Sorry for the late reply but as they say “better late than never”.
My recent research suggests roughly a 5% chance to spawn predators/vermin from completely rotten poop (i.e. when it gets so rotten it despawns from the map).
To test this I debugged 10000 units of bird litter in one tile and waited long enough for it to completely rot. Nothing spawned. I then spawned 120 units of bird litter and put one unit on each empty space of a barn. After it all rotted 6 coyotes “crawled out of the bird litter”. My conclusion is that to attract predators it is better to spread the poop on a large surface than keep it all in one big pile.
Unfortunately it seems we won’t be able to ever make a “poop singularity”. In fact, farming meat using the carrion spawn mechanics seams to require to much effort for the payoff. If we really want infinite food and are willing to put some effort it would be much more effective to just capture an ant queen on a bear trap and get an unlimited supply of highly nutritious ant eggs.