Currently, shotzos and the like are meant to be manufactured by a special workshop as well as traded for from caravans; it wouldn't be quite right for them to breed, and even if they were "gendered", immobile creatures cannot reproduce on-site by the virtue that they are in fact, immobile. The fact that they don't reproduce doesn't effect their availability as a caravan good, so the best way to stock up on shotzos is to load up on trade goods and request them from your liaison!
[POPULATION_NUMBER:10:20]
[LARGE_ROAMING]
[FREQUENCY:1]
[CLUSTER_NUMBER:1:1]
In addition, adding these lines to the raws will give them an extremely low chance to spawn wild for extra adventure mode fun. Though small, they do indeed pack a punch, and have been observed shooting both ogres and giants to death consistently. Regardless, they do have weaknesses; their small size means that trolls and larger creatures can toss them around; either into a chasm, a river, or a pool of lava, effectively disabling them and rendering them a non-threat. Likewise, they're trivial against most megabeasts, who possess the strength to destroy them outright.
And while we're at it, a couple bits of tile trickery for those who are used to looking at pictures rather then ugly, ugly text.
Basic tile. Save into the graphics folder in the raws as a bitmap, call it "shotzo", and then copy the code bellow into a text document, using the title as said document's name.
graphics_shotzo
[OBJECT:GRAPHICS]
[TILE_PAGE:SHOTZO]
[FILE:shotzo.bmp]
[TILE_DIM:16:16]
[PAGE_DIM:1:1]
[CREATURE_GRAPHICS:SHOTZO]
[DEFAULT:SHOTZO:0:0:AS_IS:DEFAULT]
<?xml version="1.0" ?>
<creatures>
<creature gameID="SHOTZO" file="shotzo.png" sheetIndex =0 >
<variant special="Normal" sheetIndex =0 frames = "0"/>
<variant special="Normal" sheetIndex =1 frames = "1"/>
<variant special="Normal" sheetIndex =2 frames = "2"/>
<variant special="Normal" sheetIndex =3 frames = "3"/>
</creature>
</creatures>
To insert into stonesense, first save the above picture as a png with the name "shotzo.png", and then proceed to save the code above this sentence as an xml file, so something like "cannon.xml", ect. Then, once you have both files completed, go into stone sense's creature folder, place them in, and open up the "index" folder. type down the name of the xml file into the list with the rest, without a pound. Now you can enjoy watching your cannons jerkily spin around as you integrate them into your defense!