Wednesday, July 11, 2018

Apex Predators and Their Territories

Bored of your world's animals? Just mash 'em together!
When you are building a wilderness, it's important to build your encounters carefully. A well-constructed random encounter table can give the players a sense of the real-world ecology of an area. They will encounter lots of small animals and predators, and only rarely find a huge monster like a dragon or hydra.

But how many is too much? Dragons needs a lot of room to fly, build nests, have subjects, etc. Even smaller animals like wolves need space to claim as their territories. So let's look at the numbers, and figure out how to avoid the wilderness equivalent of the "vampire in room 34" problem.

(For reference, the Vampire in Room 34 is a problem where monsters that are powerful enough to merit entire backstories and territories are reduced to hit points and damage for a party to overcome. It was first dealt with by Tracy Hickman, the creator of Ravenloft.)

Animal Studies

Let's start with an underlying assumption: we're using 6-mile hexes. 1-mile and 60-mile aren't usually used for overland travel, and we want to show the some diversity in the territories of these creatures.

A 6-mile hex has an area of about 35 square miles. We'll look at two types of terrain: open terrain, such as grasslands and deserts, and complex terrain, such as forests, mountains, or even coral reefs.

Now, some real-world references:

I would consider any area with major human activity to be a complex terrain site. I also picked eagles and coyotes (or their D&D counterpart jackals) for a reason: they are both Small creatures, and from a rules perspective require similar amounts of food.

From this data we can conclude that a creature that can fly or swim in an environment can control a territory about three times as large as that of a land-based creature.

If you check out the coyote info link, you'll also find a kind of unusual statistic: packs of coyotes generally have a smaller territory that solitary coyotes. This is because obligations to the pack, such as raising pups, prevent their hunters from venturing too far afield. If the monster has a site they wish to protect, it could reduce the area of their territory by half or more.

Essentially, territory is based on a compromise between needs and costs. Needs include resources and proper reproductive space (like a nest, cave, or beach). Costs include defending the area and protecting it from other predators. If a pack can't properly provide members to defend their borders, they will retreat and allow their territory to shrink, giving up resources but enabling themselves to protect their homes better.

Another thing that affects territory is the open/complex nature of the terrain. This can vary wildly in nature, but generally, complex terrain supports more biodiversity than open space. A coyote pack could control multiple hexes in a desert, but for ease we can simply say that in open terrain, a predator's territory doubles.

We also have to account for size differences. Larger creatures need more food! It's difficult to find a good comparison point, but based on the food requirements for different creature sizes, we can make the easy assumption that a creature one size larger requires twice as much territory to supply it with food.

So, what about mythical creatures?

Despite being imaginary, still not as unusual as the platypus
Well, some monsters aren't going to follow these rules. Undead, aberrations, oozes, fiends, celestials, constructs, fey, and elementals aren't native and likely have very different ideas about territory and who they consider threats.

Also, intelligent creatures, such as humanoids, dragons, giants, and some plants/monstrosities, are going to be able to control their territories more deliberately than simply giving and taking resources. A Dragon or Sphinx guarding treasure will purposefully shrink their territory in order to remain hidden, but rampaging Giants will spread further than they need to.

So, these rules apply to unintelligent beasts, monstrosities, and plants. But that doesn't mean those other creatures won't affect territories! Much like how human presence can make a space into complex terrain, creatures that act like predators will be treated as such by the creatures who don't know any better. 

For example, a Dragon that controls its territory intelligently will still be treated as another predator by a Purple Worm, and they will probably give each other space if either one of them is confronted by evidence of the other. Smaller predators, such as wolves, might avoid the Dragon's territory, knowing they will die if they try to hunt in that area.

Intelligent creatures might also domesticate or enslave monsters that would otherwise have larger territories. An Ogre might have quite a large area it hunts in, but an Ogre enslaved by Goblins will eat what it is fed and not travel into areas the Goblins wouldn't go. This could be a mutually-beneficial situation: a human tribe could protect a pack of wolves, while the wolves provide companionship and share their food.

So, how do we turn this information into a random encounter table?

D&D vs. Predators

I like using 2-dice encounter tables, like those depicted in the DMG (page 87). This gives a good probability curve to the table, which better reflects the nature of an environment. At the very least, it allows you to put a named Dragon on your random encounter list without the PCs running into them 1 in every 8 or 12 rolls.

So, we can use the above information (remember, 1 hex equals about 36 sq. miles) to generate a chart listing how much territory a particular predator needs.

Some of these territories can overlap, as well. In complex areas, predators that use camouflage can hide from other, larger predators. Small/medium predators likely have nothing to fear from Gargantuan beasts, who will seek larger food sources.

This means each hex can have one huge or gargantuan predator in it, and that creature will likely control several hexes. You can also sprinkle a few other predators in the hex, more if they are pack hunters or have a nest to protect. Then, every other entry should be a humanoid, a benign creature, a location encounter or a "trap" encounter (such as walking through a patch of poisonous plants).

Here's an example encounter list that would make sense for a single mountainous hex. I've taken the entries from the Xanathar's Guide encounter list. The mountains would be considered complex terrain.

Goats: A staple of any good ecosystem
Roll 2d4
  1. n/a
  2. 1 Wyvern (controls 4 hexes, roams skies, nest in another hex)
  3. 1d2 Hippogriffs (mostly benign creatures, prey for the Wyvern)
  4. A small shrine dedicated to a lawful neutral god, perched on a stone outcropping (location encounter)
  5. 1d6 Goats (benign creatures, prey for the Hippogriffs and Basilisk)
  6. 1d10+5 Tribal Warriors (humanoids, can be reasoned with, they made the small shrines)
  7. 1 Giant Elk (mostly benign creature, prey for the Wyvern)
  8. 1 Basilisk (lives underground, protective, controls 1/3 hex, stays out of wyvern's way)

This builds an ecosystem that the players can explore. The lower-food-chain monsters are more plentiful, and the players might run into a monster well beyond their level (since Wyverns are CR 6 and this table comes from the level 1-4 encounter list).

If you want to expand beyond a single hex, you can create an entire region using these guidelines. Of course, a larger area is going to have more biodiversity, so you can make a larger table. We can make a 24-hex mountainous region, then add predators to the table until they add up to that amount. 

Roll d12+d8
  1. n/a
  2. 1 Ancient Red Dragon (controls 8 hexes)
  3. 1 Fire Giant (controls 2 2/3 hexes)
  4. 1d4 Trolls (control 1 1/3 hexes)
  5. 2d4 Harpies (control 1/3 hex within dragon's area, dragon ignores them)
  6. 1d8+1 Hippogriffs (prey for larger animals)
  7. 1d6+2 Orcs (control 1/3 hex in dragon's area, servants of dragon)
  8. A row of 1d10+40 stakes upon which the bodies of dwarves are impaled (placed by orcs)
  9. 1d8 fissures venting steam that partially obscures a 20-foot cube above each fissure (location encounter)
  10. 1d8+1 Giant Goats (prey for larger animals)
  11. 3d6 Goats (prey for larger animals)
  12. 2d8+1 Aarakocra (humanoid encounter)
  13. 1d4+3 dwarf trailblazers/scouts (humanoid encounter)
  14. 1d10 Giant Eagles (control 2 hexes in Roc's area, servants of Roc)
  15. 1d8 fissures venting poisonous gasses (trap encounter)
  16. A distant mountain whose peak resembles a tooth (location encounter)
  17. 1 Bulette (protecting nest, controls 2/3 hex)
  18. 1d4 Stone Giants (possibly benign encounter, control 1 1/3 hex)
  19. 1d4 Air Elementals (no need to hunt, but they protect a portal to the elemental plane of air, other animals give them 2 hexes of space as if the elementals controlled it)
  20. 1 Roc (controls 8 hexes)

So far, I enjoy this system, since it makes you think about territories and how these creatures might interact. What do the borders of the Roc's territory look like? Are there occasional aerial skirmishes where it touches the dragon's area? The Bulette and Elementals might get more aggressive the closer you get to their homes. The dwarves don't have territory, being intelligent, but they might be able to provide some insight into avoiding the dragon's domain.

Also, if you were to actually map out these territories, you could also let the players know where they are when a specific encounter occurs. For example, if the party is crossing the mountain range and you roll a random encounter, you could pinpoint where the party's location is based on what you rolled. This assumes they roll a dangerous encounter, of course. Most of the time their encounters will be relatively benign.

This is why most D&D products have you roll a d20 before making a random encounter check, then only give a combat encounter on a 17 or higher. An ecosystem can only support so many predators. I prefer to make a table weighted towards benign encounters, that way I can give my group something interesting to check out even if they don't end up entering combat.

You can only fit so many flesh-eating bugs into a single cave system before you run out of flesh
I hope this information was enlightening to you when it comes to building your own random encounters! For the more nature-inclined PCs, it can be fun to learn about the different creatures inhabiting your world.

Thanks for reading!

No comments:

Post a Comment