Saturday, November 12, 2011

Optimal Foraging Theory and D&D Wilderness Mechanics: A Half-Assed Treatment

Said Spawn of Endra:

Hunting seems to be a hot topic in the last day or so, between this spell of Mr. Bat's that causes people to hunt (a great spell to clear a bunch of people out of a village so you could steal their stuff, if you ask me), and this Simple Hunting mechanic laid down by Mr. Talysman. I always dig what Talysman puts forth. His posts are often what I wish I could come up with instead of my own posts that are 80% material that only I find amusing, and maybe have 20% of something useful for anybody else. As I commented on his post, I think he's got a simple mechanic that is also nicely granular. But wilderness foraging rules still just stick in my craw, and I've touched on that once before when looking at the Joy of Cooking Grindhouse Edition.

In the comments to Tal's post I bitched about "Why is wilderness food-getting all hunting and no plant gathering?", and I said "Well when I'm in Belize I just go eat bush food and look at me I'm so special." What kind of a twat writes stuff that? But anyway, to me hunting game is just a big risk and big waste of time for the traveler. Here's my take on wilderness adventuring hunting.

First, why are you in the wilderness? You either have a specific goal to get to and you've decided it's quicker to risk going off-road to reach it, or you've got a vague sense that there's something in a general area and you've got to explore the hex until you find it. Or you got teleported there or whatever other deus ex machina scenario. [I have literally never played a hex crawl session, so please jump in and tell my why else you are in the wilderness.]

Second, why are you hunting? You ran out of rations, I guess. Is this bad planning? Lack of player skill? Or did something steal your rations, or they got rained on? Hmm. Well if it's either of the latter cases, the DM cares about not hand-waiving* the particulars of wilderness adventuring.  If one has to resort to a hunting mechanic, simple or otherwise, one is probably the DM that wants grit and realism in the hexcrawl (or delights in another tool to throw shit at the PCs perhaps?). As a player, well, I'm going to buy so many iron rations and commission a 500gp sack for them that is both waterproof and has a chainmail outer lining before I play in your game.

The PC is hunting because he/she/it has no food. The player is hunting because the DM is stripping away attribute points like CON or STR (and CHA, obviously -- starving people are just NOT attractive), and probably HP. So I propose this axiom or something:

No hunting mechanic should exist without a preceding starvation mechanic 

That's a problem with LabLord, which otherwise has a decent (i.e., plant-gathering option) mechanic: the penalties for starvation are left to the DM. Raggi's Grindhouse Rules (p.36) do give a mechanic, which is a Save vs. Poison each day or lose 1 CON. At the same time, he acknowledges the real problem is dehydration -- Save or CON is at half.

Note that I'm not proposing any mechanics myself. First off I'm too busy, otherwise lazy and stupid to do so. Second, I don't see the realism that it would add as adding fun overall. Any hunting mechanic must exchange PC time for caloric returns. That's at some cost of movement rates through the wilderness. Depending on the starvation mechanic, in most real situations one is better off just moving on toward the goal rather than spending time and energy chasing game they may not catch, i.e, get out of the wilderness. Time spent hunting is also time for Wandering Monsters to appear. They may either kill you or solve your starvation problem by becoming food. At worst, I envision a space where the party has to devote all their time to hunting rather than moving, and so end up in a positive feedback loop that locks them into sitting in place and not adventuring because they need to devote all their time to hunting. Sucks to that ass-mar. 

Why hunt when you can gather?
I'm an archaeologist, and I draw on the anthropological traditions of cultural ecology and what is typically called human behavioral ecology in my work, among a billion other things. Before starting this post , I went back to some classics looking for data to show why hunting shouldn't take precedence over plant gathering. And I got confused. Here's a classic on Ache foraging by Hawkes et al. (1982)** that shows that deer and peccary are the highest ranked resources they encounter in Paraguay, and most plants and insects are lower ranked:

The ranking is based on the caloric return per unit of time devoted to search, pursuit, and handling/processing. So big animals are higher ranked, and when encountered they should always be taken as opposed to the palm hearts that present themselves at the same time (which are lower ranked due low calories and processing time). Beyond a point of caloric return per unit of time, some potential food sources should always be excluded from the diet, no matter how abundant or easy to get:

Ei/hi is energy per handling time by resource, and E/t is energy return per time invested in foraging given the breadth of resources in the diet (i.e., the return at rank 4 is for a diet that includes resources ranked 1-4 inclusive). It happens that plants are more abundant, so the encounter rate for these resources is higher than for game, but in this group of foragers a lot of the diet is made up of game (about 75% during the period of this study). But it's important that as the diet breadth increases, (the number of resources acquired from rank 1 to rank 12 increases), the average returns of foraging per hour increase. So all the stuff from rank 7 to 10, including the larvae, birds, palm products, capuchin monkeys, lead to overall higher average returns.

These returns are in kcal/hr, so for a 2000 kcal/day diet, this is going to mean ~2.5 hr foraging/PC/day when plants and all the better stuff is included (~800 kcal/hr return). If you only take big game (the two 1st ranked resources) and ignore other foods, you'll get big caloric returns when you bag them, but the hourly return rate goes down to ~100 kcal/hr, so it's going to take 8 times as long if you're picky. That assumes you're in Paraguay and you're with subsistence foragers, or have a good ranger, etc.

If you added the costs involved in devoting so much time to hunting, like random monsters encounters with no loot reward, some other plot-related time-crunch, then all of these things get shifted around. More time spent foraging = more bad stuff, and therefore PCs are foolish to go for the big kill. They should get on to their goal, and not sink time into hunting big game. But again, the DM and the players need to know the costs of starvation for these types of evaluation and decision-making to have any meaning.

And next time I put my money where my mouth is: The Spawn of Endra cooks gopher soup in Belize.

*Is it hand-waving or hand-waiving? Discuss on
** The reference is: Kristen Hawkes, Kim Hill, & James F. O'Connell. (1982).Why Hunters Gather: Optimal Foraging and the Aché of Eastern Paraguay. American Ethnologist, Vol. 9, No. 2, Economic and Ecological Processes in Society and Culture, pp. 379-398.


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  2. Also an archaeologist (I have a MS anyway) and I largely agree with you, but some of this is dependent on differentials in environment and the character knowledge. Some plant foods, especially those that require processing, are not going to be obvious calorie sources to the uninitiated, which I think might slant people towards hunting if they are on unfamiliar terrain. Furthermore, glacial/polar environments are probably going to require hunting regardless of the danger involved, because during much of the year, if not all of it, edible plant products are going to be in short supply.
    Anyway, great post. I think I'll write up some starvation and foraging rules at some point as a result. I envy you your field work, I'm out of academia and trapped stateside these days.

  3. @Aos:

    Yes, I agree that the habitat that you're in and even more so the knowledge of the habitat is a big big issue here. That's partly why my comments on Tal's post were sort of twatish. When I first was in the bush in Belize the environment was completely unintelligible to me, to the point that I couldn't even distinguish between plants in front me as things, let alone edible or not. Meaning, I couldn't SEE individual plants, it was all just a mass of foliage. I had to learn through being with Maya folks what could be eaten and how you get the edible parts.

    This is where I back away from verisimilitude in gaming, because the attempt to get to realism can just get too crunchy to be fun. So without some sort of bushcraft skill or whatever, how does an adventurer know what to eat? How do you role play that? Did they learn as kids, and so start with knowledge of only certain habitats? Did they learn on previous wilderness adventures? I think Tal's follow up post on foraging does good stuff in that regard, since he leaves the possibility of folks finding poisonous food, which suggests that one might have general foraging knowledge as an adventurer, but may not always get it right. (And he also does it succinctly, which I admire.)

    And I'm sorry to hear you're trapped in the states, though I'm in the middle of writing my diss, so being out of academia sounds utterly delightful to me right now. That's probably why OFT suddenly shows up in this post about gaming ... ugh!

  4. My mistake, I didn't read the leading post first.
    I'll admit that when I saw the title for this one, I cringed a little because it brought me right back to grad school. I only emerged in January so I'm still a little theory shy. Goos luck with your diss.

  5. It's hand-waving, obviously. You wave your hand, perhaps even literally, and you say "Oh, don't worry about that". Like Obi-Wan; "This is not the crunch you're looking for".

    ...anyway, good post!

  6. @Aos: I cringed a little when I started writing it! I almost gave up the second part of the post last night. Makes my brain hurt.

    @John: You're probably right. But "This is not the crunch you're looking for" is the perfect way to sum up this post. That'll have to go up on the Bons Mots section later this evening.

    Rock out!

  7. Good points... and, for the record, the reason I wanted hunting (and foraging) rules was a cross between "another tool to throw shit at the players" and "players always bring up stuff like that".

    I need to redo the basic mechanic, but I have a starvation and malnutrition rule based on simple disease rules: improvise effects based on a one-line disease description, with keywords based on levels (mild, severe, fatal) and frequency of rolls (normally daily, but slow diseases roll weekly, fast diseases roll hourly.) There are two or three other modifier keywords, like "wasting" or "crippling". So, malnutrition causes slow severe weakness (roll weeky, failure means the disease gets worse, from "mild" to "severe") and can be ignored for many dungeon expeditions, while starvation is a severe wasting weakness (roll daily, same progression, but also lose 1 hp per failed roll.)

    Simple enough that I could do it without charts, but detailed enough to inject some variety, which is what I look for in rules and mechanics.

  8. @ Tal: Thanks for bringing the earlier posts to my attention. I assumed you must have a starvation mechanic back there somewhere. I admire your simple and internally coherent mechanical 'aesthetic' (if that's the right word). That sort of clarity probably explains why you're able to put down something concise and useful in 2 paragraphs where I'm compelled to flail away for pages. I hope you decide to go ahead with the Liber Zero project, because I'd love to see all this stuff in one place.

  9. Thanks! A lot of the stuff that's uniquely my interpretation is going to be in Liber Blanc rather than Liber Zero, because I want to keep LZ close to the original... although what "close to the original" means is waiting for further clarification (i.e., I get a look at Delving Deeper.)

  10. I was inspired to write that post by the Hunting Song by Korpiklaani, it is meant to create a diversion or obstacle for either players or, if they are quick enough, their adversaries.

  11. I'm sure it is literally "hand-waving" (as John Evans points out) but I like the concept of "hand-waiving" a lot in the RPG context.

  12. And the one gopher that got away is still singing "I'm all right, nobody worry 'bout me!"

  13. @Peter: I'll forgive you the Kenny Loggins stuck in my because: a) it's Caddyshack; and b) I just checked out your Wall of Sleep spell post -- sweet stuff. I look forward to seeing Black Sabbath exegesis.