Players' actions can have a noticeable effect on the ecology in regions of Calydon.
For example, animals will tend to breed quickly, but come from player-inaccessible "dens" to prevent extinctions, but with heavy player activity, specific species may become sparse.
Population imbalances will equilibrate without intervention over the course of days.
Animals will move in "pride" like structures, with varying design based on the species. At the "center" of prides the matriarch and/or patriarch are typically found. Outer rims of prides will typically be more scattered, weaker members, Other prides will have fast and scarce scouts. Other prides still may have their strongest, to defend the packs.
Monsters will not have discrete power based on their species (like narrow level ranges in WoW areas), but rather a function of their age. Of course some areas will bear over-representations of specific ages.
Groups of animals will exhibit their own organizational structure (like ecology notes in 1st ed. D&D)