1 00:00:03,120 --> 00:00:04,503 Australia. 2 00:00:05,214 --> 00:00:08,841 A vast country of breathtaking natural beauty. 3 00:00:10,553 --> 00:00:14,847 Teeming with extraordinary and iconic animals. 4 00:00:18,635 --> 00:00:21,720 Among them, eastern grey kangaroos 5 00:00:21,731 --> 00:00:24,898 Found in the south-east in their millions. 6 00:00:26,226 --> 00:00:28,986 For the males, known as bucks, 7 00:00:29,813 --> 00:00:32,814 Their drive to perpetuate their species 8 00:00:32,825 --> 00:00:35,034 Means a life full of risk... 9 00:00:37,913 --> 00:00:39,913 ..And reward. 10 00:00:43,169 --> 00:00:45,753 From joey to buck... 11 00:00:47,590 --> 00:00:49,798 ..It's a battle for survival. 12 00:00:54,013 --> 00:00:56,096 As they roam the land, 13 00:00:56,265 --> 00:00:58,140 Climb up the social ladder... 14 00:00:59,176 --> 00:01:02,019 ..And fight for their mating rights... 15 00:01:04,106 --> 00:01:06,523 ..In a bid to secure their legacy. 16 00:01:11,113 --> 00:01:14,698 This is the secret life of the kangaroo. 17 00:01:16,610 --> 00:01:18,660 (kookaburra laughing) 18 00:01:23,042 --> 00:01:25,042 (birdsong) 19 00:01:32,292 --> 00:01:34,927 In each young kangaroo buck's life, 20 00:01:36,222 --> 00:01:40,057 The moment comes when he has to face a challenge. 21 00:01:49,235 --> 00:01:52,152 Fighting and defeating a bigger, higher-ranking male 22 00:01:52,363 --> 00:01:54,947 Could ensure access to better grazing... 23 00:01:56,817 --> 00:01:58,784 ..And the chance to mate. 24 00:02:00,746 --> 00:02:02,746 But the stakes are high. 25 00:02:07,244 --> 00:02:09,002 (hissing) 26 00:02:09,079 --> 00:02:11,130 A serious injury could be fatal. 27 00:02:16,336 --> 00:02:19,171 Sniffing is the prelude to confrontation. 28 00:02:22,259 --> 00:02:24,143 The kangaroo on the left is justin. 29 00:02:27,681 --> 00:02:30,265 He's been named by researchers studying the behavior 30 00:02:30,276 --> 00:02:33,193 Of a large population of eastern grey kangaroos 31 00:02:33,270 --> 00:02:35,195 At sundown national park, 32 00:02:35,272 --> 00:02:39,199 On the border of queensland and new south wales. 33 00:02:42,037 --> 00:02:45,780 His challenger on the right is a new arrival to the area, 34 00:02:45,791 --> 00:02:50,169 A wandering male trying to assert his dominance. 35 00:02:52,372 --> 00:02:55,174 The intruding male instigates the challenge. 36 00:02:56,302 --> 00:03:00,012 He coughs, which can be a sign of submission. 37 00:03:02,132 --> 00:03:06,018 But then he provokes justin and paws at him to goad him. 38 00:03:07,137 --> 00:03:10,731 Justin can either back down or retaliate. 39 00:03:12,234 --> 00:03:14,234 In an instant, both kangaroos 40 00:03:14,311 --> 00:03:16,228 Are up on the balls of their feet, 41 00:03:16,238 --> 00:03:18,396 Standing as tall as they can, 42 00:03:18,407 --> 00:03:21,200 Each hoping to intimidate his opponent. 43 00:03:23,320 --> 00:03:27,039 For a moment, the intruding male appears to back down. 44 00:03:29,076 --> 00:03:31,043 But after a brief pause... 45 00:03:32,254 --> 00:03:34,913 ..He renews the challenge. 46 00:03:34,924 --> 00:03:38,217 Like a boxer in a ring, he circles around his opponent. 47 00:03:43,015 --> 00:03:45,098 Perhaps trying to outmaneuver him. 48 00:03:48,178 --> 00:03:50,229 Kangaroos usually attack head-on. 49 00:03:54,768 --> 00:03:56,735 He circles again. 50 00:04:09,875 --> 00:04:13,168 Justin times his flying kick perfectly. 51 00:04:16,456 --> 00:04:18,674 It's a decisive blow. 52 00:04:23,055 --> 00:04:25,889 Justin swings his body to cement his victory 53 00:04:25,966 --> 00:04:28,058 In a display of strength. 54 00:04:30,896 --> 00:04:33,397 Then he sprays urine to assert his dominance. 55 00:04:38,404 --> 00:04:40,320 Meanwhile, two younger males 56 00:04:40,397 --> 00:04:42,406 Playfully spar behind the older males. 57 00:04:46,236 --> 00:04:49,288 Imitating the moves they'll need when they're older. 58 00:04:58,999 --> 00:05:01,133 The intruder has been defeated. 59 00:05:07,424 --> 00:05:10,726 His hand is dangling, clearly injured. 60 00:05:13,180 --> 00:05:15,180 If it doesn't heal quickly, 61 00:05:15,190 --> 00:05:17,515 He'll find it hard to feed 62 00:05:17,526 --> 00:05:19,943 And his boxing days will be over. 63 00:05:26,952 --> 00:05:29,369 Fighting is a potentially defining moment 64 00:05:29,446 --> 00:05:31,413 In these young bucks' lives. 65 00:05:32,866 --> 00:05:34,958 It's a form of ritualized behavior 66 00:05:35,035 --> 00:05:37,252 Which separates them from the females. 67 00:05:48,215 --> 00:05:51,391 While female kangaroos live in established home ranges, 68 00:05:51,518 --> 00:05:55,479 Clustering together in a largely peaceful social group known as a mob... 69 00:05:59,068 --> 00:06:01,902 ..Life for males is far more hazardous. 70 00:06:06,992 --> 00:06:10,118 Many roam the countryside in search of mates. 71 00:06:11,154 --> 00:06:14,239 This necessitates being exposed to risk 72 00:06:14,249 --> 00:06:16,375 To secure the future of their genes. 73 00:06:18,495 --> 00:06:22,214 And, above all, males need to assert themselves. 74 00:06:29,598 --> 00:06:34,393 For all bucks, a large part of life is about body image. 75 00:06:35,512 --> 00:06:37,437 Large males like tim, 76 00:06:37,514 --> 00:06:40,515 Who only visit sundown during breeding season, 77 00:06:40,526 --> 00:06:45,278 Like to impress with their big muscles and strong stature. 78 00:06:46,281 --> 00:06:48,031 Both to attract potential mates 79 00:06:48,108 --> 00:06:50,158 And to scare off rivals. 80 00:07:13,633 --> 00:07:15,475 Giant is an alpha male 81 00:07:15,644 --> 00:07:17,635 Who regularly visits a mob of kangaroos 82 00:07:17,646 --> 00:07:20,305 Which lives and grazes on a golf course 83 00:07:20,315 --> 00:07:22,441 In anglesea, victoria. 84 00:07:28,490 --> 00:07:30,574 Researchers named him with good reason. 85 00:07:32,319 --> 00:07:35,454 His large and muscular arms are a sign of great strength. 86 00:07:43,589 --> 00:07:45,881 Kangaroo males never stop growing... 87 00:07:47,593 --> 00:07:51,261 ..And studies have found that in some kangaroo species 88 00:07:51,338 --> 00:07:54,598 Muscle size is directly related to mating success. 89 00:07:59,688 --> 00:08:01,605 Forelimb measurements show that whereas 90 00:08:01,681 --> 00:08:04,682 Female muscle growth is proportional to body size, 91 00:08:04,693 --> 00:08:06,943 Male upper-body musculature 92 00:08:07,020 --> 00:08:09,529 Becomes disproportionate to the rest of their bodies 93 00:08:09,606 --> 00:08:11,364 As they mature... 94 00:08:13,535 --> 00:08:16,495 ..Resulting in beefed-up arms and chests. 95 00:08:18,040 --> 00:08:21,374 A fully-grown male can weigh 190 pounds... 96 00:08:22,544 --> 00:08:25,537 ..And can stand seven-and-a-half feet tall 97 00:08:25,547 --> 00:08:28,131 With an added three feet of tail. 98 00:08:32,137 --> 00:08:37,140 But while larger muscles may lead to more opportunity for passing on his genes, 99 00:08:37,217 --> 00:08:39,559 The extra bulk may also come at a cost 100 00:08:39,636 --> 00:08:41,603 For a large male like giant. 101 00:08:45,475 --> 00:08:48,568 While there's plenty of grass here on the golf course, 102 00:08:48,779 --> 00:08:51,488 Maintaining a larger body weight can be much harder 103 00:08:51,565 --> 00:08:53,532 When food and water are scarce... 104 00:08:55,410 --> 00:08:59,371 ..A common occurrence during scorching australian summers. 105 00:09:06,079 --> 00:09:08,079 As well as on the golf course, 106 00:09:08,090 --> 00:09:10,173 Wandering males are a common sight 107 00:09:10,250 --> 00:09:12,551 In the seaside town of anglesea. 108 00:09:14,421 --> 00:09:16,972 Particularly in the woodland near the beach. 109 00:09:21,094 --> 00:09:23,144 And even urban parks. 110 00:09:24,773 --> 00:09:28,525 Males will travel through on their way to find fresh mobs 111 00:09:28,602 --> 00:09:30,569 And new grazing. 112 00:09:34,616 --> 00:09:38,034 These large, wandering males may have better reproductive success 113 00:09:38,111 --> 00:09:40,111 Roaming around during breeding season 114 00:09:40,122 --> 00:09:43,039 As it allows them access to more females. 115 00:09:47,120 --> 00:09:50,630 The greatest distance a male eastern grey has been recorded covering 116 00:09:50,841 --> 00:09:54,551 Is 155 miles over a nine-month period. 117 00:10:10,319 --> 00:10:12,319 (birdsong) 118 00:10:13,822 --> 00:10:15,313 Kangaroos are well-adapted 119 00:10:15,324 --> 00:10:18,450 For a life both out on the pasture and on the move. 120 00:10:22,489 --> 00:10:25,665 Whenever they're out from the protective cover of woodland, 121 00:10:25,751 --> 00:10:27,626 They're potentially vulnerable. 122 00:10:30,172 --> 00:10:32,547 But they can escape quickly by hopping. 123 00:10:43,185 --> 00:10:45,435 Adult eastern greys have been clocked hopping 124 00:10:45,512 --> 00:10:48,563 At a top speed of 39 miles per hour. 125 00:10:51,693 --> 00:10:53,601 Kangaroos can achieve these speeds 126 00:10:53,612 --> 00:10:56,071 Due to special tendons in their ankles. 127 00:10:58,617 --> 00:11:01,701 Up to 50 per cent of the energy used for the first hop 128 00:11:01,778 --> 00:11:05,863 Is reused in the next hop by the extensor tendons 129 00:11:05,874 --> 00:11:08,124 Which act like elastic bands. 130 00:11:14,549 --> 00:11:17,467 To make it even easier, when a kangaroo is hopping, 131 00:11:17,544 --> 00:11:20,136 He doesn't need to make any effort to breathe. 132 00:11:26,386 --> 00:11:30,480 The kangaroo's diaphragm muscle, which controls breathing, 133 00:11:30,557 --> 00:11:33,149 Is pulled down by the action of hopping up... 134 00:11:36,896 --> 00:11:40,156 ..And is pushed in the other direction when he lands. 135 00:11:45,822 --> 00:11:49,582 This means each breath is perfectly in time with his hopping. 136 00:11:52,421 --> 00:11:54,662 And it's far easier to breathe when moving 137 00:11:54,673 --> 00:11:56,715 Than standing still. 138 00:12:01,596 --> 00:12:03,588 This energy-efficient way of traveling 139 00:12:03,598 --> 00:12:06,507 Means that males can cover vast distances 140 00:12:06,518 --> 00:12:10,353 In search of mobs and mates with relative ease. 141 00:12:19,990 --> 00:12:23,783 But being on the move means that males constantly face 142 00:12:23,860 --> 00:12:25,744 More dangers than females. 143 00:12:26,872 --> 00:12:30,457 As well as having to deal with heat and possible dehydration, 144 00:12:30,533 --> 00:12:32,709 They risk being hit by cars... 145 00:12:36,006 --> 00:12:40,759 ..Shot by farmers... And caught in wire fences. 146 00:12:50,637 --> 00:12:53,521 But it's not just full-grown bucks who face peril. 147 00:12:56,893 --> 00:13:01,896 For kangaroo males, a more hazardous life begins in the pouch, 148 00:13:01,907 --> 00:13:05,408 The pocket where marsupial mothers raise their young, 149 00:13:06,328 --> 00:13:08,328 Known as joeys. 150 00:13:11,908 --> 00:13:16,336 Ensuring the survival of their joeys can be a challenge for kangaroo mums. 151 00:13:18,590 --> 00:13:20,006 And it's especially difficult 152 00:13:20,083 --> 00:13:22,842 Getting male joeys through to the point of independence 153 00:13:22,919 --> 00:13:25,804 When they leave the pouch at around nine months. 154 00:13:27,015 --> 00:13:30,850 Over 50 per cent of male joeys die before they're weaned, 155 00:13:30,927 --> 00:13:33,645 A far higher proportion than of female joeys. 156 00:13:38,860 --> 00:13:42,529 Researchers are uncertain why male joeys are more vulnerable. 157 00:13:45,024 --> 00:13:47,867 One theory is that their bodies expend more energy 158 00:13:47,944 --> 00:13:50,778 Putting on muscle and growing larger bones, 159 00:13:50,789 --> 00:13:52,956 Rather than developing fat reserves 160 00:13:53,032 --> 00:13:55,708 That help them survive in leaner times. 161 00:14:02,717 --> 00:14:05,552 Researchers have also found that raising male joeys 162 00:14:05,628 --> 00:14:07,595 Can deplete a kangaroo mother. 163 00:14:09,891 --> 00:14:12,475 Studies have shown that mums with male joeys 164 00:14:12,552 --> 00:14:14,552 Have to eat more grass... 165 00:14:14,563 --> 00:14:15,895 Which puts them under pressure, 166 00:14:16,106 --> 00:14:18,806 Especially when food supplies are scarce. 167 00:14:21,644 --> 00:14:24,737 So when there's food around, they need to eat faster. 168 00:14:30,737 --> 00:14:34,914 Females are very unlikely to successfully raise joeys two years running 169 00:14:34,991 --> 00:14:36,875 If the first is a boy. 170 00:14:37,994 --> 00:14:39,919 If a mum has a girl first, 171 00:14:39,996 --> 00:14:43,590 She has an 86 per cent chance of her next baby surviving. 172 00:14:46,011 --> 00:14:47,927 Whereas if her first is a boy, 173 00:14:48,138 --> 00:14:51,347 Her declining body condition reduces that success rate 174 00:14:51,424 --> 00:14:53,474 To just 50 per cent. 175 00:15:12,028 --> 00:15:14,913 During the years between weaning from their mothers... 176 00:15:16,124 --> 00:15:19,951 ..And their first serious efforts at fighting and mating... 177 00:15:22,789 --> 00:15:26,925 ..Young males will need to feed and feed. 178 00:15:30,972 --> 00:15:33,514 When they're born, kangaroo joeys are tiny... 179 00:15:36,803 --> 00:15:38,937 ..Less than one inch in size... 180 00:15:41,566 --> 00:15:43,858 ..And weigh less than a tenth of an ounce. 181 00:15:48,564 --> 00:15:50,648 By the time they leave the pouch, 182 00:15:50,659 --> 00:15:52,825 They will weigh around 13 pounds. 183 00:15:54,654 --> 00:15:57,655 And to become sexually mature and start mating, 184 00:15:57,666 --> 00:15:59,749 They'll need to put on bulk. 185 00:16:05,498 --> 00:16:09,008 The growing kangaroos need to maximize the nutrition they can get 186 00:16:09,085 --> 00:16:11,386 From their low-energy grass diet. 187 00:16:13,139 --> 00:16:16,599 And their ability to regurgitate their food when it's semi-digested 188 00:16:16,676 --> 00:16:18,843 Helps them do this. 189 00:16:21,681 --> 00:16:23,690 Kangaroos have a digestive system 190 00:16:23,766 --> 00:16:25,775 Very similar to other grazers - 191 00:16:25,852 --> 00:16:27,819 Like cows and sheep. 192 00:16:30,949 --> 00:16:33,941 This process, known as chewing the cud, 193 00:16:33,952 --> 00:16:36,619 Combined with special bacteria in their guts 194 00:16:36,696 --> 00:16:38,195 Which ferments the grass, 195 00:16:38,206 --> 00:16:41,958 Turns grazing into an energy-efficient way of feeding. 196 00:16:47,215 --> 00:16:49,048 This enables kangaroos to survive 197 00:16:49,125 --> 00:16:52,093 Over areas of inhospitable habitat in australia. 198 00:16:54,881 --> 00:16:57,724 One reason why the population of eastern greys 199 00:16:57,800 --> 00:17:00,018 Stands at a healthy 16 million. 200 00:17:15,744 --> 00:17:18,161 Joeys stay with their mothers until they're fully weaned 201 00:17:18,237 --> 00:17:20,538 At around 18 months. 202 00:17:22,325 --> 00:17:24,241 They won't be sexually-mature adults 203 00:17:24,252 --> 00:17:27,045 Until they're around four to five years old. 204 00:17:30,592 --> 00:17:32,249 But, like any male teenagers, 205 00:17:32,260 --> 00:17:35,470 There's plenty to learn about life as a young buck. 206 00:17:40,101 --> 00:17:42,101 How to approach females. 207 00:17:42,187 --> 00:17:44,062 How to look cool. 208 00:17:46,191 --> 00:17:48,265 And how to fight. 209 00:17:51,279 --> 00:17:53,112 For the dominant males in waiting, 210 00:17:53,189 --> 00:17:56,115 Play-boxing is part of essential preparation 211 00:17:56,242 --> 00:17:58,117 For their fight to the top. 212 00:18:09,789 --> 00:18:11,798 In sundown national park, 213 00:18:11,874 --> 00:18:15,093 Four-year-old doodle is a typical teenage male. 214 00:18:17,639 --> 00:18:19,797 While he's not big enough to mate yet, 215 00:18:19,808 --> 00:18:21,808 He's working hard on his image... 216 00:18:27,056 --> 00:18:29,107 ..And trying to look macho. 217 00:18:34,823 --> 00:18:36,823 He needs to assert his masculinity 218 00:18:36,899 --> 00:18:39,066 By standing as tall as he can, 219 00:18:39,077 --> 00:18:40,910 With one forearm out 220 00:18:40,987 --> 00:18:43,621 And the other scratching his chest or his back. 221 00:18:48,837 --> 00:18:50,253 A key part of looking cool 222 00:18:50,329 --> 00:18:53,131 Comes down to this nonchalant attention seeking. 223 00:19:01,391 --> 00:19:05,184 While he still lives in the same national park as his mother, 224 00:19:05,395 --> 00:19:09,188 Doodle has moved further away from her home range since weaning. 225 00:19:12,685 --> 00:19:17,188 Female kangaroos typically stay within the same areas as their mothers 226 00:19:17,198 --> 00:19:19,657 And males are more likely to disperse. 227 00:19:22,278 --> 00:19:26,205 It's thought that this may be an evolutionary strategy 228 00:19:26,282 --> 00:19:28,875 Which reduces the chances of inbreeding. 229 00:19:43,132 --> 00:19:45,766 Doodle still lives close to his half-brother. 230 00:19:47,136 --> 00:19:49,103 They share a dad. 231 00:19:50,315 --> 00:19:52,389 They were born two months apart 232 00:19:52,400 --> 00:19:55,193 And have migrated to the same area together. 233 00:19:57,063 --> 00:20:00,323 Once they're fully grown, they can start to travel greater distances 234 00:20:00,399 --> 00:20:02,733 And take off from sundown... 235 00:20:02,744 --> 00:20:04,744 Along with other larger males. 236 00:20:10,326 --> 00:20:14,212 But while they're still here, like any teenage boys, 237 00:20:15,840 --> 00:20:19,258 They'll practice their moves on the females as much as they can. 238 00:20:30,096 --> 00:20:32,146 (birdsong) 239 00:20:38,279 --> 00:20:40,696 The adolescent bucks' interactions with females 240 00:20:40,773 --> 00:20:42,949 Are rather like teenage crushes. 241 00:20:44,452 --> 00:20:46,285 Doodle might be too young to mate, 242 00:20:46,371 --> 00:20:49,705 But that doesn't stop him from trying to woo an older female. 243 00:21:01,377 --> 00:21:04,804 His efforts mostly consist of following the female around... 244 00:21:07,308 --> 00:21:09,267 ..And grazing alongside her. 245 00:21:14,807 --> 00:21:17,233 Sometimes he tries grazing in front of her... 246 00:21:20,396 --> 00:21:22,280 ..Hoping to get noticed. 247 00:21:23,324 --> 00:21:25,908 It's not the most sophisticated approach. 248 00:21:29,155 --> 00:21:31,205 And then... 249 00:21:32,500 --> 00:21:34,292 ..He clucks. 250 00:21:35,411 --> 00:21:37,336 Clucking is the noise males make 251 00:21:37,413 --> 00:21:39,338 To express their interest in females. 252 00:21:39,415 --> 00:21:42,091 (clucking) 253 00:21:42,168 --> 00:21:44,927 It's the kangaroo equivalent of the pick-up line. 254 00:21:49,434 --> 00:21:52,059 But his efforts are falling on deaf ears. 255 00:21:53,095 --> 00:21:55,855 The female has a small joey in her pouch. 256 00:21:57,266 --> 00:22:00,860 This means that she won't be ready to mate again for a few months. 257 00:22:11,205 --> 00:22:14,165 Eastern grey females are seasonal breeders... 258 00:22:15,201 --> 00:22:18,336 ..With peak births occurring between December and March. 259 00:22:25,970 --> 00:22:27,720 But they're polyestrous, 260 00:22:27,797 --> 00:22:31,766 Meaning that they can have more than one breeding cycle in a year. 261 00:22:37,565 --> 00:22:39,982 While a joey is in the pouch for nine months, 262 00:22:41,069 --> 00:22:43,227 A female may return to estrus 263 00:22:43,237 --> 00:22:45,363 When the joey is around five months old. 264 00:22:52,330 --> 00:22:54,413 If the female conceives at this point, 265 00:22:54,490 --> 00:22:57,416 She's able to do something extraordinary. 266 00:22:57,493 --> 00:22:59,418 She can keep that embryo in waiting 267 00:22:59,587 --> 00:23:02,380 Until her current joey is ready to vacate the pouch. 268 00:23:03,591 --> 00:23:06,425 She can also conceive again at different times of the year 269 00:23:06,502 --> 00:23:09,336 If her current joey doesn't survive. 270 00:23:09,347 --> 00:23:14,091 So young males like doodle work on the basis of persistence. 271 00:23:16,929 --> 00:23:20,064 Keeping up his moves on the female could mean that one day... 272 00:23:21,943 --> 00:23:25,018 ..Doodle could be in the right place at the right time 273 00:23:25,029 --> 00:23:27,238 And get a chance to mate. 274 00:23:41,295 --> 00:23:45,047 Pestering females is a constant part of a buck's life at any age. 275 00:23:51,556 --> 00:23:54,974 Justin, who previously won the fight with another male, 276 00:23:55,560 --> 00:23:58,477 Is trying to woo a female resting in the shade. 277 00:24:00,306 --> 00:24:02,306 He makes his interest clear 278 00:24:02,316 --> 00:24:04,483 By clucking and posturing in front of her. 279 00:24:06,562 --> 00:24:08,863 But she's doing her best to ignore him. 280 00:24:11,400 --> 00:24:14,452 Her trembling reveals that she doesn't want him near her. 281 00:24:17,248 --> 00:24:19,072 Justin's scratching is a sign 282 00:24:19,083 --> 00:24:21,083 That he's not being too forceful. 283 00:24:30,252 --> 00:24:32,887 She sniffs the scent glands in his chest. 284 00:24:35,600 --> 00:24:38,434 But that doesn't seem to pique her interest. 285 00:24:40,688 --> 00:24:43,013 But he doesn't give up 286 00:24:43,024 --> 00:24:45,149 And follows her when she takes off. 287 00:24:52,033 --> 00:24:53,616 Her lack of interest could be a sign 288 00:24:53,692 --> 00:24:55,993 That she's currently not in estrus. 289 00:25:01,375 --> 00:25:04,376 For the males, the key to successful mating 290 00:25:04,453 --> 00:25:08,506 Is knowing when a female is more likely to be receptive to their advances. 291 00:25:20,719 --> 00:25:24,221 So male kangaroos will check females regularly 292 00:25:24,232 --> 00:25:26,941 For any signs of reproductive readiness. 293 00:25:43,751 --> 00:25:46,410 Doodle sniffs a female's urine 294 00:25:46,420 --> 00:25:48,420 As well as her cloaca... 295 00:25:48,497 --> 00:25:51,549 The opening used for both reproduction and excretion. 296 00:25:53,427 --> 00:25:55,594 He can detect hormones that will tell him 297 00:25:55,671 --> 00:25:57,596 Whether she'll soon be ready. 298 00:26:04,522 --> 00:26:06,605 As females get closer to ovulating, 299 00:26:06,816 --> 00:26:10,109 Males like justin become increasingly persistent. 300 00:26:15,199 --> 00:26:19,276 But if he's not high enough ranking, or still too young, 301 00:26:19,287 --> 00:26:21,620 Then this is mostly as far as he gets. 302 00:26:38,556 --> 00:26:41,056 Some males have to resort to sneaky tactics 303 00:26:41,133 --> 00:26:43,517 To ensure that they get the chance to mate. 304 00:26:47,315 --> 00:26:49,315 While it's predominantly the larger males 305 00:26:49,391 --> 00:26:51,442 Who reserve the mating rights... 306 00:26:52,820 --> 00:26:55,654 ..Researchers at sundown have identified another class 307 00:26:55,865 --> 00:27:00,242 Of lower-ranking males who do sometimes get the girls. 308 00:27:04,832 --> 00:27:07,291 These males have been dubbed 'homeboys'. 309 00:27:08,753 --> 00:27:11,337 Smaller, less assertive males 310 00:27:11,413 --> 00:27:13,330 Who are less likely to be strong enough 311 00:27:13,341 --> 00:27:15,424 For the vagaries of life on the road. 312 00:27:18,846 --> 00:27:22,348 So they stick around with sundown's regular mobs. 313 00:27:22,424 --> 00:27:24,516 And when the opportunity arises - 314 00:27:25,511 --> 00:27:28,354 Usually outside the main breeding season - 315 00:27:28,430 --> 00:27:30,481 They're there to take it. 316 00:27:33,694 --> 00:27:36,695 Dna tests have revealed a surprising number of joeys 317 00:27:36,772 --> 00:27:40,532 Are fathered by these more opportunistic lower-ranking males. 318 00:27:53,872 --> 00:27:57,341 It's September and early summer in australia. 319 00:27:58,636 --> 00:28:01,679 It's now that the main breeding season gets underway 320 00:28:02,548 --> 00:28:05,307 And wandering males seize their chances. 321 00:28:06,802 --> 00:28:09,687 Tim joins a mob of kangaroos in a small park... 322 00:28:10,731 --> 00:28:12,690 ..On his way back to sundown. 323 00:28:14,735 --> 00:28:17,736 He identifies a female and spends several days 324 00:28:17,947 --> 00:28:19,738 Grazing near her. 325 00:28:30,492 --> 00:28:32,909 He detects that she's close to estrus 326 00:28:32,920 --> 00:28:36,714 And wherever she goes, he follows. 327 00:28:40,845 --> 00:28:43,721 He waits until the timing's right. 328 00:28:53,858 --> 00:28:56,567 Tail stroking is part of the ritual. 329 00:29:01,365 --> 00:29:04,575 And then he gets what he's been waiting for. 330 00:29:07,288 --> 00:29:09,788 Mating can be a protracted process... 331 00:29:09,865 --> 00:29:11,749 With regular breaks in the action. 332 00:29:31,553 --> 00:29:34,772 But even after that, tim's work still won't be done. 333 00:29:36,892 --> 00:29:39,818 Although he'll play no part in parenting, 334 00:29:39,895 --> 00:29:42,780 He needs to ensure that he successfully reproduces. 335 00:29:44,566 --> 00:29:47,785 So he'll spend time guarding his mate from rival males. 336 00:29:54,418 --> 00:29:56,543 Then he'll be on the move again. 337 00:30:16,524 --> 00:30:19,316 It's not long before tim arrives at sundown... 338 00:30:22,029 --> 00:30:24,604 ..Along with a number of other larger males, 339 00:30:24,615 --> 00:30:26,439 Including jimmy, 340 00:30:26,450 --> 00:30:29,368 Who've made their way back here for breeding season. 341 00:30:34,449 --> 00:30:37,617 Now the competition between them all begins in earnest. 342 00:30:37,628 --> 00:30:39,870 (hissing) 343 00:30:39,880 --> 00:30:43,841 The posturing, preening and picking fights escalate... 344 00:30:44,960 --> 00:30:48,303 ..To establish who is top buck and who gets to mate. 345 00:30:50,465 --> 00:30:54,601 For the most part, males know their rough position in the pecking order. 346 00:30:55,804 --> 00:31:00,858 And the hierarchy is often kept in place with long, penetrating stares. 347 00:31:06,073 --> 00:31:07,322 (coughs) 348 00:31:07,399 --> 00:31:09,733 A submissive cough can be enough 349 00:31:09,743 --> 00:31:11,910 To prevent an escalation in hostilities. 350 00:31:22,089 --> 00:31:26,884 If that fails, males need to stand up to show how big they are. 351 00:31:32,600 --> 00:31:34,933 Males of all ages are jostling for position. 352 00:31:46,438 --> 00:31:50,741 For the teenagers at sundown, this is still an important time of year. 353 00:31:59,117 --> 00:32:01,418 Rivalries are established. 354 00:32:03,130 --> 00:32:05,839 And they get to fight with their peers... 355 00:32:06,550 --> 00:32:09,885 ..Determining the pecking order for the seasons to come. 356 00:32:16,185 --> 00:32:17,976 (hiss) 357 00:32:23,567 --> 00:32:24,983 At four years old, 358 00:32:25,069 --> 00:32:27,945 Doodle may not yet be able to take on the top bucks... 359 00:32:30,074 --> 00:32:32,950 ..But he's getting himself into plenty of contests. 360 00:32:37,164 --> 00:32:39,957 This is a typical teenage boy fight. 361 00:32:42,828 --> 00:32:44,711 There's less decisive kicking... 362 00:32:45,589 --> 00:32:47,881 ..And more grappling and arm waving. 363 00:32:54,598 --> 00:32:57,599 Doodle leans his head right back to protect his eyes 364 00:32:57,676 --> 00:32:59,643 From his opponent's sharp claws. 365 00:33:06,026 --> 00:33:09,903 Both bucks keep hopping, learning to balance with their tails. 366 00:33:16,620 --> 00:33:18,620 Testosterone levels are raging. 367 00:33:20,624 --> 00:33:23,542 And young upstarts are brawling all over the place. 368 00:33:33,220 --> 00:33:35,470 Fights are more common among the lower ranks 369 00:33:35,547 --> 00:33:37,681 Who don't have high status to defend. 370 00:33:47,067 --> 00:33:49,067 But at this time of year, 371 00:33:49,144 --> 00:33:51,778 The larger males have one thing on their minds. 372 00:33:58,078 --> 00:34:02,039 Mating rights are hard-won and not given up lightly. 373 00:34:20,267 --> 00:34:22,851 All-out battle poses risks, 374 00:34:22,928 --> 00:34:26,063 But if they have to fight, the big males come well-armed. 375 00:34:35,857 --> 00:34:38,075 As well as their muscular forearms, 376 00:34:39,953 --> 00:34:43,205 Their long, sharp claws are a real threat to eyes and ears. 377 00:34:45,334 --> 00:34:48,919 The muscular tail acts as a fifth limb during warfare. 378 00:34:51,298 --> 00:34:55,008 The bucks can balance on their tails to produce a powerful kick. 379 00:34:58,213 --> 00:35:00,964 While the sharp claws on the tips of their toes 380 00:35:00,974 --> 00:35:02,766 Can do damage. 381 00:35:04,311 --> 00:35:07,646 An even greater threat comes from the force of the kick itself, 382 00:35:07,722 --> 00:35:10,607 Which can break bones and injure organs. 383 00:35:11,318 --> 00:35:14,945 Luckily, male kangaroos have thicker skin on their stomachs. 384 00:35:15,823 --> 00:35:17,823 This acts as a dermal shield, 385 00:35:17,899 --> 00:35:21,201 Which offers some protection from the force of a running kick. 386 00:35:37,669 --> 00:35:40,137 Justin tries his luck with another female. 387 00:35:46,261 --> 00:35:48,937 But just as he's getting interested, 388 00:35:49,014 --> 00:35:51,148 Alpha male tim arrives on the scene. 389 00:35:57,856 --> 00:36:01,274 All justin can do is defer to the higher-ranking male. 390 00:36:04,288 --> 00:36:07,080 And tim turns his attention to the female. 391 00:36:19,219 --> 00:36:21,845 Tim rubs his scent on the nearest bush. 392 00:36:31,306 --> 00:36:34,733 This is a way both of showing his supremacy over other males... 393 00:36:36,061 --> 00:36:38,236 ..And leaving a message for other females. 394 00:36:46,163 --> 00:36:48,163 He also does this by urinating, 395 00:36:48,240 --> 00:36:50,248 Though he catches the unfortunate female 396 00:36:50,417 --> 00:36:52,042 In the face. 397 00:37:10,103 --> 00:37:14,439 Tim continues to prowl the meadow, asserting his dominance. 398 00:37:17,352 --> 00:37:20,278 Males who are nervous, or don't want to fight, 399 00:37:20,447 --> 00:37:24,241 Sometimes tremble in the presence of an alpha like tim. 400 00:37:32,292 --> 00:37:36,127 He'll expect a male below him to give a submissive cough. 401 00:37:40,801 --> 00:37:44,302 When he doesn't get it, tim walks on his tiptoes 402 00:37:44,379 --> 00:37:46,462 To intimidate the other kangaroo. 403 00:37:46,473 --> 00:37:48,306 (hisses) 404 00:37:48,475 --> 00:37:50,383 That does the trick. 405 00:37:50,394 --> 00:37:52,978 The subordinate coughs as he backs away. 406 00:37:59,403 --> 00:38:03,280 As they graze, tim continues to growl at the nervous male. 407 00:38:05,993 --> 00:38:07,993 (birdsong) 408 00:38:11,406 --> 00:38:13,290 (squawking) 409 00:38:17,495 --> 00:38:20,163 Younger males will take any chance they can 410 00:38:20,173 --> 00:38:22,257 To raise their status. 411 00:38:24,011 --> 00:38:26,845 Teenager doodle is chasing a smaller rival... 412 00:38:28,932 --> 00:38:31,308 ..When they startle an older, larger male. 413 00:38:34,021 --> 00:38:37,272 Doodle mistakes his reaction for a sign of submission 414 00:38:37,349 --> 00:38:39,357 And lunges at the higher-ranking buck. 415 00:38:40,944 --> 00:38:44,321 Initially it appears that doodle's boldness has paid off. 416 00:38:50,862 --> 00:38:53,371 But the bigger male quickly regains his composure 417 00:38:53,498 --> 00:38:56,374 And stands tall to show his superior size 418 00:38:56,585 --> 00:38:58,460 With a big scratch. 419 00:39:04,468 --> 00:39:08,345 Doodle submits and peace is restored. 420 00:39:15,562 --> 00:39:20,398 It's been a few weeks since justin first fought and beat the visiting male. 421 00:39:23,478 --> 00:39:26,112 His rival suffered an injury to his wrist. 422 00:39:27,574 --> 00:39:29,407 But with his arm now healed, 423 00:39:29,534 --> 00:39:31,368 The intruder returns for round two. 424 00:39:41,588 --> 00:39:43,421 Brief, frantic periods of fighting 425 00:39:43,590 --> 00:39:47,425 Are often broken with a pause to posture and assess the opponent. 426 00:39:55,936 --> 00:39:58,019 The conflict resumes again. 427 00:40:28,385 --> 00:40:32,220 It's not always easy to declare a clear winner in a kangaroo fight. 428 00:40:34,975 --> 00:40:38,435 But this time justin doesn't manage to see off the intruder... 429 00:40:39,646 --> 00:40:42,272 ..So he won't gain status from this fracas. 430 00:40:55,403 --> 00:40:59,164 Unlike justin, who is still fighting his way up the ranks, 431 00:40:59,240 --> 00:41:02,959 A larger alpha like tim will rarely need to fight. 432 00:41:04,713 --> 00:41:08,247 When he challenges a smaller kangaroo over a female, 433 00:41:08,258 --> 00:41:10,467 The subordinate will jump away quickly. 434 00:41:20,687 --> 00:41:23,346 But when tim comes up against a proper rival, 435 00:41:23,356 --> 00:41:26,516 Jimmy, who could threaten his access to females, 436 00:41:26,526 --> 00:41:28,610 He knows he needs to challenge him. 437 00:41:52,377 --> 00:41:54,710 Tim's persistent posturing and scratching 438 00:41:54,721 --> 00:41:58,515 Right where jimmy's feeding can't go unchallenged. 439 00:42:03,555 --> 00:42:06,147 And tim gets what he's been asking for. 440 00:42:09,653 --> 00:42:13,196 Within seconds, tim and jimmy are squaring up. 441 00:42:28,079 --> 00:42:30,672 It's over quickly, but it's decisive. 442 00:42:46,097 --> 00:42:49,482 Jimmy rubs his scent on the ground to assert his dominance. 443 00:43:11,706 --> 00:43:15,675 Then declares himself the winner with a high stand. 444 00:43:26,646 --> 00:43:29,522 Tim's lowered head implies that he agrees. 445 00:43:33,236 --> 00:43:35,612 He picked on the wrong opponent this time. 446 00:43:43,488 --> 00:43:45,663 Having declared himself the winner over tim, 447 00:43:45,740 --> 00:43:49,751 Jimmy does what only a high-ranking male can do. 448 00:43:52,163 --> 00:43:54,213 He assumes mating rights. 449 00:43:58,887 --> 00:44:01,679 The female he selects has a joey at foot, 450 00:44:01,890 --> 00:44:03,681 But by smelling her urine 451 00:44:03,892 --> 00:44:06,601 Jimmy determines that she's in estrus 452 00:44:06,678 --> 00:44:09,312 And therefore capable of conceiving again. 453 00:44:11,766 --> 00:44:14,609 After sniffing and tail-groping... 454 00:44:15,862 --> 00:44:18,854 ..Jimmy gets the opportunity to pass on his genes 455 00:44:18,865 --> 00:44:21,199 To the next generation. 456 00:44:33,546 --> 00:44:35,672 At first, the female seems willing. 457 00:44:40,378 --> 00:44:42,512 Then she breaks away. 458 00:44:56,903 --> 00:44:59,395 Jimmy is reluctant to end the mating, 459 00:44:59,406 --> 00:45:02,156 But the female defiantly stands her ground. 460 00:45:13,753 --> 00:45:15,712 The pair mate again. 461 00:45:24,848 --> 00:45:27,181 But once more, she wants to get away. 462 00:45:30,770 --> 00:45:33,271 After finally escaping jimmy's grip, 463 00:45:33,347 --> 00:45:35,398 The female resumes grazing. 464 00:45:42,699 --> 00:45:44,782 Jimmy guards her closely. 465 00:45:47,862 --> 00:45:49,862 After successfully mating, 466 00:45:49,873 --> 00:45:52,582 He won't be letting rivals anywhere near her. 467 00:46:09,726 --> 00:46:12,810 For those males who aren't getting a chance to mate, 468 00:46:12,979 --> 00:46:17,231 Cementing their position in the pecking order remains the top priority. 469 00:46:23,323 --> 00:46:25,648 Undeterred by his last fight, 470 00:46:25,658 --> 00:46:28,785 Justin continues to battle his way up the ranks. 471 00:46:43,918 --> 00:46:46,469 Moving from one fight to the next. 472 00:46:53,928 --> 00:46:56,679 If he survives this season unscathed, 473 00:46:56,689 --> 00:47:00,650 He may have what it takes to one day be top buck in sundown. 474 00:47:10,945 --> 00:47:15,289 Meanwhile, doodle is still trying his luck with the females. 475 00:47:24,959 --> 00:47:29,262 Maybe next year. 476 00:47:33,050 --> 00:47:39,981 ♪♪ 477 00:47:40,057 --> 00:47:46,988 ♪♪ 478 00:47:47,064 --> 00:47:54,287 ♪♪