1 00:01:03,607 --> 00:01:09,079 Crocodiles hail from the great age of reptiles over 70 million years ago. 2 00:01:11,087 --> 00:01:14,238 Since then, the world has changed dramatically... 3 00:01:14,407 --> 00:01:17,558 but amazingly, they have changed little. 4 00:01:22,207 --> 00:01:24,516 They're the only great reptile predator... 5 00:01:24,687 --> 00:01:26,996 to have outlived the dinosaurs. 6 00:01:32,207 --> 00:01:35,244 Ancient they may be but 70 million years on... 7 00:01:35,407 --> 00:01:38,717 they're still the most successful freshwater predator. 8 00:01:38,887 --> 00:01:41,401 Most of the waterways in the tropics these days... 9 00:01:41,567 --> 00:01:44,001 have their own species of crocodile. 10 00:01:44,167 --> 00:01:47,523 How come they've been so successful for so long? 11 00:01:47,687 --> 00:01:52,044 It seems their design when it first appeared was already very advanced... 12 00:01:52,207 --> 00:01:55,199 and it's kept them successful ever since. 13 00:01:55,367 --> 00:01:58,803 This film reveals the nature of that success. 14 00:02:09,247 --> 00:02:13,399 Crocodiles may have scored an early evolutionary bull's eye... 15 00:02:13,567 --> 00:02:17,799 but there's much more to their staying power than brute strength. 16 00:02:34,007 --> 00:02:37,158 Only now, by exploring their complete world... 17 00:02:37,327 --> 00:02:40,717 above and below water, by day and night... 18 00:02:40,887 --> 00:02:44,800 can we fully appreciate just how sophisticated they are. 19 00:03:09,567 --> 00:03:13,116 Underwater, crocodiles have perfect poise. 20 00:03:13,287 --> 00:03:16,802 They can control their buoyancy like a submarine. 21 00:03:18,567 --> 00:03:23,402 To dive, they breathe out which reduces their lung volume. 22 00:03:23,567 --> 00:03:25,922 They can sink without trace. 23 00:03:36,967 --> 00:03:41,483 While submerged a protective membrane closes over their eyes... 24 00:03:41,647 --> 00:03:43,239 like swimming goggles. 25 00:03:46,487 --> 00:03:48,921 Crocodiles are cold-blooded. 26 00:03:49,527 --> 00:03:51,916 They rely on the temperature of sun and water... 27 00:03:52,087 --> 00:03:55,124 to heat themselves up or to cool down. 28 00:04:05,367 --> 00:04:07,085 But when fully charged... 29 00:04:07,247 --> 00:04:11,206 they are capable of breath-taking power and speed. 30 00:04:17,047 --> 00:04:21,359 They're the most dangerous freshwater predator on the planet. 31 00:04:29,727 --> 00:04:34,039 Even Tyrannosaurus Rex couldn't match this winning formula. 32 00:04:36,327 --> 00:04:41,082 It's a design that has allowed them to spread around the tropical world. 33 00:04:41,247 --> 00:04:46,765 This extended family includes alligators of temperate waterways... 34 00:04:48,367 --> 00:04:51,518 Gharials of the Indian subcontinent... 35 00:04:52,167 --> 00:04:55,079 and caiman of tropical South America. 36 00:05:01,087 --> 00:05:03,726 They've even invaded the sea. 37 00:05:08,327 --> 00:05:13,196 Crocodiles have special glands which enable them to tolerate saltwater. 38 00:05:13,647 --> 00:05:17,640 This is how they've colonised new rivers along the coast. 39 00:05:28,007 --> 00:05:31,602 But only a few species can migrate across oceans. 40 00:05:31,767 --> 00:05:34,998 The real specialists, the saltwater crocodiles... 41 00:05:35,167 --> 00:05:37,681 are affectionately known as "salties". 42 00:05:37,847 --> 00:05:40,839 They've been seen 1000 kilometres from land... 43 00:05:41,007 --> 00:05:45,478 encrusted with barnacles, as they search for new island homes. 44 00:05:47,927 --> 00:05:51,840 This pioneering spirit and their unique character... 45 00:05:52,007 --> 00:05:54,965 has made them a universal threat. 46 00:06:15,367 --> 00:06:18,439 Crocodiles deserve their tough reputation... 47 00:06:18,607 --> 00:06:21,280 but they aren't just solitary killers. 48 00:06:21,447 --> 00:06:26,680 In the calm of the Florida swamps we can begin to see them in a new light. 49 00:06:36,647 --> 00:06:39,559 They are reptiles with social skills... 50 00:06:39,727 --> 00:06:42,878 and American alligators are particularly chatty. 51 00:06:43,047 --> 00:06:44,526 During the breeding season... 52 00:06:44,687 --> 00:06:48,282 an expressive chorus of bellows, grunts and hisses... 53 00:06:48,447 --> 00:06:52,156 rises from their densely vegetated swamps. 54 00:06:58,647 --> 00:07:01,639 The males are calling to distant females... 55 00:07:01,807 --> 00:07:05,117 but their bellows sometimes attract rivals. 56 00:07:14,327 --> 00:07:17,319 There are snappy ways to make your feelings known... 57 00:07:17,487 --> 00:07:19,921 if you end up in the wrong company. 58 00:07:24,047 --> 00:07:26,959 The resident male only shows a bit of muscle... 59 00:07:27,127 --> 00:07:29,766 if the rival fails to get the message. 60 00:07:46,887 --> 00:07:51,358 He's made his point and he can now focus on finding a mate. 61 00:07:59,087 --> 00:08:01,396 Vibrations within his muscle walls... 62 00:08:01,567 --> 00:08:04,923 send sound waves rippling out in to the swamp... 63 00:08:05,087 --> 00:08:08,397 powerful enough to make the water dance. 64 00:08:34,407 --> 00:08:37,479 Part of his roar radiates at such low frequency... 65 00:08:37,647 --> 00:08:40,002 that human ears can't hear it. 66 00:08:40,167 --> 00:08:44,285 But these subsonic calls have astounding penetration... 67 00:08:44,447 --> 00:08:48,884 travelling four times faster and further under the water. 68 00:08:50,407 --> 00:08:53,444 Only with special low frequency recordings... 69 00:08:53,607 --> 00:08:57,122 can we appreciate what the female alligator hears. 70 00:09:07,967 --> 00:09:12,085 She finds his romantic rumblings irresistible. 71 00:09:54,567 --> 00:09:58,355 Even though the call may come from the remotest parts of the swamp... 72 00:09:58,527 --> 00:10:00,757 she is soon on his wave length. 73 00:10:01,207 --> 00:10:04,119 Then they have a more intimate conversation... 74 00:10:04,287 --> 00:10:06,562 conducted in body language. 75 00:10:27,647 --> 00:10:31,925 Their relationship is sealed, touchingly. 76 00:10:50,327 --> 00:10:53,842 Crocodiles are extremely sensitive to touch. 77 00:10:54,007 --> 00:10:58,444 Their armour-plated toughness would appear to be only skin-deep. 78 00:11:05,847 --> 00:11:08,315 Such complicated language and behaviour... 79 00:11:08,487 --> 00:11:11,445 is exceptional among today's reptiles... 80 00:11:11,607 --> 00:11:14,883 but crocodiles might provide a tantalising rear window... 81 00:11:15,047 --> 00:11:19,723 on the social life of their ancient relatives, the dinosaurs. 82 00:11:23,007 --> 00:11:27,000 Nile Crocodiles are the most fraternal crocs of all. 83 00:11:27,207 --> 00:11:29,118 Once a year, they hang out together... 84 00:11:29,287 --> 00:11:32,677 soaking up the sun at traditional mating places. 85 00:11:34,727 --> 00:11:38,083 These are far from being lazy afternoons. 86 00:11:38,247 --> 00:11:39,965 The group is very organised... 87 00:11:40,127 --> 00:11:44,245 so individuals keep a careful eye on movements within it. 88 00:11:45,047 --> 00:11:50,326 An adult male, over five metres long, is the centre of attention. 89 00:12:00,167 --> 00:12:05,560 Up to ten females spend much of their time in the water soliciting him. 90 00:12:05,727 --> 00:12:09,197 They bear their throats as a gesture of appeasement. 91 00:12:14,807 --> 00:12:17,526 Body signals are also used by the male. 92 00:12:17,687 --> 00:12:21,839 He shows-off with noisy water displays. 93 00:12:36,207 --> 00:12:40,803 These postures enhance his attractiveness to females. 94 00:12:50,047 --> 00:12:52,436 It is they who often take the lead... 95 00:12:52,607 --> 00:12:56,282 by rubbing themselves along the length of his body. 96 00:13:10,807 --> 00:13:13,799 At first he snubs both of them. 97 00:13:13,967 --> 00:13:18,916 But the rubbing releases a pungent oil from glands under their jaws. 98 00:13:20,167 --> 00:13:24,080 Both sexes are highly sensitive to this crocodile perfume... 99 00:13:24,247 --> 00:13:28,365 and the male answers with his own musky message. 100 00:13:36,847 --> 00:13:41,637 The scent in the water is particularly potent prior to mating. 101 00:14:14,167 --> 00:14:18,683 Several weeks later, the females are ready to make their nests. 102 00:14:19,687 --> 00:14:23,600 Even when basking, adults rarely move far from the water. 103 00:14:23,767 --> 00:14:28,318 It's ironic that the first critical part of crocodilian life... 104 00:14:28,487 --> 00:14:30,523 is spent on land. 105 00:14:34,567 --> 00:14:39,436 Crocodile babies are born encased in eggs but they must still breathe air. 106 00:14:39,607 --> 00:14:44,556 It's essential this mother lays her clutch beyond the high water mark. 107 00:14:56,007 --> 00:14:58,123 The eggs will be so at risk... 108 00:14:58,287 --> 00:15:02,326 from drowning, predators and temperature fluctuations... 109 00:15:02,487 --> 00:15:07,197 that she relies on exactly the same nest position year after year. 110 00:15:07,807 --> 00:15:12,244 These time-honoured sites are a measure of the experienced care... 111 00:15:12,407 --> 00:15:14,637 that crocodile mothers provide. 112 00:15:20,327 --> 00:15:25,799 Once the excavation is complete she lays her eggs in a trance-like state. 113 00:15:25,967 --> 00:15:29,801 She's entering a deep commitment to her offspring. 114 00:15:45,847 --> 00:15:48,919 The hole will become an incubator. 115 00:15:49,087 --> 00:15:50,884 Crocodile eggs will only develop... 116 00:15:51,047 --> 00:15:55,916 if they remain between a steamy 27 and 34 degrees... 117 00:15:57,207 --> 00:15:59,641 so her choice of site is critical. 118 00:16:09,567 --> 00:16:14,436 Nest chambers from equatorial African plains to Himalayan river valleys... 119 00:16:14,607 --> 00:16:17,326 all remain within this temperature range... 120 00:16:17,487 --> 00:16:21,480 but no-one knows how crocodile mothers get it right. 121 00:16:31,087 --> 00:16:36,036 Once the nest is sealed, the mothers keep vigil for 90 days. 122 00:16:44,567 --> 00:16:48,924 Temperature determines the sex of the developing eggs. 123 00:16:49,087 --> 00:16:52,159 A half degree difference between the top and bottom of the nest... 124 00:16:52,327 --> 00:16:56,320 can markedly affect the ratio of males to females. 125 00:16:56,487 --> 00:16:59,638 Given the changes in climate that the world has experienced... 126 00:16:59,807 --> 00:17:03,686 it seems incredible that crocodiles have survived at all. 127 00:17:19,087 --> 00:17:22,602 Overall, enough males and females emerge... 128 00:17:22,767 --> 00:17:28,046 but these baby Nile crocs face more immediate threats to existence. 129 00:17:28,367 --> 00:17:32,519 Raiders might be drawn to their combined noise and smell. 130 00:17:33,367 --> 00:17:38,282 Hopefully their mother will hear their calls and reach the nest first. 131 00:18:06,647 --> 00:18:08,046 Once she digs them out... 132 00:18:08,207 --> 00:18:13,156 they must reach the relative security of water as quickly as possible. 133 00:18:21,087 --> 00:18:23,521 The babies could probably find their own way... 134 00:18:23,687 --> 00:18:26,759 but they are only safe if they stick together. 135 00:18:26,927 --> 00:18:31,682 So their mother transports them to water herself. In her mouth. 136 00:18:43,367 --> 00:18:47,326 The skin of her lower jaw stretches into a hanging cradle... 137 00:18:47,487 --> 00:18:50,843 in which she can carry fifteen or so at a time. 138 00:18:53,127 --> 00:18:56,437 It's a snug fit, once you're in. 139 00:19:02,767 --> 00:19:05,327 Her forty-or-so eggs hatch simultaneously... 140 00:19:05,487 --> 00:19:08,206 so she'll have to make several trips. 141 00:19:24,167 --> 00:19:26,442 The clamourings of the hatchlings... 142 00:19:26,607 --> 00:19:30,202 constantly remind her to return to the nest... 143 00:19:38,207 --> 00:19:42,280 and ensure that no-one misses the last bus. 144 00:20:03,087 --> 00:20:05,920 She releases them into a nursery pool. 145 00:20:06,087 --> 00:20:09,124 They must make the most of her tender loving care. 146 00:20:09,287 --> 00:20:13,121 They have only a few weeks under her watchful eye. 147 00:20:19,527 --> 00:20:23,361 For safety's sake, they call to each other and to her... 148 00:20:23,527 --> 00:20:26,997 conversations which continue into adulthood. 149 00:20:27,167 --> 00:20:29,681 The 18 different sounds they'll use... 150 00:20:29,847 --> 00:20:34,762 represent a vocabulary more typical of mammals than of reptiles. 151 00:20:38,287 --> 00:20:42,360 Unlike mammals, their rate of growth is affected by temperature. 152 00:20:42,527 --> 00:20:46,839 The warmer it is, the quicker the food digests into body bulk. 153 00:20:47,247 --> 00:20:49,636 Over a lifetime under a tropical sun... 154 00:20:49,807 --> 00:20:53,800 they may grow 4000 times bigger than this. 155 00:21:02,927 --> 00:21:05,043 Their mother won't eat at all. 156 00:21:05,527 --> 00:21:08,041 She's protecting her infants from being eaten... 157 00:21:08,207 --> 00:21:10,084 even by other crocodiles. 158 00:21:48,447 --> 00:21:51,325 The mother successfully defends her own brood... 159 00:21:51,487 --> 00:21:56,038 but it's a grim reminder that crocodiles eat just about anything. 160 00:21:58,407 --> 00:22:01,205 Her babies will learn that successful crocodiles... 161 00:22:01,367 --> 00:22:03,562 take all their dietary chances. 162 00:22:04,847 --> 00:22:08,317 Their hunting technique is there from birth. 163 00:22:08,487 --> 00:22:11,604 With eyes, ears, and nose at water level... 164 00:22:11,767 --> 00:22:15,760 they mirror the tactics they'll use as adults. 165 00:22:57,127 --> 00:22:59,436 These shoreline snacks... 166 00:22:59,607 --> 00:23:03,077 may be wildebeest or zebra in years to come. 167 00:23:31,167 --> 00:23:34,955 They rely on communal living to survive this tender age... 168 00:23:35,127 --> 00:23:38,199 but competition between the youngsters is intense. 169 00:23:38,367 --> 00:23:43,077 Despite their mother's protection, only two percent will survive. 170 00:23:54,647 --> 00:23:58,117 The babies of caiman, a type of South American crocodile... 171 00:23:58,287 --> 00:24:00,721 face even shorter odds. 172 00:24:02,567 --> 00:24:05,923 Wildlife may seem abundant in their Venezuelan marsh... 173 00:24:06,087 --> 00:24:10,046 but that's because the water elsewhere is drying up. 174 00:24:11,847 --> 00:24:14,236 Even the fish are out of water. 175 00:24:19,287 --> 00:24:21,926 The dry season is five months long... 176 00:24:22,087 --> 00:24:24,999 but in some years it's more severe than usual. 177 00:24:25,167 --> 00:24:30,195 Unexpectedly, animals can be left high, if not exactly dry. 178 00:24:46,327 --> 00:24:50,115 Eventually some of these watercourses will dry up completely... 179 00:24:50,287 --> 00:24:53,836 leaving many caiman exposed and dehydrated. 180 00:24:58,207 --> 00:25:03,486 Temporary skin relief is provided by this ultimate of face packs. 181 00:25:03,647 --> 00:25:06,764 Mud is an effective crocodilian sun screen. 182 00:25:13,127 --> 00:25:15,687 Cooling water is at a premium. 183 00:25:15,847 --> 00:25:19,123 The remaining pools are becoming overcrowded. 184 00:25:21,927 --> 00:25:26,000 At such pressing times the adults usually rub along. 185 00:25:26,167 --> 00:25:28,158 However, babies could be eaten by them... 186 00:25:28,327 --> 00:25:31,922 so this is no place for a mother to raise her young. 187 00:25:37,287 --> 00:25:40,757 Fortunately they can expect complete maternal attention... 188 00:25:40,927 --> 00:25:43,725 during this five month period of danger. 189 00:25:53,567 --> 00:25:58,004 The shrinking watercourse becomes hazardous for the babies. 190 00:25:58,167 --> 00:26:00,601 Drastic measures are called for. 191 00:26:08,407 --> 00:26:12,036 Night-time cameras reveal they'll make a run for it... 192 00:26:12,207 --> 00:26:14,084 under the cover of dark. 193 00:26:19,767 --> 00:26:23,885 Their escape will be risky, for it is made over land. 194 00:26:24,607 --> 00:26:26,120 Mother leads the way. 195 00:26:37,447 --> 00:26:41,679 It's a while before the babies have the courage to join her. 196 00:27:03,527 --> 00:27:06,997 Calls of reassurance and maybe her musky smell... 197 00:27:07,167 --> 00:27:10,125 encourage the hatchlings out of the water. 198 00:27:35,127 --> 00:27:37,163 She follows good instincts. 199 00:27:37,607 --> 00:27:41,725 Night-time temperatures are safer for tiny cold-blooded bodies... 200 00:27:41,887 --> 00:27:43,957 and there are fewer threats about. 201 00:27:44,127 --> 00:27:49,281 But this is a long march that must be concluded by daybreak. 202 00:28:22,007 --> 00:28:24,396 Their mother's acute sense of smell... 203 00:28:24,567 --> 00:28:27,127 brings them to their watery destination... 204 00:28:27,287 --> 00:28:30,006 with less than an hour to spare. 205 00:28:45,727 --> 00:28:48,161 There's plenty of water for her babies... 206 00:28:48,327 --> 00:28:50,966 to survive the rest of the dry season. 207 00:29:02,567 --> 00:29:06,003 But lots of other females have had the same idea... 208 00:29:06,167 --> 00:29:08,840 and there's only room for one adult. 209 00:29:09,727 --> 00:29:14,482 The mothers must fight, or as is more often the case, simply leave. 210 00:29:18,247 --> 00:29:20,681 Their offspring are far from abandoned. 211 00:29:20,847 --> 00:29:23,805 The remaining female will adopt and protect them all... 212 00:29:23,967 --> 00:29:26,162 over one hundred of them. 213 00:29:36,447 --> 00:29:40,326 This super-mum carries her burden lightly. 214 00:29:42,407 --> 00:29:47,686 Family life may be unconventional but crocodiles do grow up in company. 215 00:29:47,967 --> 00:29:52,483 As hunting adults, this may prepare them for dedicated teamwork. 216 00:30:01,847 --> 00:30:05,317 Especially if there's a rare dish on the menu. 217 00:30:10,247 --> 00:30:13,637 Migrating zebra cross the Mara River in Kenya... 218 00:30:13,807 --> 00:30:16,799 on only a few occasions each year. 219 00:30:18,647 --> 00:30:23,721 Resident Nile Crocodiles can't afford to miss these fleeting chances. 220 00:30:23,887 --> 00:30:25,718 So they co-operate. 221 00:30:26,567 --> 00:30:28,797 From different places under the banks... 222 00:30:28,967 --> 00:30:33,006 they spend days waiting and watching the nervous herds. 223 00:31:04,647 --> 00:31:08,560 Only when the zebra commit themselves to a departure point... 224 00:31:08,727 --> 00:31:12,402 do the crocodiles take up their final positions. 225 00:31:22,527 --> 00:31:25,439 The current drags the zebra downstream... 226 00:31:25,607 --> 00:31:30,397 so five or six crocodiles cover the crossing from different angles. 227 00:31:35,727 --> 00:31:39,606 It's hard work for crocodiles too, but they can submerge... 228 00:31:39,767 --> 00:31:44,318 taking advantage of deeper, slower currents, to move closer. 229 00:31:56,367 --> 00:32:00,326 Their approach is stealthy, measured and tactical... 230 00:32:00,567 --> 00:32:03,559 as if moving in on a chosen victim. 231 00:32:39,007 --> 00:32:41,885 The current is flowing in the zebra's favour. 232 00:32:42,047 --> 00:32:46,643 It buffets the crocodiles out of position and they can't get a grip. 233 00:32:57,967 --> 00:33:02,085 The zebra's wide rump gives it a big advantage. 234 00:33:38,447 --> 00:33:43,840 Adult zebras also have a vicious kick which could break a crocodile's jaw. 235 00:33:44,247 --> 00:33:48,559 That might mean starvation, so crocodiles are also taking risks. 236 00:34:07,487 --> 00:34:11,605 A lot of effort results in little success for the crocodiles. 237 00:34:11,767 --> 00:34:16,636 But only until smaller, more vulnerable animals enter the water. 238 00:34:20,447 --> 00:34:24,759 At any time the zebras can be ambushed by frightening power... 239 00:34:31,687 --> 00:34:33,484 and lightening speed. 240 00:34:38,807 --> 00:34:42,402 The baby zebra faces several waves of attack. 241 00:35:04,647 --> 00:35:07,320 This is the advantage of teamwork. 242 00:35:19,647 --> 00:35:24,721 Most of the year, life along Africa's rivers is even more of a struggle. 243 00:35:30,687 --> 00:35:35,477 The dry season in Zambia's Luangwa Valley can be unsparing. 244 00:35:51,087 --> 00:35:55,126 Even vegetarians are forced to scavenge. 245 00:36:12,327 --> 00:36:16,036 But crocodiles still thrive on the edge. 246 00:36:27,647 --> 00:36:32,084 Far from being dependent on large mammals like wildebeest or zebra... 247 00:36:32,247 --> 00:36:36,001 crocodiles have extraordinarily adaptable diets. 248 00:36:36,207 --> 00:36:38,198 We've not known this until now... 249 00:36:38,367 --> 00:36:41,484 because we've never seen them hunting at night. 250 00:36:46,647 --> 00:36:49,844 What crocodiles do at night has remained a mystery... 251 00:36:50,007 --> 00:36:53,886 because they will only move around naturally in total darkness. 252 00:36:54,047 --> 00:36:57,642 So only with the use of invisible infrared light... 253 00:36:57,807 --> 00:37:01,197 can we see their nocturnal habits for the first time. 254 00:37:04,647 --> 00:37:06,683 In the Luangwa River shallows... 255 00:37:06,847 --> 00:37:12,001 a Nile crocodile hunts for less glamorous prey. It's stalking fish. 256 00:37:42,127 --> 00:37:46,325 Over the year, crocodiles fatten-up on fish and molluscs... 257 00:37:46,487 --> 00:37:48,205 rather than mammals. 258 00:37:55,447 --> 00:37:58,803 Mammals come and go, but the muddy river bottom... 259 00:37:58,967 --> 00:38:03,404 is always a good place to stir up snails, for instance. 260 00:38:12,407 --> 00:38:17,083 The crocodile is a flexible feeder in its methods too. 261 00:38:17,247 --> 00:38:19,397 It uses its armour plated body... 262 00:38:19,567 --> 00:38:24,721 as sinuously as a length of fishing net to corral fish towards the shore. 263 00:38:57,247 --> 00:39:01,320 Within their element, crocodiles equally deserve the title: 264 00:39:01,487 --> 00:39:03,205 "King of the beasts". 265 00:39:21,047 --> 00:39:23,845 Only when the dry season becomes desperate... 266 00:39:24,007 --> 00:39:27,044 are these two great hunters of land and water... 267 00:39:27,207 --> 00:39:29,357 likely to come face to face. 268 00:39:43,407 --> 00:39:47,844 But only the crocodile is bold enough to leave the safety of water... 269 00:39:48,007 --> 00:39:50,965 and meet the lion on its home ground. 270 00:40:34,807 --> 00:40:39,164 Few animals would actively take on a whole pride. 271 00:41:16,887 --> 00:41:20,163 The lions are simply frustrated. 272 00:41:24,207 --> 00:41:26,437 Especially when the smell of their supper... 273 00:41:26,607 --> 00:41:29,883 coaxes other crocodiles out of the water. 274 00:42:08,807 --> 00:42:11,275 Crocodiles have thick skins. 275 00:42:11,447 --> 00:42:16,362 The lions are forced to defend their meal by moving to a different table. 276 00:42:19,887 --> 00:42:22,924 They just leave nothing but scraps behind. 277 00:42:45,007 --> 00:42:48,079 The reptiles have stronger stomachs than the mammals. 278 00:42:48,247 --> 00:42:51,159 Lions can only cope with the chewy parts. 279 00:42:51,327 --> 00:42:53,966 Crocodile digestive juices are so acidic... 280 00:42:54,127 --> 00:42:59,201 that they can break down skin, bone and horn, to be turned into muscle. 281 00:43:04,887 --> 00:43:08,482 There's no such thing as crocodile left-overs. 282 00:43:15,287 --> 00:43:17,278 Their exceptional sense of smell... 283 00:43:17,447 --> 00:43:21,201 enables them to capitalise quickly on the demise of others. 284 00:43:21,367 --> 00:43:26,122 And at the end of the dry season the smell of death is everywhere. 285 00:43:32,007 --> 00:43:35,443 A mother hippo mourns her baby. 286 00:43:37,527 --> 00:43:40,963 Crocodiles have good reason to be wary of adult hippos... 287 00:43:41,127 --> 00:43:44,278 so they wait for the grieving mother to go. 288 00:43:57,687 --> 00:44:00,963 Food, any food, is hard to find. 289 00:44:01,767 --> 00:44:07,205 Crocodiles from up to 7 km away recognise the whiff of opportunity. 290 00:44:21,207 --> 00:44:26,122 One dead hippo attracts over 100 hungry crocodiles. 291 00:44:26,607 --> 00:44:31,761 But there's no feeding frenzy. This is crocodile queuing. 292 00:44:43,407 --> 00:44:46,240 The reason for this patient approach? 293 00:44:46,407 --> 00:44:50,480 Crocodiles have a powerful grip and sharp teeth... 294 00:44:50,647 --> 00:44:54,686 but their jaws don't move sideways. They can't chew. 295 00:44:56,847 --> 00:44:59,839 So they have to eat large animals together. 296 00:45:00,007 --> 00:45:04,046 One or two crocodiles effectively brace the carcass in their jaws... 297 00:45:04,207 --> 00:45:07,324 while others wrench off smaller pieces of flesh... 298 00:45:07,487 --> 00:45:10,001 by spinning their bodies round. 299 00:45:16,607 --> 00:45:18,882 Everyone waits their turn. 300 00:45:40,767 --> 00:45:43,042 With such tolerant table manners... 301 00:45:43,207 --> 00:45:47,997 it might take 24 hours to satisfy the whole queue of diners. 302 00:46:46,607 --> 00:46:51,601 Too readily, perhaps, we have cast crocodiles as ruthless predators... 303 00:46:51,927 --> 00:46:55,715 when they are also well-mannered, adaptable creatures. 304 00:46:58,127 --> 00:47:01,802 And too readily we have called them primitive... 305 00:47:01,967 --> 00:47:03,798 when our own human design... 306 00:47:03,967 --> 00:47:08,165 has yet to stand up to their successful test of time. 307 00:47:09,447 --> 00:47:14,396 In evolutionary terms, the crocodile has every reason to smile.