Creating original animal species is not only fun to do, it's also a great way to add uniqueness to your fictional world. It could be something as simple as changing existing animals into something new, or something as difficult as creating an entirely new and original species.
Whichever you choose, the steps will be roughly the same. But if you're going for a unique and original species, you might have a little more work to do than when you go for an alteration of an existing species. It all depends on how detailed you want to get.
In this guide I'll be going through the major aspects of creating a species, aspects which have a strong influence on the end results, and factors which also matter in the real world. While everything in this guide is mostly suggestion based instead of strict guidelines, hopefully it'll get you thinking and inspired nonetheless.
Note that this guide is aimed at animals in particular. There's a separate guide for creating (arguably) more intelligent species (orcs, elves, humans, etc), which can you find right here. There are less aspects and less rules to take into account for more intelligent species, hence the separate guide.
Before we even begin creating a species it's best to have a rough idea of what you want to create. What type of animal do you want? A fish? Mammal? Insect? A mix of multiple types? As you progress with the creation process the type might change slightly or completely, but you have to start somewhere.
Is your animal nocturnal, diurnal, crepuscular (active at twilight), or something else completely? Perhaps your animal lives deep underwater or underground, and won't have a real sense of day and night.
It may seem like a small thing to think about, but it'll be of huge importance later on when you start giving it features, including its senses.
Another aspect you'll want to consider is how realistic you want your animal to be. The more realistic it is the more rules you'll have to follow. A dragon with enormous wings might look cool, but realistically it might be too heavy to actually be able to fly. A mammoth with gigantic tusks might have a balance issue, and a lion with massive tusks might have issues actually biting its prey.
Depending on the world you've created these rules might not apply as much, and they're not always as important anyway. It heavily depends on the purpose of your world. Some will have to look incredible, some will have to be as realistic as possible and some are a mix of a lot of things. Whatever the world is you've created, make sure the animals you create fit within it.
So you have a rough idea of what type of animal you wish to create. Now you'll have to decide how original you want to be. Will it be your own version of a dragon? Will it be a hybrid animal, like a mix of a dog, a goat and a snake? Will it be a completely original being of your own imagination? Or will it be a mix of two or more of it all?
Altering an existing animal will generally have more restrictions. People are familiar with a specific idea of the original, so deviating too much from it might not work all that well.
Hybrid animals are fun, but they too have some restrictions. The original animals, and the idea people have of those are still present, so those ideas are often expected in some shape or form. A great example of hybrid animals are the animals in the 'Avatar: The Last Airbender' universe.
If you need inspiration for hybrid animals, check out the names in the animal species name generator on my other site.
Original animals can be amazing, but because they're original they also require the most work. All the details will have to be worked out yourself instead of being able to 'copy paste' everything from existing animals.
Obviously you can take elements from existing animals, how original you want to be depends entirely on you.
Before we delve deeper into the more important aspects of an animal, it's good to take a note of the rarity of your animal. How rare it is will have an impact on many of the other aspects of an animal, like its behavior and its position in the food chain.
Rarity doesn't just apply to how many there are either. There could be millions of individuals, but some might have a rare feature, like a different fur color, an abnormal size, or an extra long tail. You can compare this somewhat to albinism.
Now that it's time to add features to your animal it's important to consider the world it lives in. For a mammal who has to be fast to either catch a prey or escape from being the prey, 4 legs are generally a better choice than 2.
If your fish lives in a gentle sea, it might not need large, powerful fins in order to swim quickly. It can simply drift around in safety.
A bird who lives or flies at higher altitudes will need far larger wings than birds who stay near the ground.
There's a whole lot to cover when creating your animal, ranging from how it moves to how it eats, and from how it protects itself to how it attacks others.
The best way to cover all this is by simply starting at one point and working your way to the other. Depending on the animal you might start with the feet, its tail or its head.
Here's an example, which starts from the feet: Think about how large and powerful the feet need to be to survive your world and the other animals you may have added. How many feet does it have? If there's only 2, it will have to keep its balance somehow. Humans have toes to do so, some species simply have huge feet.
The legs, how strong are they? Do they have to be strong to fight or strong to run? Does your animal leap from tree to tree, or can it swing on the branches? How big is its torso, and how big will its legs have to be to support that torso?
Does your animal have arms, or four (or more) legs? Or a combination of both (like a centaur)? Does it walk on its feet like a human, on its paws like a lion, on both its hands and feet like some monkeys, or can it do both like a bear?
Does your animal need claws? Perhaps to kill its prey or crush open fruits or tree bark. Does it have long or short fingers, and how many of them? Does your animal have an opposable thumb, or is a different finger opposable? How nimble are its fingers? Nimble enough to use natural tools?
What about its head, how big is it, and what shape does it have? How many eyes does it have, and how good is its sight? What about at night? What about its other senses?
Obviously I didn't cover every aspect in this example, but hopefully it shows how to pretty much build an animal from scratch. But remember that these rules of what an animal might need won't apply too much to less realistic animals.
The inside is a less important detail if you're designing an animal mostly for looks, but a potentially fun one to play with. Give it larger lungs and a larger heart, and it might be able to run faster or longer. Maybe it needs several stomachs to digest its food, like cows, or maybe it has special glands which do all sorts of crazy stuff.
Having said that, one important aspect is whether your animal is warm or cold blooded, or maybe something else. Cold blooded animals have to eat less often, but they obviously can't live in cold areas.
While it's nice to have an animal which is ideal for living in its region, sometimes it's nice to add some features to make it look better. Those features might provide a different purpose, like finding a mate, or they may have lost their original purpose due to evolution.
For example, many bird species have brightly colored males. This is terrible for survival purposes, as they don't exactly blend into their surroundings. However, these colors might help attract a mate during mating season.
Some animals have horns or remnants of horns. At one point they might have been useful to survive, but their food chain or habitat may have changed to a point where they're no longer needed.
There are plenty of features you can add, and plenty of ways to still ensure they're realistic. As long as you don't overdo it, you can give an animal a whole range of special features to make it look amazing.
Changing parts of the body can make an animal look cuter or fiercer. Obvious changes to make an animal cute are fluffy fur, big eyes, and just being tiny. To make an animal look fierce you could give it smaller eyes, big teeth, claws, or tusks.
Other, less obvious and sometimes less realistic changes you can make for a cute look are: big ears, big hands and feet, tiny hands and feet, small nose, whiskers, a round body, and a big mouth. For a fiercer look you generally go the opposite way, but a big mouth is also recommended for a fierce look.
The way your animal looks isn't the only thing you have to decide, you also have to decide how it sounds. Fortunately there are plenty of animal sounds you can take inspiration from, but if you're looking for something more original and creative, try changing existing sounds, they don't have to be sounds from nature either.
Changing the speed or pitch of a sound can make it unique in an instant. It'll require a little imagination, but we're creating an imaginary animal here. Alternatively, you could simply find sound clips online, put them in one of the many free audio programs to change them, and play around with it.
Another way of thinking of new sounds is trying to imagine how an animal would sound if it tried to make the sound a different animal makes. For example, imagine what a dog would sound like if it tried to sound like a crow, or what a bear would sound like if it tried to howl like a wolf.
Most animals can't mimic the sound of another animal, so by imagining what it would sound like if one animal tried, you essentially imagine a new sound.
One last note, not all animals sound like you'd expect them to. Some sound absolutely monstrous even though they look cute, I'm looking at you koala, you make some freaky sounds. Others sound adorable when you'd expect them to sound fierce, like the cheetah, who sounds like an adorable kitten when it calls for others.
For some inspiration or just general fun, look up the sounds of the following animals: Lynx, (brushtail) possum, koala, elephant rumble/growl, guinea pig, elk, maned wolf, rhino, wolf mouse, desert rain frog, and the howler monkey.
Most animals have subspecies, so while this is another great way of making your animal look better or different, it's also something which is almost essential to ensure your world is realistic.
Some subspecies have changed based on their surroundings and difference in food supply, like polar bears, grizzly bears, and black bears. Others may have been bred for their difference, like all the species of dogs.
We've partially covered this by designing our animal when we decided on reasons why the animal might have strong legs or big feet. However, you may also wish to cover its diet and its position in the food chain. While this won't affect the looks of this animal all that much, it will affect the other animals you might still wish to create within that same food chain. If your animal is at the bottom of the food chain, it means it gets eaten by another animal. That animal will have to be able to eat this current animal, so your options will be limited slightly in that regard.
Something else to consider is how often and how much your animal has to eat.
How an animal reproduces could affect how it looks in terms of special features, like the pouches of kangaroos, or the features which attract a mate, like the bright feathers of a bird, but in most cases it will have little affect on how an animal looks.
However, whether an animal lays eggs, gives birth to live young, or does something completely different, is something you'll have to think about. It'll affect the animal's behavior (protective or not), it might affect the way it chooses a mate, and it might affect the strength of the body.
At the same time it's also affected by the animal's life in general. For example, rabbits have to reproduce quickly and a lot, or risk extinction due to the high amount of predators.
Another reproduction aspect is whether or not your animal can reproduce with other species, and what the end result is. In real life there are many species which can breed with other, similar species. Most species which result from this are sterile and thus cannot reproduce further, but that's not always the case.
Examples of such hybrids are: mules (male donkey + female horse), ligers (male lion + female tiger), cama (llama + camel), beefalo (buffalo + cattle), zonkey (zebra + donkey), grolar bear (grizzly + polar), and wholphins (false killer whale + dolphin).
An animal's behavior is another feature which helps make yours unique. Is it a pack animal or does it live on its own? Does it go into hibernation during the winter or does it migrate instead? Does it stick to a specific area, perhaps its own territory, or does it simply wander the world? If it has a territory, does it build a home or is nature its home? Maybe it only builds a home during mating season, like how a bird builds a nest.
There's a whole lot that comes to how an animal behaves. Take both its instincts and its intelligence into account, and go as small or as big as you want. Some animals merely eat, sleep, mate and die, others go the extra mile.
A detail which may not be of importance to your world, but is worth mentioning, is whether or not your animal can be domesticated, and if it can be tamed.
Taming an animal simply means subduing its wild side so it can be handled by humans (or other species), but that's all that changes, and under enough stress or other factors the original wild side can come out.
Domesticating an animal means changing it at a genetic level. It involves generations of breeding specific traits, which take out the uncontrollable wild sides, and turning the animal into what's essentially a new species. Real life examples are the domestication of the wolf into dogs, wild cats into cats, wild boars into pigs, and wild horses into horses.
Some factors which prevent domestication are: refusing to breed in captivity, unpredictable or overly aggressive behavior, impractical to keep around, picky eater, slow growth and/or long life cycle, skittish or frightened nature, and a lack of a social hierarchy, which allows for humans to be seen as their master.
This detail is an important one when your animal is supposed to be a mount or work animal for example, so try to create somewhat of a behavioral pattern.