Pretentious Introduction

I’m not a biologist or an expert on anything that has ever existed in the universe ever (except for stuff I made up) by any means, but I study it often on my own because I have nothing better to do with my life. I’m going to brief you on the basics of an ecosystem, and what a fantasy animal will need to survive, if you’re going to go so far as to make up your own animals (and if you are you’re really cool). I tried to fact-check as best I could here but I’m very bad at explaining things clearly and probably misread something along the way. A large amount of this is recollections of what I learned in biology and zoology classes, backed up by my good friend Wikipedia.

So, I’ll start with niches.


In an ecosystem—like a coral reef, a desert, or mountains—each animal occupies a set niche. The niche is pretty much what an animal eats and where it lives, its set place in the ecosystem and where it belongs in the food chain. If you knock out an animal’s population, its niche will have to be filled by another animal.

Example: Deer

Deer eat grass and weeds, so naturally they will go to where they will find this type of food, or will be born in it because their parents came to where they found food. If there isn’t another ruminant animal in the area, the niche is unoccupied, and deer who move into the area will move into that niche. If another ruminant moves into the area and there isn’t enough food, there will be competition between the two species, and whoever manages to push out the other animal will be the new occupant of the niche. If a shepherd moves to the edge of the forest with his flock of sheep, the sheep are probably going to push the deer back into the deeper woods, because they now have strange, woolly competition from their strange, woolly cousins.

However, if a goatherd were to move to the edge of the forest with his flock of goats, the competition pressure on the deer would be a little less. Goats are browsers—they’ll eat grass, but they’ll eat the leaves of shrubs too. Actually goats eat a lot of things they shouldn’t eat but that’s another rant entirely.

What about things with similar diets that are not brought by humans/not ravenous invading ruminants?

Rabbits often live in forests, and they eat vegetation as well, but their populations are controlled by human hunters or carnivorous things (as with deer). The rabbits are so small though that their territory is quite small as well, and rabbits and deer can coexist without much trouble. The trouble with the sheep being in the same area is that there are usually a lot of sheep in a herd, and in a large concentration they can chow down a small area in no time at all. If the sheep were evenly distributed over a large area, there would be less of an issue with there being enough grass for deer and sheep to eat.

The point is that if their niche is being overtaken by another animal of similar size and similar niche, such as antelope or sheep, deer will seek food elsewhere. Do you like to fight other shoppers at the grocery to get the last box of Captain Crunch? And then do you like to get kicked in the face afterwards so you drop it and you don’t get the Captain Crunch anyway? Deer don’t like that either.

Speaking of food, let’s talk about what animals have to get their food, and another things they have to survive with.


All creatures need something such as speed, stealth, size, armor, a weapon, or a combination of those, to survive. They have these as adaptations to their environments. Cheetahs are a paragon of speed on land, making hunting easier. Cuttlefish change color to blend in with their environments. Elephants survive because they’re just too huge for most predators to take down. Rhinos have thick skin like armor. Sharks have jagged teeth for munching on their food and biting whatever tries to bite it.

Example: Deer are actually quite dangerous when sufficiently enraged

Deer (at least all the ones I ever knew) didn’t want to be eaten, so they go where they will find cover. A forest with a mix of coniferous (pine) trees and deciduous (pretty much every tree that is not a pine) trees, with a few clearings for grass to grow, is a good place for a deer to live. A deer also has long legs and can run quite fast, allowing it to dart around trees and be hard to hit with an arrow. It has flat teeth, allowing it to chew its grass into a pulp. Its ears are very sensitive to the slightest sound, making hunting one a little difficult if you happen to step on a twig or rustle a shrub or shoot yourself in the foot. It also has antlers, which means a painful headbutt if you make a buck angry.

Since I’m getting bored with the deer example I’ll use some other cool animal: everyone’s favorite fast cat, the cheetah!

Example: Cheetahs can run faster than you and your grandma

Cheetah adaptations include a lithe body, incredible swiftness, and lots of jaw strength. A cheetah isn’t too big, but it definitely has speed and a weapon, located in its mouth. That’s all they need. If you’ve ever watched a video of a cheetah hunt, sometimes they first wait for a gazelle to come into view (stealth in action, like what a lion does). A gazelle can run fast as well, so a cheetah must work hard to make the kill. Its thin body is more aerodynamic and speedy than that of a more heavily-built tiger or leopard. Once the cheetah pounces it administers a bite to the gazelle’s neck and holds it there until it dies. Then the cheetah can eat it. Victory for the cheetah!

If a cheetah were in the forest, it would probably hunt deer as well, but its speed does not offer too much control, and the cheetah would probably hit a tree. That’s why it lives in the savanna. Not because it knows consciously that it would hit a tree in a forest so it stays out of the forest, but it hangs around the plains because of the wide open space, and there is prey there. It won’t crash into a tree if there aren’t any trees where the gazelles are, and the grass provides cover while it’s sneaking around. Here is a video by National Geographic that shows a couple of brothers’ attempts at getting a gemsbok calf for dinner. This one explains its various adaptations for speed.

Example: Jellyfish float like butterflies and sting like bees

And an underwater example, so I’ll stop using so many mammals. Jellyfish are not fish—they’re cnidarians, and they look pretty harmless. They resemble plastic bags with tentacles. But the tentacles have things called nematocysts, which are stinging cells. Most jellyfish aren’t very big, so it doesn’t have a size advantage. (A rare example is a Lion’s mane jellyfish.) It doesn’t have speed; it swims by squeezing its body to move forward. A person can out-swim one pretty easily. Its body is squishy and feels like gelatin. It doesn’t even have a brain or blood. But those nematocysts are very painful, and the nematocysts of some species are deadly. Even these are not completely infallible—there’s a kind of fish that swims in the tentacles of man-o-wars, a dangerous colony made of jellyfish relatives called medusas, without any trouble at all. Loggerhead turtles can make an easy meal of the man-o-war. Most jellyfish don’t have to worry about much though, since in general animals are smart enough not to go near one. Here is a video explaining some more about jellyfish, and some shots of a cute kind of tiny jellyfish.

Example: Cuttlefish, which you might not see unless you get very close

One of my favorite animals is a cuttlefish, which like a jellyfish is not actually a fish (it’s a mollusk). They eat things like small crabs and small fish. Most kinds of cuttlefish are pretty small except for a larger variety that lives in the Great Barrier Reef. They’re related to the squids and look a lot like them. Their size isn’t an advantage because dolphins aren’t afraid of munching on them, and it probably couldn’t outswim a dolphin anyway. It’s squishy and if it smacked you with a tentacle it wouldn’t hurt. They do have a pretty cool way of surviving though. Cuttlefish can change their colors in less than a second by using special cells in their bodies called chromatophores. They can blend in easily with their surroundings by turning the same color as the sand or coral nearby. It can also make intimidating displays of weird rippling colors, letting you know you’re bothering it. You can see a freaked-out cuttlefish in action here and a segment from NOVA about cuttlefish.

Example: Humans, cooler than you might know

We’re actually pretty extraordinary animals. For what seems like no reason whatsoever, some ancestor of ours decided to stand up and use his hands for something other than walking on. Walking upright was a large evolutionary step, if you believe Darwin was correct. Our brains got larger this way (compare the brain size of a four-legged animal to a human brain’s) and our hands got around to painting the walls of caves and making tools. Nowadays humans are using them to type things and slice fruit and punch people. We basically survived by being really smart.

Now, let’s look at the food chain, or at least the parts that involve the deer, in this foresty environment.

The Food Chain

If you didn’t pay attention in school, I’ll give you a quick rundown of how the food chain operates, using a simple example in the forest environment. If you remove a step or two, the intricate balance is lost.

It all starts with the sun

This is where the grass gets its energy. The grass is a producer, meaning it doesn’t eat stuff to get its energy, it uses sunlight and water to make its food. Of course there is a lot of grass because there is a lot of stuff for it to make food with. The more food there is, the bigger a population gets. Humans are an extreme example of this, except that humans have also slapped once-common diseases into submission as well as harnessing agriculture, something other animals can’t do. If you’ve ever wondered why humans are so numerous, now you know.

The grass is then devoured mercilessly

The deer is a consumer, which is the opposite of a producer in that it has to eat stuff to get energy. A deer is also an herbivore—it only eats plants. Deer belong to the suborder Ruminantia, which also includes sheep, antelope, goats, and cows. They are cud-chewers, which basically means they eat grass, throw it up in their mouths, and eat it again so they can extract every possible nutrient from it. It’s gross, but ruminants don’t think so. So the deer is usually found munching grass and wandering around in its foresty home. It have to eat a lot of food because grass doesn’t have a lot of energy compared to the deer.

The deer is then devoured mercilessly

The deer is then hit in the brain with an arrow by a human in a fantasy-type world, where its skin is tanned and turned into leather and its meat salted and stored for the winter. Also its antlers might be used for things like tools or hanging above your fireplace. Humans don’t have to eat a lot of the deer to get enough energy, because the deer already has a load of energy stored from eating a ton of grass. And if something were to eat a human, like a horrible ravenous manticore, it probably wouldn’t have to eat too many to be full. We humans are quite energetic if you’ll pardon the terrible pun.

So that’s how a food chain works. Armed with this information, you can pave new trails in fantasy creature creation and possibly kill someone with it. Good for you.

Playing God

When making a fantasy creature, think of its habitat and its niche. What kinds of animals live in this habitat? What niche will this fantasy creature belong to? What does it eat? Will it kick out the native population of creatures of that same niche? Because, after all, you can’t have a lot of one kind of ruminant and a lot of another kind of ruminant in a small area. If the habitat is too small, then one of them is going to have to go.

Example: Dragons

Let’s go to a mountainous environment, and pretend that’s where dragons live. A dragon is a carnivore, so it would probably push back any other carnivores, such as mountain lions, into other parts of the mountains, because what chance has a mountain lion got against a dragon? Also, a dragon also usually has to have a lot of territory, because it’s so huge.

Example: Salamanders

Salamanders, the fictional kind, live in fire. Yes, fire. If a fantasy creature lives in a normally inhospitable environment, like fire, you don’t have to worry about niche. The salamander has an unconquerable niche in a fantasy setting unless you happen to create another type of fire-dwelling creature. (Real salamanders would die if you put them in a fire, so please don’t do that.)

Example: Sea Monsters

Some sea monsters depicted on old maps are beasties that look like serpents, only really huge. If there were any carnivorous whales or sharks near the sea monster’s habitat, they’d probably have to seek meals elsewhere because the sea monster would be eating all the fish. It might even eat the whales and sharks themselves if it wanted to. As a twist you could make it a filter-feeder, but this would remove baleen whales from the sea monster’s habitat.

The Process

Now I’m going to walk you through two different creatures I made up. One is a swordolphin, and the other is an annoying flour bug.


I had to make up some kind of animal to live in the ocean of an Earthlike world. What kind of animals live in the ocean? According to the primordial soup theory, life itself began in the ocean, so there must be a lot of creatures there. The ocean covers nearly three-quarters of the world. The diversity of life in the sea is quite wide: sponges, whales, hydras, seal lions, fish, worms, sea slugs, starfish, coral…

I decided to base the creature on a dolphin, but it would be like 30 feet long instead. I gave it small but sharp teeth and a long “nose” like a marlin’s, and I had it practice the same hunting technique as a marlin—hit a fish with its nose, and while it’s stunned, go scoop the fish up in its mouth. I also gave it two dorsal fins like Giglioli’s whale, a characteristic that does not occur on any known animal. The swordolphin occupies the niche of “eater-of-big-fish”. I made it a solitary animal, only gathering together to mate, with the mother eaters-of-big-fish taking care of their baby monsters until they are big enough to survive on their own. I figured these creatures would have a lifespan of maybe twenty years, and they mate a few times over the course of their lives. It’s essentially a giant mammalian swordfish. The animals that would probably not be around are other kinds of dolphins, carnivorous smallish whales, and maybe marlins.

Annoying flour bug

I wanted to bother the people that lived in the farming village at the feet of some large mountains, but I didn’t want to set a plague on them. So I went with making a type of beetle that eats grain and is often found in their flour mills. I don’t know a lot about beetles, because frankly there are just too many of them. But they have quite a few things in common. They all have a tough exoskeleton that doesn’t protect them from the bottoms of your shoes coming down hard upon their backs, but it prevents ants and things from nibbling on their soft innards. They have antennae that they use to feel around, and all have six legs. A lot of them can fly.

(Do you have the heebie-jeebies right now? I do. I hate bugs.)

So my made-up beetle, I said, would be smallish and a bit easy to completely miss if you aren’t looking for it. It would maybe be the color of the grain it’s so fond of. So I made it vaguely the size of a grain of wheat, and darker than a grain of wheat. Just enough to blend in. I also made its antennae a bit small so it could blend in even more with its food. And for good measure I gave it wings, and they reproduce by having their eggs fertilized and buried in some loose earth near food until the little baby beetles hatch and crawl out of the dirt. Now the people of the village have a pest to look out for, and I’m going to have the farmers hire people in the village to pick out the beetles and squish them for a quick buck. Unfortunately some get overlooked and probably turned into flour.

Recap, or alternately, the tl;dr version

So there’s a basic creature creation from start to finish. That swordolphin is kind of simple, but you can get about as complicated as you want, so as long as…

Except you don’t have to take any of this seriously and I wasted about twenty minutes of your life now. I should be ashamed of myself. You also don’t have to think this out as much as I’ve obviously done, because not everyone has to be a geek nerd dork biologist wannabe and completely overexplain every little thing like I just did.


  1. SlyShy on 13 September 2008, 15:39 said:

    Nice article. I agree it’s really important to keep track of how species effect the surrounding habitat. To take an example from our favorite author again, you can see a very clear example of species overcrowding in the Boer mountains as Eragon and Arya traveled to Tarnag. There were what, like five unique species, and three mundane species of animals there? For one thing it is ridiculous to even have all the “special” animals in your series all in one place, but it’s also silly how you have these extremely powerful creatures all crammed into the same mountain.

    Another issue I’d be really interested in hearing you address is overpopulation. Some species, like dragons, are always written to be very long lived. But if, at the same time, they are laying several eggs, how have dragons not over populated? Most authors don’t consider the issue in enough detail, and have the annoying “dragons are dying out” trope.

  2. Kitty on 13 September 2008, 17:11 said:

    Thank you. I was going to put in something about how Paolini made dragons the wrong way but it was already really lengthy…

  3. SlyShy on 13 September 2008, 22:42 said:

    Could always write a second article. ;)

  4. Rocky on 15 September 2008, 15:11 said:

    An excellent article, Kitty. This was obviously not copypaste material, but information you know and use as second nature. Fantastic work. Ecosystem is actually something I haven’t thought about very much at all, so this was definitely an eye-opener in many aspects.

    Looking forward to your future articles.

  5. Zahano on 13 October 2008, 00:09 said:

    Great job, Kitty!

  6. Max on 29 October 2009, 16:44 said:

    Heh, I’ve got a race that has an incredibly long lifespan, but they’d solved overpopulation long ago when they started their bloody gladiatorial fights.

    Also, the females have a very small amount of egg cells, so each female can only give birth to about 3 or 4 children.

  7. Diana on 14 November 2012, 18:14 said:

    I just wanted to point out that flour beetles exist in real life. They’re called Tribolium, and you did a very good job of applying your logic so that your fantasy flour beetles bear a striking resemblance to the real life example. The main differences are that Tribolium rarely fly even though they have wings, and their eggs are laid in the flour/grain and the larvae crawl around in it. Makes for some serious ickiness if you’re about to make a nice cake with that new bag of flour, only to open it and find that it’s been infested! (Unrelatedly, the larvae are great for leg regeneration studies. It’s what I’m currently doing a research project on for my bio professor.)

    Also, while I love how you thought carefully about niches, like you illustrated with the rabbits/deer, often having a niche that’s just different enough means two creatures can coexist. And the ocean is an example where one has to tread carefully—apparently there’s this paradox about how the ocean supports much more biodiversity than one would think possible. Something about how all the plankton have such a short lifespan anyway they reproduce like whoa and don’t have to worry too much about competition because chances are they’ll get eaten up almost immediately anyway. I don’t remember if this ends up helping creatures that aren’t plankton, but if it does, then there’s a decent chance that a filter-feeding kraken can coexist with baleen whales. At the very least, you could use that logic to handwave why creatures in the same or similar niches can coexist in some cases, even outside of the ocean.

  8. Tim on 15 November 2012, 04:24 said:

    We’re actually pretty extraordinary animals. For what seems like no reason whatsoever, some ancestor of ours decided to stand up and use his hands for something other than walking on.

    No, that’s not what anyone says happened.

    Ok, start at the beginning; the common ancestor of humans and modern primates was an arboreal primate. It had hands adapted for gripping branches and an upper body adapted for swinging, forward-facing eyes for depth perception, and a brain adapted to recognising patterns so that it could figure out what was a branch and what wasn’t while swinging at speed.

    Now, even this primate could use its hands to grip objects (other climbers such as squirrels and raccoons can do that perfectly well) which is an advantage in itself because being able to lift food to your mouth means your head is upright and looking for things trying to jump you. But a knuckle-walking primate has to choose between either moving or using its hands because its legs are short and not adapted to standing upright. While this is fine up in the trees, when foraging on the ground it makes you vulnerable. But hands gave you something of a trump card.

    See, primates are social creatures, and we can pick things up. So we used our monkey minds to figure out that predators didn’t like a group of ten or fifteen hollering assholes hucking junk at them, and would only still try to eat us if they were absolutely starving hungry. Along with this, our dexterous hands, monkey minds and depth perception allowed us to pick things up and use them. Modern chimpanzees make use of simple tools like rocks and sticks to do things they can’t do with their own bodies, and our ancestors did the same.

    Now, using tools in the animal kingdom is basically playing with the cheats on, and evolution favoured the primates who were best at using their hands, meaning those with straighter spines who previously would have made fucking useless lemurs because there was no call for a straight spine up a tree. Even a slightly upright posture frees both hands, and then you can carry objects.

    Carrying objects is even more awesome than throwing them! Suddenly we didn’t have to go to food as a group, we could camp out somewhere safe and send out the stronger monkeys to bring stuff back for everyone to eat. And with our pattern-recognising monkey minds, monkey voices and monkey hands, we could coordinate ourselves in any number of complex monkey plans.

    Then a particularly smart monkey realised that certain things tended to become fire, using its pattern recognising monkey mind, and tried to repeat the pattern. Being able to make fire is the animal kingdom’s super cheat mode because everyone is hard-wired to be scared of fire, even things trying to eat your children, and as diurnal creatures we naturally fear darkness because things try to eat us then. So, we become less afraid, they become more afraid. This was a recipe for monkey success.

    Then we discovered that if you put some kinds of stuff on walls it stays there, and we used our monkey minds to invent patterns and told each other what the monkey symbols meant. Suddenly any monkey who learned the symbols could draw on the wisdom and experiences of generations of monkeys and learn that Crocodile Not Friend without having to experience the unfriendliness of the crocodile. Being able to store the collected knowledge of hundreds of monkeys meant each monkey was now as smart as a hundred monkeys. Everyone knew if you pounded tough food with rocks you didn’t have to chew it and that lions didn’t like having sharpened sticks thrown at them even slightly and that if you cut animal fur like this you could put it over your head and it wouldn’t fall off. This meant we didn’t need our big monkey jaw or a lot of our monkey strength or our monkey fur anymore, so we gradually became less monkey and more like we are today.

    You can see traces of our arboreal past in a lot of the symbolism we attach to things; trees represent life and safety, good is up and bad is down, dragons being a cultural symbol in civilisations which have never met (the traditional dragon being a mixture of snake, lizard and hunting bird, three things that happen to eat monkeys), etc.

    So my made-up beetle, I said, would be smallish and a bit easy to completely miss if you aren’t looking for it. It would maybe be the color of the grain it’s so fond of. So I made it vaguely the size of a grain of wheat, and darker than a grain of wheat. Just enough to blend in. I also made its antennae a bit small so it could blend in even more with its food.

    I think you’re considering it too much in terms of the artificial niche you’ve put it in and not enough in terms of the niche it occupied before human civilisation came along.

    Let’s say I’m a beetle that eats grains. Right, so I live in a field where grain-producing plants grow, and I roam around looking for fallen grains. My main threat here isn’t human farmers looking for me, it’s creatures like rodents that are looking for grains but will happily eat me if they find me. This means disguising myself as a grain is pointless because I’ll just be eaten for a different reason; I’m best off blending in with the soil and having the ability to run fast and hide, dig down in the soil or fly away. This would generally favour a dark colour that will blend in with the ground, not one that matches the grain.

    My other possible survival strategy would be to be noxious to eat so animals avoid me, which is actually good from the perspective of farmers needing to find me since grinding up noxious beetles will spoil the flour.

    Now the people of the village have a pest to look out for, and I’m going to have the farmers hire people in the village to pick out the beetles and squish them for a quick buck. Unfortunately some get overlooked and probably turned into flour.

    Actually if you’re waiting that long it’s way too late. The problem with flour beetles isn’t that they add valuable protein to your flour, it’s that you end up with flour that’s full of beetle shit.

  9. Tim on 16 November 2012, 05:29 said:

    Oh, also

    Humans don’t have to eat a lot of the deer to get enough energy, because the deer already has a load of energy stored from eating a ton of grass. And if something were to eat a human, like a horrible ravenous manticore, it probably wouldn’t have to eat too many to be full. We humans are quite energetic if you’ll pardon the terrible pun.

    It doesn’t really work that way. Animal metabolisms generally use less than 50% of the energy that goes into them to do useful work, with the rest being lost as heat or excreted. This means that as you go down a food chain the energy density of each successive animal decreases, which is why you don’t see high-order ultra-predators like dragons.

    While it might looks like a deer eats a lot of grass, a given mass of grass contains more useful energy than a given mass of deer. The reason we don’t all eat grass is that a deer’s body turns grass into things that can be used to run a deer, so some animals cut out that phase because things suited to running a deer are just fine for running a wolf.

    Food chains rarely exceed four stages; producer, primary consumer, secondary consumer and tertiary consumer. An example of that would be a plant, which is eaten by a herbivorous bug, which is eaten by a scavenging mouse, which is eaten by an owl. While something might eat the owl, nothing makes a habit of eating owls because it’s easier to eat mice and cut out the middle man.

    Consuming humans for food would be like humans feeding deer to wolves and then eating the wolves. While a dragon or manticore wouldn’t say no to a human it could take easily, humans are too much hassle for too little reward, and they’d mostly compete with us to eat the deer.

    The salamander has an unconquerable niche in a fantasy setting unless you happen to create another type of fire-dwelling creature.

    Well, there’s a certain problem with that niche since there aren’t many environments that are on fire all the time, and presumably something with the ability to extinguish fire would be able to eat them pretty easily.