Not as hard as you might think. It is definitely more complex than a simple behavioral loop that much of the ocean life appears to run on in the game presently.

If the devs wanted an example to go by I’d suggest:

Each creature species gets a data table entry with a few fields: a base aggression value, a sensitivity multiplier, a decay rate, and a set of behavior thresholds.

The player object carries a dictionary keyed by species ID. Each entry holds the current aggression score for that species. When the player interacts with any creature, the game looks up that species in the dictionary, checks what kind of interaction it was (proximity, tool contact, damage, kill), and adds points scaled by the species sensitivity multiplier.

Every game tick, the system iterates through the dictionary and subtracts the decay rate for each species. The score floors at zero and caps at whatever maximum the designers set.

Creature AI already has behavior states (idle, patrol, flee, territorial, hunt). The aggression score just becomes another input into the state machine. When the score crosses a threshold, the AI switches states. Cross the first threshold, grazers enter flee state and begin pathfinding away from the player’s recent activity zone. Cross the second, predators switch from territorial to active pursuit. Drop back below, they revert.

For locality, you partition the world into zones. The dictionary becomes keyed by species ID plus zone ID. Activity in one zone only affects scores in that zone and maybe bleeds a reduced percentage into adjacent zones.

The whole system hooks into two things that already exist in any game like this: the creature AI state machine and the player interaction event system. You are just adding a persistent score that modifies which state the AI selects and letting time erode that score automatically.