"Downtown L.A. the ultimate modern American city." "But Los Angeles' skyscrapers are built over the graves of thousands of extinct ice age beasts." "Today all we have are memorials to these vanished animals." "But imagine if they had survived into present day..." "They would have had to adjust to a very human world." "The reality is mammoths never made it beyond the end of the last ice age," "but many other creatures did." "And over the past 14,000 years or so, they've had to adapt to an increasingly human landscape, a landscape of concrete and steel." "ln this programme we will travel back into the past to investigate why the giant beasts of North America became extinct." "And to find out how those animals that did survive have adapted to life in our modern world." "To find the answers, we need to rewind history around 14,000 years to a time when the first people set foot in North America." "The continent was about to undergo a profound change a change these new arrivals may have played a part in." "Throughout the ice age North America was home to a variety of giant creatures..." "But in little more than a thousand years of the first humans arriving, almost two thirds of the largest animals were extinct." "What role did people play in this mass extinction?" "To learn about their lives you have to look at the clues they left behind." "Archaeological finds tell us that the first people in North America had an advanced stone age technology." "They were master flint knappers meticulously chipping and sharpening pieces of flint to make spears and cutting tools." "From the examples they left behind, it's obvious they were well equipped to hunt." "And we know from spear points found alongside mammoth remains that these hunters tackled even the biggest beasts on the continent." "Mammoths would have been a prized source of protein, providing enough meat to feed their families for weeks." "The hunters probably worked in pairs or small groups." "Any mammoth straying from its own herd would have been singled out." "But even on its own, a mammoth was still highly dangerous... and an attack required stealth and teamwork." "One of the hunters may have acted as a decoy, distracting the animal while others surrounded it." "And these hunters had another trick up their sleeve." "Using a specially crafted wooden stick called an atlatl, they were able to launch sharp pointed darts more than 40 metres." "So we know these people were efficient hunters but could they really have wiped out all the mammoths on the North American continent?" "Today, the remains of mammoths in particular their tusks may help answer that question." "To read the clues contained within these tusks you need to look at the mammoth's closest living relative - the elephant." "Elephant tusks grow throughout their lives, with the tip being the oldest part." "Mammoth tusks show the same pattern of growth as modern elephants." "Each year of life is represented by a ring just like tree rings." "But tusks can also be a record of the more stressful periods in an elephant's life." "As bulls mature, they're forced out of the family group and have to fight to survive." "During this stressful time, they don't have so much energy for growth, so the space between each ring is narrower." "These same signs appear in young male mammoth tusks, but those living in North America at the end of the ice age laid down their stress rings 3 years earlier than usual." "ln other words, it seems that young males were leaving the herd at an earlier age." "Some scientists believe the only thing that could cause such a major change in mammoths' social structure would be hunting by humans." "If hunting pressure was extreme enough to push the mammoths to extinction, then we would expect them to survive in areas that people couldn't reach." "And for a while they did here on Wrangel Island off the coast of Siberia." "There are no mammoths on Wrangel Island today, but it is home to another large animal the polar bear." "And there is evidence that polar bears and mammoths once lived side by side during the last ice age." "They would have shared the island's meagre offerings." "This inhospitable and isolated place seems to have been a sanctuary for mammoths." "The Wrangel Island herds were the last on the planet to survive." "Remarkably, they survived here long after their North American relatives had all died out." "But they were still on borrowed time." "When people finally reached Wrangel Island, 4,000 years ago, these last remaining mammoths also became extinct." "The events on Wrangel Island mirrored what had happened on the North American continent." "Mammoths only became extinct after they came into contact with people." "But there is a problem with the idea that hunting caused the mass extinction." "Mammoths were not the only animals to disappear." "Camels survived for millions of years in North America, but disappeared around the same time as the mammoths." "Wild horses first evolved here and became dominant grazers..." "Yet they too vanished soon after the ice age ended." "But there's little evidence to suggest that humans hunted horses or camels." "This seems to go against the hunting argument." "So what else could have triggered such large- scale extinctions?" "The other major possibility is climate change." "The ending of the ice age was a turbulent, erratic period." "ln some areas rain patterns were shifting, bringing moisture back to dry landscapes and turning grassland into forest." "Other regions of the continent were plunged into prolonged periods of drought." "For grazers such as horses, this led to a massive change in habitat one they were not flexible enough to overcome." "As the land dried out, many grass-eaters disappeared." "We may never know for certain what killed off most of the larger animals at the end of the ice age." "We do know it was a time of coincidence people were arriving just as the climate was in a state of change." "Both may have played their part." "Whichever was responsible, more than 70 species vanished for good." "But some large animals did survive, and still live here today." "Sabre-tooths died out, but another big cat survived." "The puma may have been more able to adapt because its diet is more varied, and includes small prey." "The grizzly bear also lived through the post ice age changes and now thrives in North America." "Once again, a varied diet of meat and plants made it a versatile survivor." "The moose is now the largest browser on the continent." "During the last ice age moose were restricted to the far north but, after the ice melted, they spread south." "They took the place of mastodons and the larger stag moose both of which became extinct." "Bison too were to benefit from the post ice age changes." "They managed to survive the drought, eventually expanding in number to replace the horse as dominant grazer." "As ruminants with multi-chambered stomachs bison can extract more nutrients from grass and this may help explain why they survived when other grazers such as the wild horses did not." "While all these creatures were adapting to their changing landscape, another animal was just beginning to make North America its home." "It's thought the dog arrived with early people and its descendants are still with us today." "The Carolina dog lives in the woods of South Carolina." "Like most primitive dogs, it makes its den in the ground or in hollow tree trunks." "The Carolina dog is often called the American Dingo." "It does look like its Australian relative, but links between the two may go deeper than that." "Genetic analysis of the Carolina dogs suggests they are closely related to primitive wild dogs like the dingo and may trace their ancestry all the way back to the first dogs to enter North America." "The Carolina dogs are pack animals, with a strict hierarchy topped by an alpha male." "Like most wild dogs they hunt in groups... but many of the kills they make are small." "Rabbits and small rodents make up a large part of their diet in what can become a collective feeding frenzy." "At the end of the ice age these dogs' ancestors also had access to other sources of food." "They may have hung around the camps of early native people... scavenging for scraps." "But although they lived on the fringes of human society, the early wild dogs were certainly not pets." "Exactly when they arrived in North America is still uncertain, but it's likely that they slipped in after the extinction of the ice age beasts, during a time of massive change." "Eventually, the continent became more settled." "Over the next few thousand years, people adapted to the many regions of the continent and their varying lifestyles were shaped by the landscape they lived in." "Then more than 14,000 years after the first people set foot in North America, another wave of immigrants brought changes that would have a dramatic impact on the landscape and wildlife of the New World." "Just over 500 years ago," "Europeans arrived in North America." "And with these colonisers came an animal that hadn't been seen here for thousands of years." "The horse returned to the Americas, now tamed and carrying the Spanish conquistadors." "This new form of transport was rapidly adopted by the native people, which was bad news for some native animals." "Bison had once lived alongside the wild horses of North America and had prospered at the end of the ice age while the horses became extinct." "But now the new tame horse became the bison's enemy." "The horse's speed and stamina gave native people an advantage over their prey that they never had before." "The horse was an even bigger ally to the increasing number of European settlers spreading out across the continent." "They killed millions of bison for their meat and hides." "By the mid-1800s the horse and the cowboy had come to symbolise the wild west." "And of course, with the cowboys came cattle." "As the bison quickly vanished from the landscape, cattle filled their place." "Meanwhile increasing numbers of the tame horses escaped into the wild." "These feral horses became known by the Spanish name: mustang." "They put extra pressure on the dwindling bison numbers by competing for their grazing sites and drinking holes." "Mustangs formed social groups led by a dominant stallion, echoing their prehistoric relatives that lived here during the ice age." "Bred to carry the weight of a rider, mustangs are larger than those early wild horses but they still display the same kind of behaviour." "By the early 1800s the wild horse was well and truly back in North America." "But how did other wildlife on the continent survive alongside growing human populations?" "Some wild creatures did the reverse of mustangs by becoming tame and choosing to live close to people." "The purple martin became an unofficial mascot for native inhabitants in the eastern half of the continent." "Here people erected special nesting sites to encourage the birds to stay." "Where purple martins had once laid their eggs in hollow trees, in time they came to rely almost totally on people to provide nests for them." "These artificial nests were made from dried out squashes known as gourds." "The shape made them perfect nesting sites for these birds." "But what triggered this special relationship in the first place?" "It's possible the insect-eating martins helped to control pests living around native American camps." "Whatever the original reason, the traditional tie between people and purple martins survives to this day." "But now in keeping with the modern world, hollow gourds have often been replaced by high-rise apartment blocks." "This special relationship between purple martins and people is one of the few in North America to cross cultural boundaries between native groups and European settlers." "Other animals to cross this cultural divide did so for different reasons." "More than 50 million wild turkeys were living in North America when the first Europeans arrived." "They were occasionally hunted by the native people, but the European settlers had a taste for turkey and they took this to extremes." "As hunting intensified, wild turkey populations plummeted." "The turkey became a central part of Thanksgiving Day celebrations and was almost hunted to extinction." "At first the Europeans relied heavily on local food supplied by native people." "But as they settled in, their farming practices began to shape the landscape of North America." "The plough allowed them to farm larger areas of land, helping to feed the expanding population." "While this new type of agriculture robbed many animals of their habitat, others were to reap the benefits." "Birds such as grackles, cowbirds and redwing blackbirds, exploded in numbers, feeding off the waste remains of farming." "These pest birds were already common around small native farms in the east." "Now large scale farming of crops such as corn, wheat and barley fuelled their numbers to epidemic proportions." "Despite these pests," "North America's agriculture kept on booming, becoming big business." "Great swathes of a once wild landscape have been turned over to farming." "And farming fuelled the growth of another habitat one that would become an even bigger challenge to North America's wildlife." "The modern city was born." "The city is an artificial environment, built around the needs of millions of people." "And yet it also offers unexpected opportunities for wildlife." "This burrowing owl lives in one of the biggest, hi-tech urban sprawls of North America." "It maintains a tenacious foothold in Silicon Valley." "Burrowing owls originally lived on open prairies, but they've been forced to adapt to city life because the urban environment has grown around them." "They survive by occupying any tiny sliver of grassland that remains." "Like many city animals, they take advantage of the darkness to protect them, and move around mostly at night." "These adaptable birds traditionally nest in the burrows of prairie dogs, but in the city a piece of old pipe will do." "The parents split their duties the father does much of the hunting, but in this case it's the mother that actually feeds the chicks." "The burrowing owl's ability to hover gives it time to judge an attack before pouncing on its prey." "The owls can raise anything from one to 12 chicks in a summer season." "To survive, their young will have to quickly learn to negotiate the dangers of city life." "Longer hunting trips are sometimes necessary as open land disappears." "But so long as the city can still provide food and shelter, these owls will remain a part of the urban landscape." "A few hundred miles south of Silicon Valley, another city has grown up on the edge of a desert." "This is Bakersfield, California." "It sits on an underground reservoir of water, enabling its residents to live in a suburban idyll." "This modern day oasis has provided sanctuary for a rare animal one that emerges at night." "The San Joaquin Kit fox is one of the smallest and rarest foxes in the world." "Yet, remarkably, it flourishes on Bakersfield's busy street corners." "Although many of these city foxes do get killed by cars, the population as a whole is thriving." "That's because the regular supply of water means a regular supply of prey, including voles and ground squirrels." "Playing on the streets at night is dangerous, but for the pups, it's vital for improving their co-ordination." "Parents keep a vigilant eye on their antics." "Despite the hazards of city life, the Bakersfield kit foxes are now crucial to the overall survival of the species." "The promise of an easy source of food is a good reason why animals live in cities, especially at times of year when food is hardest to find in the wild." "During the winter months Anchorage in Alaska is home to North America's largest browser - the moose." "But a moose during the day is a little obvious, so they prefer to move around by night." "While most of the human population sleeps, the moose wander the streets in search of food." "Moose mainly browse on trees and shrubs but they will also sample something new... they have a soft spot for pumpkins left out after Halloween." "As many as a thousand moose may enter Anchorage in winter." "Snowfall here is lower than in surrounding hills and gardens offer a tempting spread of food." "ln fact, moose were in this area long before the city existed and Anchorage inhabitants are understanding of their local vandals." "Unfortunately, this tolerance sometimes comes at a cost." "Christmas decorations are a minor inconvenience to a hungry moose." "But there's another reason why the city centre is a tempting winter hangout." "It's one place where their major predator, the wolf, rarely dares to go." "It may seem strange, but human habitats are often safer for wildlife than the real wild." "Black skimmers usually nest on beaches... but not here in Texas." "This disused car park is a near perfect location for raising chicks  and only a short flight from a plentiful supply of food." "Skimmers get their name from their unusual feeding technique their extended lower bill detects fish just below the water surface." "The heavy use of east coast beaches by people has threatened skimmer numbers." "It's ironic that this man made car park, made out of crushed oyster shell, should become a substitute." "Skimmers raise their chicks on a fish diet." "But they serve the portions whole, which can cause problems for their young." "The increasingly human landscape of North America can make wildlife spectacles a rare event." "But there are situations when it brings nature closer to people." "That's exactly what has happened here at this power plant in Florida." "These are West Indian Manatees residents of the Florida coast." "People and manatees don't usually get along." "lncreasing boat traffic has become a big threat to manatees and some bear the scars of painful encounters with boat propellers." "But there is at least one place in Florida where the manatees benefit from humans being around." "Clean, hot water released from this power plant turns a man-made inlet into a hot tub." "And during winter months, when sea temperatures drop below 20 degrees centigrade, manatees gather here to keep warm." "It's actually an artificial version of the natural hot springs where manatees traditionally congregate." "But this particular location seems to be extremely popular." "During the coldest spells, more than 300 manatees can gather here." "With so many of these shy creatures in one place, the power plant has become a tourist attraction." "It may not be the most scenic setting, but this is a unique chance to see one of the largest gatherings of manatees in the world." "People have become dependent on industry to support their modern lifestyle." "So too it seems has some of North America's wildlife." "Every September, the skies over Portland," "Oregon become crowded with Vaux's swifts." "These birds have chosen a 30-metre chimney stack as a place to roost." "Tens of thousands funnel down into the disused chimney, where they huddle together for the night." "Vaux's swifts traditionally roost communally in hollow trees, but as many of North America's forests are destroyed, they've turned to man-made structures." "This mass roosting takes place soon after the summer nesting season it's a chance for the birds to moult before they fly south for the winter." "As Vaux's swift numbers reach a peak in mid September, they attract attention from the locals." "Coopers hawks and Peregrines pluck a meal from the tumbling mass of birds." "ln as little as 20 minutes, as many as 40 thousand swifts pack into the chimney for the night." "While a Portland chimney has become a substitute for a tree, another roosting creature has chosen a road bridge in Austin," "Texas as its cave." "Visitors to Austin have to wait till evening for a glimpse of what lurks within the bridge." "As the sun goes down, Mexican free-tailed bats begin a breath-taking commute out of the city." "This exodus only takes place in summer... free-tailed bats arrive in Texas for the spring, returning to Mexico for the winter." "More than a million of them leave the city at dusk and head into surrounding countryside to feed on insects." "The sky over Austin swarms with these aerial commuters." "It's incredible that so many bats cram into tiny spaces underneath the bridge." "But the battle for living space is now an everyday fact of city life." "The most populated North American city is New York." "Here, space is a precious commodity, with more than 8 million people fighting for their share." "With so little ground space left, having a garden can require a head for heights." "It's difficult to imagine any animal getting a foothold in this bustling city." "But some do." "The red-tailed hawk is well known in mid town Manhattan." "It manages to survive here because New York has the ultimate in urban gardens" " Central Park." "This park, created in the mid 1800s, has become a focal point for wildlife and the people of Manhattan." "It's also prime hunting ground for red-tailed hawks." "And they have the perfect nesting site right next to it." "They've moved in on the top floor of this expensive Manhattan apartment block." "It acts like a surrogate tree supporting their large nest." "Their high-rise residence also provides a perfect lookout and a launch pad for ambushing prey." "A meaty New York diet means these birds continue to survive in North America's most hectic city." "Despite our increasingly urban lifestyles, we still have a deep-rooted desire to connect with nature." "And in modern day North America it's possible to fulfil that desire in all manner of ways." "This may look like a safari through the African savannah." "ln fact, it's a theme park in Florida, and it allows people to experience a world outside their own." "ln some ways they are visiting a land from another time." "14,000 years ago large parts of North America's landscape and wildlife were just like the savannah of modern Africa." "With a stretch of our imagination, we can still put ourselves in the shoes of the first people who explored that vast, dramatic landscape... and encountered giants never seen before." "ln this series we have seen how fossil bones and other evidence can provide clues to that distant past." "And that evidence has helped to recreate a continent that no longer exists..." "A lost Wild New World." "And you can find out more about the making of Wild New World and the wildlife of prehistoric North America right now."