First, the proposed effects and timeline of hunger:
The need to eat would not be immediate, nor would the immediate effects of not eating be severe. Ideas on how this might work for homins have been posted earlier, but I realize now I have contributed nothing on it's possible workings for the rest.
The five stages (Full, Hungry, Very Hungry, Ravenous, and Starving) would have different effects, not just on mob behavior, as posited earlier, but on the state of the mobs health. I do not count death as the last stage, but rather as the result of the previous ones.
Full: The animal is not only content to remain where it is, but is at full health/ability.
Hungry: The animal is still at full health/ability, but recognizes the need to eat. If food is not nearby, it will wander around (possibly in a logical, if not intelligent manner) until food is found and consumed, therin after, returning to it's claimed territory.
Very Hungry: The animal will search for food as above, but lack of caloric and nutritional intake have begun to take their toll, albeit only slightly (as when you or I miss eating for a day). A possibility for this stage would be that they are at 90% of their max health and physical damage. Special attacks (such as a Najab's spit, Ocyx fire, or a Shala's whatever-it-is-but-it looks-cool-and-hits-alot-of-nearby-targets) would remain at full power, regardless of hunger level. While muscels may lack the energy to move as well as normal, the acid in a Najabs spit may well remain undiluted by hunger.
Ravenous: The animal is not thinking well at all. It's body has gone from not having quite enough energy to supply it's needs, to actually digesting bits of itself in an attempt to stay alive. Health and physical damage are at 50% usual maximum, although, as always, special attacks are unaffected.
Starving: The animal is, quite simply, insane from hunger. It will most likely die (as everything looks like food to it, including it's kith and kin) and it's Health and physical damage are both at 10% of usual maximum (special attacks unchanged). Since any confrontation will likely result in it's death, and it will initate such confrontation at it's first opportunity, death is very likely. There is, however, a chance that it will manage to prevail, no matter how mercifull death might be at this point.
These stages take a long time to occur, and, once a balance has been achieved, the last one may never be reached (barring special circumstances, such as an event).
Herbivores are continually grazing. They are therefore, most of the time, not hungry. During the winter, they may have a, for example, 5% chance (randomly determined) per day of dropping one hunger level. If they do not drop a level on any given day, their hunger level goes up one, to a maximum of full (introducing obesity may well be a step to far...for now). Therefore, while it is possible that a herbivore may starve to death during the winter, it is very unlikely. We do, after all, live on a plant. They may succumb to aggressive, predator-like behavior during the final stage of decline, but would likely only attack other herbivores, i.e., they would be suffering the effects of stage 5 (starvation) (10% health/physical damage maximum) but would have the behavior of a predator in stage 1 (hunger). The likely hood of Herbivore starvation, as well as the seasons in which it may occur, may well be altered to allow for events on Atys, the Great Drought of Year XXXX, for example.
Predators may well follow eating patterns observable in real life, one large meal, then a period of relaxation. All time periods given are Ryzom days/weeks(7 day) not RL ones. For instance, say a Varinx is at full satiety. It will be content to loll about in it's den/territory/spawn point, as it's needs are currently fulfilled. After two days, it begins to feel hunger, prompting it to go out and search for food. If successful, it returns to it's den, once again content. If not, it continues it's search, and, after one week of having nothing to eat, enters stage two, Very Hungry. If no sustenance is found within the next week, stage three, ravenous, is entered. One more week, and it will be Starving. After one week of starvation, death occurs. I realize these time periods seem long, but many animals (humans included) can survive for long periods of time without food, so long as water is available. They are hardly at the peak of health, and may well suffer long-term health detriment, but they are still breathing. In addition, the long timeframe for these occurrences provides for a more easily balanced system, without the incredible, and possibly impossible, complexity of an Earth ecology.
Once a predator has had it's meal, regardless of hunger stage, it will recieve an internal flag to stop and digest, possibly after returning to it's den. After one day, having been fed, it's hunger stage will go up by one. If it is still motivated to hunt (stage Hungry or lower) it will return to the field, once again on the prowl. This cycle will continue untill it is full or dead.
With the above example, it would require aproximately 120 herbivores to keep a single predator at the peak of health for a year, or around 50 to keep it at the "Hungry" level per year, assuming a year is the same, or close to the same length or time as an earth one. This is a bit less than what is required for an Earth predator, but we have to consider the limits of current technology
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Because of this, herbivores, as on Earth, would have to have dramatically higher birth (read: spawn) rates than predators, and/or spawn more times per year. Remember the sophistry earlier in the thread about homins being unable to afflict true death. Extinction of a species would almost certainly be a game ender, no matter how realistic.
Scavengers would behave (as on Earth) as cleanup crews and a sort of ecological fail-safe. Their exact stimuli would have to be balanced by the developers if this system were actually introduced, but it could function much like this: Scavengers depend on predators for support. A single predator can support 10 scavengers. Therefore, if there are 20 predators in a given area, there may be around 200 scavengers. Should the number of predators decrease, due to a decrease in prey population, the number of scavengers would at first decrease. After a certain period of time (during which the prey animals have spawned once or twice, increasing their population), the scavengers who survive will take on predator behavior, up to that of stage 2, so they will attack herbivores with preference, or homins or other scavengers should no prey animals be available. This will continue until predators can once again support them, and then they will revert back to clean-up crew. Should the number of predators grow too high, scavengers could be set to attack them (rationalized by saying that they are defending their food). This will continue until such time as there is a propper balance of all three groups within an area. In this way, although predator/scavenger/prey populations will fluctuate, they will remain balanced. In some years overall population would be high, in others it would be low.
As for Spawn rates, a posibility may be that for every two predators, one to two(random) offspring will be created once per year. For scavengers, for every two they will produce five to ten(random) twice per year. A pair of herbivores could produce 15-30(random) at the beginning of Spring, Summer, and Autumn. This abnormally high birth rate is a result of the server necessity of having lower populations in total. It may be necessary (because of the aforementioned server limitations) to stagger the birthrate of herbivores more, so long as each pair produces 45-90 offspring per year.
As a final safety measure, once per year, one predator, ten scavengers, and 50 herbivores will spawn, whether or not any others exist to procreate.
OOC: