0:00:05 > 0:00:10We're living through THE golden age of dinosaur discoveries.
0:00:10 > 0:00:12From all over the world,
0:00:12 > 0:00:15a whole new generation of dinosaurs has been revealed.
0:00:17 > 0:00:21From the biggest giants and the deadliest killers...
0:00:21 > 0:00:23to the weird and the wonderful.
0:00:30 > 0:00:34from the Arctic...to Africa.
0:00:36 > 0:00:38From South America to Asia.
0:00:41 > 0:00:46Using the latest evidence, for the first time...
0:00:46 > 0:00:50we have a truly global view of these incredible animals.
0:01:03 > 0:01:05In this episode,
0:01:05 > 0:01:08we explore the last generation of killer dinosaurs...
0:01:09 > 0:01:12..carnivores that took killing to a new level.
0:01:13 > 0:01:18At the end of the Cretaceous period, 75 million years ago,
0:01:18 > 0:01:22these hunter-killers had spread throughout the globe.
0:01:25 > 0:01:26In the southern continents,
0:01:26 > 0:01:31it was the powerful and muscular Abelisaurids that reigned supreme.
0:01:34 > 0:01:38Whereas in the north, it was the famous Tyrannosaurs that dominated.
0:01:44 > 0:01:4875 million years ago, the Dinosaur Park formation in Canada
0:01:48 > 0:01:52was home to two of the largest Tyrannosaurs.
0:01:53 > 0:01:56The biggest and heaviest was Daspletosaurus.
0:01:59 > 0:02:01In 2009, medical scanners were used
0:02:01 > 0:02:05to look inside the brain cases of these killers.
0:02:07 > 0:02:11Of all the dinosaur groups, Tyrannosaurs were discovered
0:02:11 > 0:02:15to have one of the largest areas devoted to smell...
0:02:15 > 0:02:18something that would give them a clear hunting advantage.
0:02:24 > 0:02:26Back then, Cretaceous Alberta
0:02:26 > 0:02:30was a vast coastal river plain covered in forests...
0:02:32 > 0:02:35..the perfect hunting grounds for Daspletosaurus.
0:02:39 > 0:02:41At nine metres and three tonnes,
0:02:41 > 0:02:44it's the dominant predator in these forests.
0:02:46 > 0:02:50Here, it relies on its acute sense of smell and hearing,
0:02:50 > 0:02:52as much as its sight, to hunt its prey.
0:03:03 > 0:03:05Chasmosaurus,
0:03:05 > 0:03:09a rhino-sized behemoth, bristling with defensive horns...
0:03:10 > 0:03:14..and an opponent befitting a killer like Daspletosaurus.
0:03:59 > 0:04:04Of all the tyrannosaurs, T Rex might be the most famous,
0:04:04 > 0:04:07but the evolutionary blueprint for these predators
0:04:07 > 0:04:12was laid down 10 million years earlier, with Daspletosaurus.
0:04:15 > 0:04:20Tyrannosaurs' effectiveness as killers is clear from their anatomy.
0:04:20 > 0:04:25They're massive, with huge, strong skulls, and powerful muscular necks.
0:04:25 > 0:04:30Forward-facing eyes make tracking moving prey easy.
0:04:30 > 0:04:32They've famously short arms,
0:04:32 > 0:04:36but with these giant Tyrannosaurs, it's all about the bite.
0:04:37 > 0:04:42They had the most powerful bite of any dinosaur with teeth that,
0:04:42 > 0:04:45unlike the thin, flesh-tearing blades of Carnosaurs,
0:04:45 > 0:04:50are thick and strong, easily able to crush bone and kill.
0:04:55 > 0:05:00However, this Daspletosaurus has lost the element of surprise.
0:05:20 > 0:05:23The odds are now stacked in the Chasmosaur's favour.
0:05:25 > 0:05:29Even the most deadly predators fail more often than they succeed.
0:05:36 > 0:05:40Tyrannosaurus appeared locked in a deadly evolutionary arms race
0:05:40 > 0:05:43with the horned dinosaurs.
0:05:43 > 0:05:46As one got bigger, so did the other.
0:05:46 > 0:05:49It's a predator-prey relationship that endured
0:05:49 > 0:05:51for more than 65 million years.
0:05:54 > 0:05:59Most striking are the head frills of the horned dinosaurs.
0:05:59 > 0:06:04The imposing frill of Chasmosaurus is actually made of thin bone
0:06:04 > 0:06:08and wouldn't stop the bite of a Tyrannosaur.
0:06:08 > 0:06:12But by making it look much bigger, it had the desired effect.
0:06:13 > 0:06:19The horns and frills of these dinosaurs acted as visual deterrents,
0:06:19 > 0:06:22even if they offered little physical protection.
0:06:22 > 0:06:25It meant that a fully grown Chasmosaurus
0:06:25 > 0:06:28would usually be safe from most predators.
0:06:34 > 0:06:37This Daspletosaurus is just a youngster.
0:06:44 > 0:06:48Even two Daspletosaurs pose little threat.
0:07:00 > 0:07:05But in 2005, a remarkable discovery was announced.
0:07:05 > 0:07:08In the Two Medicine Formation of Montana,
0:07:08 > 0:07:13a new dig revealed had unearthed something quite extraordinary...
0:07:13 > 0:07:16a collection of Daspletosaurus fossils,
0:07:16 > 0:07:20all buried at the same place at the same time.
0:07:31 > 0:07:35The implication is that Daspletosaurus hunt in gangs.
0:07:44 > 0:07:48Tyrannosaurs, like Daspletosaurus, were so successful that,
0:07:48 > 0:07:52by the late cretaceous, they were the apex predator across virtually
0:07:52 > 0:07:54all of North America and Asia.
0:07:56 > 0:08:02In Asia, there was Alectrosaurus, Alioramus and Tarbosaurus.
0:08:02 > 0:08:05In America, Albertosaurus, Gorgosaurus,
0:08:05 > 0:08:08Daspletosaurus and T Rex.
0:08:09 > 0:08:12But moving further north, evidence of Tyrannosaurs
0:08:12 > 0:08:14becomes increasingly rare.
0:08:16 > 0:08:21In Alaska, fossils have been excavated close to the Arctic Ocean.
0:08:22 > 0:08:27It's the richest source of dinosaurs that lived in the polar regions...
0:08:27 > 0:08:31and it seems here, a different type of killer dominated.
0:08:36 > 0:08:39The most common plant-eater in this region
0:08:39 > 0:08:43is the highly social Edmontosaurus.
0:08:43 > 0:08:47They're the largest duck-billed dinosaur in North America...
0:08:54 > 0:08:59..and they are the perfect prey for a very different type of predator.
0:09:07 > 0:09:10Troodon may not look as lethal as a Tyrannosaur,
0:09:10 > 0:09:14but fossil evidence suggests that these too were deadly hunters
0:09:14 > 0:09:18surviving entirely on a diet of meat.
0:09:23 > 0:09:28At first sight, it appears the adult Edmontosaurus have little to fear.
0:09:28 > 0:09:3212m in length and weighing 3.5 tonnes,
0:09:32 > 0:09:35they physically dwarf this diminutive predator.
0:09:39 > 0:09:44Troodon were usually small, two-metre dinosaurs...
0:09:44 > 0:09:48but the teeth from the Alaskan Troodon showed something remarkable.
0:09:48 > 0:09:53These Arctic predators were almost twice as big as normal.
0:09:56 > 0:10:02Troodon not only survived here, they positively thrived.
0:10:04 > 0:10:06And that's because their hunting prowess
0:10:06 > 0:10:09comes into its own after sunset.
0:10:17 > 0:10:20This is a land where, after late summer,
0:10:20 > 0:10:23there are more hours of darkness than light.
0:10:40 > 0:10:44Troodon famously have the largest brains
0:10:44 > 0:10:47relative to their body size of any dinosaur...
0:10:49 > 0:10:54..although what appears more important are their eyes.
0:10:57 > 0:11:01Not only are they forward facing, making them active hunters,
0:11:01 > 0:11:03but they are exceptionally large.
0:11:05 > 0:11:09These are predators that can hunt equally well after dark.
0:11:17 > 0:11:22Although the group offers protection,
0:11:22 > 0:11:24predators always choose the easiest prey,
0:11:24 > 0:11:27so it's the juvenile Edmontosaurs that are at risk.
0:12:02 > 0:12:04Separated from the group,
0:12:04 > 0:12:06this youngster has made a dangerous mistake.
0:12:54 > 0:12:58The Alaskan dinosaur bone beds are dominated
0:12:58 > 0:13:01by juvenile Edmontosaurus remains.
0:13:01 > 0:13:05Some show clear evidence of Troodon bite marks.
0:13:06 > 0:13:10It seems, despite its small size, Troodon thrived here
0:13:10 > 0:13:13by exploiting the vulnerability of the juveniles
0:13:13 > 0:13:16throughout the long, dark, winter months.
0:13:28 > 0:13:30With a steady food supply,
0:13:30 > 0:13:34it means Troodon can survive the harsh Arctic winters.
0:13:35 > 0:13:38And, in doing so, grew to almost double the size
0:13:38 > 0:13:40of their cousins further south.
0:13:42 > 0:13:44But these were the exception.
0:13:49 > 0:13:54Wherever else Tyrannosaurs lived, they were the largest predator,
0:13:54 > 0:13:58living in groups that consist of both youngsters and adults.
0:14:13 > 0:14:19In these deadly packs, youngsters provide the speed, adults the power.
0:14:20 > 0:14:24It's a hunting strategy that they use to deadly effect.
0:14:58 > 0:15:02But despite appearances, this mob attack isn't carefully planned.
0:15:06 > 0:15:09There is no strategy behind the actions of the gang.
0:15:09 > 0:15:13It's merely opportunism.
0:15:13 > 0:15:17And when the kill has been made, the next battle soon begins.
0:15:30 > 0:15:35In many Tyrannosaurs, we find holes and gouges on the skulls,
0:15:35 > 0:15:39injuries which turn out to be bite marks made by other Tyrannosaurs.
0:15:41 > 0:15:44In one Daspletosaurus fossil, the tooth marks indicate
0:15:44 > 0:15:48that an individual had been subject to several attacks.
0:15:50 > 0:15:52In another, the tip of a tooth
0:15:52 > 0:15:55was left embedded in the bone of its skull.
0:15:57 > 0:16:00From this evidence, we can assume that such groups
0:16:00 > 0:16:01were far from harmonious...
0:16:05 > 0:16:09..and they certainly aren't democratic.
0:16:09 > 0:16:12In this world, the strongest takes all.
0:16:19 > 0:16:23Tyrannosaurs' domination of the globe might have been total,
0:16:23 > 0:16:28had it not been for a strange quirk in the arrangement of the continents.
0:16:29 > 0:16:3475 million years ago, the planet had a clear north-south divide,
0:16:34 > 0:16:37with no physical link between the parts of the globe.
0:16:37 > 0:16:43It meant the Tyrannosaurs couldn't spread to the southern continents.
0:16:43 > 0:16:46Here, a different type of killer reigned supreme.
0:16:49 > 0:16:52These were Abelisaurids.
0:16:55 > 0:16:58In the last ten years, Madagascar has provided
0:16:58 > 0:17:02the most comprehensive evidence about these predators.
0:17:05 > 0:17:0970 million years ago, Madagascar was already an island.
0:17:14 > 0:17:17But its climate was much hotter and drier than today.
0:17:23 > 0:17:28In the Cretaceous period, Madagascar was subject to devastating droughts.
0:17:30 > 0:17:32And big predators like Majungasaurus
0:17:32 > 0:17:35are especially vulnerable to starvation.
0:17:35 > 0:17:39Scavenging is the only way to survive.
0:17:43 > 0:17:47We thought Majungasaurus was the top predator here.
0:17:49 > 0:17:53But then, in 2003, some bones of a number of Majungasaurs
0:17:53 > 0:17:56were reported gouged with teeth marks.
0:17:59 > 0:18:03It appeared there was a bigger, more brutal killer at large.
0:18:17 > 0:18:20Majungasaurus also shares the plains
0:18:20 > 0:18:23with smaller dinosaurs like Rahonavis.
0:18:47 > 0:18:52Being smaller means Rahonavis needs less food to survive.
0:19:00 > 0:19:05A carcass will attract every big predator for miles around.
0:19:19 > 0:19:22A male Majungasaurus,
0:19:22 > 0:19:24attracted to the feast.
0:19:26 > 0:19:31It is more than capable of challenging for the carcass.
0:20:30 > 0:20:34Majungasaurus has short arms and can't grasp.
0:20:36 > 0:20:39Like Tyrannosaurs, it's all about the bite.
0:20:48 > 0:20:51The shape of Majungasaurus' skull and teeth
0:20:51 > 0:20:55suggests a very different biting style to the flesh-tearing dinosaurs.
0:20:55 > 0:20:59With a broad, short and muscular skull...
0:20:59 > 0:21:03it was a dino better adapted to biting and gripping,
0:21:03 > 0:21:05rather than slashing its prey.
0:21:07 > 0:21:09This fight is about more
0:21:09 > 0:21:12than just winning the feeding rights to a carcass.
0:21:40 > 0:21:43When the bite marks on the mauled Majungasaurus remains
0:21:43 > 0:21:45were studied more closely...
0:21:47 > 0:21:50..the marks on the bones were found to match
0:21:50 > 0:21:53the only large carnivore in the region.
0:21:53 > 0:21:57There is no bigger killer in these lands than Majungasaurus.
0:21:57 > 0:22:03This is the first, irrefutable evidence of dinosaur cannibalism.
0:22:05 > 0:22:09It might seem shocking, but it's a behaviour that clearly shows
0:22:09 > 0:22:11the most successful killers
0:22:11 > 0:22:15will exploit any situation to their maximum advantage.
0:22:22 > 0:22:24Daspletosaurus.
0:22:35 > 0:22:38With a bite force unmatched by any other dinosaur in the region,
0:22:38 > 0:22:43these are killers in a completely different league.
0:23:04 > 0:23:09And this group have congregated to take advantage of an annual event.
0:23:12 > 0:23:14In Dinosaur Provincial Park,
0:23:14 > 0:23:16thousands of bones have been discovered,
0:23:16 > 0:23:20scattered across the same rock layer.
0:23:20 > 0:23:23They belong to the horned dinosaur Centrosaurus...
0:23:25 > 0:23:29..and they appear to be the bone beds of vast killing fields,
0:23:29 > 0:23:33sites of wholesale slaughter.
0:23:44 > 0:23:48This vast herd of Centrosaurus are on the move...
0:23:49 > 0:23:53..from their nesting sites on coastal lowlands to the east.
0:23:56 > 0:23:59Unwittingly, they're moving towards almost certain death.
0:24:02 > 0:24:07Seasonal monsoons drives the Centrosaurs inland,
0:24:07 > 0:24:09away from coastal flooding.
0:24:21 > 0:24:24It's what the Daspletosaurus have been waiting for.
0:24:43 > 0:24:46Herding behaviour protects the many...
0:24:46 > 0:24:48but at the expense of the few.
0:25:22 > 0:25:26And things are about to get worse for the Centrosaurs.
0:25:35 > 0:25:40With a flooded river ahead and the Daspletosaurus behind,
0:25:40 > 0:25:44the stage is now set for a massacre.
0:25:53 > 0:25:56But despite the rich pickings, it's not the Daspletosaurs
0:25:56 > 0:25:59that are responsible for the scale of the slaughter.
0:26:13 > 0:26:18There's an even more deadly killer at work here.
0:26:31 > 0:26:37Severe monsoon rains have transformed shallow rivers into lethal torrents.
0:27:06 > 0:27:09The real killer is the weather itself.
0:27:26 > 0:27:31Recent studies of this dense bone bed indicate that 96% of the bones
0:27:31 > 0:27:34are of a single species - Centrosaurus -
0:27:34 > 0:27:39and relatively few of the bones display any bite marks.
0:27:39 > 0:27:42The fossil evidence suggests that this was a mass drowning...
0:27:44 > 0:27:48..the result of widespread seasonal flooding...
0:27:48 > 0:27:53an event that we have seen repeated in over 20 different sites.
0:28:01 > 0:28:05And when the waters recede, new opportunities emerge.
0:28:07 > 0:28:12Events like these provide easy pickings for predators.
0:28:12 > 0:28:16But even in the fight for rotting flesh,
0:28:16 > 0:28:20Daspletosaurus's authority is absolute.
0:28:22 > 0:28:25Tyrannosaurs in the north and Abelisaurids in the south
0:28:25 > 0:28:28were the supreme killers of their age.
0:28:31 > 0:28:35They dominated every continent where they were found.
0:28:39 > 0:28:45And together, they were the last of the killer dinosaurs.
0:29:06 > 0:29:09Subtitles by Red Bee Media Ltd
0:29:09 > 0:29:12E-mail subtitling@bbc.co.uk