1 00:00:22,360 --> 00:00:26,600 There are more than 5,000 species of frogs and toads, 2 00:00:26,600 --> 00:00:29,920 and they come in all colours, shapes and sizes. 3 00:00:31,160 --> 00:00:34,400 Over the years, I've filmed many different kinds of them, 4 00:00:34,400 --> 00:00:35,840 from across the world. 5 00:00:37,120 --> 00:00:41,520 This is the largest frog in the world, the goliath frog. 6 00:00:41,520 --> 00:00:45,560 And here in the leaf litter of this Madagascan forest, 7 00:00:45,560 --> 00:00:48,520 is the tiniest of them all. 8 00:00:53,680 --> 00:00:55,640 They can hop and climb. 9 00:00:59,680 --> 00:01:01,880 They can parachute from the tree tops. 10 00:01:03,360 --> 00:01:06,320 And burrow deep into the ground. 11 00:01:06,320 --> 00:01:10,400 Some, seemingly, can even walk on water. 12 00:01:14,000 --> 00:01:17,560 Frogs, like newts and salamanders, are amphibians, 13 00:01:17,560 --> 00:01:21,200 cold blooded animals that need water to survive. 14 00:01:21,200 --> 00:01:25,080 But despite this, they have colonised some of the hottest 15 00:01:25,080 --> 00:01:27,080 and the coldest places on Earth. 16 00:01:28,760 --> 00:01:32,760 Frogs are truly fascinating. 17 00:01:32,760 --> 00:01:34,800 You many not have thought much about them 18 00:01:34,800 --> 00:01:37,360 and they don't necessarily grab the headlines, 19 00:01:37,360 --> 00:01:41,120 but there's more to frogs than you might suppose. 20 00:01:56,400 --> 00:02:02,040 Frogs were the first creatures that I kept when I was a boy, 21 00:02:02,040 --> 00:02:06,640 and I thought they were fascinating and beautiful, 22 00:02:06,640 --> 00:02:09,040 and I still think they are. 23 00:02:09,040 --> 00:02:14,640 They were, of course, the first creatures to move up onto land. 24 00:02:34,760 --> 00:02:38,520 Today's frogs are descended from a group of amphibians that 25 00:02:38,520 --> 00:02:41,960 lived around 300 million years ago, 26 00:02:41,960 --> 00:02:44,960 and they were very like the modern salamander. 27 00:02:44,960 --> 00:02:49,000 That is to say, they had a very, very long spine 28 00:02:49,000 --> 00:02:54,680 with about 30 vertebrae in it, ending in a tail. 29 00:02:54,680 --> 00:02:58,600 But then about 250 million years ago, 30 00:02:58,600 --> 00:03:00,960 an intermediate form appeared, 31 00:03:00,960 --> 00:03:03,880 like this fossil from Madagascar, 32 00:03:03,880 --> 00:03:07,000 and already you can see a difference. 33 00:03:07,000 --> 00:03:09,240 Most importantly, the spine, 34 00:03:09,240 --> 00:03:13,440 instead of being 30 vertebrae long, is only about 15. 35 00:03:13,440 --> 00:03:17,400 The tail has almost been lost altogether. 36 00:03:17,400 --> 00:03:20,440 The hind legs are very much bigger. 37 00:03:20,440 --> 00:03:24,280 Compare that with today's amphibian. 38 00:03:24,280 --> 00:03:30,520 Most significantly, its spine is now, again halved. 39 00:03:30,520 --> 00:03:33,880 But the pelvis has become greatly elongated. 40 00:03:35,320 --> 00:03:38,920 But that's nothing compared with what has happened to the legs. 41 00:03:38,920 --> 00:03:41,720 They are gigantic. 42 00:03:41,720 --> 00:03:45,600 So you can see that this animal is a leaper. 43 00:03:49,120 --> 00:03:55,080 And today, some exploit these spectacular legs very dramatically. 44 00:04:01,080 --> 00:04:05,360 This little frog is an amazing jumper. 45 00:04:05,360 --> 00:04:09,600 It can leap 30 times its own body length, 46 00:04:09,600 --> 00:04:12,040 and there are some that can go even farther. 47 00:04:12,040 --> 00:04:16,440 One can leap 55 times its body length, 48 00:04:16,440 --> 00:04:20,520 equivalent to me jumping the length of a football pitch. 49 00:04:30,320 --> 00:04:33,160 In the 1930s, in the United States, 50 00:04:33,160 --> 00:04:36,760 frog leaping became something of a craze. 51 00:04:36,760 --> 00:04:39,560 People bet on how far a frog could jump. 52 00:04:50,760 --> 00:04:54,280 Even beauty queens took part in frog-jumping contests, 53 00:04:54,280 --> 00:04:55,960 each with her own pet. 54 00:05:15,160 --> 00:05:18,880 In the past, people couldn't understand how a frog could leap 55 00:05:18,880 --> 00:05:25,080 so far, but a little scientific research revealed how it does it. 56 00:05:38,240 --> 00:05:40,960 When a frog is in its sitting position, 57 00:05:40,960 --> 00:05:43,880 its leg muscles are contracted. 58 00:05:43,880 --> 00:05:47,000 This stretches the leg tendons. 59 00:05:51,400 --> 00:05:54,440 Tendons are elastic like rubber bands. 60 00:05:58,640 --> 00:06:03,120 Stretching them stores energy within them. 61 00:06:03,120 --> 00:06:08,000 And then, when the frog jumps, the tendons release that energy, 62 00:06:08,000 --> 00:06:09,760 like firing a catapult. 63 00:06:12,920 --> 00:06:15,920 And the frog is propelled into the air. 64 00:06:31,000 --> 00:06:35,160 When this skittering frog from India jumps, 65 00:06:35,160 --> 00:06:38,360 it simultaneously extends its webbed toes 66 00:06:38,360 --> 00:06:42,000 so that it virtually bounces across the surface of the water. 67 00:06:57,240 --> 00:07:01,000 The webs between the toes, so useful for swimming, 68 00:07:01,000 --> 00:07:03,840 can also help when moving around on land. 69 00:07:04,920 --> 00:07:09,000 The gliding leaf frog has such extensive webbing that 70 00:07:09,000 --> 00:07:13,560 when it jumps, the outstretched toes of its feet act like parachutes 71 00:07:13,560 --> 00:07:17,920 and keep it in the air long enough to travel considerable distances. 72 00:07:43,320 --> 00:07:47,000 When the first amphibians emerged from the water, the only 73 00:07:47,000 --> 00:07:51,240 animal sounds to be heard on land were the whirrs and hums of insects. 74 00:07:51,240 --> 00:07:54,480 CROAKING 75 00:07:54,480 --> 00:07:58,000 But the amphibians also needed to communicate with one another, 76 00:07:58,000 --> 00:08:01,800 and soon they added their own croaks and whistles. 77 00:08:01,800 --> 00:08:08,040 CROAKING AND WHISTLING 78 00:08:10,280 --> 00:08:14,480 Frogs blow air from their lungs, through vocal chords 79 00:08:14,480 --> 00:08:16,120 and so produce a croak. 80 00:08:16,120 --> 00:08:22,040 But the muscles that do that are comparatively weak, so many species 81 00:08:22,040 --> 00:08:28,320 amplify the sound with resonators, cheek pouches or throat pouches. 82 00:08:28,320 --> 00:08:32,400 FROG CROAKS 83 00:08:58,040 --> 00:09:01,320 One purpose for calling is to find a mate. 84 00:09:03,480 --> 00:09:07,760 A female gliding leaf frog in the jungles of South America 85 00:09:07,760 --> 00:09:11,320 is listening to all the males calling around her. 86 00:09:16,360 --> 00:09:20,120 Then she sets off in the direction of the loudest voice, 87 00:09:20,120 --> 00:09:24,760 because the owner is likely to be the strongest male, the best mate. 88 00:09:30,120 --> 00:09:32,400 It's a long haul. 89 00:09:41,360 --> 00:09:45,360 On the way, she has to avoid the weaker males. 90 00:09:48,880 --> 00:09:50,400 It's not all that easy. 91 00:09:50,400 --> 00:09:53,240 She has to fight off several at a time. 92 00:10:11,880 --> 00:10:16,080 Eventually, the strongest male gets his reward. 93 00:10:16,080 --> 00:10:19,440 It's a case of he who shouts loudest. 94 00:10:34,200 --> 00:10:38,560 This is called the splendid leaf frog, 95 00:10:38,560 --> 00:10:40,680 and quite right, too. 96 00:10:40,680 --> 00:10:43,320 Most frogs communicate with their voice, 97 00:10:43,320 --> 00:10:45,880 by croaking or indeed squeaking. 98 00:10:45,880 --> 00:10:47,840 And this one does, too, 99 00:10:47,840 --> 00:10:50,560 but it has rather a quiet voice 100 00:10:50,560 --> 00:10:54,840 and it also communicates by using its legs. 101 00:10:56,720 --> 00:11:01,000 What he'll do is to use them to wave to other frogs. 102 00:11:01,000 --> 00:11:05,640 And its legs are specially adapted for the purpose. 103 00:11:05,640 --> 00:11:08,320 They have flaps on them 104 00:11:08,320 --> 00:11:13,040 so they appear to be specially wide and prominent. 105 00:11:14,760 --> 00:11:19,240 This waving technique is something I once filmed with another 106 00:11:19,240 --> 00:11:21,160 beautiful frog. 107 00:11:21,160 --> 00:11:26,400 We found it several years ago in the rain forests of Panama. 108 00:11:36,360 --> 00:11:41,520 This is a golden Panama male, and he is looking for a mate. 109 00:11:42,800 --> 00:11:44,960 But a rival stands in his way. 110 00:11:47,960 --> 00:11:52,240 Just in case his call can't be heard above the sound of water, 111 00:11:52,240 --> 00:11:57,160 he reinforces his message with a visual signal, a wave. 112 00:11:59,920 --> 00:12:01,760 His rival waves back. 113 00:12:03,840 --> 00:12:07,240 He repeats his signal so there's no misunderstanding. 114 00:12:20,600 --> 00:12:23,440 But now another male arrives. 115 00:12:23,440 --> 00:12:25,320 He too is looking for a female, 116 00:12:25,320 --> 00:12:28,240 and he isn't going to let anyone stand in his way. 117 00:12:30,600 --> 00:12:34,480 This kind of argument has to be settled with a wrestling match. 118 00:12:37,040 --> 00:12:38,360 That should teach him! 119 00:12:42,840 --> 00:12:45,720 The loser submits, lowering his head. 120 00:12:57,800 --> 00:13:01,160 And the winner continues his hunt for a mate. 121 00:13:05,600 --> 00:13:11,480 Finally, a large golden female arrives. Just the ticket! 122 00:13:11,480 --> 00:13:17,400 HE CROAKS 123 00:13:24,840 --> 00:13:28,000 He waves to show he's interested. 124 00:13:29,120 --> 00:13:31,160 She waves back. 125 00:13:48,720 --> 00:13:52,160 It's a success. His waving courtship has worked. 126 00:13:57,880 --> 00:14:03,360 Calling and waving are comparatively subtle ways of attracting a female. 127 00:14:03,360 --> 00:14:06,320 Other frogs use a more macho approach. 128 00:14:11,880 --> 00:14:14,480 Rains, on the African savannah. 129 00:14:26,600 --> 00:14:31,200 The African male bullfrog, one of the biggest of all frogs. 130 00:14:31,200 --> 00:14:33,760 He fights for the right to mate. 131 00:14:47,320 --> 00:14:50,600 The males assemble in a newly-filled pond 132 00:14:50,600 --> 00:14:54,080 and battle with each other to establish who is the strongest. 133 00:15:09,400 --> 00:15:12,760 The winner will mate with most of the females here. 134 00:15:16,320 --> 00:15:18,960 No such luck for the loser. 135 00:15:28,360 --> 00:15:32,680 Courtship techniques vary widely, but for one remarkable little 136 00:15:32,680 --> 00:15:38,720 brown frog in Madagascar, the key to mating rituals is skin colour. 137 00:15:43,120 --> 00:15:48,560 Following a bout of heavy rain, the frogs all gather at a waterhole. 138 00:15:48,560 --> 00:15:53,960 The females are still brown, but the males have turned a bright yellow. 139 00:16:00,480 --> 00:16:04,080 This enables males and females to tell each other 140 00:16:04,080 --> 00:16:07,880 apart in the multiple mating that is about to happen. 141 00:16:18,600 --> 00:16:21,680 They have to judge the moment very precisely. 142 00:16:21,680 --> 00:16:25,520 There must be enough water in which to lay their eggs, 143 00:16:25,520 --> 00:16:28,960 but not so much that the eggs are washed away. 144 00:16:30,920 --> 00:16:34,880 CROAKING 145 00:17:15,560 --> 00:17:19,200 After a few hours, the orgy is over, 146 00:17:19,200 --> 00:17:23,160 and the males turn back to brown again. 147 00:17:23,160 --> 00:17:26,360 It will happen all over again next year, 148 00:17:26,360 --> 00:17:29,920 when the rains return and more eggs are laid. 149 00:17:34,400 --> 00:17:37,040 When speeded up, you can watch 150 00:17:37,040 --> 00:17:40,200 the extraordinary way in which eggs develop. 151 00:18:05,920 --> 00:18:09,240 These eggs were laid by a leaf frog. 152 00:18:09,240 --> 00:18:14,800 And inside the jelly of each one, you can see a little tiny dot. 153 00:18:14,800 --> 00:18:19,040 And if you look closely, you may even see it move. 154 00:18:19,040 --> 00:18:21,640 And over the next five or seven days, 155 00:18:21,640 --> 00:18:24,600 they will continue to develop until they are strong enough 156 00:18:24,600 --> 00:18:29,320 to emerge from the egg and drop into water beneath. 157 00:18:48,440 --> 00:18:52,200 And then over the next four or five weeks, 158 00:18:52,200 --> 00:18:54,960 an enormous transformation takes place. 159 00:18:58,640 --> 00:19:02,320 The gills, which enabled the tadpole to breathe in water, 160 00:19:02,320 --> 00:19:03,880 gradually disappear. 161 00:19:06,440 --> 00:19:10,920 The tadpole's intestines, accustomed to a vegetarian diet, 162 00:19:10,920 --> 00:19:15,760 have to be completely remodelled to allow them to digest animal tissues. 163 00:19:17,160 --> 00:19:20,680 Its skull, which was made of cartilage, turns to bone 164 00:19:20,680 --> 00:19:22,720 and the backbone grows. 165 00:19:24,920 --> 00:19:30,080 The tadpole's legs get larger as the tail shrinks, absorbed by the body. 166 00:19:31,160 --> 00:19:32,520 It's an astonishing 167 00:19:32,520 --> 00:19:36,720 and radical transformation, which takes around six weeks. 168 00:19:45,640 --> 00:19:47,720 A pond in Madagascar. 169 00:19:47,720 --> 00:19:49,520 Not a good place for eggs 170 00:19:49,520 --> 00:19:53,840 because it's full of fish that would eat frogs' eggs given the chance. 171 00:19:55,840 --> 00:20:00,920 So this little frog lays her eggs on the leaves of trees 172 00:20:00,920 --> 00:20:03,040 that overhang the pond. 173 00:20:03,040 --> 00:20:07,720 The tadpoles are maturing quickly, but there is danger here, too. 174 00:20:11,040 --> 00:20:15,040 A predatory wasp has found the clumps of spawn. 175 00:20:21,640 --> 00:20:25,840 It manages to slice its way through the protective jelly. 176 00:20:32,040 --> 00:20:36,840 And now it starts to chew up the tadpoles. 177 00:20:46,400 --> 00:20:47,960 But these tadpoles, 178 00:20:47,960 --> 00:20:51,880 although only five days old, can react to such attacks. 179 00:20:51,880 --> 00:20:57,440 The vibrations, created by the wasp, stimulate them to hatch prematurely. 180 00:20:59,080 --> 00:21:03,080 The jelly liquefies and the tadpoles travel down the leaf 181 00:21:03,080 --> 00:21:04,960 and drop into the water below. 182 00:21:12,760 --> 00:21:16,240 They may be underdeveloped, but they can swim 183 00:21:16,240 --> 00:21:19,520 and they stand a better chance of survival in the pond than 184 00:21:19,520 --> 00:21:21,960 they did with the wasp on their leaf. 185 00:21:25,480 --> 00:21:29,560 These youngsters had to survive without parental care, but other 186 00:21:29,560 --> 00:21:33,600 frog parents go to great lengths to look after their offspring. 187 00:21:38,360 --> 00:21:43,920 This little frog is tiny, hardly bigger than my thumb nail. 188 00:21:46,800 --> 00:21:49,280 It is a strawberry poison-dart frog. 189 00:21:49,280 --> 00:21:50,920 It may be very small, 190 00:21:50,920 --> 00:21:55,160 but when it comes to caring for its young, it's a real champion. 191 00:22:05,880 --> 00:22:10,120 It lives in the wet lowland forests of Central America. 192 00:22:26,560 --> 00:22:32,240 This female is guarding a clump of newly-fertilised eggs. 193 00:22:34,920 --> 00:22:37,680 She and her mate will keep watch, 194 00:22:37,680 --> 00:22:41,400 making sure that their offspring are safe from predators. 195 00:22:42,960 --> 00:22:47,200 But the leaf litter is drying out and the tadpoles need water. 196 00:22:47,200 --> 00:22:50,200 She must move them, and fast. 197 00:22:50,200 --> 00:22:53,480 So she encourages one of them to jump on to her back. 198 00:22:54,640 --> 00:22:59,400 But it's not a pond on the forest floor that she's looking for now. 199 00:22:59,400 --> 00:23:05,680 She wants a bromeliad, a vase plant, and they grow up in the branches. 200 00:23:13,320 --> 00:23:17,440 Climbing a tree as tall as this is an immense journey for such 201 00:23:17,440 --> 00:23:19,000 a tiny creature. 202 00:23:29,840 --> 00:23:32,920 A bromeliad plant has a tiny permanent 203 00:23:32,920 --> 00:23:34,800 pool of water at its centre, 204 00:23:34,800 --> 00:23:38,440 an excellent nursery for a tadpole. 205 00:23:38,440 --> 00:23:41,640 And there she delivers it. 206 00:23:53,240 --> 00:23:56,520 But she has several tadpoles. 207 00:23:56,520 --> 00:24:00,440 So now she must rush back to the others down on the ground. 208 00:24:03,280 --> 00:24:08,480 She collects them one by one and carries each to its own bromeliad. 209 00:24:17,200 --> 00:24:20,880 She continues to make her long, arduous journeys, 210 00:24:20,880 --> 00:24:24,360 while the male guards the remaining eggs on the forest floor. 211 00:24:30,920 --> 00:24:35,200 But the little bromeliad pools don't have any food in them. 212 00:24:35,200 --> 00:24:41,360 So she lays an unfertilised egg in each one for each tadpole to eat. 213 00:24:44,920 --> 00:24:49,760 A single egg won't sustain a developing tadpole for very long. 214 00:24:49,760 --> 00:24:53,320 So she has to return to each pool every few days 215 00:24:53,320 --> 00:24:55,920 and deliver another food parcel. 216 00:24:55,920 --> 00:24:59,480 This continues for the next two weeks, 217 00:24:59,480 --> 00:25:03,080 during which time, she will have travelled over half a mile. 218 00:25:04,560 --> 00:25:08,000 An astonishing distance for such a tiny creature. 219 00:25:10,800 --> 00:25:15,280 Eventually, the tadpole develops into a froglet large enough 220 00:25:15,280 --> 00:25:17,640 to leave the pool and fend for itself. 221 00:25:21,160 --> 00:25:23,360 Mum has done her job well. 222 00:25:24,640 --> 00:25:28,920 But it isn't always the female who takes on the task of rearing 223 00:25:28,920 --> 00:25:29,960 the young. 224 00:25:31,840 --> 00:25:33,920 Sometimes, the male does. 225 00:25:37,760 --> 00:25:41,120 And one of those lives in the mountains of northern Spain. 226 00:25:44,040 --> 00:25:48,520 This little creature is called a toad because its skin is rather dry. 227 00:25:48,520 --> 00:25:52,560 But the names frog and toad are largely interchangeable, 228 00:25:52,560 --> 00:25:56,040 for all amphibians with this shape are very closely related. 229 00:25:57,040 --> 00:26:00,080 This one is known as the midwife toad. 230 00:26:02,360 --> 00:26:06,480 When they mate, the male clasps the female with his arms 231 00:26:06,480 --> 00:26:09,880 and squeezes until she releases her eggs. 232 00:26:13,840 --> 00:26:16,760 They emerge in a long chain of jelly, 233 00:26:16,760 --> 00:26:19,440 and as they do so, he fertilises them. 234 00:26:27,000 --> 00:26:29,880 He then hitches them up around his hind legs 235 00:26:29,880 --> 00:26:32,000 and then the pair will then separate. 236 00:26:39,520 --> 00:26:43,160 She leaves and he carries them around 237 00:26:43,160 --> 00:26:46,440 until the time comes to deposit them in water. 238 00:26:51,520 --> 00:26:55,520 The midwife toad is not the only species in which the male 239 00:26:55,520 --> 00:26:57,120 takes care of the young. 240 00:27:05,560 --> 00:27:08,480 The African bullfrog is quite a character. 241 00:27:08,480 --> 00:27:14,000 It's the biggest frog in Africa and it's very aggressive. 242 00:27:14,000 --> 00:27:17,360 It's got a very powerful bite, for one thing. 243 00:27:17,360 --> 00:27:20,280 But in spite of that, it's a devoted father. 244 00:27:25,920 --> 00:27:31,600 Bullfrogs spawn in little pools around the margins of a larger pond. 245 00:27:31,600 --> 00:27:36,160 And after mating is over, one male stays to watch over them all. 246 00:27:37,240 --> 00:27:41,320 But the water is evaporating and the tadpoles are now crowded 247 00:27:41,320 --> 00:27:46,480 together in a single pool, and that too is now drying up. 248 00:27:49,960 --> 00:27:53,400 The tadpoles will be dead within an hour, 249 00:27:53,400 --> 00:27:56,480 unless the male can do something to save them. 250 00:28:00,240 --> 00:28:02,920 And he starts doing just that. 251 00:28:02,920 --> 00:28:06,320 He begins to dig a channel to connect the tadpoles' 252 00:28:06,320 --> 00:28:08,560 little pool to the main pond. 253 00:28:10,560 --> 00:28:12,000 He must be quick. 254 00:28:28,160 --> 00:28:31,920 It's a major task, but he is determined. 255 00:28:40,840 --> 00:28:42,760 Down they swim. 256 00:29:07,400 --> 00:29:10,040 The tadpoles are saved! 257 00:29:31,040 --> 00:29:35,480 But perhaps the prize for fatherly care should go to a rare 258 00:29:35,480 --> 00:29:38,640 little frog that lives in the forests of Chile. 259 00:29:41,920 --> 00:29:44,440 This is Darwin's frog. 260 00:29:46,400 --> 00:29:50,240 After the female has laid her eggs on the moist ground 261 00:29:50,240 --> 00:29:54,160 and the male has fertilised them, he, apparently, eats them. 262 00:29:54,160 --> 00:29:58,800 But they go, not into his stomach but into his throat pouch. 263 00:30:00,800 --> 00:30:04,120 And there they develop, and wriggle. 264 00:30:08,200 --> 00:30:10,120 And when they're ready... 265 00:30:11,760 --> 00:30:13,400 ..one jumps out. 266 00:30:19,080 --> 00:30:20,560 And another. 267 00:30:30,840 --> 00:30:33,960 Giving birth from your mouth is pretty odd, 268 00:30:33,960 --> 00:30:37,440 but what about producing babies from your back? 269 00:30:39,360 --> 00:30:44,000 The Surinam toad is an aquatic species from South America. 270 00:30:44,000 --> 00:30:48,080 The female produces around 100 eggs at a time. 271 00:30:50,960 --> 00:30:54,920 The male collects them and steers them on to the female's back. 272 00:31:01,080 --> 00:31:02,840 And there they stick. 273 00:31:14,480 --> 00:31:19,120 The skin on the female's back then begins to swell around them. 274 00:31:21,080 --> 00:31:25,960 A membrane grows over them and eventually completely encloses them. 275 00:31:29,080 --> 00:31:32,760 After a couple of days, they've virtually disappeared. 276 00:31:36,400 --> 00:31:40,640 A few weeks later, the young hatch as tadpoles. 277 00:31:50,960 --> 00:31:55,760 In some Surinam toads, the young remain within their mothers' 278 00:31:55,760 --> 00:32:01,560 back so long that they emerge not as tadpoles but little froglets. 279 00:32:30,280 --> 00:32:35,360 It's certainly an odd way of producing young, but it works. 280 00:32:51,280 --> 00:32:54,560 All adult amphibians are hunters. 281 00:32:54,560 --> 00:32:59,240 To help them catch their prey, they have a secret weapon - 282 00:32:59,240 --> 00:33:01,440 a special kind of tongue. 283 00:33:16,160 --> 00:33:20,080 The extendable tongue is an amphibian invention. 284 00:33:20,080 --> 00:33:21,920 No fish ever had one. 285 00:33:25,280 --> 00:33:28,920 And the tongue is not attached to the back of the mouth like ours, 286 00:33:28,920 --> 00:33:30,240 but to the front. 287 00:33:42,280 --> 00:33:44,720 Frogs eat worms and insects. 288 00:33:44,720 --> 00:33:47,880 And the larger the frog, the bigger prey it will tackle. 289 00:33:50,160 --> 00:33:53,040 And some species, like these cane toads, 290 00:33:53,040 --> 00:33:57,600 will eat almost anything, including one another. 291 00:34:11,160 --> 00:34:15,080 It's recently been discovered that way back in prehistory, 292 00:34:15,080 --> 00:34:19,520 there were some frogs big enough to catch mammals. 293 00:34:23,680 --> 00:34:27,200 A few years ago, fragments were found in Madagascar 294 00:34:27,200 --> 00:34:33,880 of a really giant frog dating back from about 65 million years ago. 295 00:34:33,880 --> 00:34:37,280 This is part of its skull. 296 00:34:37,280 --> 00:34:40,240 Here is the orbit of the eye. 297 00:34:40,240 --> 00:34:42,840 And this is where its spine... 298 00:34:42,840 --> 00:34:46,120 The spine would have run down here. 299 00:34:46,120 --> 00:34:48,720 And this is the right cheek. 300 00:34:48,720 --> 00:34:54,560 So the animal's head, when complete, would have been about that wide. 301 00:34:54,560 --> 00:34:56,600 So this really was a monster. 302 00:34:57,600 --> 00:35:00,200 And here is a computer reconstruction 303 00:35:00,200 --> 00:35:01,720 of the complete skeleton. 304 00:35:05,200 --> 00:35:07,040 The scientists who worked on it 305 00:35:07,040 --> 00:35:11,400 referred to it among themselves as a devil frog. 306 00:35:11,400 --> 00:35:13,960 And when the time came to give it a scientific name, 307 00:35:13,960 --> 00:35:16,880 they called it Beelzebufo. 308 00:35:16,880 --> 00:35:19,680 65 million years ago was just towards 309 00:35:19,680 --> 00:35:21,920 the end of the reign of the dinosaurs. 310 00:35:21,920 --> 00:35:28,400 So maybe this giant frog actually ate hatchling dinosaurs, 311 00:35:28,400 --> 00:35:33,000 as been shown in this artist's imaginative reconstruction. 312 00:35:35,520 --> 00:35:40,080 Some frogs today also have teeth, but they don't chew with them. 313 00:35:40,080 --> 00:35:42,440 The teeth are used either for defence 314 00:35:42,440 --> 00:35:45,560 or as a way of gripping prey. 315 00:35:49,600 --> 00:35:53,960 This large monkey frog is in the process of swallowing a cricket. 316 00:35:57,280 --> 00:36:02,840 And, strangely perhaps, it uses its eyes to help it do so. 317 00:36:08,440 --> 00:36:09,760 We're waiting for it to burp. 318 00:36:09,760 --> 00:36:12,320 LAUGHTER 319 00:36:24,720 --> 00:36:29,800 As a frog swallows, it pulls its bulging eyes downwards 320 00:36:29,800 --> 00:36:33,760 so that they help to push the food down its throat. 321 00:36:45,960 --> 00:36:48,400 Most frogs have very big eyes. 322 00:36:48,400 --> 00:36:52,360 They have to be big because frogs, since they don't have necks, 323 00:36:52,360 --> 00:36:55,640 can't turn their heads to look to one side. 324 00:36:58,520 --> 00:37:01,480 Instead, their two eyes, between them, 325 00:37:01,480 --> 00:37:05,720 give a frog an almost 360-degree vision. 326 00:37:10,720 --> 00:37:14,760 They also have a kind of see-through third eye-lid, 327 00:37:14,760 --> 00:37:19,320 which protects their eyes underwater without blocking their sight. 328 00:37:19,320 --> 00:37:22,560 The red-eyed tree frog's third eyelid has a distinctive 329 00:37:22,560 --> 00:37:26,480 green pattern, which, when out of water, helps with camouflage. 330 00:37:29,160 --> 00:37:34,560 Frogs have managed to adapt to a surprising range of environments. 331 00:37:40,880 --> 00:37:45,800 The little red-eyed tree frog lives up in the forest canopy, 332 00:37:45,800 --> 00:37:47,320 catching insects. 333 00:37:47,320 --> 00:37:51,400 And to do that, of course, it has to be an expert climber. 334 00:37:52,680 --> 00:37:57,600 So, not surprisingly, they have very special hands and feet. 335 00:38:15,800 --> 00:38:19,720 Its toe-pads are highly complex structures. 336 00:38:22,360 --> 00:38:26,920 Each has a large surface area, which helps it get a good grip. 337 00:38:30,160 --> 00:38:33,080 Between the six-sided skin cells, 338 00:38:33,080 --> 00:38:36,600 there are small channels which fill with a sticky mucus. 339 00:38:36,600 --> 00:38:41,400 This acts as a continuously renewed glue, but one that allows 340 00:38:41,400 --> 00:38:45,960 the frog to peel off its foot and re-attach it as it climbs. 341 00:38:45,960 --> 00:38:49,880 Some frogs have evolved a way of using their hands 342 00:38:49,880 --> 00:38:52,520 and feet in a quite remarkable way. 343 00:39:00,880 --> 00:39:03,320 In the remote rain forests of South America, 344 00:39:03,320 --> 00:39:06,360 there's a small amphibian known as a waterfall toad. 345 00:39:15,480 --> 00:39:20,520 It, like so many frogs, is a favourite meal of snakes. 346 00:39:34,760 --> 00:39:37,560 Many frogs avoid their enemies by hopping, 347 00:39:37,560 --> 00:39:42,280 but this little toad can't hop more than an inch or so. Instead, 348 00:39:42,280 --> 00:39:46,200 when a swift retreat is needed, it has other techniques. 349 00:39:49,760 --> 00:39:52,480 Free-falling, which is easy, 350 00:39:52,480 --> 00:39:55,400 and stopping, which is more difficult. 351 00:40:18,080 --> 00:40:22,600 Above the rain forests, there are mountains so drenched with rain 352 00:40:22,600 --> 00:40:27,600 that the rocks are bare, except for a coat of slimy black algae. 353 00:40:30,040 --> 00:40:33,080 And here you can find the pebble toad. 354 00:40:35,880 --> 00:40:39,640 But there are predators here, too. 355 00:40:51,760 --> 00:40:57,400 This is a toad-eating tarantula, an expert in ambushing its prey. 356 00:41:00,640 --> 00:41:03,720 The pebble toad can't hop very far either, 357 00:41:03,720 --> 00:41:06,120 but it has a different defence. 358 00:41:16,960 --> 00:41:19,440 It clenches its muscles so tightly 359 00:41:19,440 --> 00:41:21,920 that it becomes as bouncy as a rubber ball. 360 00:42:00,840 --> 00:42:04,480 Danger averted and no damage done. 361 00:42:08,040 --> 00:42:12,640 But hunters are everywhere - not only on the ground, but in the sky. 362 00:42:21,520 --> 00:42:24,400 Camouflage is an excellent defence. 363 00:42:24,400 --> 00:42:27,680 Blink and you could easily miss this Darwin's frog. 364 00:42:44,800 --> 00:42:47,680 Most frogs are beautifully camouflaged 365 00:42:47,680 --> 00:42:51,440 so that it's very difficult sometimes to spot them. 366 00:42:51,440 --> 00:42:53,160 But this one, 367 00:42:53,160 --> 00:42:56,720 which is the tiger-striped monkey frog from South America... 368 00:42:58,200 --> 00:43:03,200 ..has tiger stripes - orange and black - 369 00:43:03,200 --> 00:43:04,960 on the inside of its legs. 370 00:43:04,960 --> 00:43:08,720 So when it's sitting like that, it looks green. 371 00:43:08,720 --> 00:43:10,760 But if they're threatened by a predator, 372 00:43:10,760 --> 00:43:15,120 they can suddenly open their legs and reveal 373 00:43:15,120 --> 00:43:18,360 that orange and black underbelly, 374 00:43:18,360 --> 00:43:21,000 which, people think, puts off a predator. 375 00:43:24,240 --> 00:43:28,000 The great majority of frogs rely on camouflage. 376 00:43:30,360 --> 00:43:35,840 But a few take the other option - conspicuousness. 377 00:43:35,840 --> 00:43:38,680 Bright colouring can be a warning that an animal is 378 00:43:38,680 --> 00:43:42,960 unpleasant to eat. But some are more than merely unpalatable. 379 00:43:44,280 --> 00:43:48,960 This is the golden poison-dart frog from Colombia. 380 00:43:48,960 --> 00:43:53,440 And its skin contains enough poison to kill ten human beings, 381 00:43:53,440 --> 00:43:57,240 which is why I'm taking no chances and wearing gloves. 382 00:43:57,240 --> 00:44:01,520 Traditionally, the people in Colombia used that poison 383 00:44:01,520 --> 00:44:04,160 to tip their blow-pipe darts. 384 00:44:04,160 --> 00:44:06,040 But of course, for the frog, 385 00:44:06,040 --> 00:44:09,360 the poison serves as a defence against predators. 386 00:44:09,360 --> 00:44:13,400 And many poison-dart frogs are very brightly coloured, just to 387 00:44:13,400 --> 00:44:17,240 warn predators of what would await them if they did take a mouthful. 388 00:44:21,800 --> 00:44:25,840 The toxicity of frog skin has traditionally been exploited 389 00:44:25,840 --> 00:44:30,600 by local people, but modern medicine has also found ways of using it. 390 00:44:37,120 --> 00:44:39,320 One chemical compound from the skin 391 00:44:39,320 --> 00:44:41,800 of the tri-coloured poison-dart frog... 392 00:44:43,200 --> 00:44:47,160 ..is being used in the development of a groundbreaking pain-killer... 393 00:44:49,120 --> 00:44:52,760 ..several hundred times more powerful than morphine. 394 00:44:57,960 --> 00:45:00,200 A frog doesn't drink, 395 00:45:00,200 --> 00:45:03,800 it absorbs all the water it needs through its skin. 396 00:45:03,800 --> 00:45:07,320 It also gets most of its oxygen in the same way. 397 00:45:10,880 --> 00:45:15,200 But a permeable skin that allows water to flow in also allows 398 00:45:15,200 --> 00:45:18,760 it to flow out, and for some that can be a problem. 399 00:45:20,360 --> 00:45:22,240 If there's a dry spell, 400 00:45:22,240 --> 00:45:26,080 this giant monkey frog from South America 401 00:45:26,080 --> 00:45:29,040 produces a kind of ointment from glands 402 00:45:29,040 --> 00:45:32,800 in its skin, which it uses as sun cream. 403 00:45:37,360 --> 00:45:39,840 At the beginning of the dry season, 404 00:45:39,840 --> 00:45:43,920 it takes steps to make sure that it doesn't get sun-burnt or dry out. 405 00:45:46,240 --> 00:45:50,760 And with their supple joints, frogs can manage to reach all those 406 00:45:50,760 --> 00:45:54,800 odd places that the rest of us find a little tricky. 407 00:46:04,440 --> 00:46:07,040 The dry season can last for weeks. 408 00:46:07,040 --> 00:46:09,760 So it's best to be really thorough. 409 00:46:25,520 --> 00:46:28,680 Some frogs however, never leave water at all. 410 00:46:31,720 --> 00:46:35,040 This is the highest lake in the world - Lake Titicaca 411 00:46:35,040 --> 00:46:36,800 in the Peruvian Andes. 412 00:46:41,640 --> 00:46:45,080 And the frog that lives here has very different problems. 413 00:46:47,080 --> 00:46:49,640 At 4,000 metres above sea level, 414 00:46:49,640 --> 00:46:52,160 there's very little oxygen in the atmosphere, 415 00:46:52,160 --> 00:46:53,760 and therefore in the water. 416 00:46:55,240 --> 00:46:58,160 So the frog has developed bizarre-looking flaps 417 00:46:58,160 --> 00:47:01,800 and folds that increase the skin's surface area, 418 00:47:01,800 --> 00:47:05,080 and therefore its ability to absorb oxygen. 419 00:47:10,720 --> 00:47:15,480 The frog also increases the flow of water across its skin by doing 420 00:47:15,480 --> 00:47:17,680 what looks like press-ups. 421 00:47:35,200 --> 00:47:38,720 Because their skin is so sensitive to their surroundings, 422 00:47:38,720 --> 00:47:42,400 frogs are important biological indicators. 423 00:47:42,400 --> 00:47:44,760 If there are environmental problems, 424 00:47:44,760 --> 00:47:48,200 they're among the first creatures to be affected. 425 00:47:48,200 --> 00:47:50,720 But that permeability has also led, 426 00:47:50,720 --> 00:47:53,920 in recent years, to alarming declines. 427 00:47:55,800 --> 00:47:59,680 This, crouched on a leaf, 428 00:47:59,680 --> 00:48:02,880 is one of the rarest frogs in the world. 429 00:48:02,880 --> 00:48:05,600 It's called the lemur leaf frog 430 00:48:05,600 --> 00:48:08,160 and it lives in Costa Rica. 431 00:48:08,160 --> 00:48:11,400 Once it was widespread there, but today, 432 00:48:11,400 --> 00:48:14,040 it's been reduced to a very small area. 433 00:48:20,320 --> 00:48:25,520 It's nocturnal and lives in the humid rainforest of the lowlands. 434 00:48:25,520 --> 00:48:30,400 Unusually for a leaf frog, it has no webbing between its toes 435 00:48:30,400 --> 00:48:34,080 and its stick-like legs give it a very distinctive walk. 436 00:48:45,920 --> 00:48:48,240 What a lovely little creature. 437 00:48:49,960 --> 00:48:53,760 Here in the Manchester Museum, they're studying the species 438 00:48:53,760 --> 00:48:55,760 and doing their best to conserve it, 439 00:48:55,760 --> 00:48:57,880 both by breeding it in captivity 440 00:48:57,880 --> 00:49:02,320 and partly by going out to Costa Rica and studying it in the wild. 441 00:49:02,320 --> 00:49:05,760 The cause for its loss in numbers is three-fold - 442 00:49:05,760 --> 00:49:08,520 loss of habitat, pesticides 443 00:49:08,520 --> 00:49:12,040 and a particularly lethal kind of fungus called a chytrid. 444 00:49:18,600 --> 00:49:22,160 The fungus causes the cells in a frog's skin 445 00:49:22,160 --> 00:49:24,320 to suddenly multiply, 446 00:49:24,320 --> 00:49:26,960 so that the outer layers thicken. 447 00:49:29,320 --> 00:49:33,080 That blocks the flow of essential salts through the skin. 448 00:49:34,400 --> 00:49:37,360 The muscles then can't function properly... 449 00:49:40,240 --> 00:49:44,040 ..and eventually the heart simply stops beating. 450 00:49:56,040 --> 00:50:00,240 Scientists think that chytrid fungus started to spread 451 00:50:00,240 --> 00:50:04,000 back in the 1940s, when African clawed frogs, 452 00:50:04,000 --> 00:50:06,480 which were probably carrying the fungus, 453 00:50:06,480 --> 00:50:08,280 were shipped all over the world 454 00:50:08,280 --> 00:50:12,640 for medical research, including pregnancy testing. 455 00:50:12,640 --> 00:50:17,160 Today, chytrid fungus is spreading uncontrollably, 456 00:50:17,160 --> 00:50:20,160 causing the extinction of some frog species 457 00:50:20,160 --> 00:50:23,720 and the severe decline of many others. 458 00:50:23,720 --> 00:50:27,280 It's the worst infectious disease ever recorded 459 00:50:27,280 --> 00:50:30,040 in terms of the number of species affected. 460 00:50:31,680 --> 00:50:35,800 Almost a third of all amphibians are now threatened with extinction, 461 00:50:35,800 --> 00:50:38,560 including the lemur leaf frog. 462 00:50:40,400 --> 00:50:44,560 The future of this little frog is still hanging in the balance, 463 00:50:44,560 --> 00:50:47,800 but hopefully the work that's being done here in Manchester 464 00:50:47,800 --> 00:50:50,520 will prevent it from becoming extinct. 465 00:50:50,520 --> 00:50:53,760 But other frogs have not been so lucky. 466 00:50:57,080 --> 00:51:00,960 Over the years, I've filmed a number of different species, 467 00:51:00,960 --> 00:51:03,920 some of which are now extinct in the wild. 468 00:51:09,240 --> 00:51:12,520 The waving golden frogs we filmed in Panama 469 00:51:12,520 --> 00:51:16,320 belonged to one of the last remaining populations. 470 00:51:16,320 --> 00:51:20,120 The chytrid fungus was already spreading up from South America. 471 00:51:20,120 --> 00:51:24,640 So when we had finished, scientists collected all they could find 472 00:51:24,640 --> 00:51:27,920 and took them to specially sterilised breeding centres 473 00:51:27,920 --> 00:51:31,960 to keep them in safety until such time, if ever, 474 00:51:31,960 --> 00:51:33,760 the fungus disappears 475 00:51:33,760 --> 00:51:37,760 and they can be reintroduced to their original home. 476 00:51:54,200 --> 00:51:58,960 But despite the decline, the fact that frogs are such adaptable 477 00:51:58,960 --> 00:52:01,640 creatures does offer some hope. 478 00:52:03,480 --> 00:52:08,080 Some species, after all, manage to survive in places that might 479 00:52:08,080 --> 00:52:12,560 seem to spell certain death for creatures with moist skins. 480 00:52:14,200 --> 00:52:17,680 This is part of the Australian desert where several years 481 00:52:17,680 --> 00:52:19,240 can pass without rain. 482 00:52:26,560 --> 00:52:30,440 It's a great relief when at last the drought breaks. 483 00:52:34,520 --> 00:52:39,080 And then, amazingly, little toads emerge from the sand. 484 00:52:48,920 --> 00:52:52,280 Numbers of them appear almost simultaneously. 485 00:52:52,280 --> 00:52:55,280 They have specially large legs to help them dig, 486 00:52:55,280 --> 00:52:57,840 which gives them their name - spade-foots. 487 00:53:21,640 --> 00:53:25,880 Now they must mate, if possible, before the sun rises. 488 00:53:36,920 --> 00:53:42,120 The desert dries very quickly, even after the heaviest of storms. 489 00:53:45,360 --> 00:53:48,560 Temperatures rise to 50 degrees Centigrade. 490 00:53:48,560 --> 00:53:53,320 Now any water on the surface will evaporate instantly. 491 00:53:53,320 --> 00:53:58,280 But the toads are already retreating and will soon be back underground. 492 00:53:59,560 --> 00:54:02,400 It really is a miracle that they're here at all. 493 00:54:09,920 --> 00:54:14,160 The spade-foot toad is not the only frog species to adapt 494 00:54:14,160 --> 00:54:16,720 to extreme environmental conditions. 495 00:54:20,160 --> 00:54:25,520 Of all the frogs in the world, this perhaps is the most extraordinary. 496 00:54:25,520 --> 00:54:29,040 It's called the wood frog and it lives in America, 497 00:54:29,040 --> 00:54:32,240 north of the Arctic Circle. 498 00:54:32,240 --> 00:54:35,000 And it survives some of the coldest 499 00:54:35,000 --> 00:54:37,280 temperatures on Earth, 500 00:54:37,280 --> 00:54:41,280 and it does so by becoming frozen solid. 501 00:54:59,720 --> 00:55:02,520 As the winter frost starts to bite, 502 00:55:02,520 --> 00:55:05,960 ice begins to form on the frog's skin. 503 00:55:19,440 --> 00:55:22,280 The liver goes into overdrive, 504 00:55:22,280 --> 00:55:27,120 producing glucose which is pumped around the body by the heart. 505 00:55:34,320 --> 00:55:39,440 This glucose acts like an anti-freeze within the cells, 506 00:55:39,440 --> 00:55:41,560 preventing them from freezing. 507 00:55:43,920 --> 00:55:46,840 Instead, ice forms around them. 508 00:55:46,840 --> 00:55:52,200 The blood, however, is frozen and all the organs are encased in ice. 509 00:55:54,160 --> 00:55:56,040 And the heart stops. 510 00:56:08,920 --> 00:56:13,920 But then, months later, spring at last returns. 511 00:56:19,720 --> 00:56:24,000 And the ice around the wood frog begins to melt. 512 00:57:11,280 --> 00:57:15,680 The wood frog's ability to survive is truly extraordinary, 513 00:57:15,680 --> 00:57:19,600 and that does give us the hope that maybe, in spite of the threats 514 00:57:19,600 --> 00:57:21,240 that face them today, 515 00:57:21,240 --> 00:57:24,760 frogs as a whole will continue to live on this planet. 516 00:57:24,760 --> 00:57:28,080 It would be truly sad if we lost them. 517 00:57:42,720 --> 00:57:43,760 That's it.