Disclaimer: The world of Attack On Titan belongs to Hajime Isayama. I'm just doing my own thing off in the corner.
Once, man was the most dangerous creature. They killed prey for food, predators for hunting. Until one day, out of nowhere, a creature appeared that was only interested in eating them. In response, mankind disappeared behind a huge wall.
Even after that, these great beasts show no interest in anything else. Man is their only prey. Without anything to hunt, they roam the area surrounding the walls, ignoring all else. Perhaps they are looking for strays to wander into their reach.
The other animals don't mind. The great creatures don't hunt them, and with man gone, they can prosper. Deer and wildcats, who once lived their lives in hiding, become bolder. Bison, hunted nearly to destruction, begin to range back into the territory they had fled. Packs of wolves roam freely.
One pack is different from the others, a holdover from the days long since when all animals were bigger. Their legs are longer than the lesser wolves, their jaws stronger, their muscles thicker. These wolves are elite hunters, although they won't hesitate to drive other beasts from their own kills. Their alpha is the undisputed king outside the wall.
Like any king, he ponders how best to use his domain to benefit his family. In particular, he wonders about the great beasts. The creatures are enormous. One carcass would surely feed his pack for a long time. Even if other scavengers plunder the kill, there will be enough.
He considers this as he snaps up a rabbit. One gigantic beast passes in front of him, some distance away. This one won't do. Even for these mammoth wolves, it's too big to kill.
The thought lingers in his mind. A bison is bigger than a wolf, but it can be brought down, and it's good to eat. The great creatures don't hunt, and so they must be prey. He ignores the small thought that their scent isn't quite right.
One night he spots a smaller great creature, moving oddly slowly across the plain. It's still much bigger than the wolves, but this one is small enough that they can take it down. Perhaps it's a cub. The wolf raises his head and howls. His packmates, scattered amongst the trees, howl in return. It's decided. This will be tonight's prey.
The wolves circle around the creature. It doesn't seem to be aware of them, even though they have no shelter here to hide their approach. It emboldens the wolves, and they charge, snarling. The great creature still doesn't notice them and tries to continue walking. A beta wolf, the brother of the alpha's mate, barely avoids being stepped on. At least this beast is slower with its feet than deer are. Most of the pack carry scars from being kicked by a deer's sharp hooves.
The wolves can't tear out the great creature's throat, even if they jump, but there are other ways to hunt. The alpha female sinks her teeth into the back of the beast's leg, showing her pups how to cripple their prey. They're old enough now to accompany their elders on the hunt and learn to feed themselves, but they're still too small to help take down a creature like this one. They watch as the older wolves tear out chunks of flesh from the creature's hamstrings and tendons. It's not long before the beast topples forward. It even falls slowly.
The wolves crowd around, ripping at its throat. The creature flails, refusing to die. The wounds on its legs slowly disappear, but it's not coordinated enough to get up, not with the wolves still attacking.
They can't kill it like this, though. Even though they've opened the creature's jugular and windpipe, it keeps struggling. The wolves are baffled. They've never encountered a creature that can survive this.
One young female, tired of trying to push her way in to the cluster around the throat, circles around the creature's head and sinks her teeth into the back of its neck. The creature jerks sharply.
The alpha sees that she has found a weakness. He leaps over the creature's body and joins her, his daughter from a previous litter. His larger jaws tear deeper into the back of the creature's neck, and together he and his daughter finish it. It's time to eat.
He closes his jaws and tears away a chunk of flesh. He tosses it and catches it at the back of his jaw. It disappears between his teeth.
The wolf can't frown, but he jerks up another bite. This one, too, vanishes before he can swallow.
He takes one more mouthful. This one he doesn't try to eat. He just holds it and waits. It's gone in moments.
Around him, his pack is having the same trouble. They try to eat, but the meat won't last long enough. The carcass itself is dissolving, mist rising from the remnants. The pack will go hungry tonight, even though they spent energy in the hunt.
The alpha raises his head and snarls. The other wolves know what he feels.
There will be no more hunting of the great creatures.
Time passes. The seasons change, and change again. New generations of mammoth wolves grow and hunt, forming their own packs. The lesser wolves have been driven off to find other territory elsewhere. The mammoth wolves feed mainly on deer, the most reliable source of prey, or the bison that have been growing in number. If they get a good chance, they might hunt a massive boar. Boars are dangerous, though, to hunters or any beast that crosses them, so for the most part even wolves steer clear. It's better to use only a little energy on easier meals.
Wildcats inhabit the trees. They've been growing, too, over the generations. They still aren't nearly as big as the wolves, but they're big enough that one can kill a deer if it drops onto the animal's back from an overhanging branch.
There's another kind of creature that roams the area sometimes. Running animals, bigger than deer, but not quite as fast. They have bigger heads and strange shapes on their backs. Many of them pull large objects behind them.
They've been appearing more and more lately.
The wolves watch them from among the trees. It soon becomes clear that the shapes on their backs are another species of animal. When the herd comes close to one of the great creatures, the smaller animals leave the deer-like beasts and soar through the air like birds or bats. They kill the great creatures far faster than the ancestors of these wolves. It's useless, of course. As long before, the carcass vanishes before the hunters can feed. It seems they realize this, as the smaller beasts return to the almost-deer without trying to eat.
The wolves don't understand. Why kill if you aren't hungry?
It doesn't matter. They're more interested in the creatures that aren't deer. They have more meat on them than deer. They smell like living creatures, with blood and sweat. What will their meat taste like? Will they be good to eat? They are strange creatures, these animals that let other beasts ride on their backs. But they smell like prey, and they have no antlers or horns.
As they run, the beasts stay close to their herd. They don't stop to graze or drink. It means there are fewer opportunities for the wolves, who continue to watch and wait.
The smaller beasts, they see, are a strange patchwork of colors, with dark uppercoats, tawny forelegs, white bellies, and grey hind legs. Most have short manes of varying colors on their heads. The wolves don't care about them. They don't look like they have much meat on their bodies. They seem more like the tree creatures the wildcats usually eat than anything the wolves interact with.
A chance comes when a group of riders leave the not-deer to kill two of the great creatures. The not-deer slow, waiting for the other beasts to return.
The wolves leap forward, snarling. The not-deer see them instantly. White shows all the way around their eyes. They hesitate for just a moment before long-buried instinct prompts them to bolt.
It's too late. Some of the pack have circled around and block their way. Two not-deer juke to the side as the wolves snap their teeth and get away. The wolves let them go. One will be enough.
They close in on the remaining beast, circling to block its escape. The creature swings its head around to watch them. The whites of its eyes show, but it doesn't seem afraid. Instead, it screams a challenge.
The wolves pause for a moment. They haven't seen this reaction before. One of the young ones from the last litter, barely more than a puppy, charges forward anyway. He lunges, clearly hoping to close his jaws on the beast's throat.
The not-deer crouches back on its hind legs and strikes out with the fore. There's a heavy thud, and the youngster yelps and skitters back on three legs. The older wolves see that although the beast's hooves aren't as sharp as a deer's, they're much harder, and they gleam oddly in the light.
This will have to be a coordinated attack. Dart in from all sides, and give it as few chances to kick them as possible. The older wolves watch for openings before leaping in to bite, but bite they do.
Another youngster leaps for the beast's back like a wildcat. The creature twists its body as it jumps, dislodging her instantly and tossing her away. She regains her feet and lunges back in. She approaches from the side this time and tears a chunk of flesh from the top of its foreleg. The beast lurches and swings its head around to bite at her, but an older wolf takes the opportunity to latch onto the beast's neck. The free wolves target the other legs, and soon their prey crumples to its knees.
A wildcat sees two animals, like the ones that migrate through her forest from time to time. These have been separated from the herd. She considers them from her perch in a tree.
The two alphas begin to feed first. Their siblings and offspring soon join them. There's meat enough on this animal for all of them.
A yipping sound interrupts them, and one of the smaller creatures – a rider – swings down to them. This one has a tawny mane. The wolves bristle at it and growl. This is their kill.
The creature yowls at them, brandishing its forepaws. It appears to have one very long claw on each paw. The wolves aren't impressed. Such long claws would surely hinder movement more than they would help in hunting. This beast is balanced on its hind legs to keep the claws from getting in the way of its motion, but it would be very easy to knock an animal like that off its feet.
The young wolves keep eating, anxious to fill their bellies before the others drive them away. The alpha male, though, approaches the strange animal with his ears flat and a snarl on his lips. He won't let this creature stop his pack from eating their fill.
Another beast joins the first. This dark-maned one is no bigger, but it has eyes like a predator. The other adult wolves and the strongest of the puppies raise their heads.
The newcomer lays a paw on the first creature's shoulder and makes a soft sound. Its companion whines in response. The dark-maned one growls slightly.
The wildcat eats quickly. Often wolves or a boar will drive her away from her larger kills, and this one had put up quite a struggle. She has the future to think about.
The tree creatures have retreated, joining company with their pack. Most of the pack are mounted again on not-deer, some of them sharing. One of the others, bigger than the two who faced the wolves, lets out an earsplitting whistle like a bird's shriek. Another echoes it. They don't seem to get the response they wanted, and after conferring with their pack the two set off on their own.
The wolves don't care. They have their food, and it's time to feast.
The wildcat hears the sounds of a creature making its way through the forest. She raises her head to listen better. In a moment, she slinks into the shadows for one of her many hideaways.
The interloper is a small group, two strange animals on the back of another beast like the one she killed. One of them senses her kill and jumps to the ground. It uncovers the carcass – she growls, deep in her throat, too low for them to hear. Even if she were louder, they probably wouldn't hear, because the beast begins to yowl.
The one that stayed mounted chitters at it. The beast on the ground responds. The other animal makes a noise again, louder this time, and the first joins it on the back of the third creature. The group disappears into the woods.
The cat continues to watch from her shelter. She doesn't move, even long after the sounds fade away. Just in case, she won't return to her meal just yet.
The not-deer and their riders return to the wall. The wolves and the wildcats continue to hunt as they need. Deer and bison forage and try to band together against their predators. New generations are born and grow up, and watch as more and more groups of the strange creatures come into their territory before returning to the walls.
And the giant beasts continue to wander, feeding only on one kind of animal while ignoring all the rest.
A/N: This was born after a discussion with AutumnMobile12 about giant animals outside the wall. (By the way, if you haven't read AutumnMobile12's Levi squad fic Tavern Ventures, you really should.) Originally it was just going to be about the wolves, but i felt like wildcats would also be thriving, so i worked them in a little. I also wanted to include European bison, which have been hunted nearly to extinction in the real world. They'd probably do pretty well in this setting.