Ice Worlds

* Title
* I
* II
* III
* VI

***“ Within the snow-covered forest, a tense standoff develops between ancient rivals, Pachyrhinosaurus and Nanuqsaurus. ”***

― The official Apple TV+ episode synopsis for *Ice Worlds*
***Ice Worlds*** is the fourth episode of the first season of Prehistoric Planet.

## Segment I: *Dromaeosaurus*

The episode begins with a view of the aurora borealis in the far north of America. Footprints are seen in the snow, leading to the one who left them. In the early hours of the first morning of spring, a sleeping *Dromaeosaurus* wakes up, scratches herself for a while, and rushes off into the forest, digging through the snow and the rocky ground in hopes of getting a meal where she has found food before. Focusing on a beetle as it climbs up a branch, flipping its wings in preparation for takeoff, she prepares her attack, jumping and snapping up at the beetle just as it flew off the branch, getting her first meal in a long while.

***“ The little dromaeosaurs must work together if they are to take on big prey. And here comes their first chance of the season; a herd of hadrosaurs. These duckbilled dinosaurs pass through here every year, nomads in search of the fresh vegetation brought by the spring. They're huge. The only chance the dromaeosaurs will have is to work as a team. ”***

― **David Attenborough**, *Ice Worlds*
As the sun rises over the mountains of Alaska for the first time in almost three months, two dromaeosaurs nuzzle each other before turning their attention to the bellows of a herd of dinosaurs in the distance.

***“ As winter slackens its grip, meltwater begins to flow with great power. The herd must wade through this deep, fast-flowing water. The leaders try to select the safest crossing. The herd follow cautiously. Young keep close to their parents. Putting a foot wrong here could cost them their life. The adults awaiting their turn grow nervous, and this bottleneck gives the dromaeosaurs a chance. ”***

― **David Attenborough**, *Ice Worlds*
The *Edmontosaurus* herd, arriving for food that comes up during spring, faces an icy river, enlarged and made faster and stronger by the melting ice. The dromaeosaurs aware that some of the hadrosaurs won't survive the river crossing. Seeing the cautious herd held up by the river's icy bank, hesitant on traversing the hazardous river crossing, three dromaeosaurs make their way down the snowy cliff face of the upland forest, rushing at some of the juveniles in the herd, harassing and intimidating them. This, in turn, causes panic to spread through the whole herd, and soon, every member is frantically running and wading through the collapsing ice of the river. In the chaos, some of the juvenile hadrosaurs are left by their parents on the other side of the river.

One mother watches as her calf is dragged away by the currents, and tries to keep up with her offspring in hopes that it would make it. Fortunately, the young hadrosaur manages to climb up the snowy bank of the river, almost slipping off back into the river before successfully hauling itself up to reunite with its parent. Finally, both join the herd as they continue on their journey, leaving the dromaeosaurs on the other side of the raging rapids.

***“ The dromaeosaurs seem to have missed their chance. But the river has done their work for them. There are always casualties. It's a feast, and more food than these hunters have had all winter. In the ice world, seasonal opportunity is brief, spring is short, and summer will soon be over. There's a lot to be done before the challenges of winter return. ”***

― **David Attenborough**, *Ice Worlds*
Not everyone is lucky to have survived. The three dromaeosaurs rush down the rocky banks of the river to claim the reward of their combined efforts and the river's unforgiving power, a dead juvenile hadrosaur. The three begin feasting on the body, with one briefly squabbling with another before going back to eating. The segment ends with the hadrosaurs, among them the lucky calf and its mother, traveling onwards alongside the frozen, fragile ice covering the massive river they just crossed.

## Segment II: *Ornithomimus*

**Ice Worlds**, Segment II
**Setting**
Prince Creek Formation, Alaska, USA

In the second segment of the episode, as spring begins, several male *Ornithomimuses* gather on an island formed by sediments deposited by a river. The theropods set up nests with twigs and rocks built around shallow holes they dug in the ground in a bid to attract females and convince them which one of them is the best male to mate with. Unfortunately for the latecomers, this leaves them with almost no room to form their nest. One male, a twig in his mouth, is driven off by others who already set up their nests (for they do not want their nests to be touched by others), forcing him to resort to settling by edge of the island.

***“ Late arrivals find that space is already in short supply. The only space left is on the island's margin. And finding a place to nest is only just the start. When eggs are eventually laid, they would need to be kept warm in a bed of vegetation. Finding enough nesting material is not easy... which is why some Ornithomimus resort to thievery. ”***

― **David Attenborough**, *Ice Worlds*
Even so, establishing a nesting spot is just the first step. The late arrival, pondering on how he is to build his nest and make it inviting and warm enough to entice females, realizes that he can simply steal nesting materials that the other males have already worked hard on setting up. When one male just a short distance away temporarily leaves his nest, the late arrival sneaks up to the nest and steals off a branch, placing it in his own nest. The other male returns and places a new twig, but he appears to realize that his nest has been pillaged for materials. When he turns his back, the late arrival tries to sneak in once more, but he turns around, already suspicious of nearby nest thieves. The late arrival stops in his tracks and looks around, pretending to be interested in something else. When the other male finally turns his back again, the thief steals yet another twig from his nest.

***“ In colonies like this, thievery can be so common, that some nesting material, at one time or another, will have been part of almost every nest on the island. But robbery is risky. ”***

― **David Attenborough**, *Ice Worlds*
However, when the thief tries to sneak in for a third time, the other male finally catches him in the act, driving him off by raising his arms and hissing at him, causing the thief to stumble back and run off. However, yet another problem arrives as a pair of *Edmontosaurus* cross the river, potentially interested in eating the leafy branches that make up the nests of some. Though the thief does not have much on his nest yet, given how his nest is by the island's edge, the one most likely to be trampled, he waves his feathered arms and hisses at the hadrosaurs to dissuade them from approaching his nest, just in case. With that hadrosaurs seemingly uninterested, he turns around and is greeted by the sight of the neighbor he tried stealing from continuing to build his nest, which is now far more well-made and covered in more vegetation.

***“ It can take several years to perfect nest-building skills. But success doesn't only rely on experience. In a crowded colony, there's always another potential victim. ”***

― **David Attenborough**, *Ice Worlds*
As he tries to sneak in and steal some materials, his neighbor, now fully aware of his thievery, momentarily pauses his work to get up, stomping the ground as he hisses and looks down on the thief. Even so, the thief finds yet another opportunity as another male to his left leaves his nest, and runs towards it to steal some parts from it. He looks at the direction his neighbor has gone in twice, making sure he isn't looking before taking a twig from his nest. The segment ends with a zoomed-out shot of the river islands from high up, a great sanctuary for both the eggs and the future young of *Ornithomimus*.

## Segment III: *Olorotitan*

**Ice Worlds**, Segment III
**Setting**
Udurchukan Formation, Amur Oblast, Far East Russia

***“ The long necks of these dinosaurs are particularly elegant, and give them their name. 'Olorotitan', giant swan. ”***

― **David Attenborough**, *Ice Worlds*
In the third segment of the episode, 17 female *Olorotitans* make a precarious journey through a volcanic field, traveling in a thin line across a narrow path flanked by numerous vents of toxic gases. The hadrosaurs risk taking this deadly path every year to lay their eggs in warm, volcanic soil, laying and burying them in mounds. When the juveniles the hatch, the mothers greet their newborn children and bring them some vegetation to eat. Being young, the juveniles appear quite playful. As the long days of summer continue, horsetails quickly take over the fields, providing constant food for the *Olorotitans*. The juveniles, still as playful as ever (with some even playing with their discarded eggshells), grow quickly in this land of plenty. Even so, these same warm conditions also prove to be productive for problems. As adults drink from a slow flowing body of water, mosquitoes spawn and soon begin to spread, pestering the hadrosaurs nonstop.

***“ Every year, this paradise turns into a living hell. Hadrosaurs have surprisingly-thin skin, and so have little defense against bloodsucking insects. Constant irritation makes it hard to feed, and they become dangerously weakened. And babies can lose blood in life-threatening quantities. ”***

― **David Attenborough**, *Ice Worlds*
As the plague of mosquitoes worsens, the herd moves on. One mother, checks on one of her children, a juvenile struggling to stand, much less walk forward, as several mosquitoes target it. Struggling against the insects herself, with some even swarming on her face and eyes, the mother decides to cut her losses, and abandons her child, who collapses, seemingly succumbing to the mosquitoes. The herd moves up to higher ground, where the winds bring them some relief, but it appears that not everyone is able to go that far, and another juvenile is seen being abandoned by its mother, helpless and unable to move due to the continued assault of the mosquitoes.

***“ Of the hundreds of hadrosaur babies born, only one in ten survive their first year. But those that do have a good chance of reaching adulthood. By nesting in this volcanic valley, the parents give their young the best possible start in life. ”***

― **David Attenborough**, *Ice Worlds*
Some *Olorotitans* have gathered atop a rocky cliff overlooking the fields and rivers below, with one mother looking over her surviving children as they play. Just then, the juveniles notice something calling from the back of the cliff, prompting their to mother to look behind her. Right there and then, a juvenile, likely one of those that have been abandoned to the mosquitoes earlier, comes up to the cliff, running back to rejoin its siblings and its mother. With this hopeful turn of events, the segments ends with the *Olorotitans* moving on from the rocky cliffs, continuing on their journey.

## Segment IV: Troodontid

In the fourth segment of the episode, a lightning storm, formed by the warm summer conditions, sets a forest in the Arctic ablaze.

***“ Most animals flee from the flames. But for some, the disaster creates opportunities. This six foot-long dinosaur, a troodontid, is one of the smaller members of the theropod group. ”***

― **David Attenborough**, *Ice Worlds*
One troodontid, slowly walking in the midst of the flames, tries to pinpoint the source of the sounds it hears, the calls of distress of other animals. It stalks around the forest, waiting for some of these other creatures to flee the flames and run straight into it. Eventually, the troodontid comes across a stick, smoking embers on its tip. Realizing what it can do with this, the troodontid runs off with the burning twig in its mouth, eventually dropping it by a tree that still seems unaffected by the flames.

***“ At the fire's edge, troodontids gather to prey on animals that are trying to escape the flames. Anything that spreads the fire creates more opportunities for the most ingenious Arctic hunter of its time. ”***

― **David Attenborough**, *Ice Worlds*
With this action, the forest fire spreads, and several *Cimolodons* rush out of the woods, right where the troodontid is waiting to ambush and pursue them. The theropod eventually grabs one of the multituberculates with its jaws, pinning it to the ground while shaking its neck, snapping it in the process. Its hunt a success, the predator gets up, holding the limp body of its latest kill by the neck, shaking it one last time before letting loose a single chirp of satisfaction, slightly flaring out the feathers on the back of its head.

## Segment V: *Antarctopelta*

***“ In the Antarctic, ice clings to the highest mountains even in the summer months, but now, with temperatures falling, and the days shortening, the polar winter is spreading once more across the land. Animals must now prepare for its return. The Southern Hemisphere has its own species of dinosaurs. These three are young Antarctopelta, small plant-eating dinosaurs. They're also one of this world's most heavily-armored animals. Even so, youngsters are safer together. ”***

― **David Attenborough**, *Ice Worlds*
The fifth, penultimate segment of the episode takes place in Antarctica, just right when autumn is heralding the return of winter. Layers of snow and frost, once limited to just the highest of areas, begin to crawl back down to the lower regions, with the glaciers once more building up, and a river cascading down the side of a mountain slowly being claimed by the ice. In the forest, three young *Antarctopelta* prepare for winter hibernation.

***“ This far south, the plants on which they depend stop growing for months on end. As winter approaches, these juveniles spend more time resting. Sheltering together conserves heat, and therefore energy. With powerful front limbs, they can enlarge this winter den. But each time they return, they've grown a little bigger. Their den seems a little smaller, and the brotherly bond starts to wear a little thin. ”***

― **David Attenborough**, *Ice Worlds*
As they journey through the woods, one of them tries to pick some of the remaining vegetation from the roots of a tree. It is clear, however, that, in a short while, there will be little to no food, hence, the next few months would be a time of rest rather than a time of feeding. The three juveniles eventually find the small cave in which they rest in every winter. Unfortunately, this time, given their size, only two of the three ankylosaurs can fit in the cave. With his brothers making it clear that he can no longer share the den with them, the third *Antarctopelta* dejectedly sets off on his own to look for a place to rest.

***“ For every growing animal, this is a vulnerable time, a time when they need to separate and each take its first tentative steps to find a territory of its own. ”***

― **David Attenborough**, *Ice Worlds*
As his brothers sleep snugly in their den, the young *Antarctopelta* lies uncomfortably in the open, on the leaf-littered floor of the forest, with the noticeable increase in fog indicating the short time left before the cold times really close in. Unable to properly sleep, he is left with no other choice but to get up and continue the search for shelter and avoid the freezing winter.

***“ Herds of hadrosaurs are once again on the move. With little to eat, these huge herbivores return to look for food in warmer lands, leaving others to endure the freezing polar winter. ”***

― **David Attenborough**, *Ice Worlds*
The *Antarctopelta* eventually makes it to an open, stony field, coming across a herd of hadrosaurs searching for warmer areas where there is more food. One hadrosaur tries to check for food from a log, to no avail. For a moment, this individual and the *Antarctopelta* regard each other before continuing on their journey down opposite paths, the *Antarctopelta* searching for a place to rest in and wait the incoming winter out, the hadrosaurs looking for a more bountiful region that can sustain them.

***“ Finding a suitable territory can take animals far from the place where their lives began. It's a search that many will not survive. A cave, perhaps. ”***

― **David Attenborough**, *Ice Worlds*
Once more in a forest, the *Antarctopelta* makes his way down the woodland's rugged, treacherous grounds. Eventually, however, he finds himself facing down the mouth of a large cave.

***“ Even in the coldest months, the temperature in most caves hardly varies. But he is not the first to be attracted by this one. This cave glows. These are the tiny lures of fungus gnat larvae that produce light to attract their insect prey. This is the perfect place for an Antarctopelta to escape the worst winter weather. He'll be safe beneath these strange living stars, while outside, snow begins to fall. ”***

― **David Attenborough**, *Ice Worlds*
Walking down a stony slope, the *Antarctopelta* takes a good look of the large, warm cavern, its ceiling lit up by the whitish-blue glow of silky threads, the lures of fungi to attract insects for them to eat. Having found refuge from winter at last, the *Antarctopelta* makes his way to a corner of the cave and curls up to take his well-earned rest.

## Segment VI: *Pachyrhinosaurus* and *Nanuqsaurus*

  **Ice Worlds**, Segment VI
**Setting**
Prince Creek Formation, Alaska, USA

In the sixth and final segment of the episode, as the coldest months begun to take hold of the Arctic, a herd of *Pachyrhinosaurus* forages through the forest, feeding on what little food they can find in the snow. Even though their autumn rut is over, two less-dominant males clash heads in order to establish which one is superior. Almost immediately, both are confronted and driven away by an old bull *Pachyrhinosaurus*. The old bull proceeds to scratch his left flank on a tree, and, as he turns to move somewhere else, it is revealed that he has a raw, open wound on his right leg (likely due to constant conflicts).

***“ Battling males barely have time to eat or rest. With food now scarce, it's hard to rebuild strength, and injuries take longer to heal. To make matters worse, the Arctic's most powerful predator is always on the prowl... Nanuqsaurus, a smaller relative of T. rex, it's still just big enough to tackle a Pachyrhinosaur. ”***

― **David Attenborough**, *Ice Worlds*
Just then, a pair of *Nanuqsaurus* emerge from behind the trees, with a third coming from another side of the forest shortly after. Rather than try to ambush a member of the herd, the tyrannosaurs seem to choose playing the long, strategic game. Walking menacingly towards the herbivores, the ceratopsians, fearing the threat of isolation (which would make them easier targets for predators), retreat to an open area, where they can take up a better defensive position.

The herd, consisting of 21 adults and 3 juveniles, form an impenetrable circle, bellowing at the predators as they try to look for a way to attack. At times, when a tyrannosaur gets too close, one of the ceratopsians would charge out of the circle to knock them down, forcing the *Nanuqsaurus* to temporarily retreat. As the blizzard worsens and the herbivores get more disoriented, the *Nanuqsauruses* continue testing for weakness, even as the *Pachyrhinosauruses* continue to charge at them whenever they get too close. Once the blizzard has become too severe, both sides of the standoff hunker down and rest. But when the blizzard has passed, the conflict resumes. While the *Nanuqsauruses* come in from one side of the circle, one *Pachyrhinosaurus* on the opposite side of the circle begins running, prompting the rest of the herd to panic and rush away as well, the tyrannosaurs in hot pursuit.

***“ As the chase goes on, one tiring bull fails to keep up with the rest, until all he can do is turn and face his attackers. ”***

― **David Attenborough**, *Ice Worlds*
One tiring bull, lagging behind the rest, is left behind. Ironically, it is the same dominant male from earlier, as made clear by the chipped-off tip of his right frill horn, the notch in the horn arrangement of the right edge of his frill, and the scar on his back right leg. It appears that, with the life he lead, he has inevitably doomed himself to such a moment. With no other option, he turns and faces his attackers, the trio of tyrannosaurs closing in on him.

***“ One Pachyrhinosaur has lost a battle. But the war will go on all winter. The animals here now face months of total darkness before the sun returns and brings relief to the extraordinary creatures in the world of ice. ”***

― **David Attenborough**, *Ice Worlds*
In the struggle, the bull is dragged down to the ground, pinned, and killed. Two female *Pachyrhinosauruses* stay behind for a while and watch as the *Nanuqsaurus* pack feasts on the once-dominant bull, giving out one last bellow before leaving to rejoin the rest of the herd.

## Uncovered Segment: Did Dinosaurs Hunt in Packs?

  **Did Dinosaurs Hunt in Packs?**
**Subject**
The plausibility of dinosaurs (even large tyrannosaurs) engaging in pack-hunting.

**Experts**
Dr. Susannah Maidment, Dr. Darren Naish
This segment, based on the final segment of the episode involving a trio of *Nanuqsaurus* hunting members of a *Pachyrhinosaurus* herd, discusses the possibility of pack hunting in dinosaurs. While many people tend to remember dinosaurs for their bones (with one example brought up in the segment being "monospecific bonebeds", sites with accumulations of just a single species of animal), evidence can also be found in other traces they left, like footprints. The presence of tracks left by multiple individual theropods imply that dinosaurs are capable of hunting together.

***“ In 2014, scientists in British Columbia discovered trackways made by three tyrannosaurs that had all been walking side by side. These animals had all been moving together in the same direction, all within just a few meters within each other. ”***

― **Dr. Darren Naish**, *Lead Scientific Consultant*
Basis for such behavior can also be formed by observing some predators alive today. Despite being large and powerful enemy to bring down some prey on their own, some big, intelligent mammals like lions, wolves, and orcas rely on cooperation to take down prey, usually herbivores larger than themselves. This behavior can also be seen in the closest living relatives of the dinosaurs, birds.

***“ In birds, the modern cousins of tyrannosaurs, group hunting behavior is fairly common, it's seen in various seabirds, in some crows, and also in various falcons, hawks and eagles. In some species, like the American Harris hawk, groups of related individuals work together to capture prey. ”***

― **Dr. Darren Naish**, *Lead Scientific Consultant*
As some studies show, when times are hard and large prey is available, predators are more likely to form packs. And such circumstances make themselves clear in the Arctic Circle, even back in the Late Cretaceous Period, justifying how the tyrannosaurs in that area are likely to cooperate and help bring down some of the largest, most formidable herbivores by that time.

## Fauna

*Dromaeosaurus albertensis**Edmontosaurus sp.**Ornithomimus edmontonicus**Olorotitan arharensis*Alaskan Troodontid*Cimolodon nitidus**Antarctopelta oliveroi*Antarctic Hadrosaurid*Pachyrhinosaurus perotum**Nanuqsaurus hoglundi*