1 00:00:37,127 --> 00:00:40,403 Reptiles and amphibians are sometimes thought of 2 00:00:40,487 --> 00:00:44,719 as primitive dull and dim-witted. 3 00:00:44,807 --> 00:00:48,322 In fact of course they can be lethally fast 4 00:00:48,407 --> 00:00:49,920 spectacularly beautiful 5 00:00:50,007 --> 00:00:53,761 surprisingly affectionate and very sophisticated. 6 00:01:00,247 --> 00:01:04,240 They have remarkably varied ways of catching their prey 7 00:01:05,847 --> 00:01:08,156 and of defending themselves. 8 00:01:10,927 --> 00:01:13,646 They can produce a great turn of speed 9 00:01:15,047 --> 00:01:17,720 and fight with impressive zest. 10 00:01:29,967 --> 00:01:34,199 Some have spectacular colours and show off to one another. 11 00:01:37,127 --> 00:01:39,277 They communicate with calls... 12 00:01:39,367 --> 00:01:40,766 (CROAKING) 13 00:01:41,287 --> 00:01:42,606 (HIGH-PITCHED CROAKING) 14 00:01:44,327 --> 00:01:46,124 ...and with gestures. 15 00:01:49,967 --> 00:01:51,798 And there. Thats it. 16 00:01:53,967 --> 00:01:55,480 The full works. 17 00:01:57,407 --> 00:02:00,001 Reptiles have scaly skins 18 00:02:00,647 --> 00:02:03,764 and amphibians soft moist ones. 19 00:02:07,327 --> 00:02:09,761 None of them live at a uniform pace 20 00:02:09,847 --> 00:02:12,202 but switch from the fast to the slow lane 21 00:02:12,287 --> 00:02:14,482 within a year or an hour. 22 00:02:18,687 --> 00:02:22,362 Unlike us they get their energy directly from the sun 23 00:02:24,847 --> 00:02:27,441 and although being called "cold-blooded" 24 00:02:27,527 --> 00:02:29,836 might suggest they are unemotional 25 00:02:29,927 --> 00:02:33,636 they can be touchingly warm-hearted as mates... 26 00:02:33,727 --> 00:02:35,206 (GRUNTING) 27 00:02:38,127 --> 00:02:39,845 ...and as parents. 28 00:02:50,247 --> 00:02:52,522 And thats just the beginning. 29 00:02:53,407 --> 00:02:57,719 There are a whole lot of other warm-hearted truths to be discovered 30 00:02:58,247 --> 00:03:00,807 that give the phrase "life in cold blood" 31 00:03:00,887 --> 00:03:02,286 a completely new meaning. 32 00:03:13,727 --> 00:03:15,604 The Galapagos Islands. 33 00:03:16,447 --> 00:03:21,362 Some of the reptiles that live here are particularly skilful at solving 34 00:03:21,447 --> 00:03:25,235 the problems of getting their energy directly from sunshine. 35 00:03:26,607 --> 00:03:31,203 Marine iguanas face a major thermal challenge 36 00:03:31,287 --> 00:03:33,801 every morning of their lives. 37 00:03:33,887 --> 00:03:36,481 During the night their bodies cooled 38 00:03:36,567 --> 00:03:39,525 and now they must warm up quickly 39 00:03:39,607 --> 00:03:43,122 in order that they can become active and start feeding. 40 00:03:44,047 --> 00:03:46,800 Their bodies and skins are black 41 00:03:46,887 --> 00:03:49,765 which is very efficient at absorbing heat 42 00:03:49,847 --> 00:03:54,841 and they bask with their black flanks broadside to the sun. 43 00:04:00,447 --> 00:04:03,280 The rate at which they absorb warmth 44 00:04:03,367 --> 00:04:05,358 is invisible to the naked eye 45 00:04:05,447 --> 00:04:09,076 but very clear indeed to a thermal camera. 46 00:04:09,807 --> 00:04:13,277 First thing theyre cold and purplish blue. 47 00:04:13,367 --> 00:04:15,562 But slowly as they warm up 48 00:04:15,647 --> 00:04:18,639 a golden glow spreads through their bodies 49 00:04:19,807 --> 00:04:22,526 and eventually after half an hour or so 50 00:04:22,607 --> 00:04:25,599 they become as hot as the rocks beneath them. 51 00:04:26,367 --> 00:04:28,323 Once they are thoroughly warmed up 52 00:04:28,407 --> 00:04:31,001 marine iguanas can maintain their body temperature 53 00:04:31,087 --> 00:04:33,840 just about as constantly as I can 54 00:04:33,927 --> 00:04:36,441 and whats more at about the same level 55 00:04:36,527 --> 00:04:40,679 or indeed slightly higher around 37 degrees centigrade. 56 00:04:43,367 --> 00:04:45,164 Now they need to feed. 57 00:04:45,247 --> 00:04:49,399 There is nothing to eat on or around these barren rocks except seaweed 58 00:04:49,487 --> 00:04:51,921 and to get that they will have to swim. 59 00:04:53,727 --> 00:04:57,356 But the sea around here is surprisingly cold 60 00:04:57,447 --> 00:05:01,360 around 1 2 to 1 6 degrees centigrade 61 00:05:01,447 --> 00:05:06,043 and only the bigger iguanas can absorb enough heat 62 00:05:06,127 --> 00:05:10,962 to power the dives to enable them to go to the seaweed at any depth. 63 00:05:14,607 --> 00:05:18,077 However their bodies are now thoroughly warmed up. 64 00:05:18,967 --> 00:05:22,357 The thermal camera shows them as golden yellow 65 00:05:22,447 --> 00:05:25,803 as they clamber down over the cold blue rocks 66 00:05:25,887 --> 00:05:27,718 and dive into the sea. 67 00:05:44,767 --> 00:05:48,555 Although their islands lie almost exactly on the equator 68 00:05:48,647 --> 00:05:51,161 the sea here is permanently chilled 69 00:05:51,247 --> 00:05:55,240 by a cold current that sweeps up from the depths of the ocean 70 00:05:55,327 --> 00:05:58,842 so they wont be able to stay in the water for very long. 71 00:05:58,927 --> 00:06:01,043 They have no time to waste. 72 00:06:02,487 --> 00:06:07,117 In the shallows close to the shore the seaweed has been heavily cropped. 73 00:06:07,207 --> 00:06:10,244 To get a good meal they may have to dive to at least 74 00:06:10,327 --> 00:06:12,557 1 2 feet five metres. 75 00:06:15,767 --> 00:06:19,043 Theyre able to reduce the chilling effect of the cold water 76 00:06:19,127 --> 00:06:21,960 by closing down the blood supply to their limbs 77 00:06:22,047 --> 00:06:24,038 and the outer part of their bodies. 78 00:06:24,127 --> 00:06:26,721 But even so their body temperature may drop 79 00:06:26,807 --> 00:06:28,604 by 1 0 degrees or so. 80 00:06:29,367 --> 00:06:32,518 A cooling like that would kill a human diver. 81 00:06:36,647 --> 00:06:38,956 After five to 1 0 minutes on the sea floor 82 00:06:39,047 --> 00:06:41,242 most iguanas have had enough 83 00:06:41,327 --> 00:06:42,965 and they return to the surface 84 00:06:43,047 --> 00:06:46,039 and the life-saving warmth of the rocky shore. 85 00:06:51,567 --> 00:06:54,286 A recently emerged iguana is black. 86 00:06:54,367 --> 00:06:56,358 Its chilled to the bone. 87 00:07:02,527 --> 00:07:06,156 Now they need heat in order to be able to digest 88 00:07:06,247 --> 00:07:09,000 that meal of seaweed and they get that 89 00:07:09,087 --> 00:07:14,161 by spread-eagling themselves on these black hot sun-baked rocks. 90 00:07:17,407 --> 00:07:19,762 Their image warms from black 91 00:07:21,567 --> 00:07:22,886 to purple 92 00:07:24,167 --> 00:07:26,920 and then from red to orange. 93 00:07:30,487 --> 00:07:32,682 In the evening the temperature falls 94 00:07:32,767 --> 00:07:37,045 and they huddle together to retain their warmth as long as possible. 95 00:07:42,607 --> 00:07:44,916 They will have to wait until the following morning 96 00:07:45,007 --> 00:07:49,000 before they can re-warm themselves sufficiently to feed again. 97 00:07:52,807 --> 00:07:55,685 Most kinds of lizards have this daily schedule. 98 00:07:55,767 --> 00:07:58,918 Side-blotched lizards in California certainly do. 99 00:07:59,807 --> 00:08:03,766 You can see from the colour of my face that my body is warm. 100 00:08:05,007 --> 00:08:06,884 Thats because Ive got a central heating system 101 00:08:06,967 --> 00:08:09,481 which I have fuelled with my breakfast. 102 00:08:09,567 --> 00:08:12,445 In fact, about 80% of what I eat 103 00:08:12,527 --> 00:08:16,202 is used in keeping my body temperature high and steady. 104 00:08:17,647 --> 00:08:20,605 These lizards however squander very little of the energy 105 00:08:20,687 --> 00:08:23,599 they get from their food on warming themselves. 106 00:08:23,687 --> 00:08:27,236 They like the marine iguanas get nearly all they need for that 107 00:08:27,327 --> 00:08:29,522 by basking on the warm rocks. 108 00:08:30,287 --> 00:08:34,166 And so important is the need for warmth 109 00:08:34,247 --> 00:08:37,523 that the females actually choose their males 110 00:08:37,607 --> 00:08:41,520 on the basis of which has the best under-floor heating. 111 00:08:44,647 --> 00:08:48,435 Each male sits on his pile of boulders doing press-ups 112 00:08:48,527 --> 00:08:51,837 to signal his ownership and to warn off other males. 113 00:08:53,447 --> 00:08:57,804 Intruders are confronted immediately and if necessary attacked. 114 00:09:11,247 --> 00:09:15,843 And the victor returns to sit on his wonderfully warm throne. 115 00:09:21,727 --> 00:09:24,480 Look at his rocky kingdom with a thermal camera 116 00:09:24,567 --> 00:09:27,240 and its immediately clear why its so precious. 117 00:09:27,327 --> 00:09:30,763 The rocks are very much hotter than the surrounding grassland 118 00:09:30,847 --> 00:09:35,602 and big tall ones catch the sun earlier and retain its heat longer. 119 00:09:36,647 --> 00:09:39,605 So not only does the sun warm him from above 120 00:09:39,687 --> 00:09:41,757 his rocks do from beneath. 121 00:09:42,847 --> 00:09:48,240 The most powerful dominant male has naturally the best pile of rocks 122 00:09:48,327 --> 00:09:51,922 and not surprisingly almost all the females. 123 00:09:58,167 --> 00:10:01,398 But is it the males themselves or their assets 124 00:10:01,487 --> 00:10:03,955 that the females are interested in? 125 00:10:04,047 --> 00:10:09,997 To find out lets move their hot rocks and give them to a subordinate male. 126 00:10:24,487 --> 00:10:28,116 The females quickly recognise that a more desirable residence 127 00:10:28,207 --> 00:10:29,925 has appeared in the neighbourhood 128 00:10:30,007 --> 00:10:32,123 and start to move across. 129 00:10:35,847 --> 00:10:38,122 And the sex-starved wimp 130 00:10:38,207 --> 00:10:41,279 suddenly finds himself amazingly popular. 131 00:10:44,527 --> 00:10:50,204 So the females do indeed go for the males with the hottest rocks. 132 00:10:54,607 --> 00:10:57,121 These lizards on a small islet off the shores 133 00:10:57,207 --> 00:11:00,119 of Minorca in the Mediterranean get their heat 134 00:11:00,207 --> 00:11:03,404 from another and very unusual source. 135 00:11:05,047 --> 00:11:06,366 Ow. 136 00:11:06,567 --> 00:11:08,285 (LAUGHING) 137 00:11:08,367 --> 00:11:09,516 Sorry. 138 00:11:11,207 --> 00:11:12,435 They are very curious. 139 00:11:12,527 --> 00:11:17,760 Im the new boy on the block the new object in their environment 140 00:11:18,487 --> 00:11:21,206 and that one just gave me a little nip. 141 00:11:23,407 --> 00:11:26,285 They investigate the world around them by tasting it 142 00:11:26,367 --> 00:11:29,484 and theyre still trying to work out what I am. 143 00:11:34,127 --> 00:11:38,166 Their island is rocky and not particularly rich in food. 144 00:11:38,247 --> 00:11:40,522 The lizards are primarily insect eaters 145 00:11:40,607 --> 00:11:43,724 but during the flowering season they also take nectar. 146 00:11:43,807 --> 00:11:46,116 They collect it from plants like spurge 147 00:11:46,207 --> 00:11:47,481 which is very common. 148 00:11:47,567 --> 00:11:51,958 And they have a very special relationship with this flower. 149 00:11:52,407 --> 00:11:55,399 Its called the dead-horse arum 150 00:11:55,487 --> 00:11:58,240 and it certainly looks like carrion and... 151 00:11:58,887 --> 00:12:00,525 (COUGHING) Oh dear. 152 00:12:00,607 --> 00:12:03,519 It smells very strongly of carrion. 153 00:12:03,607 --> 00:12:06,405 As a consequence of both its looks and its smell 154 00:12:06,487 --> 00:12:08,603 it attracts carrion flies. 155 00:12:09,327 --> 00:12:12,763 Of course its the flies that the lizards are after. 156 00:12:14,767 --> 00:12:17,804 But as well as providing food for the lizards 157 00:12:17,887 --> 00:12:21,596 this extraordinary flower helps them in another way. 158 00:12:22,487 --> 00:12:26,605 This central part which is called a spadix 159 00:12:27,327 --> 00:12:31,798 is slightly warm as you can see from a thermal camera. 160 00:12:33,287 --> 00:12:36,757 The chemical process that produces the disgusting smell 161 00:12:36,847 --> 00:12:38,519 also creates heat 162 00:12:38,607 --> 00:12:41,963 and raises the temperature of the flower by up to five degrees 163 00:12:42,047 --> 00:12:43,446 above the surroundings 164 00:12:43,527 --> 00:12:47,998 sufficiently high for a lizard to warm itself on it on a cold morning. 165 00:12:48,087 --> 00:12:50,442 And in case you find that hard to believe 166 00:12:50,527 --> 00:12:53,439 here is confirmation from the thermal camera. 167 00:12:53,527 --> 00:12:56,200 The purplish-blue lizard quickly takes on 168 00:12:56,287 --> 00:12:59,404 the same temperature and colour as the arum. 169 00:13:05,607 --> 00:13:09,077 And sitting on arums brings another benefit. 170 00:13:12,287 --> 00:13:13,606 Breakfast. 171 00:13:14,087 --> 00:13:17,682 A fly lured by the smell crawls inside. 172 00:13:21,527 --> 00:13:24,599 The lizard hears the fly buzzing within. 173 00:13:26,567 --> 00:13:29,161 The fly of course cant find anything it wants 174 00:13:29,247 --> 00:13:31,238 but now it cant get out. 175 00:13:31,327 --> 00:13:34,637 The entrance to the flower is blocked by the lizard. 176 00:13:45,367 --> 00:13:47,756 And the lizard gets an easy meal. 177 00:13:56,127 --> 00:13:59,039 Two months later the arum flowers have shrivelled 178 00:13:59,127 --> 00:14:01,163 and produced their fruits. 179 00:14:03,407 --> 00:14:04,886 Until 20 years ago 180 00:14:04,967 --> 00:14:07,879 the lizards ignored these withered bundles. 181 00:14:07,967 --> 00:14:10,606 After all they hardly look like food. 182 00:14:11,087 --> 00:14:13,840 But then a particularly inquisitive individual 183 00:14:13,927 --> 00:14:18,205 sampled a fruit and found the soft flesh around the seed rather good. 184 00:14:19,407 --> 00:14:22,365 The habit spread and now the whole lizard population 185 00:14:22,447 --> 00:14:24,244 uniquely in the Mediterranean 186 00:14:24,327 --> 00:14:26,761 have become arum fruit eaters. 187 00:14:30,287 --> 00:14:34,439 They do take a bit of swallowing but seeds passing through a lizards gut 188 00:14:34,527 --> 00:14:37,803 not only survive but germinate even more easily. 189 00:14:39,367 --> 00:14:43,406 As a result the arums which were rather scarce here 20 years ago 190 00:14:43,487 --> 00:14:46,877 have suddenly become abundant all over the island. 191 00:15:04,687 --> 00:15:08,760 A cold windswept island off the coast of South Africa 192 00:15:08,847 --> 00:15:13,398 is not the first place you would go to if you were looking for reptiles. 193 00:15:13,487 --> 00:15:17,605 But here on Dassen Island among penguins and seagulls 194 00:15:18,207 --> 00:15:21,244 there is one of the greatest concentrations of tortoises 195 00:15:21,327 --> 00:15:23,602 to be found anywhere on Earth. 196 00:15:25,407 --> 00:15:29,480 There are about 2000 of them on this one tiny island. 197 00:15:34,927 --> 00:15:37,885 The penguins and other birds thanks to their warm blood 198 00:15:37,967 --> 00:15:40,276 are active no matter how cold it is 199 00:15:40,367 --> 00:15:43,245 but the tortoises have to wait for the day to warm up 200 00:15:43,327 --> 00:15:45,887 before they can get about their business. 201 00:15:51,247 --> 00:15:55,286 They bask in the sunshine powering up their bodies to the optimum 202 00:15:55,367 --> 00:15:58,837 working temperature of 33 degrees centigrade 203 00:15:58,927 --> 00:16:01,202 and then they go off to feed. 204 00:16:16,487 --> 00:16:20,036 As the day progresses the temperature rises quickly 205 00:16:20,127 --> 00:16:23,802 and even before noon its too hot for comfort. 206 00:16:23,887 --> 00:16:26,526 The tortoises have to head for shade. 207 00:16:41,407 --> 00:16:46,003 In the late afternoon it gets cooler and the tortoises venture out again. 208 00:16:46,687 --> 00:16:49,155 For them this is the best time. 209 00:16:49,607 --> 00:16:53,122 Theyre thoroughly warmed up theyve digested their morning meal 210 00:16:53,207 --> 00:16:55,596 and theyve got energy to spare. 211 00:17:03,047 --> 00:17:05,083 The males begin to fight 212 00:17:06,327 --> 00:17:08,761 jousting like medieval knights 213 00:17:08,847 --> 00:17:12,522 using a projection on the front of the shell like a lance. 214 00:17:13,167 --> 00:17:14,566 (EXCLAIMS) 215 00:17:17,607 --> 00:17:20,804 The technique is to get the spike under your opponent 216 00:17:20,887 --> 00:17:23,606 and then flick him over onto his back. 217 00:17:28,207 --> 00:17:30,767 Contests can last for half an hour. 218 00:18:06,287 --> 00:18:10,963 The loser tries to right himself but the winner keeps biting his legs. 219 00:18:24,727 --> 00:18:29,039 At last the victor loses interest and goes off to find the female 220 00:18:29,127 --> 00:18:31,960 who caused the argument in the first place. 221 00:18:32,407 --> 00:18:35,843 As for the loser if he doesnt manage to right himself soon 222 00:18:35,927 --> 00:18:38,487 he may cook in the sun. 223 00:18:46,607 --> 00:18:49,644 Tortoises are able to sunbathe out in the open 224 00:18:49,727 --> 00:18:51,877 because their strong bony shell gives them 225 00:18:51,967 --> 00:18:54,322 almost complete protection from predators. 226 00:18:58,607 --> 00:19:02,043 Less well-armoured reptiles like lizards 227 00:19:02,127 --> 00:19:07,679 are vulnerable of course to hawks and coyotes and foxes and cats. 228 00:19:08,207 --> 00:19:12,678 And in the morning when those warm-blooded animals are already active 229 00:19:13,247 --> 00:19:16,125 the lizards are cold and cant move fast. 230 00:19:16,927 --> 00:19:18,201 So they have a problem. 231 00:19:18,927 --> 00:19:21,805 But they also have a solution 232 00:19:21,887 --> 00:19:23,764 secret sunbathing. 233 00:19:25,287 --> 00:19:29,075 You really cant see them until youre right on top of them. 234 00:19:31,607 --> 00:19:33,643 And theres one there. 235 00:19:35,167 --> 00:19:36,839 Im in Arizona 236 00:19:36,927 --> 00:19:42,126 and that at my feet is a lizard buried in the sand up to its neck. 237 00:19:44,247 --> 00:19:47,045 Even while its buried it can use the sunshine 238 00:19:47,127 --> 00:19:48,606 to warm its whole body. 239 00:19:48,687 --> 00:19:51,645 It can control the supply of blood to its head 240 00:19:51,727 --> 00:19:54,639 so that it pools in a cavity behind the eye. 241 00:19:55,927 --> 00:19:58,646 Soon the blood there is as much as five degrees 242 00:19:58,727 --> 00:20:01,844 above the temperature of the rest of its body. 243 00:20:01,927 --> 00:20:05,237 Then the animal opens the major blood vessels in its neck 244 00:20:05,327 --> 00:20:07,397 and the hot blood circulates 245 00:20:07,487 --> 00:20:09,921 so that its whole body is thoroughly warmed 246 00:20:10,007 --> 00:20:12,919 even though its still mostly below ground. 247 00:20:20,847 --> 00:20:23,839 This is a horned lizard 248 00:20:26,407 --> 00:20:27,886 and very beautiful too. 249 00:20:27,967 --> 00:20:31,676 This particular species is called the regal horned lizard 250 00:20:31,767 --> 00:20:36,602 because it has this splendid crown of spikes at the back of his neck. 251 00:20:37,647 --> 00:20:40,445 When he is hidden they break up the outline of his head 252 00:20:40,527 --> 00:20:42,916 and so you hardly see him at all. 253 00:20:43,527 --> 00:20:46,405 And now in the warmth of my hand and in the sunshine 254 00:20:46,487 --> 00:20:48,796 I guess he has warmed up quite a lot. 255 00:20:48,887 --> 00:20:53,278 And if I put him down he now at last may be able to run for it. 256 00:20:55,007 --> 00:20:57,077 And indeed he does. 257 00:21:05,327 --> 00:21:09,605 South African armadillo lizards which live on these rocky outcrops 258 00:21:10,247 --> 00:21:14,035 have a different solution to the problem of safe sunbathing. 259 00:21:15,047 --> 00:21:17,880 Theyve turned it into a social activity. 260 00:21:20,647 --> 00:21:22,524 Whole families of them live together 261 00:21:22,607 --> 00:21:25,201 in the crevices among the rocks and in the morning 262 00:21:25,287 --> 00:21:28,040 they all emerge to warm up in the sun. 263 00:21:30,007 --> 00:21:32,999 Of course there is safety in numbers. 264 00:21:34,807 --> 00:21:38,322 There are lots of eyes to spot danger if it appears. 265 00:21:50,847 --> 00:21:55,238 And when one sunbather takes fright they all dive for safety. 266 00:21:56,807 --> 00:22:00,197 If a predator is quick it is possible to grab one 267 00:22:00,287 --> 00:22:03,484 but even then an armadillo lizard is not going to be an easy meal. 268 00:22:03,567 --> 00:22:04,556 Ow. 269 00:22:04,647 --> 00:22:05,636 (LAUGHING) 270 00:22:05,767 --> 00:22:09,362 They have an additional form of defence. 271 00:22:09,447 --> 00:22:11,324 They bite their tails. 272 00:22:12,207 --> 00:22:15,643 The reason they do that is that it covers up 273 00:22:17,167 --> 00:22:19,203 their vulnerable underside 274 00:22:19,887 --> 00:22:24,836 and exposes only these very sharp spiny scales 275 00:22:24,927 --> 00:22:29,955 which is very good protection against predators like snakes or mongooses. 276 00:22:31,247 --> 00:22:34,319 They stay like this for quite a long time 277 00:22:34,407 --> 00:22:37,479 before they are confident enough to uncurl. 278 00:22:37,567 --> 00:22:40,286 Ill put him down and see how he does. 279 00:22:54,247 --> 00:22:59,526 Sunset necessarily brings an end to activity for most reptiles. 280 00:23:01,967 --> 00:23:03,559 But not for all. 281 00:23:05,287 --> 00:23:06,606 A leopard gecko. 282 00:23:06,687 --> 00:23:09,076 It like most geckos is nocturnal 283 00:23:09,167 --> 00:23:12,079 and it manages to get all the heat it needs from the rocks 284 00:23:12,167 --> 00:23:16,763 which retain something of their warmth for several hours after the sun has set. 285 00:23:18,527 --> 00:23:20,916 This male is in search of a mate. 286 00:23:21,647 --> 00:23:23,877 She is less brightly coloured. 287 00:23:28,567 --> 00:23:30,762 They inspect one another. 288 00:23:35,407 --> 00:23:37,443 He collects her scent with his tongue 289 00:23:37,527 --> 00:23:39,836 and discovers that not only is she female 290 00:23:39,927 --> 00:23:42,157 but shes sexually available. 291 00:23:48,927 --> 00:23:50,519 Hes interested. 292 00:23:54,967 --> 00:23:58,164 He nibbles her neck and strokes her flanks 293 00:23:58,247 --> 00:24:01,319 all part of his elaborate courtship routine. 294 00:24:08,807 --> 00:24:10,718 Copulation begins. 295 00:24:13,927 --> 00:24:16,361 This is the time in mammals and birds 296 00:24:16,447 --> 00:24:19,007 when the sex of the young is determined 297 00:24:19,087 --> 00:24:22,284 but not in a number of reptiles including geckos. 298 00:24:22,807 --> 00:24:27,562 Once again its temperature that profoundly influences their lives. 299 00:24:29,847 --> 00:24:32,600 The female goes away to lay her eggs. 300 00:24:34,887 --> 00:24:37,196 She has chosen a place where the temperature 301 00:24:37,287 --> 00:24:39,562 is about 31 degrees. 302 00:24:39,647 --> 00:24:42,844 As her body is the same temperature as her environment 303 00:24:42,927 --> 00:24:45,157 she cant heat her eggs by sitting on them 304 00:24:45,247 --> 00:24:47,078 as warm-blooded birds do 305 00:24:47,167 --> 00:24:51,001 so theyre exactly the same temperature as the rocks beneath. 306 00:24:53,167 --> 00:24:56,045 After a couple of months both eggs begin to hatch. 307 00:25:01,087 --> 00:25:03,442 The first to emerge is a male. 308 00:25:12,167 --> 00:25:14,476 And the second will be too. 309 00:25:14,567 --> 00:25:17,559 Its the temperature which has determined that. 310 00:25:17,647 --> 00:25:19,683 If it had been a few degrees lower 311 00:25:19,767 --> 00:25:22,884 both eggs would have developed into females. 312 00:25:32,087 --> 00:25:36,319 Crocodiles have their sex determined by temperature in a similar way. 313 00:25:37,567 --> 00:25:41,845 This clutch belongs to the Indian fish-eating crocodile the gharial. 314 00:25:50,447 --> 00:25:52,005 (CALLING) 315 00:25:55,407 --> 00:25:58,240 The female has heard the calls from below ground 316 00:25:58,327 --> 00:26:00,363 made by her hatching young 317 00:26:00,447 --> 00:26:03,803 and is helping them to dig their way out of the sand. 318 00:26:12,967 --> 00:26:16,357 They immediately make their way down to the water. 319 00:26:19,527 --> 00:26:21,324 And mother goes too. 320 00:26:36,287 --> 00:26:39,597 Here of course they are nice and warm. 321 00:26:39,687 --> 00:26:41,803 Water retains its daytime heat 322 00:26:41,887 --> 00:26:43,684 better and longer than rock 323 00:26:43,767 --> 00:26:45,644 so unlike many other reptiles 324 00:26:45,727 --> 00:26:47,718 gharials and other crocodilians 325 00:26:47,807 --> 00:26:51,004 have enough energy to feed actively all night. 326 00:27:03,607 --> 00:27:05,245 (HISSING) 327 00:27:20,607 --> 00:27:24,316 While being nocturnal is unusual among reptiles 328 00:27:24,407 --> 00:27:26,637 its the norm for amphibians. 329 00:27:27,287 --> 00:27:30,962 Their skin is not scaly and watertight like a reptiles. 330 00:27:31,047 --> 00:27:34,005 Its soft moist and permeable. 331 00:27:34,087 --> 00:27:37,636 If they exposed themselves to sunlight for any length of time 332 00:27:37,727 --> 00:27:40,002 they would dry out and die. 333 00:27:40,087 --> 00:27:43,966 So most frogs only leave their shelters at night. 334 00:27:47,847 --> 00:27:50,520 Since they cant absorb sunshine directly 335 00:27:50,607 --> 00:27:53,201 they either get their heat from their surroundings 336 00:27:53,287 --> 00:27:55,596 or draw their energy from the fat reserves 337 00:27:55,687 --> 00:27:58,520 that they built up when the feeding was good. 338 00:27:58,607 --> 00:28:00,598 But even so they seldom hop 339 00:28:00,687 --> 00:28:03,565 unless they have very good reason to do so. 340 00:28:05,247 --> 00:28:10,526 This frog however the South American waxy monkey frog is exceptional. 341 00:28:12,287 --> 00:28:17,202 Its one of the few that can tolerate direct sunshine for any length of time. 342 00:28:19,767 --> 00:28:24,397 And that is because it secretes a wax from glands on its neck. 343 00:28:37,727 --> 00:28:41,481 No human sunbather goes to more trouble than they do 344 00:28:41,567 --> 00:28:44,798 to make quite sure that every part of their skin 345 00:28:44,887 --> 00:28:46,718 is properly anointed. 346 00:29:11,647 --> 00:29:15,401 The sunshine may also bring them an extra benefit. 347 00:29:15,487 --> 00:29:18,684 It probably protects them from the fungal infections 348 00:29:18,767 --> 00:29:21,964 to which many moist-skinned amphibians are prone. 349 00:29:29,967 --> 00:29:34,483 In the rainforests of Central America the air is heavy with moisture. 350 00:29:35,007 --> 00:29:37,885 So the poison arrow frogs can risk basking 351 00:29:37,967 --> 00:29:39,764 in the little patches of sunshine 352 00:29:39,847 --> 00:29:43,442 that dapple the forest floor and if they begin to dry out 353 00:29:43,527 --> 00:29:46,166 they can retreat into the leaf litter. 354 00:29:47,007 --> 00:29:48,759 (CROAKING RAPIDLY) 355 00:29:49,327 --> 00:29:51,966 The sunshine gives them sufficient energy 356 00:29:52,047 --> 00:29:55,801 to permit the extravagance of calling almost continuously 357 00:29:55,887 --> 00:29:58,196 in defence of their territories. 358 00:30:01,687 --> 00:30:04,042 They even have enough spare energy 359 00:30:04,127 --> 00:30:07,358 to indulge in long battles with their neighbours. 360 00:30:54,967 --> 00:30:58,755 These fights can go on for well over half an hour at a time 361 00:30:58,847 --> 00:31:02,157 until both contestants are completely exhausted. 362 00:31:09,447 --> 00:31:14,282 So a moist skin limits not only where amphibians can live 363 00:31:14,367 --> 00:31:16,597 but how energetic they can be. 364 00:31:17,247 --> 00:31:21,877 Out in the sunshine dry-skinned reptiles have more options. 365 00:31:23,447 --> 00:31:26,883 By collecting solar power so efficiently 366 00:31:26,967 --> 00:31:31,563 reptiles need to use very little of the energy they generate themselves 367 00:31:31,647 --> 00:31:33,239 to warm their bodies. 368 00:31:33,327 --> 00:31:35,602 In fact they use around a tenth 369 00:31:35,687 --> 00:31:38,759 compared with a mammal of a similar size. 370 00:31:38,847 --> 00:31:41,805 That means they dont have to eat very often. 371 00:31:42,407 --> 00:31:47,800 A puff adder like this one can wait almost indefinitely for its next meal. 372 00:31:48,567 --> 00:31:52,196 Amongst predators patience really is a virtue. 373 00:31:57,367 --> 00:32:01,485 Whilst waiting for a meal to wander within striking distance 374 00:32:01,567 --> 00:32:04,400 a snake shuts down its body processes 375 00:32:04,487 --> 00:32:07,559 so that it uses the minimum amount of energy. 376 00:32:07,647 --> 00:32:10,764 Only the equivalent of a pilot light is left on 377 00:32:11,407 --> 00:32:14,046 and it can remain like this for weeks. 378 00:32:17,007 --> 00:32:20,761 All around it mammals are expending their energy in a way that 379 00:32:20,847 --> 00:32:24,726 compared with the snake seems extraordinarily extravagant. 380 00:32:38,407 --> 00:32:43,527 But when a snake needs to move fast it can do so with lightning speed. 381 00:32:53,127 --> 00:32:58,406 Once its prey is secured a snake can take its time over its meal. 382 00:33:00,087 --> 00:33:03,841 This gigantic python is feeding on a deer. 383 00:33:04,807 --> 00:33:08,516 A python kills its prey by wrapping its coils around it 384 00:33:08,607 --> 00:33:12,077 and squeezing its victim so tightly and for so long 385 00:33:12,167 --> 00:33:13,759 that it can no longer breathe. 386 00:33:14,527 --> 00:33:17,405 But swallowing its meal takes time. 387 00:33:18,607 --> 00:33:23,317 The deer will go down head first. Its much easier that way. 388 00:33:33,287 --> 00:33:37,519 The ligaments connecting the snakes upper and lower jaw are elastic 389 00:33:37,607 --> 00:33:40,075 so that it can engulf the deers head 390 00:33:40,167 --> 00:33:43,000 even though it is much bigger than its own. 391 00:33:43,607 --> 00:33:46,963 With its mouth stretched tightly around its meal 392 00:33:47,047 --> 00:33:49,277 the snake cant breathe in a normal way. 393 00:33:50,087 --> 00:33:54,365 But its able to push the top of its windpipe right out of its mouth 394 00:33:54,447 --> 00:33:56,756 and so continue to take in air. 395 00:34:17,087 --> 00:34:22,115 After some hours all that can be seen of the deer are its hind legs. 396 00:34:33,967 --> 00:34:36,527 Once the meal has been completely swallowed 397 00:34:36,607 --> 00:34:40,077 the inner workings of the snakes body change greatly. 398 00:34:42,567 --> 00:34:46,037 Its digestive processes switch to full power 399 00:34:46,127 --> 00:34:48,880 and increase their activity 40 times. 400 00:34:48,967 --> 00:34:51,959 There is an explosion of biochemical activity. 401 00:34:53,327 --> 00:34:56,478 The liver the secretions of which power digestion 402 00:34:56,567 --> 00:34:59,161 doubles in size within two days. 403 00:35:00,967 --> 00:35:03,845 The heart grows by some 40% 404 00:35:07,487 --> 00:35:12,402 It will take the python at least a week to completely digest this enormous meal 405 00:35:13,127 --> 00:35:17,803 but then it will not need to feed again for months or even a year. 406 00:35:21,127 --> 00:35:25,598 This ability to switch off helps reptiles and amphibians in another way. 407 00:35:28,447 --> 00:35:31,041 A baby North American painted turtle. 408 00:35:31,847 --> 00:35:34,964 It and the rest of its clutch have only just hatched. 409 00:35:36,247 --> 00:35:41,640 But its late in the year and the chill of winter has already begun. 410 00:35:41,727 --> 00:35:44,525 If the hatchlings clambered out of their hole now 411 00:35:44,607 --> 00:35:46,518 they would find nothing to eat. 412 00:35:46,607 --> 00:35:48,837 So they stay where they are. 413 00:35:54,727 --> 00:35:58,322 The temperature will fall to minus 1 0 degrees. 414 00:36:00,967 --> 00:36:05,563 Ice crystals grow around the babies and even inside their bodies 415 00:36:06,327 --> 00:36:09,922 but their tissues are protected by a kind of antifreeze. 416 00:36:12,927 --> 00:36:15,999 This would kill any mammal or bird. 417 00:36:19,807 --> 00:36:23,561 They remain in this deep freeze for up to six months. 418 00:36:30,567 --> 00:36:32,956 But spring comes at last. 419 00:36:39,247 --> 00:36:44,037 The ice melts around them and eventually within them. 420 00:36:52,687 --> 00:36:55,759 Slowly they begin to come to life. 421 00:37:13,327 --> 00:37:16,922 It takes quite a time for them to become fully functional 422 00:37:17,007 --> 00:37:20,522 but eventually theyre ready to face the outside world. 423 00:37:33,167 --> 00:37:38,685 So by allowing their bodies to cool they have avoided the hard times. 424 00:37:50,367 --> 00:37:51,959 With the arrival of spring 425 00:37:52,047 --> 00:37:55,244 their parents are now preparing to breed again. 426 00:38:02,167 --> 00:38:03,998 The male courts the female 427 00:38:04,087 --> 00:38:07,966 by gently strumming her cheeks with his long claws. 428 00:38:12,967 --> 00:38:14,605 And she responds. 429 00:38:20,847 --> 00:38:24,396 Cold blood is clearly no barrier to affection. 430 00:38:24,487 --> 00:38:26,603 In fact reptiles can conduct 431 00:38:26,687 --> 00:38:30,441 as complex and as sensitive a courtship as many a mammal. 432 00:38:39,007 --> 00:38:44,286 This is the biggest of all living reptiles and one of the most feared. 433 00:38:44,367 --> 00:38:47,882 If one creature were to be labelled a cold-blooded killer 434 00:38:47,967 --> 00:38:51,084 it would be this a saltwater crocodile 435 00:38:51,167 --> 00:38:56,446 a monster that can grow to a length of 20 feet six metres and weigh a tonne. 436 00:39:04,487 --> 00:39:09,356 But male and female when they court blow bubbles at one another. 437 00:39:17,127 --> 00:39:21,325 He is three times her size and could easily crush her 438 00:39:21,407 --> 00:39:24,205 yet he treats her with great gentleness. 439 00:39:29,527 --> 00:39:31,279 He strokes her back. 440 00:39:43,567 --> 00:39:46,957 Slowly he aligns his body with hers. 441 00:40:14,967 --> 00:40:17,401 So union is achieved. 442 00:40:28,167 --> 00:40:32,206 Crocodiles are among the most ancient of reptiles. 443 00:40:32,287 --> 00:40:36,724 Their ancestors appeared at about the same time as the dinosaurs. 444 00:40:36,807 --> 00:40:41,198 But what about them? Were dinosaurs similarly cold-blooded? 445 00:40:44,047 --> 00:40:48,723 The rocks of the North American west are particularly rich in dinosaur fossils. 446 00:40:51,047 --> 00:40:53,481 A hundred million years ago 447 00:40:53,567 --> 00:40:57,560 this was a horizontal mudflat at the edge of a sea. 448 00:40:58,407 --> 00:41:02,195 And across it came an adult dinosaur 449 00:41:02,287 --> 00:41:05,404 with a smaller younger one trotting alongside 450 00:41:05,487 --> 00:41:09,036 leaving their footprints behind to be fossilised. 451 00:41:11,327 --> 00:41:14,444 They were iguanodons a herd of them 452 00:41:14,527 --> 00:41:17,280 together with some bird-footed dinosaurs. 453 00:41:18,647 --> 00:41:20,842 Were these all solar-powered? 454 00:41:23,247 --> 00:41:27,286 Some of the ancient reptiles had specific adaptations 455 00:41:27,367 --> 00:41:29,483 to help them collect heat. 456 00:41:29,567 --> 00:41:34,402 This is a plate from the back of a stegosaurus 457 00:41:35,087 --> 00:41:39,080 and you can still see the lines where the blood vessels ran 458 00:41:39,167 --> 00:41:42,603 which collected the heat and carried it to the rest of the body. 459 00:41:44,207 --> 00:41:47,882 So for the stegosaurus at least the need to collect heat 460 00:41:47,967 --> 00:41:52,483 seems to have been just as important as it is for its relatives alive today. 461 00:41:54,127 --> 00:41:59,326 But there are clues that suggest that ancient reptiles were better 462 00:41:59,407 --> 00:42:03,195 at maintaining their temperature than their modern counterparts. 463 00:42:03,287 --> 00:42:08,884 This is the jaw bone of a very large and very famous dinosaur. 464 00:42:12,687 --> 00:42:17,966 In life its head would have been 1 8 feet six metres above ground. 465 00:42:20,927 --> 00:42:24,124 This is the jaw of Tyrannosaurus rex. 466 00:42:32,607 --> 00:42:34,438 An animal as big as this 467 00:42:34,527 --> 00:42:38,406 has a very large body mass which retains heat very well. 468 00:42:38,487 --> 00:42:43,356 So perhaps these huge dinosaurs were in fact warm all the time 469 00:42:43,447 --> 00:42:47,360 simply because they were too big to lose all their heat overnight 470 00:42:47,447 --> 00:42:49,563 as a smaller reptile would. 471 00:42:51,727 --> 00:42:54,002 But what about when they were small? 472 00:42:54,087 --> 00:42:58,365 Were adolescent Tyrannosaurs able to maintain a steady body temperature? 473 00:42:58,447 --> 00:43:00,961 Were they in short warm-blooded? 474 00:43:02,527 --> 00:43:04,518 Evidence on that can be found in 475 00:43:04,607 --> 00:43:07,041 the microscopic structure of their bones. 476 00:43:08,807 --> 00:43:10,559 (ROARING) 477 00:43:14,607 --> 00:43:21,445 This is the leg bone of a young Tyrannosaurus 478 00:43:22,207 --> 00:43:24,118 and it has bands in it. 479 00:43:24,647 --> 00:43:27,559 The inner section formed when the animal was young 480 00:43:27,647 --> 00:43:32,163 has an open structure like the bone of a fast-growing warm-blooded mammal. 481 00:43:33,887 --> 00:43:38,085 The outer part is more dense more like that of todays reptiles. 482 00:43:38,167 --> 00:43:44,322 But whether dinosaurs were really truly warm-blooded we may never know. 483 00:43:45,727 --> 00:43:48,639 What we do know however is that dinosaurs 484 00:43:48,727 --> 00:43:51,082 were extraordinarily successful 485 00:43:51,167 --> 00:43:54,318 and dominated the Earth for 1 20 million years. 486 00:43:57,287 --> 00:44:01,041 But there are some reptiles today that can keep their body temperature 487 00:44:01,127 --> 00:44:03,766 well above that of their surroundings 488 00:44:04,407 --> 00:44:07,956 and these are the tracks of one of them. 489 00:44:08,887 --> 00:44:14,405 These giants haul themselves up out of the sea along beaches like this 490 00:44:14,487 --> 00:44:18,719 in many parts of the tropics but in order not to disturb them 491 00:44:19,207 --> 00:44:23,758 Ill turn this light out and well look for them with infrared cameras. 492 00:44:29,487 --> 00:44:31,443 Leatherback turtles. 493 00:44:31,527 --> 00:44:35,122 Like crocodiles turtles are very ancient creatures 494 00:44:35,207 --> 00:44:39,883 having first appeared at about the same time as the early dinosaurs. 495 00:44:39,967 --> 00:44:43,926 Today leatherbacks are the biggest of all reptiles 496 00:44:44,007 --> 00:44:46,237 and the most widely distributed 497 00:44:46,327 --> 00:44:49,478 for they are found all the way from these warm tropical waters 498 00:44:49,567 --> 00:44:52,035 to the freezing seas of the Arctic. 499 00:44:59,207 --> 00:45:01,880 These have come ashore on a beach in Trinidad 500 00:45:01,967 --> 00:45:04,435 where almost certainly they were hatched. 501 00:45:04,527 --> 00:45:08,042 Now they in their turn are laying their eggs here. 502 00:45:15,367 --> 00:45:20,441 Leatherbacks we know can generate heat internally 503 00:45:21,327 --> 00:45:24,399 and there is proof of that if you have a look 504 00:45:24,487 --> 00:45:29,003 at the eggs that she is laying right now on that thermal camera. 505 00:45:29,967 --> 00:45:32,276 They are emerging from her body 506 00:45:33,087 --> 00:45:38,684 and lo and behold they are bright yellow verging on white 507 00:45:38,767 --> 00:45:42,316 proving that they are warmer than their surroundings. 508 00:45:44,607 --> 00:45:47,963 And she generates that heat within her body 509 00:45:48,047 --> 00:45:51,676 from special deposits of fat so that she can maintain her 510 00:45:51,767 --> 00:45:55,157 internal body temperature up to eight degrees centigrade 511 00:45:55,247 --> 00:45:58,319 above that of the water through which she swims. 512 00:46:00,807 --> 00:46:03,116 As she sweeps away the surface sand 513 00:46:03,207 --> 00:46:05,482 you can see that the sand too is yellower 514 00:46:05,567 --> 00:46:07,922 warmer than the outside of her shell 515 00:46:08,007 --> 00:46:11,044 for it still retains the heat it acquired during the day. 516 00:46:18,807 --> 00:46:23,323 So how do leatherbacks retain that precious and expensive 517 00:46:23,407 --> 00:46:25,443 internally generated heat? 518 00:46:26,287 --> 00:46:30,599 Well to start with they have their huge size to help them. 519 00:46:30,687 --> 00:46:32,962 They really are massive animals. 520 00:46:33,047 --> 00:46:36,278 This one is getting on for two metres six feet long 521 00:46:36,367 --> 00:46:39,643 and they can grow to weigh a tonne and a half. 522 00:46:40,207 --> 00:46:43,404 And of course big objects retain their heat 523 00:46:43,487 --> 00:46:46,285 very much more readily than small ones do. 524 00:46:47,007 --> 00:46:49,396 And theres another reason. 525 00:46:49,487 --> 00:46:54,083 Now I am bright yellow going into white 526 00:46:54,167 --> 00:46:57,523 which shows that I am losing a great deal of my heat. 527 00:46:57,607 --> 00:47:01,077 But she on the other hand is very much darker 528 00:47:01,167 --> 00:47:06,002 and that is because she has an internal layer of fat 529 00:47:06,567 --> 00:47:11,721 an insulating layer just beneath the shell which wraps around her body. 530 00:47:14,087 --> 00:47:18,080 The leatherbacks are the only reptiles in the world 531 00:47:18,167 --> 00:47:20,601 to have this kind of insulation. 532 00:47:30,087 --> 00:47:33,682 Her eggs laid she fills in the hole with sand. 533 00:47:36,727 --> 00:47:39,480 And now shes on her way back to the sea. 534 00:47:41,327 --> 00:47:44,478 Life in cold blood has been a great success. 535 00:47:44,567 --> 00:47:49,482 It has after all endured for some 320 million years. 536 00:47:50,887 --> 00:47:53,162 But how did it all begin? 537 00:47:53,247 --> 00:47:58,241 To find the answer to that we have to go back in time and back to the water 538 00:47:58,327 --> 00:48:03,276 to the age when strange fish were hauling themselves up onto the land 539 00:48:03,367 --> 00:48:07,155 fish that were the ancestors of the amphibians. 540 00:48:21,287 --> 00:48:25,121 Amphibians and reptiles are not easy creatures to film. 541 00:48:26,407 --> 00:48:29,001 They certainly do interesting things 542 00:48:29,087 --> 00:48:33,046 but they also spend a great deal of time doing nothing much. 543 00:48:35,887 --> 00:48:40,403 We needed the help of scientists who really understood these creatures. 544 00:48:42,487 --> 00:48:46,366 Some workers have spent over 20 years studying their animals 545 00:48:46,447 --> 00:48:48,836 both in the lab and in the field. 546 00:48:48,927 --> 00:48:53,955 They investigate the lives of their chosen species using all kinds of gear 547 00:48:54,047 --> 00:48:57,881 some sophisticated some perhaps less so. 548 00:49:07,967 --> 00:49:10,720 With their help we had a rare chance to get 549 00:49:10,807 --> 00:49:13,685 under the skin of some of our subjects. 550 00:49:21,727 --> 00:49:26,039 Madagascar was going to be a very important location for us. 551 00:49:27,847 --> 00:49:30,361 Its a huge island 1 000 miles long 552 00:49:30,447 --> 00:49:32,438 with a great variety of habitats 553 00:49:32,527 --> 00:49:34,961 and its extraordinarily rich in reptiles. 554 00:49:40,447 --> 00:49:47,080 I first went to Madagascar back in 1 960 filming for a series called Zoo Quest. 555 00:49:50,727 --> 00:49:53,764 Back then I was trying to film all kinds of creatures 556 00:49:53,847 --> 00:49:57,760 including the monkey-like lemurs and many rare birds 557 00:49:57,847 --> 00:50:01,840 but I was particularly fascinated by the islands chameleons. 558 00:50:05,487 --> 00:50:09,162 There are in fact more species of chameleons in Madagascar 559 00:50:09,247 --> 00:50:12,284 than in all the rest of the world put together. 560 00:50:16,287 --> 00:50:18,926 There is one the pygmy leaf chameleon 561 00:50:19,007 --> 00:50:21,919 which was said to be only an inch or so long. 562 00:50:22,007 --> 00:50:24,999 I yearned to see it but Ive never found it. 563 00:50:27,767 --> 00:50:33,319 Now I was back and this time reptiles were our sole subject. 564 00:50:36,447 --> 00:50:40,042 Although Madagascar is only separated from the east coast of Africa 565 00:50:40,127 --> 00:50:44,723 by 300 miles of sea its people and particularly its animals 566 00:50:44,807 --> 00:50:47,879 are very different indeed from those on the continent 567 00:50:47,967 --> 00:50:52,040 with hundreds of species that are found nowhere else in the world. 568 00:50:53,607 --> 00:50:56,485 Once again I was in search of chameleons. 569 00:50:59,007 --> 00:51:02,044 Then all television was black and white 570 00:51:02,127 --> 00:51:05,836 but now I could film and record chameleons in colour 571 00:51:05,927 --> 00:51:08,043 and what colours they have. 572 00:51:26,247 --> 00:51:31,037 We had come in the rainy season when most creatures including reptiles 573 00:51:31,127 --> 00:51:35,279 tend to breed and are therefore particularly active and interesting. 574 00:51:36,607 --> 00:51:40,919 And this time I had the help of Bertrand Razahamatra 575 00:51:41,007 --> 00:51:45,558 a Malagasy naturalist who has made a particular study of chameleons. 576 00:51:45,647 --> 00:51:50,038 Hes worked on them for over 1 0 years and knows most kinds very well. 577 00:51:50,127 --> 00:51:54,439 I asked him about the pygmy species that had fascinated me for so long. 578 00:51:55,127 --> 00:51:58,676 -So I mean that really is full-grown? -Yes full-grown. 579 00:51:59,807 --> 00:52:03,846 -Then its only that big? -Yeah its very small. 580 00:52:06,727 --> 00:52:10,845 He suggested that although chameleons are mostly active during the day 581 00:52:10,927 --> 00:52:13,441 we should look for them at night 582 00:52:13,527 --> 00:52:16,246 because most of them turn pale in the dark 583 00:52:16,327 --> 00:52:19,717 and are therefore easily picked out in the light of our torches. 584 00:52:24,207 --> 00:52:25,276 Ah. 585 00:52:29,567 --> 00:52:31,558 What is that? 586 00:52:31,647 --> 00:52:33,365 -This is... -What species? 587 00:52:33,447 --> 00:52:38,680 -This is oustaleti. -Oustaleti. And male or female? 588 00:52:39,647 --> 00:52:41,365 -Female. -How do you know? 589 00:52:41,447 --> 00:52:43,802 The colour. 590 00:52:43,887 --> 00:52:46,845 -Theres another one. -Oh theres another. 591 00:52:46,927 --> 00:52:50,283 ATTENBOROUGH: This one was far from upset at being woken up. 592 00:52:52,047 --> 00:52:53,241 Ah. 593 00:52:54,047 --> 00:52:55,196 (ATTENBOROUGH LAUGHING) 594 00:52:55,287 --> 00:52:59,041 It fed. Thats absolutely extraordinary. 595 00:53:00,007 --> 00:53:03,124 It cant possibly feed normally in the darkness. 596 00:53:04,287 --> 00:53:08,326 It just takes advantage of our light and finds an insect. Bravo. 597 00:53:09,367 --> 00:53:11,961 Lets go and see if we can find more. 598 00:53:13,887 --> 00:53:16,276 Bertrand explained that there was another reason 599 00:53:16,367 --> 00:53:19,404 why night was the best time to look for chameleons. 600 00:53:19,487 --> 00:53:23,605 When they go to sleep they climb to the very far end of branches 601 00:53:23,687 --> 00:53:26,485 where they are out of the way of predators such as snakes. 602 00:53:26,567 --> 00:53:28,205 Theres another. 603 00:53:28,927 --> 00:53:32,761 And of course that was where we found them just as he said. 604 00:53:45,567 --> 00:53:47,205 Thats a big one. 605 00:53:49,367 --> 00:53:50,766 Beautiful. 606 00:53:52,407 --> 00:53:53,396 BERTRAND: Yes. 607 00:53:57,167 --> 00:53:59,203 ATTENBOROUGH: This one is just a baby. 608 00:54:00,327 --> 00:54:02,397 And how old do you think that is? 609 00:54:02,487 --> 00:54:05,126 -I think just a few days. -A few days. 610 00:54:08,207 --> 00:54:13,327 So even when its newly hatched it knows to come to the end of the branch. 611 00:54:13,407 --> 00:54:19,243 Yes. Yeah. Look. They choose the tip of a branch. 612 00:54:19,327 --> 00:54:22,444 -Yes. Where its very difficult to get. -Yeah. 613 00:54:22,527 --> 00:54:24,279 Of course if it was in the day 614 00:54:24,367 --> 00:54:26,483 -a bird could get it. -Yeah. 615 00:54:26,567 --> 00:54:28,398 -But at night safe. -But at night safe. 616 00:54:29,927 --> 00:54:31,519 Back in 1 960 617 00:54:31,607 --> 00:54:35,725 my chameleon-hunting techniques werent quite so expert. 618 00:54:45,287 --> 00:54:49,963 However I did discover that if you put a stick in front of a chameleon 619 00:54:50,047 --> 00:54:53,164 it would usually obligingly walk onto it. 620 00:55:01,727 --> 00:55:05,356 But now with Bertrand as my guide we could search 621 00:55:05,447 --> 00:55:08,723 for the wonderful species that I had failed to find before. 622 00:55:08,807 --> 00:55:10,445 ATTENBOROUGH: Would they be down here? 623 00:55:12,967 --> 00:55:16,960 It lives on the ground almost invisible among the leaf litter. 624 00:55:19,007 --> 00:55:20,679 -That? -There. 625 00:55:20,767 --> 00:55:23,076 But Bertrand spotted it. 626 00:55:29,327 --> 00:55:31,602 How extraordinary. 627 00:55:34,727 --> 00:55:38,800 (WHISPERING) This is a pygmy leaf chameleon 628 00:55:38,887 --> 00:55:41,481 the smallest chameleon in the world. 629 00:55:41,967 --> 00:55:43,195 -In the world. -Yeah. 630 00:55:43,287 --> 00:55:47,246 And probably the smallest reptile in the world. 631 00:55:47,327 --> 00:55:49,045 -Of any kind. -Mmm. 632 00:55:50,487 --> 00:55:54,275 (WHISPERING) You know I had heard about these 633 00:55:55,167 --> 00:56:01,197 when I was here in Madagascar 4 7 years ago. 634 00:56:02,327 --> 00:56:07,162 And I read about these and I never saw one. 635 00:56:08,527 --> 00:56:10,597 And I think it was because 636 00:56:11,567 --> 00:56:14,320 I never knew they were as small as this. 637 00:56:15,847 --> 00:56:18,964 That is absolutely extraordinary. 638 00:56:19,047 --> 00:56:24,599 Its about the size of a bluebottle a blowfly. 639 00:56:26,087 --> 00:56:30,524 -And what does it feed on? -Small flies. 640 00:56:30,607 --> 00:56:35,397 Small flies. How absolutely wonderful. 641 00:56:38,807 --> 00:56:44,325 I am astonished. That is the most marvellous thing 642 00:56:44,407 --> 00:56:48,161 I have seen for a very very long time. 643 00:56:49,727 --> 00:56:52,719 Finding the pygmy chameleon would not have been possible without 644 00:56:52,807 --> 00:56:55,605 Bertrands expertise and sharp eyes. 645 00:56:55,927 --> 00:56:59,397 Hes just one of the scientists who has helped to reveal to us 646 00:56:59,487 --> 00:57:02,399 the secret lives of reptiles and amphibians.