1 00:00:02,280 --> 00:00:05,880 The natural world is full of extraordinary animals 2 00:00:05,880 --> 00:00:08,360 with amazing life histories. 3 00:00:08,360 --> 00:00:11,920 Yet certain stories are more intriguing than others. 4 00:00:14,640 --> 00:00:17,920 The mysteries of a butterfly's life cycle, 5 00:00:17,920 --> 00:00:20,840 or the strange biology of the emperor penguin. 6 00:00:22,120 --> 00:00:26,200 Some of these creatures were surrounded by fantastic myths 7 00:00:26,200 --> 00:00:27,520 and misunderstandings. 8 00:00:29,360 --> 00:00:32,800 Others have only recently revealed their secrets. 9 00:00:34,080 --> 00:00:37,960 These are the creatures that stand out from the crowd, 10 00:00:37,960 --> 00:00:41,880 the curiosities that I find particularly fascinating. 11 00:00:49,280 --> 00:00:53,480 Some animals take fighting and sparring to an extreme. 12 00:00:55,800 --> 00:00:59,240 Kangaroos have kicks that can disembowel an opponent... 13 00:01:01,680 --> 00:01:05,560 ..while Siamese fighting fish will battle to the bitter end. 14 00:01:06,640 --> 00:01:09,960 What makes these animals such ferocious fighters? 15 00:01:17,920 --> 00:01:20,920 These are grey kangaroos. 16 00:01:20,920 --> 00:01:24,480 It's hard to imagine that anyone could think 17 00:01:24,480 --> 00:01:27,160 that such gentle, enchanting creatures 18 00:01:27,160 --> 00:01:31,840 could once have been considered as superb fighters. 19 00:01:31,840 --> 00:01:34,680 And yet, 120 years ago, 20 00:01:34,680 --> 00:01:38,160 one of them was put into a boxing ring 21 00:01:38,160 --> 00:01:41,880 and matched against a human opponent. 22 00:01:44,720 --> 00:01:48,520 In 1891, the Melbourne Punch published a cartoon 23 00:01:48,520 --> 00:01:51,280 about Jack the fighting kangaroo, 24 00:01:51,280 --> 00:01:54,720 who was pitted against a man named Professor Lendermann. 25 00:01:55,840 --> 00:01:58,040 The show attracted huge crowds, 26 00:01:58,040 --> 00:02:00,440 and soon Jack was not the only kangaroo 27 00:02:00,440 --> 00:02:02,160 to be seen in a boxing ring. 28 00:02:03,360 --> 00:02:04,720 All across the world, 29 00:02:04,720 --> 00:02:07,800 gloves were being strapped on kangaroos' front legs, 30 00:02:07,800 --> 00:02:11,960 and the questionable sport became a full-blown trend, 31 00:02:11,960 --> 00:02:14,560 which lasted well into the 20th century. 32 00:02:16,480 --> 00:02:18,440 Kangaroo boxing was big money, 33 00:02:18,440 --> 00:02:22,000 and some animals became celebrities in their own right. 34 00:02:23,520 --> 00:02:25,960 When Jack died, not surprisingly, 35 00:02:25,960 --> 00:02:28,720 he was quietly replaced with another Jack. 36 00:02:36,120 --> 00:02:39,800 Today, kangaroos are among the most familiar animals... 37 00:02:41,400 --> 00:02:43,560 ..and yet, when they were first discovered, 38 00:02:43,560 --> 00:02:46,160 they confused the scientific community. 39 00:02:48,880 --> 00:02:53,360 Early explorers described them as creatures with heads like deer, 40 00:02:53,360 --> 00:02:57,520 that stood upright like men, but hopped like frogs. 41 00:03:02,840 --> 00:03:07,280 The first image of a kangaroo seen by 18th-century Britons 42 00:03:07,280 --> 00:03:10,920 was this beautiful painting by George Stubbs. 43 00:03:11,920 --> 00:03:14,960 It was commissioned after Captain Cook's ship, the Endeavour, 44 00:03:14,960 --> 00:03:18,080 arrived back from his first voyage in 1771, 45 00:03:18,080 --> 00:03:21,600 bringing with it numerous specimens of animals 46 00:03:21,600 --> 00:03:23,920 totally unknown to Europeans. 47 00:03:23,920 --> 00:03:27,360 And one of the strangest was the kangaroo. 48 00:03:30,240 --> 00:03:32,600 Cook's crew encountered a kangaroo 49 00:03:32,600 --> 00:03:35,000 when they became the first Europeans 50 00:03:35,000 --> 00:03:37,520 to sail up the east coast of Australia, 51 00:03:37,520 --> 00:03:40,960 and their ship was beached for repairs. 52 00:03:40,960 --> 00:03:43,000 The men explored their surroundings 53 00:03:43,000 --> 00:03:45,760 and saw what the ship's naturalist described 54 00:03:45,760 --> 00:03:48,680 as "an animal as large as a greyhound, 55 00:03:48,680 --> 00:03:50,960 "of a mouse colour and very swift. 56 00:03:55,080 --> 00:03:59,320 "To compare it to any other animal," he went on, "would be impossible, 57 00:03:59,320 --> 00:04:02,840 "as it has not the least resemblance to any one that we've seen. 58 00:04:05,000 --> 00:04:09,600 "Its forelegs are extremely short, and of no use to it in walking. 59 00:04:09,600 --> 00:04:12,760 "Its hind legs again as disproportionately long." 60 00:04:15,280 --> 00:04:18,880 Before they left, they learned that the local aboriginal people 61 00:04:18,880 --> 00:04:21,520 called the mysterious animal a kangaroo. 62 00:04:23,360 --> 00:04:25,680 George Stubbs struggled to work out 63 00:04:25,680 --> 00:04:29,040 what the living creature must have looked like. 64 00:04:29,040 --> 00:04:33,160 He only had one or two simple pencil sketches like this one, 65 00:04:33,160 --> 00:04:35,600 which was drawn by one of the ship's artists. 66 00:04:37,200 --> 00:04:40,320 But he also had a dried kangaroo skin, 67 00:04:40,320 --> 00:04:42,520 and it's likely that he softened it 68 00:04:42,520 --> 00:04:44,560 and then inflated it with air 69 00:04:44,560 --> 00:04:47,840 to work out the extraordinary proportions 70 00:04:47,840 --> 00:04:50,440 of this really amazing creature. 71 00:04:50,440 --> 00:04:52,560 Eventually, he produced a likeness 72 00:04:52,560 --> 00:04:55,040 that captured the public's imagination. 73 00:05:00,680 --> 00:05:04,280 Although Stubbs' painting enchanted the Western world, 74 00:05:04,280 --> 00:05:07,720 there is still some debate today as to what kind of kangaroo 75 00:05:07,720 --> 00:05:10,480 Captain Cook's crew actually encountered. 76 00:05:12,560 --> 00:05:16,560 Early naturalists, thinking that it must be a gigantic rat, 77 00:05:16,560 --> 00:05:22,280 first gave it the name Jerboa giganteus, or "giant leaping rat". 78 00:05:24,880 --> 00:05:28,720 Today, we know that there are in fact over 50 different species 79 00:05:28,720 --> 00:05:31,000 of hopping creatures in Australia, 80 00:05:31,000 --> 00:05:32,560 and, strictly speaking, 81 00:05:32,560 --> 00:05:35,200 only the largest are called kangaroos. 82 00:05:37,440 --> 00:05:40,400 Those that are medium-sized are known as wallabies... 83 00:05:41,720 --> 00:05:44,560 ..while the smaller species go by fascinating names 84 00:05:44,560 --> 00:05:48,280 like quokka, bettong and potoroo, 85 00:05:48,280 --> 00:05:49,960 to name just a few. 86 00:05:54,320 --> 00:05:57,000 All these animals are known as macropods, 87 00:05:57,000 --> 00:05:58,760 and nearly all of them hop. 88 00:06:02,520 --> 00:06:06,200 It's this particular way of moving that may also be the reason 89 00:06:06,200 --> 00:06:09,040 for the kangaroo's unique style of kick boxing. 90 00:06:11,120 --> 00:06:14,520 This is the skeleton of a red kangaroo, 91 00:06:14,520 --> 00:06:17,600 and it's typical of all macropods. 92 00:06:17,600 --> 00:06:21,400 Kangaroos have the same basic leg bones as we do, 93 00:06:21,400 --> 00:06:23,600 but they are modified for hopping. 94 00:06:23,600 --> 00:06:26,760 The thigh bone, here, is relatively short... 95 00:06:27,920 --> 00:06:31,840 ..while the two bones of the lower leg are relatively long. 96 00:06:32,840 --> 00:06:38,040 The tendons, which connect with the muscles along the lower leg, 97 00:06:38,040 --> 00:06:43,200 act as springs, and the longer they are, the more energy they can store, 98 00:06:43,200 --> 00:06:46,880 and this allows the kangaroo to jump higher and faster. 99 00:06:48,120 --> 00:06:52,800 The ankle, on the other hand, can only move in one plane - 100 00:06:52,800 --> 00:06:54,520 backwards and forwards. 101 00:06:54,520 --> 00:06:57,000 And this gives it more stability 102 00:06:57,000 --> 00:06:59,120 when it impacts with the ground. 103 00:06:59,120 --> 00:07:02,960 And then there are these overly long feet - 104 00:07:02,960 --> 00:07:06,400 which are the reasons for the group's name, macropod, 105 00:07:06,400 --> 00:07:08,680 which means, literally, "big foot". 106 00:07:12,680 --> 00:07:16,560 The kangaroo skeleton is adapted for a life of hopping. 107 00:07:19,760 --> 00:07:21,560 But powering each hop 108 00:07:21,560 --> 00:07:25,440 are exceptionally strong elastic tendons and muscles. 109 00:07:27,800 --> 00:07:30,440 They compress with each bound... 110 00:07:32,800 --> 00:07:34,880 ..and then, when the energy is released, 111 00:07:34,880 --> 00:07:37,680 it propels the kangaroo into the air. 112 00:07:43,560 --> 00:07:46,960 And the large tail acts as a counterbalance 113 00:07:46,960 --> 00:07:48,720 to stabilise the motion. 114 00:07:52,680 --> 00:07:55,240 The impact from each landing can be so hard 115 00:07:55,240 --> 00:07:59,520 that most other animals would suffer damaged knees and broken feet. 116 00:08:02,040 --> 00:08:05,560 But kangaroos have evolved thick pads of cartilage 117 00:08:05,560 --> 00:08:07,680 which act as shock absorbers 118 00:08:07,680 --> 00:08:10,000 and help to minimise wear and tear. 119 00:08:13,680 --> 00:08:16,280 Kangaroos are not the only animals to hop, 120 00:08:16,280 --> 00:08:18,240 but they are by far the largest. 121 00:08:19,840 --> 00:08:23,000 So, it's not hard to imagine the astonishment and disbelief 122 00:08:23,000 --> 00:08:25,200 of the early European explorers 123 00:08:25,200 --> 00:08:28,200 at the sight of the giant hopping creature. 124 00:08:32,120 --> 00:08:35,400 It was not until the first live animals began to arrive in Europe 125 00:08:35,400 --> 00:08:37,200 at the end of the 18th century 126 00:08:37,200 --> 00:08:41,240 that we began to understand their curious body shape. 127 00:08:44,800 --> 00:08:47,960 Kangaroos adapted well to captivity, 128 00:08:47,960 --> 00:08:51,680 and soon became popular in early British zoos. 129 00:08:52,880 --> 00:08:55,680 People flocked to see the unusual creature. 130 00:08:57,720 --> 00:09:02,840 Soon, kangaroos were breeding so freely across the country 131 00:09:02,840 --> 00:09:06,480 that in 1806 an eminent naturalist said, 132 00:09:06,480 --> 00:09:11,400 "The kangaroo may now be considered as a great degree naturalised 133 00:09:11,400 --> 00:09:15,360 "in England, promising to render this most elegant animal 134 00:09:15,360 --> 00:09:18,160 "a permanent acquisition to our country." 135 00:09:20,720 --> 00:09:24,440 It was not long after that this book was published, 136 00:09:24,440 --> 00:09:26,920 which has an intriguing picture that sheds light 137 00:09:26,920 --> 00:09:29,760 on how the sport of kangaroo boxing may have come about. 138 00:09:30,960 --> 00:09:33,240 The author, Thomas Smith, 139 00:09:33,240 --> 00:09:36,960 visited a menagerie in the Exeter Exchange in London, 140 00:09:36,960 --> 00:09:39,320 and he describes how the animal 141 00:09:39,320 --> 00:09:43,480 wrestled with and kicked at its keeper for 10-15 minutes 142 00:09:43,480 --> 00:09:46,000 until it was reunited with its female. 143 00:09:46,000 --> 00:09:50,880 And his description was accompanied by this drawing. 144 00:09:52,080 --> 00:09:55,600 It's the first image of a boxing kangaroo, 145 00:09:55,600 --> 00:09:58,960 and shed some light on how the sport of kangaroo boxing 146 00:09:58,960 --> 00:10:00,840 may well have originated. 147 00:10:05,080 --> 00:10:08,880 Today, we know that, in the wild, this boxing happens 148 00:10:08,880 --> 00:10:12,600 when two males compete for dominance and mating rights. 149 00:10:15,920 --> 00:10:19,880 Most contests are brief and settled by posturing. 150 00:10:24,200 --> 00:10:26,760 Males will rise up on their back legs 151 00:10:26,760 --> 00:10:30,320 and display their size and large muscular forelimbs 152 00:10:30,320 --> 00:10:32,320 to impress their opponents... 153 00:10:34,200 --> 00:10:37,200 ..but when two rivals are evenly matched, 154 00:10:37,200 --> 00:10:39,440 things can get really violent. 155 00:11:00,720 --> 00:11:02,280 With their huge feet, 156 00:11:02,280 --> 00:11:06,320 they deliver kicks that can break bones and rip open a stomach. 157 00:11:13,120 --> 00:11:15,200 It's these ferocious battles 158 00:11:15,200 --> 00:11:19,680 that gave kangaroos the reputation for being champion boxers. 159 00:11:24,320 --> 00:11:27,800 The kangaroo's strange technique of fighting 160 00:11:27,800 --> 00:11:31,120 is a consequence of its odd body shape. 161 00:11:31,120 --> 00:11:35,040 Those powerful hind legs with which it strikes 162 00:11:35,040 --> 00:11:38,520 evolved in order to enable it to hop, 163 00:11:38,520 --> 00:11:42,520 and that muscular tail on which it props itself upright 164 00:11:42,520 --> 00:11:44,720 serves, normally, as a counterbalance 165 00:11:44,720 --> 00:11:46,000 when it's hopping. 166 00:11:46,000 --> 00:11:51,240 But why did this odd shape occur in the kangaroo family 167 00:11:51,240 --> 00:11:54,400 and in no other large animals in the world? 168 00:11:57,080 --> 00:12:00,280 The reason, it seems, is because of a shift 169 00:12:00,280 --> 00:12:03,720 from a life in the trees to life on the ground. 170 00:12:05,120 --> 00:12:09,600 The kangaroo's early ancestors were tree-living, possum-like creatures 171 00:12:09,600 --> 00:12:11,720 that came down to the forest floor. 172 00:12:13,920 --> 00:12:16,280 As the continent of Australia drifted north, 173 00:12:16,280 --> 00:12:18,800 some five or ten million years ago, 174 00:12:18,800 --> 00:12:21,480 a period of global cooling and drying 175 00:12:21,480 --> 00:12:25,320 saw rainforests give way to vast grassy plains. 176 00:12:26,400 --> 00:12:31,280 This provided an abundant supply of food for ground-dwelling grazers. 177 00:12:33,040 --> 00:12:37,200 And what better way to cruise the plains than by leaps and bounds? 178 00:12:41,560 --> 00:12:45,920 Hopping, in fact, is a very energy efficient way of getting around. 179 00:12:47,120 --> 00:12:49,920 Kangaroos can reach speeds of 40mph, 180 00:12:49,920 --> 00:12:52,080 yet they use half as much energy 181 00:12:52,080 --> 00:12:55,320 as a similar sized animal running on four legs. 182 00:12:58,920 --> 00:13:00,320 When kangaroos speed up, 183 00:13:00,320 --> 00:13:03,080 they don't increase the frequency of their hops, 184 00:13:03,080 --> 00:13:05,400 but, instead, lengthen their stride. 185 00:13:06,720 --> 00:13:08,200 The longer the stride, 186 00:13:08,200 --> 00:13:11,200 the more energy they pack into their muscles and tendons. 187 00:13:14,680 --> 00:13:17,880 In a vast, dry country like Australia, 188 00:13:17,880 --> 00:13:22,320 being able to travel long distances while using minimal energy 189 00:13:22,320 --> 00:13:24,240 may be crucial to survival. 190 00:13:29,600 --> 00:13:32,520 There is another, more recent, theory 191 00:13:32,520 --> 00:13:34,960 as to why it is that kangaroos hop. 192 00:13:34,960 --> 00:13:37,280 Like most mammals in Australia, 193 00:13:37,280 --> 00:13:40,200 kangaroos carry their babies in a pouch. 194 00:13:40,200 --> 00:13:42,480 But when the baby is first born, 195 00:13:42,480 --> 00:13:44,640 it's no bigger than a jelly bean, 196 00:13:44,640 --> 00:13:48,080 and it has to haul its way across its mother's abdomen 197 00:13:48,080 --> 00:13:50,440 to get into her pouch. 198 00:13:50,440 --> 00:13:56,240 To do that, it could be more important to have short, muscular, 199 00:13:56,240 --> 00:14:00,360 powerful arms to help pull themselves through the bristly fur 200 00:14:00,360 --> 00:14:02,120 than to have long front legs 201 00:14:02,120 --> 00:14:04,720 suitable for standing up and for running. 202 00:14:08,880 --> 00:14:12,240 The tiny baby is born blind and naked. 203 00:14:16,360 --> 00:14:20,400 It now has to haul itself through the thick fur on its mother's belly 204 00:14:20,400 --> 00:14:22,240 and up into her pouch. 205 00:14:24,840 --> 00:14:28,040 If it can't make the journey, it won't survive. 206 00:14:33,600 --> 00:14:37,400 The hind limbs, however, develop like those of other mammals, 207 00:14:37,400 --> 00:14:39,400 and they're much longer, 208 00:14:39,400 --> 00:14:42,600 so it could be that the kangaroo's hop evolved 209 00:14:42,600 --> 00:14:46,880 because of the difference in the growth of their fore and hind limbs. 210 00:14:54,040 --> 00:14:56,400 For the first 12 months of its life, 211 00:14:56,400 --> 00:15:00,360 the young joey spends most of its time in its mother's pouch. 212 00:15:00,360 --> 00:15:04,080 But when outside, it practises hopping and jumping, 213 00:15:04,080 --> 00:15:05,760 as well as the art of boxing. 214 00:15:09,720 --> 00:15:13,400 And its patient mother puts up with being used as a punching bag. 215 00:15:16,880 --> 00:15:20,400 It'll be another few years before this young joey 216 00:15:20,400 --> 00:15:22,880 is ready to fight for real stakes. 217 00:15:30,040 --> 00:15:31,360 With the kangaroo, 218 00:15:31,360 --> 00:15:33,680 we discovered a creature so fascinating 219 00:15:33,680 --> 00:15:37,040 that we took it into the boxing ring and made a show of it. 220 00:15:39,320 --> 00:15:43,640 Thankfully, this cruel sport is no longer deemed acceptable today. 221 00:15:45,480 --> 00:15:48,640 Now, kangaroos have lost much of their mystique. 222 00:15:50,520 --> 00:15:55,440 But their familiar exterior conceals an extremely efficient body design 223 00:15:55,440 --> 00:15:57,480 that continues to impress us. 224 00:16:00,040 --> 00:16:03,760 Our next animal also has a reputation for fighting - 225 00:16:03,760 --> 00:16:07,400 so much so that it's called the fighting fish. 226 00:16:08,560 --> 00:16:11,000 What makes this small creature so aggressive? 227 00:16:14,960 --> 00:16:18,440 These are Siamese fighting fish - 228 00:16:18,440 --> 00:16:22,840 or, to give them their scientific name, Betta splendens - 229 00:16:22,840 --> 00:16:27,160 and they come in a great variety of ravishing colours. 230 00:16:27,160 --> 00:16:29,360 So it's not difficult to understand 231 00:16:29,360 --> 00:16:31,840 why they are very popular aquarium fish. 232 00:16:31,840 --> 00:16:34,040 I used to keep them myself. 233 00:16:34,040 --> 00:16:39,160 They swim with all the grace of a virtuoso ballet dancer - 234 00:16:39,160 --> 00:16:41,480 but don't be deceived. 235 00:16:41,480 --> 00:16:45,160 Watch what happens when I lift this... 236 00:16:45,160 --> 00:16:46,480 ..and they see one another. 237 00:16:49,680 --> 00:16:51,760 Because the males are so aggressive, 238 00:16:51,760 --> 00:16:55,240 it's illegal to put them together in the same tank. 239 00:16:55,240 --> 00:16:59,160 Even so, each is determined to defend its territory. 240 00:17:00,400 --> 00:17:03,720 They distend their fins and push out their gill covers 241 00:17:03,720 --> 00:17:06,720 so that they appear larger and more imposing. 242 00:17:09,920 --> 00:17:13,040 If these two males were kept together in the same tank, 243 00:17:13,040 --> 00:17:14,800 they would soon turn on each other 244 00:17:14,800 --> 00:17:18,440 and one of them would almost certainly be killed. 245 00:17:18,440 --> 00:17:21,800 In the wild, fights between males only last a few minutes 246 00:17:21,800 --> 00:17:23,840 before one fish backs off - 247 00:17:23,840 --> 00:17:27,760 but in a confined space, they can carry on for hours 248 00:17:27,760 --> 00:17:30,920 and cause severe damage to each other. 249 00:17:30,920 --> 00:17:34,280 It's this fierceness that first attracted the attention 250 00:17:34,280 --> 00:17:36,480 of local people in Southeast Asia, 251 00:17:36,480 --> 00:17:39,720 where Siamese fighting fish occur in the wild, 252 00:17:39,720 --> 00:17:43,240 and this led to them being bred as fighting fish, 253 00:17:43,240 --> 00:17:45,280 on which people would bet. 254 00:17:47,800 --> 00:17:51,720 Villagers collected the fish from shallow pools and rice paddies 255 00:17:51,720 --> 00:17:55,800 and pitted them against each other to determine a village champion. 256 00:17:57,040 --> 00:17:59,600 It was a favourite pastime for centuries. 257 00:18:01,360 --> 00:18:04,440 And it wasn't long before people started breeding the fish 258 00:18:04,440 --> 00:18:06,280 for their fighting abilities. 259 00:18:10,440 --> 00:18:14,200 Seeing the popularity of the fights in the 19th century, 260 00:18:14,200 --> 00:18:17,680 the King of Thailand, or Siam, as it was once known, 261 00:18:17,680 --> 00:18:19,760 started collecting the fish himself. 262 00:18:22,800 --> 00:18:28,160 In 1840, the king gave some of his prized fish to a friend, 263 00:18:28,160 --> 00:18:31,640 who passed them to a physician working in Calcutta at the time, 264 00:18:31,640 --> 00:18:34,240 Dr Theodore Cantor. 265 00:18:34,240 --> 00:18:38,920 Cantor was the first to draw and describe the wild fish, 266 00:18:38,920 --> 00:18:40,680 and, by the turn of the century, 267 00:18:40,680 --> 00:18:44,000 the first ones were being imported into Europe and North America. 268 00:18:45,200 --> 00:18:47,560 One of the species that we know today 269 00:18:47,560 --> 00:18:52,560 as the Siamese fighting fish arrived in Britain in 1897. 270 00:18:52,560 --> 00:18:55,000 And this is the actual specimen. 271 00:18:56,640 --> 00:18:58,360 It looks very different 272 00:18:58,360 --> 00:19:01,200 from the flamboyant aquarium fish we know today. 273 00:19:01,200 --> 00:19:04,280 The name betta was given to the fish 274 00:19:04,280 --> 00:19:08,520 after a tribe in northern Siam who were ferocious warriors. 275 00:19:10,880 --> 00:19:12,400 For centuries, 276 00:19:12,400 --> 00:19:17,120 Siamese fighting fish were bred to increase their aggressiveness. 277 00:19:18,440 --> 00:19:21,120 But soon, different colours and fin shapes 278 00:19:21,120 --> 00:19:22,920 started to be valued, as well. 279 00:19:24,880 --> 00:19:28,240 It's likely that there were variations between populations 280 00:19:28,240 --> 00:19:31,600 and that breeders selected the more vibrant colours. 281 00:19:34,320 --> 00:19:38,400 Selective breeding also created a variety of tail fins, 282 00:19:38,400 --> 00:19:41,160 some draping down like a veil... 283 00:19:41,160 --> 00:19:44,200 ..others spiky, or half-moon shaped. 284 00:19:45,400 --> 00:19:49,080 Although today Siamese fighting fish are more widely sought after 285 00:19:49,080 --> 00:19:50,880 for their showy appearance, 286 00:19:50,880 --> 00:19:53,600 they're still one of the most aggressive of all fish. 287 00:19:54,640 --> 00:19:55,960 Given a chance, 288 00:19:55,960 --> 00:19:58,920 they will lock mouths and tear at each other's fins 289 00:19:58,920 --> 00:20:00,520 with their sharp teeth. 290 00:20:02,520 --> 00:20:06,400 It's a way of fighting that at first sight seems much the same 291 00:20:06,400 --> 00:20:08,440 as that used by many other fish. 292 00:20:10,840 --> 00:20:15,040 Cichlids in Lake Tanganyika fight in a very similar way. 293 00:20:16,600 --> 00:20:20,640 The males face their rivals head on and lock mouths. 294 00:20:21,640 --> 00:20:23,960 Each tries to push the other to the bottom. 295 00:20:30,000 --> 00:20:34,560 Cichlids may fight in much the same way as the Siamese fighters, 296 00:20:34,560 --> 00:20:37,920 but they seldom wound and never kill one another. 297 00:20:42,160 --> 00:20:45,960 Most animals fight for territories or for mates, 298 00:20:45,960 --> 00:20:48,760 and some will risk serious injury in doing so - 299 00:20:48,760 --> 00:20:52,200 but few will fight to the death, as these Siamese fish do. 300 00:20:53,200 --> 00:20:56,680 Why should this little fish be so aggressive? 301 00:20:56,680 --> 00:20:59,240 Well, it seems that it may have something to do 302 00:20:59,240 --> 00:21:01,960 with the extreme conditions in which they live. 303 00:21:05,720 --> 00:21:07,920 In the wild, they live in rice paddies 304 00:21:07,920 --> 00:21:09,880 in shallow pools and ditches. 305 00:21:11,480 --> 00:21:16,200 But suitable breeding territories in such places are in short supply. 306 00:21:19,360 --> 00:21:22,600 Keeping rivals at bay is particularly difficult, 307 00:21:22,600 --> 00:21:24,320 and only the most ferocious 308 00:21:24,320 --> 00:21:27,440 will be able to hold a territory and attract a mate. 309 00:21:30,240 --> 00:21:32,760 And the fish have another problem. 310 00:21:32,760 --> 00:21:35,880 The warm, stagnant water is low in oxygen, 311 00:21:35,880 --> 00:21:39,880 and their small gills can't keep up with the vigour of a fight. 312 00:21:41,400 --> 00:21:44,120 But they've evolved a way of dealing with that. 313 00:21:49,600 --> 00:21:51,200 Most fish breathe 314 00:21:51,200 --> 00:21:54,760 by extracting oxygen from the water with their gills. 315 00:21:54,760 --> 00:21:57,640 But one group has an additional structure 316 00:21:57,640 --> 00:22:00,440 which sits directly above the gills. 317 00:22:00,440 --> 00:22:02,720 It's called the labyrinth organ, 318 00:22:02,720 --> 00:22:07,000 and it enables the fish to extract oxygen directly from the air, 319 00:22:07,000 --> 00:22:08,800 much as our lungs do. 320 00:22:10,520 --> 00:22:14,480 It's a remarkable adaptation that allows Siamese fighting fish 321 00:22:14,480 --> 00:22:17,640 to live in waters that contain so little oxygen 322 00:22:17,640 --> 00:22:20,480 that no other fish could survive there. 323 00:22:26,600 --> 00:22:27,840 When males fight, 324 00:22:27,840 --> 00:22:31,520 they come to the surface regularly for gulps of air... 325 00:22:34,120 --> 00:22:37,680 ..but the rivals face a tactical problem. 326 00:22:37,680 --> 00:22:40,440 If one comes to the surface alone, 327 00:22:40,440 --> 00:22:43,800 it makes him vulnerable to attack from its opponent below... 328 00:22:45,200 --> 00:22:47,040 ..and from predators above. 329 00:22:50,280 --> 00:22:52,240 So, Siamese fighting fish 330 00:22:52,240 --> 00:22:55,680 have come to a seemingly gentlemanly arrangement. 331 00:22:55,680 --> 00:22:58,680 They both surface at the same time. 332 00:22:59,640 --> 00:23:02,800 This way, neither risks being attacked by the other 333 00:23:02,800 --> 00:23:04,840 when its back is turned. 334 00:23:07,280 --> 00:23:11,680 At the end of the day, all the fighting is about one thing only, 335 00:23:11,680 --> 00:23:14,760 how to attract a female and produce young. 336 00:23:14,760 --> 00:23:18,840 The female is much more drab, doesn't have the same huge fins, 337 00:23:18,840 --> 00:23:21,840 and she will do very little apart from producing the eggs. 338 00:23:21,840 --> 00:23:23,720 It's the male who builds a nest 339 00:23:23,720 --> 00:23:26,440 and cares for the young until they hatch. 340 00:23:26,440 --> 00:23:29,280 So, these males have good reason to be fierce - 341 00:23:29,280 --> 00:23:31,440 they invest a lot in breeding, 342 00:23:31,440 --> 00:23:34,600 and fighting off rivals is just the first step. 343 00:23:42,080 --> 00:23:44,160 They build a nest from bubbles. 344 00:23:46,200 --> 00:23:47,960 The male takes a gulp of air... 345 00:23:49,760 --> 00:23:52,400 ..and blows a bubble enclosed in mucus. 346 00:23:56,600 --> 00:23:58,640 He does this again and again, 347 00:23:58,640 --> 00:24:00,960 until he's created a whole raft of bubbles 348 00:24:00,960 --> 00:24:03,720 floating just underneath the surface. 349 00:24:05,920 --> 00:24:08,760 Within a few hours, the nest is complete. 350 00:24:13,200 --> 00:24:15,280 In the wild, the bubble nest is crucial 351 00:24:15,280 --> 00:24:16,880 for the survival of the eggs. 352 00:24:16,880 --> 00:24:20,240 It ensures that they remain floating near the surface 353 00:24:20,240 --> 00:24:23,560 of this stagnant water, and so get sufficient oxygen. 354 00:24:24,560 --> 00:24:28,800 Siamese fighting fish are unlikely to survive for more than a year, 355 00:24:28,800 --> 00:24:32,680 and they will produce maybe three or four broods in that time, 356 00:24:32,680 --> 00:24:35,280 but even so, each brood is very precious. 357 00:24:41,800 --> 00:24:45,120 Mating takes place directly beneath the nest, 358 00:24:45,120 --> 00:24:48,720 and the male has to lead the female to the right position. 359 00:24:52,640 --> 00:24:54,600 He now tempers his aggression 360 00:24:54,600 --> 00:24:57,560 and courts her in a surprisingly tender way. 361 00:25:01,200 --> 00:25:03,680 Finally, she releases the eggs. 362 00:25:07,480 --> 00:25:09,960 He catches each one in his mouth 363 00:25:09,960 --> 00:25:12,560 and deposits it within the nest. 364 00:25:19,720 --> 00:25:23,320 During nesting, males are at their most aggressive. 365 00:25:23,320 --> 00:25:25,360 They can't leave the eggs unguarded 366 00:25:25,360 --> 00:25:28,920 because the bubble nest is fragile and constantly needs repair. 367 00:25:30,040 --> 00:25:32,760 And other fish, including their own females, 368 00:25:32,760 --> 00:25:35,200 will also eat the eggs, given the chance. 369 00:25:35,200 --> 00:25:37,880 So, as soon as the female has released her eggs, 370 00:25:37,880 --> 00:25:40,240 he will turn on her and chase her off. 371 00:25:44,080 --> 00:25:48,840 But the usually aggressive male takes great care of his brood. 372 00:25:50,920 --> 00:25:53,640 He continually adds bubbles to the nest, 373 00:25:53,640 --> 00:25:55,920 replacing those that have burst. 374 00:26:01,440 --> 00:26:03,800 If the temperature of the water rises, 375 00:26:03,800 --> 00:26:07,280 he fans the eggs with his fins to keep them aerated. 376 00:26:11,080 --> 00:26:14,960 After 36 hours, the small fry are ready to hatch. 377 00:26:16,720 --> 00:26:18,200 Within a few months, 378 00:26:18,200 --> 00:26:21,600 the young fish will be fighting fit and ready to mate. 379 00:26:25,680 --> 00:26:27,960 And there may be another reason 380 00:26:27,960 --> 00:26:31,040 why Siamese fighting fish are so aggressive. 381 00:26:31,040 --> 00:26:33,640 Recent research on coral reef fish 382 00:26:33,640 --> 00:26:37,680 have shown that some species, as the temperature rises, 383 00:26:37,680 --> 00:26:39,960 undergo a personality change. 384 00:26:43,360 --> 00:26:46,880 Researchers working on Australia's Great Barrier Reef 385 00:26:46,880 --> 00:26:48,880 have found that some reef fish 386 00:26:48,880 --> 00:26:52,520 are either consistently timid or consistently bold. 387 00:26:54,720 --> 00:26:58,400 But global warming seems to have had an effect on their temperament. 388 00:27:00,920 --> 00:27:04,160 A rise in water temperature of just 1 or 2 degrees 389 00:27:04,160 --> 00:27:07,440 has made them 30 times more active and aggressive. 390 00:27:11,040 --> 00:27:14,360 So, could the Siamese fighters also be affected 391 00:27:14,360 --> 00:27:16,640 by the temperature of the water? 392 00:27:19,880 --> 00:27:24,560 We know that Siamese fighting fish display more the warmer the water, 393 00:27:24,560 --> 00:27:27,200 and that they can survive in temperatures 394 00:27:27,200 --> 00:27:29,800 of up to 30 degrees centigrade. 395 00:27:29,800 --> 00:27:33,160 So, perhaps it's the warmth of the stagnant water 396 00:27:33,160 --> 00:27:35,880 that makes them so aggressive. 397 00:27:38,640 --> 00:27:41,280 So, it seems that Siamese fighting fish 398 00:27:41,280 --> 00:27:44,600 will fight to the death to produce offspring... 399 00:27:45,800 --> 00:27:48,880 ..while the kangaroo's lethal kick and punch 400 00:27:48,880 --> 00:27:51,560 is the result of a body made for hopping. 401 00:27:53,960 --> 00:27:59,280 Both have certainly earned their reputations as ferocious fighters.