 239 00:25:11,510 --> 00:25:13,273 they rip into the rump and belly - 240 00:25:13,445 --> 00:25:16,380 wolfing down as much meat as they can. 241 00:25:19,651 --> 00:25:23,553 A wolf's stomach can store fifteen kilos, to digest later... 242 00:25:24,155 --> 00:25:28,683 Just as well... because the big pack's here in force. 243 00:25:46,878 --> 00:25:50,109 Our alpha male is his pack's chief protector... 244 00:25:50,282 --> 00:25:53,547 but will he lead them to defend their kill? 245 00:25:57,188 --> 00:26:00,624 Outnumbered 3 to 1 , they have a simple choice: 246 00:26:00,792 --> 00:26:03,556 back off or die. 247 00:26:21,346 --> 00:26:26,875 After all our pack's hard work, it's their rivals who benefit... 248 00:26:45,403 --> 00:26:48,031 The Jets retreat behind their frontline, 249 00:26:48,473 --> 00:26:51,237 but at least they're safe to hunt another day. 250 00:27:01,886 --> 00:27:05,913 lt's February, and this is the first fresh snowfall for months. 251 00:27:06,091 --> 00:27:08,184 The worsening conditions and deepening snow 252 00:27:08,360 --> 00:27:11,796 could make life harder for all the grazers. 253 00:27:23,608 --> 00:27:27,066 But what's bad for the wolf's prey could benefit the wolves... 254 00:27:27,345 --> 00:27:30,940 and right now, our pack needs a boost in fortune. 255 00:27:36,354 --> 00:27:38,481 The alpha female is ready to mate - 256 00:27:38,657 --> 00:27:41,751 which means a new chance to expand the pack. 257 00:27:43,762 --> 00:27:47,630 The alpha pair spends most of her six weeks on heat together. 258 00:27:48,133 --> 00:27:50,192 This close bond is vital. 259 00:27:50,402 --> 00:27:53,166 She'll need his help to raise their pups. 260 00:27:59,444 --> 00:28:02,140 Wolves mate for life and it's in the alphas' interests 261 00:28:02,313 --> 00:28:05,146 to be the only breeding animals in the pack. 262 00:28:05,350 --> 00:28:08,979 lt guarantees that all food and attention are devoted to their pups. 263 00:28:11,756 --> 00:28:16,193 At just under two, the adolescents are still too young to breed. 264 00:28:17,762 --> 00:28:21,858 When they are ready to start a family, they'll have to leave the pack. 265 00:28:31,943 --> 00:28:35,845 For all the wolves, the breeding season is the most stressful time of the year. 266 00:28:36,381 --> 00:28:39,839 But it's only at kills that tension turns to open aggression. 267 00:28:44,656 --> 00:28:50,253 To stay in peak condition, both alphas need and demand the richest pickings. 268 00:28:54,733 --> 00:28:57,065 The others must wait their turn... 269 00:29:01,773 --> 00:29:05,675 Both the alpha wolves' stress levels are at boiling point. 270 00:29:05,877 --> 00:29:07,868 The male picks on his sons. 271 00:29:13,718 --> 00:29:17,119 And his mate attacks her daughters. 272 00:29:21,626 --> 00:29:25,687 These intense outbursts keep the alphas' stress hormones sky-high, 273 00:29:25,864 --> 00:29:27,855 but also keeps them on top. 274 00:29:32,237 --> 00:29:35,400 And alpha-aggression suppresses the others' sex hormones, 275 00:29:35,573 --> 00:29:37,939 making them even more subdued. 276 00:29:42,714 --> 00:29:47,651 Whatever happens, the best thing to do is just grin and bear it. 277 00:29:54,592 --> 00:29:57,083 lf there was more than one breeding season a year, 278 00:29:57,262 --> 00:29:59,730 there'd be constant antagonism within the pack - 279 00:30:00,165 --> 00:30:02,963 and that would threaten everyone's survival. 280 00:30:29,260 --> 00:30:30,557 lt's late March. 281 00:30:30,962 --> 00:30:33,590 The deep snow and freezing conditions of the last few weeks 282 00:30:33,832 --> 00:30:37,097 have increased pressure on all the wolf's prey. 283 00:30:47,245 --> 00:30:49,145 Food is very hard to find... 284 00:30:49,380 --> 00:30:52,543 and many animals are living off their fat reserves. 285 00:30:59,390 --> 00:31:02,052 The weak are getting weaker. 286 00:31:04,062 --> 00:31:06,189 And it's up to the Jets to find them. 287 00:31:06,364 --> 00:31:08,924 But as always, they have a battle plan. 288 00:31:11,069 --> 00:31:14,197 They're heading south to a huge area of forest. 289 00:31:19,143 --> 00:31:23,876 With its open river course, this location offers both hiding places and food 290 00:31:24,048 --> 00:31:29,418 for one of the wolf's most daunting prey - moose. 291 00:31:35,927 --> 00:31:38,828 There are six moose living within our pack's territory. 292 00:31:39,497 --> 00:31:41,965 The wolves visit each one every few weeks - 293 00:31:42,133 --> 00:31:44,294 to monitor their condition. 294 00:31:49,107 --> 00:31:52,907 Their decision to come to this forest isn't a random one. 295 00:31:53,244 --> 00:31:55,439 Last time they tracked the moose that lives here, 296 00:31:55,613 --> 00:31:58,207 they detected signs of weakness. 297 00:31:58,416 --> 00:32:01,908 Now they're back, to see if there's any change. 298 00:32:08,026 --> 00:32:10,620 They wouldn't stand a chance against a healthy moose, 299 00:32:10,895 --> 00:32:13,295 but a sick animal is a different story - 300 00:32:13,464 --> 00:32:16,956 and they've come more than thirty kilometres to find out. 301 00:32:21,506 --> 00:32:24,907 But first they've got to track it down. 302 00:32:39,590 --> 00:32:43,082 The wolf hunts just as well by night as in the day. 303 00:32:48,132 --> 00:32:53,035 To help them see in low light, wolves' eyes are designed for night vision. 304 00:32:58,276 --> 00:33:00,244 Their eyes shine because a mirrored layer 305 00:33:00,411 --> 00:33:04,279 on the retina reflects all available light back into the eye. 306 00:33:04,682 --> 00:33:07,674 The clear lens in the middle sharpens the image. 307 00:33:12,757 --> 00:33:16,591 So to a wolf, the forest doesn't look so impenetrable... 308 00:33:16,761 --> 00:33:20,959 and its peripheral vision is sensitive to any sudden movement. 309 00:33:32,777 --> 00:33:36,144 The wolves split up to search by sight and smell... 310 00:33:46,858 --> 00:33:50,259 They can sniff out prey up to five kilometres away. 311 00:33:50,428 --> 00:33:55,422 All it takes is a single molecule of moose scent in a quadrillion of air molecules 312 00:33:55,600 --> 00:33:58,364 to help them identify their target. 313 00:34:05,109 --> 00:34:08,943 Up ahead, the solitary moose is looking for food. 314 00:34:11,182 --> 00:34:12,774 lt's over two metres tall, 315 00:34:12,950 --> 00:34:15,111 and weighs three hundred kilos - 316 00:34:15,286 --> 00:34:18,050 a formidable opponent for a pack of wolves... 317 00:34:23,361 --> 00:34:26,091 The moose has selected its surroundings carefully - 318 00:34:26,364 --> 00:34:30,095 the dense trees are a good protection against a wolf attack. 319 00:34:32,403 --> 00:34:35,770 And it too has finely tuned senses... 320 00:34:38,009 --> 00:34:41,968 But wherever the moose goes, it can't help leaving telltale clues - 321 00:34:42,313 --> 00:34:46,010 which could help the wolves build up a picture of their quarry. 322 00:34:48,352 --> 00:34:52,448 Millions of its hairs and skin cells constantly shower the ground... 323 00:34:57,295 --> 00:35:01,163 Every step creates a scent print from glands in its feet... 324 00:35:08,573 --> 00:35:10,973 And thanks to its high fibre diet, 325 00:35:11,275 --> 00:35:14,335 even traces of gas can linger... 326 00:35:23,554 --> 00:35:28,958 Just two kilometres away, the wolves walk into the moose's scent. 327 00:35:34,132 --> 00:35:36,498 For a short while, they stand rigid 328 00:35:36,667 --> 00:35:39,830 and point in the direction of the incoming scent. 329 00:35:49,447 --> 00:35:53,907 They take long, deep sniffs to identify the smell. 330 00:36:01,058 --> 00:36:03,322 Now they're all locked onto their target, 331 00:36:03,494 --> 00:36:06,122 they stalk upwind. 332 00:36:12,436 --> 00:36:13,903 The first clue - 333 00:36:14,138 --> 00:36:18,040 a depression in the snow where the moose rested just an hour ago... 334 00:36:19,944 --> 00:36:23,380 The alpha male investigates with quick, short sniffs. 335 00:36:23,548 --> 00:36:26,574 He inhales huge volumes of air straight up his nostrils 336 00:36:26,918 --> 00:36:29,614 and onto millions of scent receptors. 337 00:36:32,757 --> 00:36:36,386 Blowing hard back on the area dislodges even more scent particles, 338 00:36:36,627 --> 00:36:38,788 mingled with hair and skin cells. 339 00:36:38,963 --> 00:36:41,488 Each one could betray its owner... 340 00:36:44,402 --> 00:36:48,600 The heavy skin and hair loss indicates the moose is badly infested with ticks - 341 00:36:48,873 --> 00:36:51,341 and probably very weak. 342 00:36:56,881 --> 00:36:59,714 A second clue - the moose's tracks. 343 00:37:03,321 --> 00:37:07,553 The male's nose scans the footprint for the most concentrated odour. 344 00:37:12,263 --> 00:37:14,026 This time, as he exhales, 345 00:37:14,599 --> 00:37:18,262 he blows air away from the scent through slits in the side of his nose, 346 00:37:18,436 --> 00:37:20,768 so it isn't diluted by his breath. 347 00:37:25,243 --> 00:37:27,143 There's a hint of pus - 348 00:37:27,311 --> 00:37:30,405 suggesting the moose is injured and may well be lame. 349 00:37:32,617 --> 00:37:36,986 Their attention shifts from the ground to the branches above. 350 00:37:39,190 --> 00:37:42,455 They're looking for a trace of moose saliva... 351 00:37:43,894 --> 00:37:45,327 this is it. 352 00:37:48,966 --> 00:37:52,367 A foul stench suggests the moose has rotten teeth - 353 00:37:52,536 --> 00:37:54,436 a sure sign that it's old. 354 00:37:56,407 --> 00:38:00,070 And if it can't chew properly, may well be starving. 355 00:38:02,213 --> 00:38:06,809 All the evidence confirms the moose is an ideal target... 356 00:38:08,319 --> 00:38:12,153 ...but the wolves still need to get close enough before they strike... 357 00:38:15,760 --> 00:38:19,890 But given all the clues, this moose is all but dead on its feet. 358 00:39:14,985 --> 00:39:18,580 lt's late April and the wolf battlefield is changing. 359 00:39:19,890 --> 00:39:22,984 Rising temperatures stimulate new growth 360 00:39:23,361 --> 00:39:26,524 and release hibernating animals from their long sleep. 361 00:39:37,641 --> 00:39:40,667 The thaw gives the wolf's prey a welcome respite 362 00:39:41,011 --> 00:39:43,673 and offers the promise of fresh food. 363 00:39:47,818 --> 00:39:51,015 But spring isn't always an easy time for wolves. 364 00:39:51,255 --> 00:39:54,520 ln the big pack, there's mutiny... 365 00:39:59,163 --> 00:40:04,430 Fighting like this - not linked to the breeding season or a kill, is very rare. 366 00:40:04,602 --> 00:40:07,503 lt's happening because the pack has grown too big - 367 00:40:07,671 --> 00:40:09,662 the alphas' sons and daughters are now old 368 00:40:09,840 --> 00:40:12,809 and bold enough to challenge their authority. 369 00:40:16,247 --> 00:40:17,737 lf they kill their parents, 370 00:40:17,915 --> 00:40:21,248 one of the youngsters may get a chance to rule this territory. 371 00:40:21,419 --> 00:40:23,979 But force alone isn't enough. 372 00:40:29,427 --> 00:40:33,420 Do any of them have the strength of character to be a leader?... 373 00:40:38,102 --> 00:40:40,434 The big pack's in big trouble. 374 00:40:45,242 --> 00:40:47,802 Life couldn't be more different for the Jets... 375 00:40:52,850 --> 00:40:55,478 The alpha female has produced three pups 376 00:40:55,653 --> 00:40:57,985 and, this time, she's got more support - 377 00:40:58,155 --> 00:41:01,352 one of her daughters is on den-duty. 378 00:41:04,395 --> 00:41:08,855 After last year's tragedy - her mother's chosen the den site carefully... 379 00:41:10,100 --> 00:41:14,867 lt's on a steep ridge with excellent views and well inside the pack's territory. 380 00:41:16,540 --> 00:41:18,974 lt's also thirty metres from a stream - 381 00:41:20,444 --> 00:41:23,743 a vital resource for a nursing mother. 382 00:41:24,682 --> 00:41:28,641 She needs plenty of fresh water to produce more milk. 383 00:41:31,055 --> 00:41:36,550 The newborns induce a surge of puppy love in all the wolves - male and female. 384 00:41:36,727 --> 00:41:41,027 This makes the pack want to care for the pups and keeps them working as a team. 385 00:41:51,809 --> 00:41:56,576 And right now, all the other members of the team are ten kilometres away. 386 00:42:01,051 --> 00:42:05,181 This spring, there are plenty of large animals inside their territory - 387 00:42:05,923 --> 00:42:11,657 after a hard winter; some are too weak to offer much resistance to a hunting pack. 388 00:42:12,329 --> 00:42:13,728 Their job is to fill their bellies 389 00:42:13,898 --> 00:42:18,096 and take food back to the den for the alpha female and her daughter. 390 00:42:28,012 --> 00:42:31,209 From now on, they have to find enough to eat for everyone 391 00:42:31,382 --> 00:42:33,475 and keep the pups safe - 392 00:42:33,817 --> 00:42:36,684 it's survival at its simplest. 393 00:42:40,291 --> 00:42:44,751 But on the wolf battlefield, fortunes can quickly change... 394 00:42:51,435 --> 00:42:54,996 Just forty kilometres from where the Jets are feeding on their kill, 395 00:42:55,172 --> 00:42:59,131 this large river has washed up a meal for their neighbours. 396 00:43:02,613 --> 00:43:05,104 But the wolves aren't alone. 397 00:43:13,390 --> 00:43:17,019 And the young bear's just as desperate for food... 398 00:43:22,099 --> 00:43:25,694 These five young wolves are all that's left of the big pack. 399 00:43:26,036 --> 00:43:29,528 They are near starving and can't afford to lose their carcass, 400 00:43:29,707 --> 00:43:31,265 but can they defend it? 401 00:44:11,315 --> 00:44:14,580 As part of the big pack the wolves were efficient killers. 402 00:44:14,785 --> 00:44:18,949 But now this small band of youngsters struggle to fend off a young bear. 403 00:44:34,238 --> 00:44:36,365 lf this is the best they can do - 404 00:44:36,740 --> 00:44:40,039 these wolves will lose their battle to survive. 405 00:44:49,086 --> 00:44:51,919 Perhaps the big pack has finally had its day, 406 00:44:53,424 --> 00:44:57,383 but on the wolf battlefield, the seasons march on. 407 00:44:59,797 --> 00:45:01,059 lt's early August 408 00:45:01,231 --> 00:45:04,598 and the grazing animals are making the best of the rich menu available 409 00:45:04,768 --> 00:45:08,067 during the short, Rocky Mountain summer. 410 00:45:16,413 --> 00:45:18,005 Both youngsters and adults will need 411 00:45:18,182 --> 00:45:21,879 to be in prime condition for the long winter ahead. 412 00:45:22,453 --> 00:45:26,913 Now, at three months old, our pack's pups are still the centre of attention... 413 00:45:27,091 --> 00:45:29,457 and old enough to leave the den. 414 00:45:35,766 --> 00:45:40,066 Already they're showing the tenacity and character they'll need to survive. 415 00:45:55,886 --> 00:45:58,912 The alpha pair's strong leadership has paid off. 416 00:45:59,089 --> 00:46:04,049 And the pack's teamwork has given the three pups the best start in life. 417 00:46:15,472 --> 00:46:19,272 Together, they've got through the setbacks and challenges of the last year - 418 00:46:19,643 --> 00:46:24,478 and started to lay the foundations for a bigger, stronger pack. 419 00:46:42,199 --> 00:46:43,962 The pups are part of the team... 420 00:46:44,568 --> 00:46:47,162 ...and ready to take on the world. 421 00:46:58,715 --> 00:47:01,912 lt's time for the wolves to return to their life on the move... 422 00:47:08,392 --> 00:47:10,155 And the pups can begin to learn the skills 423 00:47:10,327 --> 00:47:13,922 they'll need to play their part in killing for the pack. 424 00:47:20,270 --> 00:47:26,209 The alpha female and her mate now have another generation to defend their future. 425 00:47:35,986 --> 00:47:37,578 And with their neighbours spent, 426 00:47:37,754 --> 00:47:41,781 ahead of our pack lies a land of opportunity. 427 00:47:46,496 --> 00:47:52,560 On the Wolf Battlefield, it's time for the Jets to draw a new frontline.