That’s really kind of awkward.
Kevin and Kell is probably the most prominent and oldest strip of this kind, and sets the pattern for most of the rest – but it’s a cartoon, and doesn’t need to make any sense. Thus:
- The major characters all have plot immunity, and pretty much always win. Thus Wendell (a rabbit-child) readily defeats attacks on him by nameless predators – but a full-grown tiger who’s after her mother is readily devoured by Coney (a rabbit-wolf hybrid girl) while she’s still an infant.
- Most of the sapient animals who die are simply from “the wilds” – which apparently is basically a near-limitless source of prey who usually only appear to be eaten or to point it up when the major characters are too distracted to eat them. They get no chance of winning.
- Little kids don’t die (that isn’t funny) instead of doing it all the time.
- The economy and society operates normally enough to be a recognizable backdrop despite the enormous casualty rate – which would rationally make it near-impossible to train people, make even basic schools an enormous expense, pretty much eliminate making loans, and otherwise make it awkward to keep things functioning.
- Despite the fact that the young, sick, and injured are all natural prey and can be expected to be quickly eaten, there’s a human-style medical infrastructure in place to take care of major characters – instead of a series of butcher shops.
- Major character parents value their children a great deal, despite the ongoing mass slaughter of background characters and their children. “The young and stupid are MUCH easier prey”.
- People get devoured neatly and usually don’t make a fuss about it (often being swallowed alive and whole despite how vulnerable the throat, neck, and abdomen are to even a single frantic claw-slash from the inside), since blood and stinking guts, pleading, struggling, screaming, and grieving relatives are off-putting to the readers and reduce sympathy for the major characters.
- Things like Predator-to-Prey ratio – and what so many of the species having human-like sizes, breeding, and aging patterns would do to it – are NEVER discussed.
So lets take a quick peek at reality (such as it is).
A mammalian predator in the human size range (wolf, big cat, etc) needs to catch roughly it’s own weight in prey every week. Thus a ten-year-old predator kid needs to have caught, defeated (without getting killed or seriously enough injured to let something eat him), and eaten some five hundred other kids. Yes, there’s parental care – but that just shifts the burden to killing more a bit later in life, it doesn’t really change the basic calculation.
Every additional decade he or she lives, our predator will need to do the same thing again.
So lets say that (on the average) he or she lives to be twenty-five – long enough to get through school, make some kind of contribution to society, and raise a kid or two (presuming that they start breeding as teenagers) to the point where they might be able to survive without you.
So our average predator… will be eating at least 1250 other people. And there will have to be enough breeding pairs of prey species to keep that at a reasonably steady state and to cover for accidents and diseases and such. A ratio of about 1600 to 1 is close enough to work with given these rather crude calculations.
If a given prey kid has a one-in-fifty chance of winning or inflicting sufficient injuries (clawing the inside of the throat perhaps for the popular “swallowed whole and kicking idea?) when jumped (not nearly enough to be fun in a game), then our predator kids chance of making it to adulthood at eighteen will be .99 to the 900’th power – 1 in 8500. Of course if the prey kids start helping each other intelligently, or carrying poison pills, or some such… all the predators are going to die. That’s why humans have no major predators.
For predators to function… their chance of winning a fight with a prey animal has to be closer to 99.99% (giving one a 91% chance of surviving to adulthood). Their prey must either breed extremely quickly or outnumber them enormously or some of both – and their prey must NOT act much more intelligently than they do.
Of course, basic prey-species defensive tactics include cooperation – herds, gangs, flocks, and all the other variants. If a prey species is even moderately dangerous to the predator species, and is intelligent enough to organize and plan ahead a bit… they have the numbers to massacre their predators. That’s a major reason why elephants have no real natural enemies other than humans.
If a predator is going to focus on a slow-breeding, slow-to-mature population of prey, it will be massively outnumbered or it will soon starve. If the target population is even modestly intelligent and dangerous to the predator… it will have to pick off outliers in secret or it’s going to get massacred. You can make social excuses (although excuses for “not protecting your kids” are a stretch) – but societies of prey species that don’t use such excuses will expand at the expense of the ones that don’t. In the long run, social excuses are not enough.
You can, of course, run a game in such a setting – but you’re just going to have to ignore or gloss over a LOT of the background details. You want prey-species player characters and some pretext of “balance” with predator-species player characters? The prey-species characters are going to be VASTLY more powerful than the background prey-species NPC’s. You want predators to make up 5% of the population? You’re just going to have to quietly ignore the fact that they’d pretty much wipe out the prey species (and then starve, since there’s only enough food for them for nineteen weeks) well within a year even if they turn on each other quite a bit. You want combat to be exciting enough to be interesting and to have serious consequences? Then PC’s are going to die a great deal more often than in the source material. You want your group of four predator characters to skip over three weeks? You’ll need to skip past the twelve people they killed in that time. You don’t want frantic screaming, begging, last-minute attempts at dirty tricks, weeping children, and grieving parents? Then no one is going to be taking death too seriously (there may even be volunteers, no matter how quickly any such tendency would normally be bred out). You want a supporting cast? Then you ignore the likelihood of random casualties among them.
And that’s the basic trick; once you’ve realized that you’re running a game set in a cartoon universe, then the system you’re using matters a lot less. In practical terms, however, you’re probably best off with a point-buy system to allow people to build characters of a wide variety of species and with off-the-wall abilities. Given that the opposing combative NPC’s are likely to be pretty transient (since the characters casually kill swarms of people just to live you can’t expect them to hold back against actual opponents), you won’t need too much detail there.
Personally… I like to be able to build nuanced characters, so I’d prefer a reasonably detailed system. Eclipse will (of course) do – and there are handy racial templates for human-scaled anthropomorphic animals and plenty of other creatures – but you could also use the Hero System or GURPS (although GURPS is probably too realistic for the setting). Other systems, like Ironclaw and Fuzzy Pirates, are designed for anthropomorphic role-playing – but they tend to have a lot of world-assumptions built into the rules (massive predation is NOT normally amongst them), so they can be considerably harder to work with than the more generic systems.