In order to make an environment more hazardous, creators of fiction will often include aggressive predatory beasts that occur in far larger numbers than should be possible given the environmental conditions shown. In Real Life, the larger a creature is, the more energy in the form of food from a suitable source it must consume in order to both grow so large in the first place and to sustain itself on a daily basis. If it is very active it will need even more calories just to survive. As a general rule, 100 prey animals are required to sustain the presence of just one individual predator. Despite this, there will often be a veritable horde of wild, aggressive beasts that roam a desolate wasteland or almost lifeless underground tunnels without having prey to feed on and without attacking each other. Such beasts will often be absurdly persistent when encountering humans, attacking them seemingly out of hunger that overcomes all sense of self-preservation. This occurs even if their fellows fall like flies around them, and most will never pause to gorge themselves on these fresh bodies that should appear a ready and far less risky food source to them. If they do pause to eat their own dead, it'll be played for horror, to make them seem even more ravenous.
Such ecosystems do exist, usually where humans have not caused any impact: coral reefs in Real Life, when kept perfectly pristine, play this trope to a T, to the point 85% of all biomass are sharks.
Common in post-apocalyptic fiction and on Death Worlds; in contrast to many (because the oceans are major exceptions) Real Life cases, large predators in these kinds of works seem to be less susceptible to the kind of events that should cause them to be severely depleted or go extinct than the smaller creatures they normally feed on. In fact, they often mutate into something far more powerful than their original form while at the same time getting by with less sustenance.
Note that not everything that attacks humans needs necessarily be carnivorous. Some larger herbivores like cape buffalo, rhinoceros and hippopotamus are territorial and aggressively defensive. Many creatures will attack something they think is threatening their young.
The ecological equivalent to More Criminals Than Targets, a very similar situation in fictional crime settings.
- The world outside of the walls in Attack on Titan is considered a hellish environment due to the overwhelming abundance of the Titans, who only consume humans (with a single-minded persistence), but don't actually acquire nutrition from it, meaning their vast numbers have been untroubled by a lack of prey for a century. We get an answer to this eventually: namely, that the predators were the prey.
- Pitch Black occurs on a Desert Planet, and one of the only two species the protagonists encounter are predators. They arrive to the surface in numbers which a desert biome couldn't possibly provide enough food for. To make things worse, the animals can only hunt in the dark, so their only opportunity to come to the surface for prey is one month in 22 years during an eclipse of the Binary Suns. However the world is littered with the skeletons of long dead animals, some of which were massive, but has no current signs of life. It's strongly implied the unchecked predator population has rendered their surface prey extinct. Which also explains their rather keen interest in the humans. Eventually the creatures even begin turning on each other, apparently resorting to cannibalism to sate their hunger.
- Reign of Fire, wherein the entire non-microbial population of the world seems to be humans and non-cannibalistic dragons the size of whales. However, the dragons are shown to start eating each other later in the movie. Also Lampshaded, as it was stated that the dragons would eventually start to starve and go back into hibernation, which is apparently what happened the first time around with the dinosaurs.
- Daybreakers. The whole point of the movie is that Vampires make up most of the population, and not enough humans. The only humans left are either bred for special blood banks, or rebels that try to avoid that.
- Skull Island, the location of the King Kong movies suffers from this. Carnivorous dinosaurs, other monstrous reptiles and giant insects are everywhere, and the only herbivores are Kong (who, in some versions, is rather an omnivore, as he eats people) who is The Last of His Kind (although in both The Son of Kong and King Kong Lives, another specimen of Kong's species shows up), the Stegosaurus in the 1933 movie, and the Brontosaurus herd in the 2005 movie (the 1933 film's Brontosaurus is either carnivorous or simply hyper-aggressive as it chases down and kills people).
- The 2005 remake is a bit better about this, showing some actual predator-prey relations such as the raptor-like Venatosaurus hunting giant brontosaurs, but there are still far more predators than prey. The companion book fleshes out the environment further by explaining that the entire island is in a constant free-for-all over food, with a lot of the lower-level links in the food chain having specifically evolved to eat carrion, and more herbivores are described than what appears in the film.
- Inverted in Zootopia: It's explicitly said by one of the characters that prey outnumbers predators 10 to 1 in the eponymous city. However, they're not literally predator or prey, just distant descendants thereof, thus real-world predation dynamics don't really apply. Presumably prey species are just in the majority because of inertia.
- In The Tough Guide to Fantasyland by Diana Wynne Jones, she uses this as a key pieces of evidence for the theory that fantasy worlds' ecosystems have been recently ravaged (another is the way piles of refuse around oppressed peasants' huts don't just rot away.) She comes to the conclusion that the systems are re-establishing themselves with humans at the bottom, and everything will be fine.
- Blindsight had an interesting quasi-example in the case of vampires - the human population couldn't expand fast enough to support a population of vampires, so vampires evolved the ability to enter long-term hibernation in between feeding periods so that the human population would have a chance to replenish itself.
- Lamp Shaded in The Lost World (1995), as they actually ask why the island has more predators than the prey should be able to support. The stated justification being that prions from the sheep-based feed they were given caused most animals to die young and be scavenged by the predators. The characters note that this system is doomed to collapse extremely quickly, both due to said carrion being a rapidly depleting resource and because the predators are infected now.
- In H.P. Lovecraft's The Lurking Fear, the mutated deformed cannibals number in the dozens, if not hundreds, while their abode is rather isolated and the number of people who fall victim to them is small. (It's hinted, though, that they have no problem preying on each other...)
- Nearly all animals in the Forest of Septimus Heap are carnivorous (or man-eating). Other animals almost never mentioned.
- In the underground ecosystem of the Railsea, herbivores are stated to be a small, unhappy minority. Everything else tries to eat everything else, including people who touch the open dirt between the rails for any longer than a split second.
- The Tribe of Rushing Water came across this issue in Warriors. It turns out they lived in too comfortable an area. They weren't dying nearly as much as their forest-dwelling peers, so soon the area was overpopulated with cats. This led to the tribe splitting up.
- Gary Gygax recognized that Dungeons & Dragons had this problem and tried to justify it in the 1st Edition Dungeon Master's Guide.
So many of the monsters are large predators that it is difficult to justify their existence in proximity to one another. [snip] Here are some suggestions. Certain vegetation grows very rapidly in the world - roots or tubers, a grass-like plant, or grain. One or more of such crops support many rabbits or herd animals or wild pigs or people or whatever you like! The vegetation springs up due to a nutrient in the soil (possibly some element unknown in the mundane world) and possibly due to the radiation of the sun as well. A species or two of herbivores which grow rapidly, breed prolifically, and need but scant nutriment is also suggested.
- Early D&D also had climate-appropriate herbivores on its random encounter tables. If they were removed it was presumably trimming, there not being much one can do with camels aside from staring at them. On the other hand, getting in the way of a herd of bison is all sorts of exciting.
- Justified in the lower planes - most fiends don't need to eat at all and seek prey For the Evulz - so an infernal environment could have Hungry Jungle with nothing but predators.
- GURPS: Dungeon Fantasy averts this trope, advising GMs to give some consideration to the balance between predators and prey in an ecosystem.
- Magic: The Gathering: The imbalance of Red mana on the shard of Jund means that almost every creature is a predator of some sort, with the lower end being occupied by small but poisonous lizards, goblins, and fungal mutants, and the top of the food chain being reigned over by dragons. This is represented mechanically by the Devour ability, which allows you to make a large creature even larger when you cast it by feeding it with other creatures you control, several of which were designed for just such a fate. The ecosystem of Jund is so vicious and efficient that undead do not exist despite the powerful Black mana on the shard because no corpse lasts long enough to become undead.
- The Fallout series of games have numerous examples of this: nuclear war and subsequent collapse of society has left most of the world a barren desolate wasteland with deadly radiation occuring here and there. Despite the fact that there is little prey for them, giant versions of real critters like scorpions or even flies run around, seemingly attacking only the player character and never any other creatures.
- In Fallout 3, monsters of different species will fight each other, up to and including Albino Radscorpions killing Super Mutant Behemoths if they spawn near each other. On the other hand, the number of predators seems proportional to the player character's level— Giant Mole Rats seem to die out around level 15. This would also happen in random encounters in the previous titles- it was possible to run into a group of wolves fighting with some radscorpions, for example. It just didn't happen as often because the games didn't feature an open sandbox world and the various predatory critters tended to have specific parts of the map that they'd be encountered in- you wouldn't run into both mole rats and Deathclaws in the same area, for example.
- There is a reason for this. Since being irradiated heals mutant creatures, it can safely be assumed that they're radiotrophic (like the real-life Radiotrophic fungus found at Chernobyl). They don't need to worry about living in a low-biomass environment like the desert because they get most of their energy from background radiation, which they're in no danger of running out of anytime soon.
- Metro 2033 has a very strange ecology at work: The surface world has been in the grip of nuclear winter for twenty years, nothing grows there and the air is toxic. The remnants of humanity hide out in old metro stations where the only food sources are domesticated pigs and cultivated mushrooms. The tunnels between the stations are typically infested with hideous mutants that 1) are mostly larger than humans and also faster and stronger, 2) constantly attack humans in order to eat them, 3) never seem to attack each other, despite the fact that there is more meat on their fellows than on humans. A particulary silly example is how the winged beasts called demons will swoop down on human prey that is capable of shooting at it, but leave the far more numerous nosalises (who only have their claws and teeth) alone, even ignoring the bodies of the ones you have already killed.
- In Knights of the Old Republic II, on Telos, there are Cannocks (and Bounty Hunters), which are at the very least hostile and onmivorous, but no "peaceful" or herbivorous creatures. If you point this out to Bao-Dur he reminds you that the planet's being terraformed and the cannocks were introduced to control herbivore numbers. ThenCzerka Corp hijacked the project, released too many cannocks and sent the ecosystem down the tubes. Dxun has no such excuse, though.
- Monster Hunter isn't a perfect example, since you do see herbivores and you do see predators eating each other, but the food chain still seems pretty unbalanced. What are all these giant monsters eating?
- World of Warcraft has some serious cases of this; a good example is the Hillsbrad Foothills. There's bears, yeti and giant spiders all over the place, but no major herbivorous beasts to feed them. There's a lot of areas like this in WoW.
- Most zones in WoW have "critters" which are small creatures (usually herbivores) that players cannot gain loot or experience from. One may think that critters are an intentional aversion of this trope (predatory beasts can occasionally be seen killing them), but they are never present in anywhere near large enough numbers to feed the vast hordes of predators which populate many zones.
- Most Xen wildlife in Half-Life is carnivorous. Headcrabs, at least, are confirmed in the sequel to be omnivorous. And you have to wonder what those several billion ocean leeches in Half-Life 2 are eating to sustain their population...
- Actually averted in Opposing Force. Shock Troopers are herbivores. You can find the plants they get their fruit from scattered around the facility, and can even use a baby tadpole Shock Trooper as a weapon by having it launch exploding acidic balls. How do you reload it? Feed it more fruit.
- The Elder Scrolls:
- Played straight in Morrowind, although a couple of comments and world details imply that there are more types of prey roaming Vvardenfell, the vast majority of wildlife you encounter on Vvardenfell and Solstheim are hostile predators.
- Averted in Skyrim. For every bear, sabercat and wolf pack you come across, you see a lot more deer and rabbits. Whether mammoths are preyed on is unsure, what with giants keeping and protecting them as livestock.
- In The Elder Scrolls Online the Clockwork City's "wildlife" only consists of scavengers and predators. The in-game explanation for it is that there's very little actual plant life in the City (the trees, grass etc. are all metal imitations), and the "animals" are actually Magitek cyborgs (fabricants) or outright robots (like skeevatons or brasslisks) that only exist because the City is meant to be a simulacrum of Tamriel, and Tamriel has animals so Seht put some in.
- Played to extremes in the Borderlands games, because there are no prey animals on Pandora. Everything on the planet is an Extreme Omnivore, and gleefully feeds on everything else on the planet. The closest thing you get to prey on Pandora is humanity, who is just as capable of slaughtering and eating them.
- An interesting variant occurs in the Pikmin series where every last enemy in the game is seemingly a predator to pikmin and pikmin alone. No enemy will ever try to eat another enemy, ever. Taking things even further, some enemies will go out of their way to kill pikmin but not eat them without displaying similarly territorial behavior towards other nearby wildlife. A possible explanation is that most of these enemies actually are herbivores, but view pikmin as plants. The territorial species like wollywogs might attack pikmin because they're a novel and invasive presence in their environment and they haven't acclimated to them.
- The settings of the Dark World and Lorule in The Legend of Zelda: A Link to the Past and The Legend of Zelda: A Link Between Worlds seem to be this. Pretty much every living being in both seems to be some sort of monster out for blood, making you wonder what the heck they actually feed on. It's also a case of More Criminals Than Targets (in both worlds), so how either remain somewhat stable is unknown.
- Final Fantasy XIII: The world of Gran Pulse is awash with dangerous predator-type animals, and the smaller number of herbivores includes the dinosaur/tortoise Adamantoises, which are big enough to step on anything which tries to eat them.
- There are not nearly enough rabbits and deer in Dragon's Dogma to support the many wolves you fight. Which is probably why all the wolves are so emaciated and eager to attack you in the first place.
- The amount of prey animals required to nourish the wolf packs and bears the Inquisitor will encounter in Dragon Age: Inquisition in the same (relatively) small areas of territory would strip the environment bare and cause rapid environmental collapse. There's even a gigantic dinosaur-sized "Great Bear" found in the Emerald Graves and Emprise du Lion that, while much less common than the other predatory enemies in the game, is still far too abundant for a macropredator of its caliber thanks to the nature of the game's enemy respawn system. Naturally, all of these are unrelentingly aggressive to the Inquisitor and crew to an unrealistic degree, but it's suggested in passing that their aggression is due to corruption from demons and the open rifts. Alternatively, they could have come from the Fade, since it's possible to summon animals from there.
- In Mass Effect: Andromeda, there's an insane amount of continuously-reappearing macropredators like adhi and fiends and very few prey species. It might be partially justified by the late revelation that the wildlife of Andromeda was largely bioengineered by the Jardann like the angara were and dispersed across each of the habitable planets to create ecosystems, which also explains why every planet on Andromeda has the same types of wildlife. However, it still doesn't explain why these predators are found in such absurd abundance, unless their vast numbers are consequences of the ecological havoc caused by the Scourge - however, the Scourge happened many centuries ago, by which time the ecosystem should have collapsed due to the lack of plant-eaters. The best explanation is that these species are adaptable omnivores that also fill plant-eating niches and are aggressive towards the player out of hunger and desperation due to their depleted food sources.
- On Alternia, everything is considered unsuspecting prey by everything else.
- The natives haven't gone extinct yet because they all find a wild animal and form a parent-zookeeper relationship with it soon after birth.
- A Fourth-Wall Mail Slot session in Dan and Mab's Furry Adventures states that Furrae's vampires went extinct long ago for exactly this reason— demons, cubi, undead that aren't sensitive to daylight, and dragons are all more effective predators competing for the same food source.
- In the world-famous La Brea Tar Pits, instead of the usual 1 predator for every 10 prey animals, they have the exact opposite. Most likely, a prey animal or two would get stuck in the asphalt and be unable to escape. Most prey animals know to stay away from dead and dying animals, while predators are drawn to them. Which in turn also got stuck and then attracted more predators.
- Similarly, the Kem Kem Beds in Africa (sometimes referred to as "a predator's paradise") is a notable example. This is where the famous Spinosaurus came from, and it was rivaled by many other large carnivores, including other dinosaurs, crocodiles and pterosaurs. The only confirmed plant eaters from the entire formation are two indeterminate sauropods. Apparently, the reason this environment was able to sustain so many carnivores is because of the plentiful amount of fish in the area, which made up the basis of the food chain. Some carnivores (Spinosaurus, crocodiles, pterosaurs) could sustain themselves on the fish alone, while others (Carcharodontosaurus, Sauroniops, Deltadromeus) ate crocodiles, pterosaurs, carrion and even each other.
- In Antarctica, there aren't many, if any plants to eat. As a result, the few animals that thrive there are mostly carnivorous or piscivorous.
- It has been found that many healthy tropical reef systems follow this trope. There are far more predators roaming the waters than there are grazers that they feed on; in fact, there five times as many apex predators as everything else combined. How does this system remain stable? Simple. The smaller fish breed like crazy and the carnivores keep eating them!
- Of course, the base of this food pyramid are eating microscopic organisms that are both photosynthetic, like plants, and yet capable of moving and feeding like animals. Depending how you look at it, the things that feed on this base layer are both herbivores and predators. Even then, however, the vast majority (89%) of the biomass are at the very top of the food web.
- Much of the ocean floor is home to more scavengers than prey. Since the ocean floor is too dark for plants, there are naturally no herbivores either. The base of the food web is the dead organic matter that sinks from the water above.
- Most cities have far more people (we're opportunistic omnivores, pack-hunting apex predators, and megafauna), housecats (obligate carnivores), and domestic dogs (pack-hunting carnivorous megafauna) than the local environment can support. The only way large cities work is by importing food.
- The exceptions are communities small enough for the locals to feed themselves from the nearby countryside and/or through fishing.
- The difficulty in maintaining this trope is one of the arguments used against the existence of the Loch Ness Monster. The waters of Loch Ness are extremely dark, which means there is not much plant life in the loch. The loch therefore cannot support a great number of fish that feed on those plants, and thus not many larger fish to feed on the plant-eaters. Of course, this is assuming that the animal - if it exists - eats fish.
- If you count parasites as predators, this trope becomes almost universal. It requires a large population of deer to sustain a small population of wolves, but a single deer can support thousands of external and internal parasites. Humans and the domestic animals we protect from infestation are the rare exceptions, and only in parts of the world sufficiently-affluent to ensure good sanitation, proper hygiene, preventative medical care, and safe food and drinking water.