So, my idea is [un]symple. right now rodents are just vermin that dont do ANYTHING! I think that it should be verry important that you actually protect your fortress from thesae creatures of plague and fammin. What this propposes is that rodents(rats, mice) should have the abbility to dig "tunnels" in hidden rock and walls. here is a small immage where the hidden rock is visible:
the lines in the soil walls are tunnels.
the +, * and circled R are nests(smaller to large).
The arrow-lines indicate paths that the rodents might take to get to food.
Rodents would require a different pathing system that allows them to walk through tunnels.
Alternatively, every tunnerl would have a range of how far a rodent is allowed to stray until he can dissapear back into the tunnel.
every nest can be inside hidden blocks as long as it is x spaces away from the nearest enterance/nest and y spaces away from the nearest wall/nest.
nests would spread depending on how much food they have stolen. Otherwise, nests will spread by capturing lesser vermin or if in contact with rass/wild plants(by the tunnel openings). Thi means that infestations would not spread by themselves. It woudl amlost always be the players fault for not watching them.
Here is an immage that shows how the enterance distance would effect nest rgowth(in this immage, nests do not grow deeper into the hidden zone)
This would mean that rats and mice would be able to expand across corridors and empty halls. Cat antics would involve them sitting at the enterance of a rathole and waiting to catch the rodent(with possible chances.) Cats would finally have a use.
Also, rooms with tunnels in them would have a lowered value. this introduces a new profession: Ratcatchers. Other than vermin traps(whitch should not be fail proof) and cats, ratcatchers would be a noble of sorts that finds ratholes and exposes them. Before exposure, ratholes would be invisible and only if a dwarf saw a rat run in/out of the hole then the hole would be found. A ratcatcher would also have the abbility to "cover up" a rat hole wich is sort of like engraving. a covered up rat hole would not stay covered up. rats would chew through the wall after a period of time.
Heres a picture with several examples of how ratholes would expand:
the first row shows how, when nests grow in size(from small to medium or medium to large) they can expand by making another small nest somwhere withing their radius.
The second row shows several things that large ratholes can do when they can no longer expand. The first slide demonstrates that ratholes can make non-expanding nests next to them. Theses nests therefor make the large nest a maximum size and do not expand themselves. the second tile in the second row shows how, if two large nests have a tunnel between them, then they can spawn a storage area. This basically destroys the tile at wich it is located. The benefits of this are that it spreads the food range(the range of how far the nests can expand). They can appear only if ther are atleast two large nests connected. the botom row shows how nests can expand through multiple z levels(the 1 2 and 3 repreent the z level).
Rats and mice would also not only steal/eat(make it spoil REALY fast) foood every now and then but they would also gnawl on furniture and clothing every now and then(making it get a bit x`d or xx`d).
if a nest is dug out or a tile next to it is dug out then all the rats will spawn on the tile that had the nest.
I guess you could also get announcements like "kitten has gotten stuck in a mouse hole" or "kitten has dissapeared into a mouse hole" with the results varying.
Thoughts?