Vision: A Resource for Writers
Lazette Gifford, Editor

Creature Building 101:
Part 2

by Marilyn Glazar
Marilyn Glazar


In the last creature building article we covered survival mechanisms.  Most creatures have environmental difficulties to overcome, and the methods that they use to overcome them are great for tying them into your world.  If these were the only problems that they had to overcome then the job of making them up would be fairly simple.  There are, however, a few other problems that animals have to defeat in order to continue to exist.

Chief among these problems is the question of how to obtain energy and water.  Other forms of sustenance may also be necessary.  Salt, vitamins, and trace minerals can all send animals licking, nibbling, and ingesting unlikely bits of their environment.  The need for sustenance is persistent and ever-present.  Many animals spend every waking moment foraging for food.

If that weren't problem enough, the energy almost always has to come in a very specific form.  A cow can't be fed pork chops when the hay runs out and a vampire won't be satisfied with spring salad mix and a nice vinaigrette.  In fact, the vampire wouldn't take the pork chops either, and the cow would be quite put off by the vinaigrette.  Animals are very specific about what they eat.  They don't just eat meat or plants.  They eat grasses or small mammals, or human blood.

Knowing how your creature solves the problems of its physical environment will help you figure out how it can solve its sustenance difficulties.  If it sleeps at night because its body temperature is too low for much movement, it certainly won't go hunting then.  If it has tough protective scales or water-proof hide, it won't absorb anything very well through its skin.

There are almost as many ways to solve the problem of sustenance as there are animals.  Animals on this planet almost always obtain sustenance through a relationship with another type of living thing.  This means that when you are making up one creature, you almost always have to make up another creature or plant for it to obtain sustenance from.

Most people know that herbivores eat plants and carnivores eat other animals.   These relationships are predator-prey relationships.  We tend to think of this in terms of one living thing dieing in order for another living thing to survive.  A wolf pack feeding on deer is exhibiting this kind of relationship but so is a slug feeding on lettuce.  It is important to remember that predators must strike a balance in order to survive.  If they get too good at their job they might run out of prey and die of starvation.  For this reason there are always more prey organisms than there are predators.  You might see vast herds of antelope but you won't ever see that many lions in one place.

Predation works, and it is the most common way for a creature to get energy, but it isn't the only option.  Again, lets look at a couple of real-life examples and one from the fictional realm.

The canine heartworm gets all of its sustenance, for most of its life span, from its immediate environment.  It spends most of its life in the bloodstream of a dog, and has every need catered to quite nicely.  As an adult it will move into the dog's heart or lungs where it will reproduce, sending its many tiny offspring into the bloodstream where a mosquito might carry them to another dog.  If the parasite is lucky, the dog will live for many years.  Often though, the extra strain of carrying heartworms around in the chambers of its heart will cause a dog to die.  The heartworms, of course, will die when the dog does.

Parasitism is a valid way for creatures to solve their sustenance problems.  If a source of nutrients isn't completely used up at a feeding, but is allowed to continue growing and obtaining more sustenance, then the parasite never has to go looking for food.  A great many of the parasite's survival problems can also be solved by living inside a host where environmental problems won't bother it and predators can't get to it.

The parasites we know of don't take over their host's nervous system, but the idea of a parasite taking over a human body and mind is so gruesome that practically an entire subgenre of horror and science fiction novels have dedicated themselves to it.  My particular favorite is The Puppet Masters by Robert A. Heinlein.

Another type of relationship that can solve a creature's sustenance problems doesn't involve harm for either of the creatures involved.  An example of this relationship is found in between two animals in Africa.  There's a bird called the honey guide that just loves honey but can't get to it alone.  The honey badger likes bees and larvae and has thick skin and fur to protect it from the bees' sting.  To get fed, the bird only has to find a bees' nest and lead the badger to it.  The badger does the work of tearing the nest apart and devouring the bees.  When it's done the bird gets to eat its fill of any leftover honey.  Everybody wins.  Well, everybody wins except the bees.  The badger and the bird have a mutualistic relationship.  The bees are prey.

In the real world as we know it, creatures get energy mostly by ingesting each other and plants.  In the fiction this isn't necessarily so.  One example of this would be the case of the dementors that figure highly in the plot of Harry Potter and the Prisoner of Azkaban.  Dementors don't eat.  Instead, these creatures get their power by creating fear in people and siphoning it off.  It seems that they also have a hunger for human souls that they can suck out of a person through the victim's mouth.

While dementors might seem to break some of the rules that creatures on earth follow, they do follow the rules of preditor prey relationships.  Dementors are not always successful on the hunt.  Humans can defend themselves against dementors, if they know the patronus spell.  It is also important to note that there are a lot more humans than there are dementors.  If the dementors were invincible or if there were more of them than there were people, then the creatures would not be believable.  Monsters that aren't believable aren't nearly as scary as those that seem real.

While it is important that creatures be believable, it isn't necessary that they be predictable.  Perhaps a creature could obtain some or all of its sustenance from an environmental source such as sunlight or radiation.  Maybe a formerly parasitic relationship could be thrown out of whack by circumstances and become more mutualistic.  In fiction no rules are absolute.  They are merely guidelines to help the author make a story work better.

Sustenance relationships take place between different types of organisms.  In order for a creature to really come to life, it will need to be able to reproduce itself and this almost always involves relationship between it and other creatures just like it.  In the next article we will look at reproduction.


Book Mentioned: Puppet Masters by Robert A.  Heinlein.  ISBN 0345330145


Book Mentioned:  Harry Potter and the Prisoner of Azkaban by J. K. Rowling, Mary Grandpre (Illustrator).  ISBN 0439136350

Additional Reading

If you find the idea of parasites intriguing and want to learn more about them, you might enjoy reading New Guinea Tapeworms and Jewish Grandmothers: Tales of Parasites and People by Robert S. Desowitz. ISBN: 0393304264

Web Sites of Interest

This site has pictures of parasites and examples of life cycles.

This site has a lot of information about honey badgers, including an argument against the widely used practice of calling its relationship with the honey guide mutualism.

This is a look at some marine animal mutualism.