Trophic Encounters

03 Feb, 2026

First off, kudos to Zak's really evocative idea of what I shall dub the 'Food Chain Hexagon'. I want to lay out a little bit of IRL ecological theory and explore application of it to wandering encounter tables. For fellow ecologists, I'm simplifying as much as possible to gamify things- this is what I would cover for a high school bio class, not a science symposium.

Trophic Levels:

The most important basic vocab to cover for discussions of food webs is an organism's trophic level. 'Troph' is just shorthand for talking about energy flow. You probably learned this in high school, but as a refresher- producers generate the energy in an ecosystem (and are autotrophs), which in most terrestrial ecosystems means plants. I have a whole thing I could go into about integrating plants into your TTRPGs for fun and profit but I'll save that for another time. What matters to us for a wandering encounter table is what happens above the level of producer (with the exception of, like, treants)- consumers are the organisms that cannot produce their own energy from photosynthesis (etc.) and instead get it by, well, consuming other organisms.

In a food web, we can generally see these roles clearly. Using this example from Britannica: We can see that in this simple food web, we have three levels of consumers- this is important for us for later. Consumers of the first order eat producers, second order consumers eat first order ones, and so on. Notice how organisms that eat multiple 'levels' of food are classified as their 'highest' trophic level. Also notice how organisms at one trophic level can be very different in size, diet, frequency in an ecosystem, and so on.

The other general definition I want to nail down is biomass- a pretty self explanatory term that means the entire mass of a species or group within one ecosystem. This is useful when comparing organisms of different sizes: a quail may weigh 100x the mass of a beetle, but if we have 10 quails and 1,000 beetles in an ecosystem, they would be said to have equivalent biomasses.

(Aside: I was going to use the trophic diagram in Zak's post as my example, but I realized it actually has a pretty significant error- herbivores are by definition primary consumers, so really that chart should go all the way up to Quaternary Consumers, or fourth-order. Notice how this puts zooplankton and swans at the same level.)

Okay, vocabulary lesson done. Time for math lesson.

The Ten Percent Rule

You may have noticed that generally, in an ecosystem, there are fewer carnivores than there are herbivores. This is an oft discussed joke in dungeongame circles, with all the 'what are all these monsters eating?' comments. Ecologists actually have a pretty ironclad mathematical model for studying these relative frequencies- our 'ten percent rule', or Lindeman's Law. This law examines the efficiency of an ecosystem, stating that only about 10% of the energy that passes through one trophic level is actually available to the level above it. (In practice, number's range from less than 1% to nearly 40% efficiency, depending on the organisms involved and yadda yadda).

This 10% actually represents the amount of energy-from-food that can be turned into new mass, by growth or reproduction. Living things are awfully inefficient, and we lose most of our energy doing things like chemical reactions, movement, pretending to be elfs, and other necessities of life. Taken as a whole, this means- and this is my actual point in my rambling essay- that each trophic level will contain only a tenth of the biomass of the one below it. As seen here, because 90% of the energy is lost with each act of consumption, our animals have progressively lower biomass as you ascend the pyramid. This also puts a hard cap on how many trophic levels an ecosystem can sustain- even with an incredible amount of plant biomass (such as in the Amazon or the Chesapeake Bay), you usually won't see organisms that are exclusively higher than quaternary consumers, because the diminishing returns on energy are just not worth it evolutionarily.

Okay! Ecology lesson done. Lets talk about dragons.

Ecology and the Wandering Monster

In an ecosystem defined by consumers, we have a pretty clear rule of thumb- the biomass of herbivores must be significantly more than that of the secondary consumers, which must be more than that of the tertiary, ad infinitum. Running with this, I want to use our trophic levels to fill an encounter table so that our chances of encountering a given creature are more or less in line with that creature's relative biomass in an ecosystem. Taking Zak's 2d6 table from the referenced post, I'm going to slot in trophic levels instead:

Where italics are from his and Nick Whelan's tables.

In the above example, you have a:

• ~5% chance of encountering a Quaternary consumer.
• ~17% chance of encountering a Tertiary consumer.
• ~20% chance of encountering a Secondary consumer.
• ~28% or ~46% chance of encountering a Primary consumer. While not a perfect 10% model, it actually represents the direct frequency of organisms not too poorly- you can lean into the biomass thing quite easily by using this to define group size, where primary consumers are much more likely to be found in large groups as compared to the small groups of more solitary high-order consumers.

You can either use this model to construct a food web, drawing connections between which consumers feed on which, or you can come in with a generated food web and use it to fill these 'slots'. Organisms that compete with one another will generally be on the same trophic level, while cooperative relationships will generally be on separate levels (because there's less incentive to cooperate with someone who you compete with for resources).

I think an actual practical use of this is to further develop inter-encounter connectivity. Can I find some food to propitiate this monster? If two encounters occur at once, how will they interact with each other? Did I just interrupt this predator in the middle of a meal? In the future maybe I'll add in procedures there, and maybe build a table that gives more or less 'realistic' numbers.

Utilizing Zak's super cool use of human NPCs in his predation/cooperation/competition table, I populated this table for encounters along a wooded road.