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One Million Years BC: Sabre-Tooth World

Earth- 1 Million Years Ago

It’s one million years before our time and the ice ages have arrived in earnest. Both poles are gripped in ice and thousands of square miles of tundra wilderness cloak the higher latitudes. This has driven much of the life on Earth towards the Equator, but here another change awaits. With all the water locked up in the ice caps, the tropics are drying out. Vast seas of grass now dominate the land. Nowhere is this change more obvious than in South America, where this period is known as the Pampean era. The rainforests have been pushed back to the coasts and replaced by open savannah and prairies. Here, the battle between predator and prey is intense- with no forests, there is little opportunity for games of hide and seek. This competition has bred a new race of giants. Many are too large for the traditional top predators of South America, the flightless terror birds, but a new migrant from North America is changing the balance of power. The newcomers are called smilodon, they are sabre-toothed cats, and in South America they are the new terrors of the plains.

The Sabre-Tooth

This is Smilodon fatalis, the subspecies of smilodon which inhabited most of North America. The subspescies featured in this hub is Smilodon populator.

This is Smilodon fatalis, the subspecies of smilodon which inhabited most of North America. The subspescies featured in this hub is Smilodon populator.

Smilodon

Smilodon, the famous sabre-toothed cat, is well known because of the enormous numbers of skeletons of the North American subspecies, Smilodon fatalis, which are beautifully preserved in the tar pits of La Brea in California. The South American species, Smilodon populator, was even larger than its North American cousin with long, straight front legs to hold down prey and to get an accurate bite with the sabre teeth.

Evidence: Smilodon populator is known from several sites in Brazil, Argentina and especially the Tarija formation in Bolivia.

Size: 4 feet at the shoulder.

Diet: Large grazing or browsing animals.

Time: 1.5 million-10,000 years ago.


The Terror Bird

On the isolated continent of South America, flightless predatory birds thrived long after becoming extinct elsewhere.

On the isolated continent of South America, flightless predatory birds thrived long after becoming extinct elsewhere.

Phorusrhacos

Phorusrhacos belongs to a group called the terror birds, the earliest known of which, Aenigmavis, is actually found in the Messel deposits of Germany, but was only the size of a modern and not related to the giant Gastornis which dominated the forests of the Eocene. However, in South America Aenigmavis's descendants grew huge and became the continent's top predators for millions of years.

Evidence: Only partial fossils of Phorusrhacos have been found, such as those at Monte Hermoso in Argentina, but recent finds of its North American form, Titanis, in Texas and Florida, are beginning to complete the picture.

Size: Almost 10 feet tall.

Diet: Small mammals and any carrion it could find.

Time: 27 million- 5000 years ago.

Half Tooth Defends His Territory

Ruler Of The Pride

It is a scene as old as time on these Pampean plains. Ripples of wind chase across a sea of deep grass. In the distance a vast herd of macrauchenia move through the morning haze. Just visible above the waving sea heads is the dark plumage of a phorusrhacos out hunting mammals. For millions of years this huge terror bird and his kind have been the top predators in South America and they have grown large and powerful on it, this one is almost 10 feet tall. Terror birds are lightning fast creatures, capable of achieving speeds of over 30 miles an hour; few herbivores here possess the power to escape from them.

The phorusrhacos has crouched low, using the tall grass to hide in while he watches his unsuspecting victim wander nearer and nearer across some open ground. He slowly cocks his head from side to side to judge the precise moment to strike, his fearsome hooked beak held slightly open in anticipation. The little mammal he is watching stops, perhaps sensing danger, and calls for help. The phorusrhacos stands up and charges on swift orange legs. But he is in for a surprise.

The terror bird’s victim is a smilodon cub, a baby sabre-tooth, and, although the little creature has wandered out on his own, there will be a pride nearby. The sheer pace of the terror bird means he is on to the cub before any help can arrive, but the youngster’s stumbling retreat stops the predator making a clean grab. As he closes on his victim, the phorusrhacos finds himself facing a full grown mother smilodon, her mouth wide open to reveal her enormous 8 inch fangs. The giant bird spreads his small, clawed wings in a defiant display, issuing a piercing screech of aggression. But this impressive sight fails to intimidate the huge sabre-tooth. She lunges forward, lashing with her claws and placing herself between the cub and the bird. Soon two more female smilodon appear out of the grass and then a huge lumbering male. The phorusrhacos is now way out of his league. When the male smilodon breaks into a trot, the terror bird turns and runs. The big cat knows better than to pursue him. Instead, he stops and issues a series of low, throaty roars that rumbles across the plains after the retreating bird. His calls are cut short when a playful cub sinks its teeth into the male’s short tail and he has to turn and cuff it free.

A smilodon’s roar can carry for around 5 miles across the savannah and serves not only as a warning to other predators, but also as a reminder to the other smilodon prides. To the sabre-toothed cats this sea of grass is a giant chessboard of territories, each defended by a pride. The size of each area depends on the wealth of prey that can be found there and the health of the pride that controls it. This particular pride is not large. Five females with four cubs and two adolescent females are dominated by a single male. Their territory stretches for several kilometres along the base of a cliff and contains mostly grassland, with a few stands of palms and patches of seasonal marshland.

The male took over this pride, which I shall call the ’cliff’ pride almost two years ago by killing the previous male. He is a fine example of his species, standing about a metre and a half tall with massively powerful front limbs. His relatively short back legs and stubby tail mean that he moves in a fashion similar to a hyena. So, although, he cannot run fast, he can keep up a sustained canter if needed. However, it is not his job actually to hunt. The females do all the killing; he just claims his share when they are successful, saving his strength for challenges to the pride, mainly from other males. But this male has not faced a serious challenge for his territory, as yet his sandy, spotted hide has very few scars. Despite this, one of his long sabre canines has broken off halfway down at some point. While it doesn’t impede him in any way, it does make him very recognisable.

As the pride settles down again after their run in with the phorusrhacos, the half toothed male relaxes on top of some open rock with the females and cubs around him. Before him, stretching away from the cliff, are his pride lands, which contain several herds of the small horse like creatures known as hippidiforms, and macrauchenia. The macrauchenia are large herbivores with characteristically long noses that they use to help gather food. Because they are comparatively slow moving they are the smilodon’s favourite prey, but no creature that lives here is easy meat. These are large, powerful animals and they are very difficult to isolate as individuals.

Half Tooth rolls over and lets a cub bat his ears. All the cubs here are his and most are just a few months old. They are more heavily speckled than the adults and have yet to develop their sabre teeth. It’s a picture of family peace, the king of the plains surrounded by his subjects. But there is trouble on the horizon. Across the seemingly endless plains wander the unmistakable shapes of two large male smilodon. They are brothers and, although they are strangers to this area, they have deliberately ignored the frequent scenting points that Half Tooth has left around his territory. They are here to challenge him and will not leave until there has been bloodshed.

The Giant Armadillo

The giant armadillos were known as glyptodonts, and each species possessed a spiked tail, similar to those of the ancient ankylosaur dinosaurs.

The giant armadillos were known as glyptodonts, and each species possessed a spiked tail, similar to those of the ancient ankylosaur dinosaurs.

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Doedicurus

Doedicurus was a glyptodont, related to modern armadillos and modern sloths. It did very well in South America long after disappearing everywhere else. When a land link with North America formed, Doedicurus continued to thrive but eventually succumbed with the rest of the megafauna. It may well have been still alive when humans first arrived in South America, but evidence supporting this is inconclusive.

Evidence: Many skeletons of glyptodonts are known, including those of Doedicurus, especially in the Esenada formation in Argentina.

Size: 10 feet long, weighing around 1.4 tonnes.

Diet: Browsed and grazed any vegetation it could find, possibly digging for roots and tubers as well.

Time: 2 million-10,000 years ago.

The Giant Ground Sloth

The power and size of the giant ground sloth megatherium mean that he faces no natural predators on the pampas.

The power and size of the giant ground sloth megatherium mean that he faces no natural predators on the pampas.

Megatherium

The ground sloths, although related to the tree sloths, were very different from their modern relatives. They grew to enormous sizes, with Megatherium being one of the largest, and one of the few to successfully colonise North America from South America. Ground sloths became extinct just a few thousand years ago, probably due to overhunting by humans. Because of their compartively recent extinction, there is still quite a lot of evidence of what they looked like.

Evidence: The South American species Megatherium americanum is known from many skeletons, sets of fossilised footprints and even dung and hair. Finds have come as far north as Texas and as far south as Argentina.

Size: 20 feet long and weighing around 4 tonnes.

Diet: Browsed vegetation, and possibly scavenged meat from carcasses.

Time: 1.9 million-8000 years ago.

Banishment

The next morning the sun rises into a dark overcast sky. By late morning the rain is drenching the plains. Beneath the dripping leaves of a palm grove are the dark brown shapes of two huge male doedicurus, battling for the right to mate a nearby female. It is an extraordinary trial of strength for these armoured creatures. Their rigid, domed bodies make them look slow and clumsy as they manoeuvre round each other, seeking an opportunity to strike. They push, shove, grunt and bark, even occasionally rising up on to their back legs to try to intimidate their rival. Then one will manage to land a blow with his massive spiked tail. When 90 pounds of bony club smash into thick body armour cushioned by layers of fat, it produces a sickening thud. A fine spray of water leaps off the rivals’ backs as the shock of the blow vibrates round their carapaces. But each time the victim just grunts and the fight continues. Sometimes these bludgeoning contests last for hours and individuals walk away comparatively unscathed, broken spikes or cracked armour being the worst injuries. It looks as if, despite the rain, this encounter is also going to last. From a nearby mound the ’cliff’ pride watches the contest with detachment. It’s unlikely that either doedicurus will be so weakened as to make him vulnerable to attack. Besides, the females are distracted. At dawn the two brothers stood about half a mile from the pride, issuing challenging calls. Half Tooth responded by trotting off into the long grass to find them. He has not been since. The females need to hunt, but they are worried about leaving their cubs. Eventually, around midday. Half Tooth appears out of the rain. He is covered in mud and limping. The adults in the pride stand up to greet him, but as he approaches it’s clear that he has suffered several nasty wounds to his flanks. Then through the mist come the two brothers. Their heads are up, they are watching Half Tooth- just keeping pace so that he has no opportunity to stop to rest. Outnumbered, he has lost his fight. He has been deposed and now is being driven from his former territory.

The females start to call out, but Half Tooth skirts round the pride, heading for the swamps and palm forests to the south. His future looks bleak, very few males last long after they have been ousted from their pride. With no territory to call his own and no females to hunt for him, he will be reduced to scavenging, rejected by other prides and attacked by other males. However, Half Tooth is still comparatively young and there is a slim chance that, if his wounds are not too bad, he might be able to make a comeback by claiming a new pride.

The two brothers give up the chase as Half Tooth disappears into the swampland. They then settle down to lick their wounds and watch their new pride from a safe distance. The females know what has happened, some have seen it twice in their lifetimes already. It’s all change at the top. But although this makes little difference to them, it is lethal for their cubs. The brothers know that the youngsters belong to Half Tooth, and they are not able to protect their offspring. Also, as long as the cubs are there, the females will not come into season. As far as the brothers are concerned, they must kill their defeated rival’s young in order to mate with the females and sire cubs of their own. At first the brothers do not approach the pride, they know the cubs will be defended aggressively. But the mothers cannot stay by their babies forever, they need to go hunting. Eventually, grasping their cubs delicately in their front teeth, they move off into some thorn scrub to hide them. The brothers are happy to wait.

By now Half Tooth has reached the open forest at the base of the cliffs. He is looking for shelter from the rain and heads for a large overhanging rock. Before he climbs up to the overhang he stops and sniffs the air. Just distinguishable through the rain is the stench of the giant ground sloth, megatherium. This is the first piece of luck Half Tooth has had today. If he had blundered into an enclosed space with a 4 tonne megatherium he could well have been killed instantly. As it is, he turns and stalks up to high ground to the right of the overhang; sure enough, squatting among some myrtle, is the massive hulk of an adult megatherium. His dark, shaggy coat is soaked and his powerful clawed arms are lightly stripping palm leaves, leisurely shovelling the greenery into his mouth. The lumbering beast spots the sabre-tooth and issues forth a roar. He rises up on his back legs, lifting his arms high in threat and displaying his claws, which are every bit as long as the cat’s sabre teeth. Being so powerful, megatherium have little to fear, even from smilodon, but they still have zero tolerance towards the cats approaching too closely.

Half Tooth is now in some pain. The bruises and wounds the brothers gave him are beginning to seize up in the damp atmosphere. Stumbling over the rocks he retreats from the dangerous sloth and continues his search for shelter.

Later that afternoon the brothers are completing Half Tooth’s defeat. As the rains gradually ease off they get up and shake the water out of their coats. The females of the pride have gone hunting and the brothers head for the thorn scrub. It may be that they won’t find the cubs today, but in the end it will make no difference. Every time the females have to leave their young, the brothers will try to find them and eventually they will succeed.

Just before darkness the pride females return and the mothers search for their cubs. Their low calls go unanswered. The mothers continue searching into the night, but without success, it would appear that the brothers are efficient hunters. The oldest female keeps looking for her two cubs for several days. She is probably too old to have another litter and perhaps she is aware that this is her last chance. Three days after Half Tooth was deposed, she discovers the severed head of one of her babies.

A Bizarre Herbivore

Despite being the size of modern camels, macrauchenia always have to be alert to danger. They are the favourite prey of the sabre-toothed smilodon.

Despite being the size of modern camels, macrauchenia always have to be alert to danger. They are the favourite prey of the sabre-toothed smilodon.

Macrauchenia

This bizarre looking creature is a member of a group of extinct animals called litoperns, known only from South America. No one knows how they are related to other mammals, they are assumed to be distant relatives of our familiar hoofed mammals, but this classification may change when more fossils are found. Macrauchenia was the last of its kind, when it became extinct the litopern lineage died with it.

Evidence: The first Macrauchenia skeleton was discovered by Charles Darwin on a stop over during his famous journey on board The Beagle. Since then many more remains have been found in the Lujan formation in Argentina.

Size: 7 feet at the shoulder and over 10 feet tall at head height.

Diet: Browsed on trees.

Time: 7 million-20,000 years ago.

Sabre-Tooth Hunt

Modern Social Cats

Smilodon probably lived in prides like lions do today. Through working together, lions are able to bring down prey far larger than themselves.

Smilodon probably lived in prides like lions do today. Through working together, lions are able to bring down prey far larger than themselves.

The New Regime

Across the Pampean grasslands, the weeks of heavy rain have left the ground waterlogged. Temporary pools lie hidden beneath a lush growth of new grass and for the herbivores there is no shortage of food. However, the soft heavy soil is bad news for many herd animals. Most, like the macrauchenia and the horses rely on their speed and manoeuvrability to escape predators. The ground conditions now make this difficult, something the pride of smilodon know how to turn to its advantage.

The brothers still have little to do with the females and are probably waiting for the first one to come into season. Most of the time they wander their new territory, scent marking to establish their presence. Meanwhile, four of the females are out hunting. The oldest one who lost her cubs is not among them. In fact, she hasn’t been seen for over a week, and its more than likely that she has died. The other members of the pride will miss her experience, but she has taught them well and, in her absence, they are carefully organising the death of yet another macrauchenia.

The macrauchenia herd have gathered in the open and are browsing in a mass of mimosa bushes. Normally these animals specialise in the shrubs and trees, using their extraordinary prehensile noses to pluck tasty leaves off branches. But in this time of plenty there is no need to work so hard and the flowers are an additional treat. As usual the herd is nervous. Even though these are powerful creatures, with some adults growing to over 10 feet tall, they know they are well matched by the hunting tactics of the sabre-toothed pride. As they move forward, plucking at the flowers, their heads bob up and down, scanning the horizon for danger. Of course, the smilodon are aware of this and so the four females are approaching with bellies almost scraping the ground, their muscular shoulders below the level of the grass. Through the blizzard of seed heads they keep a watchful eye on the movement of the herd.

Three of the females work their way quickly to the east of the macrauchenia; the fourth moves to the west and settles down to wait. Soon the first three are in position. Very slowly they work their way closer and closer to the herd. There are several youngsters near them, but smilodon are one of the few cats that seem just as willing to take on healthy adults as they are to attack the more vulnerable targets such as the sick and the old.

The stalkers get to within 160 feet before they are spotted, then a male brays in alarm. His call is picked up by the rest of the herd and they start to gallop off towards the west. The three cats accelerate out of their hiding places. Quickly the local female gains on a straggler but, just as she falls into step with it and prepares to strike, the macrauchenia lurches away from her. The cat stumbles as she tries to change direction and, by the time she’s recovered, her victim has gained a precious 30 feet. This extraordinary agility for such a large creature is what has saved many a macrauchenia. Unfortunately not this one. Its change of direction takes it away from the herd and right in front of the hidden fourth smilodon. It takes only a couple of strides to bring the cat beside her victim and, before it can react again, she strikes. She leaps on the herbivore’s flanks, sinking her claws into her shoulders and neck. The weight and power of the smilodon topples the macrauchenia and both animals collapse into a shallow pond in a spray of muddy water.

The herbivore kicks vigorously, but the cat is careful to throw her body clear at the front end of her victim. Keeping one paw firmly on its shoulders, she tries to anchor its head with the other. A second huntress arrives and together the two cats hold down the struggling prey. The first then opens her mouth enormously wide and clamps her sabre teeth on to the macrauchenia neck. Quickly she works her fangs deeper, eventually shearing through her victim’s windpipe, oesophagus and arteries in one go. The kicking stops as the other two females arrive and the pride settles down to feed. To do this they tear at the flesh with their incisors or chew with their back teeth, their giant fangs are of no use while eating.

It’s not long before the brothers appear to claim their share. On approach they bellow and roar to assert their authority. There is still a lot of tension within the pride, but even under normal circumstances the females would be reluctant to give up their prize. Scraps break out and there are a lot of threat displays, but inevitably the males eventually settle on the carcass. While they feed the others have to hold back or risk taking a blow. To make matters worse, other animals such as vultures and foxes, have been attracted to the kill. More significantly, two phorusrhacos have also appeared. Although these giant birds will not challenge the pride directly, they frequently use their speed to dart in and steal food.

For an hour the males jealously fend off challenges as they eat their fill. By the time the females are allowed to start eating again there are four phorusrhacos probing round the edges, as well as several smaller animals such as raccoons. They all know that the smilodon always leave a lot on a carcass because they do not want to risk breaking their long sabre teeth on bones. This gives the scavengers plenty to squabble over.

Over the next few weeks the females settle into the new regime. Food is plentiful and with no cubs to feed one of them soon comes into heat. The males have been waiting for this, although it is the female who makes the first approaches. She rolls over on her back in front of them to signal her receptiveness. The immediate effect of this is to start a fight between the brothers. So far they have cooperated in everything, but only one mate with the female and the decision has to be made with a show of force. This is something that pride males seem to be able to work out without injuring each other, next time it may be the other brother’s turn. For now, the winner will spend the next three days escorting the female around their territory mating regularly every hour.